Environmental Impact Assessment of Aerial Spraying Btk in NZ

Summary

White-spotted tussock moth (Orgyia thyellina ) is a potentially significant pest of New Zealand's natural and planted forests, horticultural crops, amenity trees and gardens. The Ministry of Forestry is considering an eradication programme for tussock moth using the biological insecticide Bacillus thuringiensis var. kurstaki (Btk). Btk would be applied in an aerial and ground-based spraying programme. This environmental impact assessment (EIA) evaluates the potential environmental impacts of the proposed spray programme. The EIA applies throughout the country.

Btk attacks only the early instar larvae of moths and butterflies. Spraying with Btk is therefore not likely to have any long term adverse effect on New Zealand's soils, waters, plants, food sources or native animals, birds and fish. Non-target moth and butterfly species which have caterpillars at vulnerable stages of development when Btk is applied will be affected in areas where the insecticide is applied. However, species and caterpillar numbers should be restored within three years of a spray programme, provided that the species is able to migrate back into the sprayed area. If a target area contains moth or butterfly species which are rare or endangered and have restricted distributions, spraying with Btk may have an adverse effect on these species. Other non-target invertebrate species will not be affected by Btk.

North American studies show that spraying with Btk has no adverse effect on public health, even for individuals who have immune system or respiratory conditions. People working directly with Btk in ground spraying operations may experience some transient irritant health effects. Locally elevated noise levels caused by low-flying aircraft are an unavoidable effect of the spray programme. However, the noise will be of short duration, with no lasting effects.

The spray programme may affect businesses involving the rearing of butterflies or moths, and may also cause traffic disruptions. In addition, a level of public concern inevitably accompanies spray programmes. Apart from these potential effects, no other economic, social or cultural impacts have been identified.

The main means for reducing the potential adverse effects of the spray programme are compliance with various relevant Acts, regulations, policies and plans; a public communications strategy; a contingency plan for emergencies; safe storage, transportation and disposal of Btk; safeguards for workers, sensitive individuals and sensitive receiving environments; and monitoring the environmental effects of the programme.

Alternative responses to tussock moth include:

doing nothing (this may result in tussock moth spreading throughout New Zealand);
using a chemical insecticide such as Dimilin (not favoured because of adverse effects on non-target organisms);
using biocontrol to reduce tussock moth populations (no biocontrol agents are known at this stage, and these techniques would not eradicate tussock moth); or
using other population control measures (techniques such as trapping and mating disruption have not yet been developed for tussock moth).

1. Introduction

1.1 Why is this Environmental Impact Assessment being prepared?

An exotic insect, the white-spotted tussock moth (scientific name Orgyia thyellina and commonly referred to as "tussock moth") has recently been found in the Auckland area. It has established and is feeding on a wide variety of plants. If it spreads throughout the country, it could become a significant pest of New Zealand's natural and planted forests, horticultural crops, amenity trees, and gardens.

There are several methods available for eradicating or controlling the tussock moth. Eradication programmes aim to completely eliminate a pest species, whereas control programmes aim to reduce the pest population to a level at which the amount of damage the pest causes is acceptable. If the research being undertaken indicates that tussock moth is likely to become a pest in New Zealand, eradication would be preferred over control ⁽¹⁾. The Government's favoured means of eradication, should this prove necessary, is to spray the affected areas with the biological insecticide known as Bacillus thuringiensis var. kurstaki (Btk).

The main purposes of this Environmental Impact Assessment (EIA) are:

to evaluate the potential environmental effects of the proposed method of eradication;
to consider how any adverse effects might be prevented or reduced; and
to compare the proposed method of eradication with alternative methods (including controlling the moth, rather than eradicating it, and doing nothing).

The EIA will also assist in obtaining the necessary approvals for any eradication programme to take place, and will act as a central source of information for any organisations or individuals with an interest in the eradication programme.

Although at the time of writing tussock moth has been found only in a small area of residential Auckland, the EIA has been written so that it may apply in any part of New Zealand to which tussock moth may spread in the future. For this reason, details of the particular areas to be sprayed are not included in the EIA. Neither is the EIA an operational document - that is, it does not contain details of site-specific spray programmes, contingency planning or monitoring programmes.

The content of this EIA represents the Ministry of Forestry's current thinking and is not official Government policy.

1.2 What is tussock moth?

The tussock moth is a member of the family Lymantriidae. It is related to the gypsy moth (Lymantria dispar ) which is a major forest pest, particularly in North America ⁽²⁾. Tussock moth is found naturally in Japan, Korea, Taiwan (Ko 1969) and China (Schaeffer 1996 ⁽³⁾) in both urban and rural areas. It does not appear to be a serious pest in these countries, but may occasionally cause problems on certain tree species. As far as is known, tussock moth has not been successfully introduced either accidentally or deliberately to any country (apart from New Zealand) outside its natural range (Bain 1996 ⁽⁴⁾). Trees which the moth feeds on overseas include mulberry, pear, cherry, plum and apple.

In Japan, the tussock moth can produce up to three generations per year in the south, and two generations per year further north ⁽⁵⁾. Females from the first one or two generations can fly, but later in the season the females are flightless. Eggs from the final generation of females overwinter and the first generation of caterpillars hatch in the spring. The female caterpillar usually has six instars and the male has five (Sato 1977) ⁽⁶⁾.

1.3 Why is tussock moth a problem?

Scientists are not yet certain of the effects that the tussock moth may have in New Zealand. Even though tussock moth is not a major pest in its native range, this does not mean that it will not cause problems in New Zealand. Many species which are not pests in their native countries have proved to cause major problems in New Zealand (eg, possums, gorse).

Literature reviews and feeding trials are being carried out by the New Zealand Forest Research Institute to determine the plant species that tussock moth may feed on, and whether it is likely to survive, reproduce and spread in New Zealand. It is expected that its host range will be wide, as it has already been recorded feeding on a number of different plants. Tussock moth could potentially become a significant pest of New Zealand's native bush, commercial forests, amenity plants and horticultural crops. More information on the impacts that may occur if tussock moth establishes in New Zealand is contained in Section 5.2 of this EIA.

1.4 What is the Government going to do about it?

If the research being undertaken indicates that tussock moth could become a significant pest in New Zealand, the Government may attempt to eradicate the moth by conducting an aerial and land-based spraying programme using the insecticide Bacillus thuringiensis var. kurstaki (commonly known as Btk). Btk is a biological insecticide - that is, it contains a strain of a naturally occurring bacterium (Bacillus thuringiensis ). Details of the proposed eradication programme are contained in Section 2 of this EIA.

1.5 Who is responsible?

The Ministry of Forestry is the government agency presently responsible for managing the Government's response to tussock moth. This is because of the potential impacts of the tussock moth on forest tree species. The Ministry of Forestry will consult closely with other government agencies including the Department of Conservation, Ministry for the Environment, Ministry of Health, Ministry of Agriculture, and Ministry of Research, Science and Technology, with research organisations such as the New Zealand Forest Research Institute and Hort Research, and with local authorities.

2. Proposed Method of Eradication

2.1 What is Btk?

2.1.1 Bacillus thuringiensis

The bacterium Bacillus thuringiensis (Bt) is a rod-shaped bacterium which occurs naturally throughout the environment (soil, foliage, water and air) in most countries of the world, including New Zealand ⁽⁷⁾. It has 22 known varieties and about 800 separate strains have been isolated.

Like many bacteria, Bt has a two-phase life cycle composed of a vegetative cell stage, which occurs when environmental conditions are favourable and the cells are young, and a spore-forming stage (known as sporulation), which occurs during adverse environmental conditions or when cells approach old age. The spores are termed endospores once they are released from the vegetative cells. A special characteristic of Bt is that at the stage when spores form, the vegetative cells of the bacterium produce substances known as protein crystals. These crystals are released into the environment, along with the endospores, when the vegetative cell degrades. The protein crystals produced by various strains of Bt contain toxins which have varying toxic properties, depending on the strain of Bt involved.

2.1.2 Commercial Development of Bt

In the 1930s, French scientists developed a Bt formulation that could be used to control caterpillar populations. Scientists of the United States Department of Agriculture (USDA) further developed the Bt formulation in the 1960s so that it could be mass produced economically. Research is continuing in several countries on the many Bt strains to test their effectiveness against caterpillars and other insects. The most important commercial varieties are variety israelensis , which controls mosquito and sandfly aquatic larvae, and variety kurstaki .

Bt formulations are widely used in New Zealand in both conventional and organic agriculture.

2.1.3 Bacillus thuringiensis var. kurstaki (Btk)

Btk is widely used to control moth and butterfly pests as it specifically affects the larvae (caterpillars) of these species. Btk formulations are produced commercially by a number of companies in the US and Europe. Large quantities of Btk have been used over the past 30 years in North America to control gypsy moth populations.

Natural epizootics (widespread insect disease) from the Btk organism have been observed only very rarely in the natural environment, and only when caterpillars are in a confined environment (USDA 1995).

2.1.4 How Does Btk Work?

The protein crystal produced by Btk includes a substance known as a delta endotoxin which is toxic to members of the Order Lepidoptera (moths and butterflies). Endospores of Btk are also toxic to many moths and butterflies. The spores and endotoxins in the protein crystal are known as the "active ingredients" in Btk formulations, because it is these ingredients which kill the insects. However, the protein crystal is not toxic until it is swallowed by a caterpillar - it must be present on a leaf and eaten by a caterpillar before it takes effect.

Once the crystal is eaten by the caterpillar it is activated by the specific conditions found in the caterpillar gut (namely, alkaline conditions and the presence of certain digestive enzymes). The toxin works by attacking the gut lining. This causes paralysis of the gut and the caterpillar stops feeding as little as two minutes after eating the Btk. The caterpillar will die of starvation two to five days later, depending on environmental conditions. Vegetative growth of Btk within the caterpillar and septicaemia caused by Btk may also help to kill the caterpillar.

Susceptibility to Btk depends on (BC MOH 1992):

the pH of the gut (a pH of 9.0-10.5 is ideal);
the presence of specific digestive enzymes which dissolve the crystals (these enzymes are present only in Lepidoptera larvae);
age and biomass of the larvae (early instar larvae are more susceptible); and
temperature (feeding rates and cell regeneration are inhibited by low temperatures).

2.1.5 Fate of Btk in the Environment

The insecticidal activity of Btk decreases relatively rapidly in the environment. Studies have shown that it has a half life of 12-32 hours, depending on environmental conditions ⁽⁸⁾ (USDA 1995). It is rapidly broken down by other micro-organisms in the environment and UV radiation. Spores adhering to the upper side of leaves may be active for only one to two days, whereas on the underside of leaves spores may be effective for seven to ten days (Ellis 1991).

The persistence of Btk in soil and water is discussed in Sections 3.3 and 3.4.

2.1.6 Why is Btk Used in Preference to Other Varieties of Bt?

Btk is used in moth eradication programmes because it is readily commercially available, it specifically targets the larvae of moths and butterflies, and it doesn't produce any toxic exotoxins ⁽⁹⁾.

2.1.7 What Other Ingredients Are Found in Commercial Formulations of Btk?

A distinction must be made between the microorganism Btk and commercial preparations of it. Formulations of Btk are complex chemical mixtures, the exact ingredients of which are kept confidential for commercial reasons (although regulatory agencies have access to this information for assessment purposes). Btk is cultured in large vats which contain water and nutrients such as sugars, starches, proteins and amino acids. Small quantities of essential elements, minerals or salts may also be added to create good growing conditions for Btk (USDA 1995). Commercial formulations consist largely of water, Btk (figures of 2.1% to 2.5% by volume have been specified by two major manufacturers), and traces of these fermentation materials.

Other substances are also added to the formulations. These substances are known as "inert ingredients" to distinguish them from the "active ingredients" (Btk). Some common additives are (BC MOH 1992):

thickening agents (which provide uniform suspension in a spray);
wetting agents (which provide better leaf coverage);
phagostimulants (which encourage the insect to feed);
anti-evaporants;
stickers (to increase retention of spray deposits); and
sunscreens (to decrease degradation of crystals by UV radiation).

The inert ingredients are potentially the most toxic components in Btk formulations, but there are only trace amounts applied in spray programmes (BC MOH 1992).

2.2 What formulation of Btk would be used?

It is proposed that a formulation known as Foray 48B be used. This formulation is manufactured by Abbott Laboratories in Chicago, USA. It is a flowable concentrate formulation (ie, it is provided in liquid form) specifically designed for low volume and ultra low volume spraying.

Foray 48B has recently been registered for use in New Zealand under the Pesticides Act 1979 for use on forests, parks, shrubs and trees for the control of Asian gypsy moth. It is suitable for both aerial and ground application (Foray 48B label information).

2.2.1 Inert Ingredients in Foray 48B

The USDA evaluated the inert ingredients in Foray 48B and found that they are all on US Environmental Protection Agency (EPA) Lists 3 or 4. List 4 contains substances which are "generally recognised as safe" and List 3 contains substances for which there is insufficient information to classify their safety (USDA 1995). The additives include substances to inhibit the growth of bacterial or fungal contaminants. These additives are approved for use in foods in the US and Canada. All of the inert ingredients have been assessed by the US EPA and various agencies in Canada with no public health threats from any of the ingredients identified (USDA 1995).

A Canadian publication has stated that the inert ingredients in Foray 48B include residual bacterial food (from potato, glucose or sucrose, corn or soya), sodium hydroxide (a pH adjuster used in chocolates, margarine and ice cream), potassium phosphate (a yeast food used by the wine industry) and a thickening agent (used in cream cheese and ice cream) (Agriculture Canada, c.1992). The manufacturer has indicated that Foray 48B contains no volatile solvents (Novo Nordisk, no date), and this has been confirmed by assessment authorities in New Zealand (MOH 1996 ⁽¹⁰⁾).

2.2.2 Potential for Contamination

One common concern about biological insecticides is that they may become contaminated with other micro-organisms such as yeasts, moulds and the faecal bacterium Streptococcus facecium . Since 1988, when strict quality control requirements were placed on North American manufacturers of Btk formulations, no substantial levels of bacterial or yeast contaminants have been found in Btk samples (USDA 1995). Each fermentation batch of Btk undergoes quality assurance tests for mammalian toxicity, microbial contaminants and formulation potency (Ellis 1991). The quality control measures are also designed to detect any changes in the Btk organism from the Btk parent strain. In addition, independent tests have confirmed a lack of contamination of the Btk formulation Foray 48B ⁽¹¹⁾.

2.2.3 Why Would Foray 48B Be Used in Preference to Other Formulations of Btk?

In some eradication programmes overseas, when public exposure to Btk was a consideration, formulations containing gamma-ray inactivated Btk spores were used. However, formulations of this type would not be used in New Zealand as the need for inactivating the spores has never been demonstrated (BC MOH 1992) and irradiation of spores may cause additional public concern.

Other formulations of Btk which are registered for use in New Zealand are Agree, Delfin and Dipel. However, these formulations are registered for use only on horticultural crops.

Foray 48B is the preferred choice for a tussock moth eradication programme in New Zealand as it is registered specifically for use on forests, parks, shrubs and trees. In addition, Foray 48B has been widely used in Canada in gypsy moth eradication programmes, including programmes in urban areas, so there is a relatively large amount of information on potential environmental effects specific to this formulation.

2.3 How would Btk be imported, transported and stored?

If a tussock moth eradication programme was undertaken in New Zealand, Foray 48B would be imported specifically for the eradication programme from the US where it is manufactured. It would be imported in bulk containers (eg, 200 or 1000 litre containers). The volume imported would depend on the area to be sprayed. An indicative volume for a 25 km2 area is 75 000 litres.

Btk would be transported from the point of importation to a secure storage site by road or rail transport. For each spraying operation, a single, secure storage area would be selected. It is likely that aircraft used in the spray programme would load the Btk directly from the selected storage area (see Section 4.5 for further details of transportation and storage requirements).

2.4 Where would the Btk be applied?

Surveys are currently being carried out to determine the extent of the tussock moth infestation. These surveys consist of visual sightings of caterpillars and egg masses. Further work is being done on the potential for using pheromone monitoring to detect male moths ⁽¹²⁾. Known pheromones of species closely related to tussock moth are being investigated. If a suitable pheromone is found, it can be used in traps to attract the male tussock moths and thereby determine the spread of the population.

The size of the area(s) to be sprayed would depend on the results of the surveys of the spread of the insect. North American eradication programmes using Btk have found that a common reason for eradication failure is that the spray was applied over an insufficient area. On the other hand, there are strong economic and environmental incentives to ensure that the size of the area to be sprayed is not too large.

A final decision to spray in an area where tussock moths have been found will depend on the costs and benefits of undertaking an eradication programme.

2.5 How and when would the Btk be applied?

2.5.1 How Would the Spray Be Applied?

Two types of spray operations are envisaged - aerial spraying and ground spraying.

Aerial Spraying

The exact details of an aerial spraying programme (ie, the type of aircraft used and the flying height) depend on the physical and social characteristics of the area to be sprayed and the potential impacts and effectiveness of the various means of aerial application. The options for aircraft type are fixed wing aircraft or helicopters. It is most likely that a combination of fixed wing aircraft and helicopters would be used. From an operational point of view, the type of aircraft (fixed wing or helicopter) is not important, provided that it can fly safely in the target area and achieve the desired standard of spray application. However, different types of aircraft have advantages and disadvantages, as outlined in Table 1 ⁽¹³⁾. Helicopters are more versatile but also have greater potential adverse effects (particularly noise).

Table 1: Comparison of Helicopters and Fixed Wing Aircraft for Applying Btk

	Advantages	Disadvantages
Helicopters	more manoeuvrable, leading to more precise spray deposition and ability to reach areas not reached by fixed wing aircraft shorter spraying time	greater noise levels narrower spray swath width
Fixed wing aircraft	quieter wider spray swath width	less manoeuvrable

The options for flying height are either 10-30 metres above rooflines, or 90 metres above ground. The advantages and disadvantages of each flying height are set out in Table 2 ⁽¹⁶⁾. In general, applying spray at a low height is more effective, but has greater adverse effects (particularly noise). At low flying heights, Btk formulation can be applied as a low volume, very fine mist, achieving a good coverage of target vegetation. At higher flying heights, a larger spray droplet size is required in order for the spray to fall to the ground. This means that the formulation must be diluted and applied in much greater quantities. The large droplets do not coat target vegetation as effectively as mist spray.

Table 2: Comparison of Potential Effects of Different Flying Heights

	Advantages	Disadvantages
10-30 m	better spray coverage more precise application less volume of Btk applied per hectare	greater noise and other nuisance effects
90 m	less noise and other nuisance effects	poorer spray coverage more off-targe spray drift greater volumes of Btk applied

Regardless of the type of aircraft used and the flying height, a number of aircraft would operate at one time. Each would be allocated an area of the total area to be sprayed (for example, if helicopters were used to spray a 25 km2 block, five helicopters could each be allocated a 1x5 km block). Both fixed wing aircraft and helicopters would fly at a speed of approximately 65 knots ⁽¹⁷⁾.

Ground Spraying

Ground spray units are employed to reach vegetation sheltered by buildings, motorways, bridges and other structures or barriers to aerial exposure. The number of ground spray units used depends on the size of the area to be sprayed. As an indication, up to five three-person ground spray units could be operating at one time in a 50 km2 spray zone.

2.5.2 When Would Spraying Take Place?

Tussock moth caterpillars must be sprayed at a susceptible age (from egg hatch to their third instar) for effective eradication. It is anticipated that the eggs will hatch in early spring, but because the full life cycle of the tussock moth has not been observed in New Zealand before, it is not certain exactly when the eggs will hatch. For this reason, egg masses are being carefully monitored for signs of activity.

An eradication programme would consist of three to five applications of Btk made at seven to ten day intervals throughout the period that the caterpillars are most susceptible. The overall duration of the spray programme may therefore be up to 40Êdays (five applications, each 10 days apart), depending on weather conditions, results of monitoring, and degree of synchronisation of egg hatch. The duration of each individual spray application would depend on the size of the area to be sprayed and the number of ground and air spraying crews operating. For example, it would take two helicopters approximately eight hours to cover a 50 km2 area. Ideally, however, spraying time would be reduced to two to three hours by having a number of aircraft operating at one time. The spraying programme will be terminated when monitoring shows that all the eggs have hatched.

Multiple applications of Btk are required because the timing of egg hatch and caterpillar development may vary slightly between caterpillars. In addition, low doses of Btk can inhibit caterpillar feeding, thereby reducing the intake of Btk for a period and allowing the insect to recover. During this time, the original dose of Btk will have degraded in the environment and, unless a repeat application is made, the caterpillar will resume feeding and mature.

The best application conditions for aerial spraying of Btk are low wind speeds (minimum 3 km/h, maximum 16 km/h ⁽¹⁸⁾), temperature less than 20 degrees C ⁽¹⁹⁾, no rain for at least 24 hours after spraying, and active feeding by the caterpillars.

The options for the time of day at which aerial spraying would take place are night spraying (ie, pre-dawn or very early morning) and day spraying. The relative advantages and disadvantages of each option are set out in Table 3 ⁽²⁰⁾. Night spraying has the significant advantage of lowering the levels of public exposure, but it also has greater nuisance effects.

Table 3: Comparison of Night Spraying and Day Spraying for Aerial Application

	Advantages	Disadvantages
Night spraying	more favourable meteorological and spray deposition conditions less traffic less public exposure	poorer visibility for pilots greater noise intrusion and intrusion from aircraft lights
Day spraying	better visibility for flying less noise intrusion	less favourable meteorological and spray deposition conditions more traffic more public exposure

Ground spraying at night also has the advantage of reducing public exposure to Btk. However, as ground spraying crews will need to enter private property, day spraying may be preferable for public communication reasons.

2.5.3 Other Details of Application

Foray 48B is designed for low volume spraying. A dose rate in the range of 40-90 BIU/ha (most likely 63 BIU/ha) would be used ⁽²¹⁾. As an indication of how much formulation this equates to, a dose rate of 60 BIU/ha is equivalent to 5 litres of product (Foray 48B) per hectare ⁽²²⁾. In the US, the typical eradication dose rate is 60 BIU/ha applied 2-3 times (USDA 1995), following a trend towards higher dose rates. Foray 48B will be applied undiluted using Micronair atomisers (for aircraft) and mist sprayers (for ground spraying). The spray equipment will be calibrated to deliver a very fine spray with a median droplet size of approximately 100 microns in diameter ⁽²³⁾. At this droplet size there is some potential for off-target spray drift (see Section 3.10.1 for details).

2.5.4 Why Would These Methods of Application Be Used in Preference to Alternative Methods?

A combination of aerial and ground spraying is the only practical method of Btk application because all vegetation on which the caterpillars may be feeding needs to be covered if the eradication programme is to be successful. Insecticides which are applied in pellets or paste forms would not be effective.

Unless the introduced population was known to be in a very confined area, it would not be practical to undertake the entire spraying operation from the ground, and ground spraying may not reach the tops of trees ⁽²⁴⁾.

2.6 How would the eradication programme be monitored?

2.6.1 Monitoring the Deposition of Spray

Precise control of where the spray falls would be achieved by fitting all aircraft with differential DGPS (digital global positioning system) so that their exact location would be precisely known at all times. The exact spray swath width would be determined using the computer simulation model FSBG (Teske et al 1993) and checked by measuring the spray pattern from the individual aircraft, using the spray mix, prior to the start of the operation. All equipment would be tested and calibrated before spraying. In addition, spray deposition would be measured on the ground in selected areas using appropriate spray traps.

2.6.2 Monitoring the Eradication of Tussock Moth

Intensive and effective monitoring of tussock moth populations is essential to determine whether the infestation has been successfully eradicated. A monitoring programme will be undertaken in the area treated in the spraying operation and in the surrounding area to cover the possibility that the moth may have spread. Potential means for monitoring include the use of pheromone traps (depending on the outcome of work described in Section 2.4) or, if no suitable pheromone is found, hand searching methods and light trapping.

For monitoring the environmental effect of the spray programme, see Section 4.11.

3. The Environmental Impacts of Spraying Btk

3.1 Introduction

This section identifies the actual and potential environmental impacts, both positive and negative, of the proposed Btk spraying programme. The term "environment" is used widely to include the natural and physical environment as well as effects on people and social, cultural and economic values.

The impacts addressed include those of the Btk formulation, and those associated with the spraying programme (aircraft noise etc.). Where available information permits, the impacts identified are specific to the Btk formulation proposed in Section 2 (ie, Foray 48B). More commonly, the available information refers to the effects of Btk formulations generally, or occasionally, simply to Bt.

Each section in this chapter addresses potential impacts on one aspect of the environment.

Identification of the potential impacts of Btk relies heavily on North American studies. This is inevitable, as it is in North America where Btk has been widely used in insect eradication programmes (eg, for gypsy moth). Two sources, in particular, are quoted frequently in the following sections of the EIA. These are ⁽²⁵⁾:

BC MOH 1992 - a publication entitled "Bacillus Thuringiensis" prepared by the British Columbia Ministry of Health as part of environmental impact information submitted in support of a gypsy moth eradication programme using Foray 48B in Vancouver in 1992; and
USDA 1995 - a multi-volume environmental impact statement prepared by the United States Department of Agriculture, the Forest Service and the Animal and Plant Health Inspection Service on gypsy moth management in the United States. One of the methods of control discussed in this comprehensive document involves the use of Btk.

At the end of each section in this chapter, a conclusion is drawn about the likely impacts of a Btk spraying programme in New Zealand, based on the available information.

3.2 How effective is Btk in eradicating tussock moth?

There are no previous examples of Btk being used to eradicate white-spotted tussock moth populations. Tussock moth is not a major pest in the countries it is found in and, therefore, there have been no efforts to control or eradicate it. Information that is available on the efficacy of Btk in eradicating moth species relates to spray programmes to eradicate or control gypsy moth populations in North America. As gypsy moth is a close relative of tussock moth, the gypsy moth data provides the best available indication of the likely effect of a Btk spray programme on tussock moth in New Zealand ⁽²⁶⁾.

3.2.1 Gypsy Moth Eradication Programmes

In North America, Btk has been used for many years to eradicate and control gypsy moth populations, with inconsistent results. In British Columbia, monitoring information is available for 80 of the at least 102 separate gypsy moth introductions that have occurred in the past 18 years. 81.2% of the infestations died out by themselves and the remaining 18.8% were sprayed and successfully eradicated ⁽²⁷⁾ (Environmental Appeal Board 1996). In some cases, eradication was achieved in one year. In other cases, two years of spraying were required. Failure of eradication programmes in the first year was often attributed to the area sprayed being too small (Agriculture Canada 1993).

A recent decision of the BC Environmental Appeal Board upheld an appeal against Agriculture Canada to ground spray Foray 48B. The main reason for declining permission to spray was that the applicant failed to show that the benefits of the spray programme outweighed the risks. In particular, the Appeal Board found that a ground spray programme alone was unlikely to eradicate the gypsy moth. The minor health risks associated with the use of Btk (see Section 3.7) were balanced against the lack of demonstrable benefits of the ground spraying programme, and permission to spray was declined (Environmental Appeal Board 1996). As gypsy moth is so widespread in North America, some groups are now questioning the ability of Btk spray programmes to effectively eradicate the moth (eg, see STOP 1995).

In the US, Btk is frequently used to control gypsy moth, rather than to eradicate it. US data on the efficacy of Btk shows that Btk spray programmes met their population reduction targets only 60% of the time in 1989-90. Since then, higher dose rates (60 BIU/ha) and the use of undiluted formulations may have improved the efficacy of the programmes (USDA 1995).

Inconsistent efficacy of Btk has been attributed to the fact that it has to be ingested and has poor residual toxicity. These features tend to make treatment success more dependent on favourable conditions ⁽²⁸⁾. In the US, factors which were found to affect efficacy include correct timing of the applications with regard to insect and leaf development, weather conditions during and after application, and quality of application (eg, good pilot skills, properly functioning equipment). The most important factors were making sure that Btk was applied to foliage on which the caterpillars were actively feeding, and applying the Btk in sufficient quantity to kill the insects (USDA 1995).

3.2.2 Likely Effect in New Zealand

The New Zealand situation differs from the North American situation with gypsy moth in that only a single introduction of tussock moth has occurred, and the moth is not yet widespread. These factors both favour successful eradication. Results of the North American gypsy moth eradication programmes suggest that Btk is likely to be effective in eradicating tussock moth in New Zealand, provided that:

all infested areas are identified;
a sufficiently large area around each infestation is treated with three to five applications of Btk;
dose rates are high enough to kill the insects (dose rates of approximately 60 BIU/ha are proposed);
the application is timed to coincide with the vulnerable stages of caterpillar development;
there are sufficient rain-free days at the ideal time of application; and
the treatment is carried out by properly trained and equipped professionals.

Forest Research Institute scientists have estimated that there is an 80-90% chance of a Btk aerial spray programme successfully eradicating tussock moth from New Zealand.

3.3 How does Btk affect soil?

3.3.1 Persistence in Soil

Bt occurs naturally in soils throughout the world ⁽²⁹⁾. The vegetative form of Btk is generally not well adapted to soil, and it requires the specialised habitat of vulnerable insects to persist. However, Bt endospores can survive in most types of soils for at least four months (BC MOH 1992). Studies show that the Btk toxins decay in soil far more rapidly than the spores (BC MOH 1992).

3.3.2 Accumulation and Movement in Soil

Repeated applications of insecticides containing Bt do not appear to increase levels of Bt in the soil. Researchers have found that Bt does not move in soil. This was determined by spraying two types of Bt in close vicinity. No cross-contamination of types was observed (BC MOH 1992).

3.3.3 Soil Fertility and Productivity

Changes in soil productivity and fertility due to Btk are not likely because of Bt's natural occurrence in soil, lack of accumulation, and relatively short persistence in soil (USDA 1995).

3.3.4 Soil Micro-organisms

Some soil invertebrates may be affected by Btk, but there has been no research on the effects this may have on rates of soil decomposition. One North American study showed increased numbers of several soil micro-organisms (bacteria, actinomycetes, fungi and nematodes) in Btk treated areas when compared with untreated areas. Another study found decreases in populations of a predatory mite closely related to soil dwelling species (USDA 1995).

3.3.5 Likely Effect in New Zealand

The information cited above suggests that Btk is unlikely to have any measurable effect on New Zealand soils.

3.4 How does Btk affect water?

Bt may enter water through direct application to surface water, runoff, or through the faeces of animals who have ingested Bt. It is unlikely that runoff would be a significant route by which Bt could enter water, as the efficacy of Btk depends on it being applied in dry weather.

3.4.1 Persistence in Freshwater

Field studies indicate that Btk may persist for several months in water. A Nova Scotia study found that 50% of Btk endospores remained viable in fresh lake water for 70 days at 20 degrees C before being inactivated by other micro-organisms in the water (Menon & De Mestral 1984).

3.4.2 Persistence in Seawater

Btk persists for a much shorter time in seawater. The study cited above showed that 50% of endospores survived only 40 days in seawater, possibly due to the bactericidal effect of seawater (Menon & De Mestral 1984).

3.4.3 Groundwater

It is unlikely that Bt could enter groundwater, as studies have shown that it does not leach out of soil (BC MOH 1992).

3.4.4 Water Quality

Water quality should not be directly affected by Btk as it is not likely to affect most aquatic organisms. Some North American laboratory studies have shown decreases in detritus decomposition rates at high doses of Btk. However, these effects are unlikely in the environment because of the lower doses of Btk used and the purification processes in natural systems (USDA 1995).

3.4.5 Drinking Water Supplies

The Nova Scotia study referred to above detected Btk in a municipal water system during the spraying programme. This implies that chlorination of the water supply (a common means of ridding water supplies of bacterial contaminants) was not sufficient to kill the Btk - a finding backed up by laboratory studies (Menon & De Mestral 1984). It is possible, therefore, that a small amount of Btk may enter public water supplies as a result of aerial spraying programmes in areas which contain water catchments or water supply reservoirs. Btk contamination may also occur if spray enters air vents of local drinking water distribution reservoirs. Ingestion of Btk through water supplies is unlikely to have any adverse effects on human health as it is not a human pathogen (see Section 3.7 below for further details on human health effects).

3.4.6 Aquatic Organisms

See Sections 3.8 and 3.9.

3.4.7 Likely Effects in New Zealand

The information cited above suggests that Btk may be present in New Zealand water following a Btk spray programme, but is unlikely to have any effect on water quality. It is possible that Btk may be present in municipal water systems if spraying takes place near water supply catchments. Btk may also enter water supplies if spraying takes place in an area supplied by tank water. However, the presence of Btk in water is not considered to cause any adverse effects on human health. Nevertheless, people may be concerned about the presence of bacteria (even non-pathogenic ones) in water supplies.

3.5 How does Btk affect plants?

3.5.1 Terrestrial Plants

Phytotoxicity (ie, adverse effects on plant health) from Btk has never been observed at field rates of application (BC MOH 1992 & USDA 1995).

If anything, applying Btk is likely to have positive effects on the health of plants by reducing populations of leaf-feeding caterpillars. In some cases, however, this effect could be undesirable. For example, Btk may reduce the population of an insect imported for the biological control of a weed species, thereby allowing the weed to thrive.

Plants which are pollinated exclusively or mainly by moths and butterflies may experience a temporary drop in seed set.

3.5.2 Aquatic Plants

North American studies have found aquatic plants to be unaffected by Btk formulations (USDA 1995).

3.5.3 Likely Effect in New Zealand

Btk is highly unlikely to have any direct toxic effects on New Zealand plants. Potential indirect effects on plants caused by Btk reducing Lepidoptera populations include:

positive effects on garden and other plants due to the reduction of leaf-feeding caterpillars (eg, white butterfly caterpillars will be killed by Btk if they are in a susceptible stage of development, thereby improving the health of some garden vegetables);
negative effects due to reduced populations of biocontrol agents. Lepidopteran biocontrol agents in New Zealand include the ragwort moth Tyria jacobaeae (introduced to control ragwort) and three species of moth recently introduced to assist in the control of gorse. It is unlikely that spraying with Btk would have a significant effect on the growth of either ragwort or gorse as the caterpillar of the ragwort moth is unlikely to be at a vulnerable stage of development when spraying takes place, and the gorse biocontrol agents have yet to become established ⁽³⁰⁾; and
negative effects on plants pollinated by moths and butterflies. Again, it is unlikely that spraying with Btk would have any adverse effects on native plants, as New Zealand's native plants are generally unspecialised in terms of pollination (ie, they are not reliant on single specialised forms of pollinator) (Wardle 1991). Introduced plants are also unlikely to be affected by reduced pollination, as even those species which were solely reliant on moth or butterfly pollination would be able to be pollinated by species which were not at vulnerable instar stages when spraying took place.

3.6 Does Btk leave a residue on crops or other sources of food?

3.6.1 Presence on Vegetables

Btk is frequently used by the food industry to control insect pests in both conventional and organic growing techniques. As part of a major study on the effects of Foray 48B Btk aerial spray programmes in Vancouver, food samples were analysed for Btk. The researchers were able to cultivate Btk from a variety of vegetables during and after the spray programme. They concluded that it was most unlikely that all of the Btk on the food came from the aerial spraying programme (Noble et al 1992).

Effects of the presence of Btk in food on human health appear to be negligible as Btk does not grow in warm blooded organisms and passes through the digestive system without producing any toxic effect. This is indicated by the lack of human health effects demonstrated in the Vancouver study (see Section 3.7) and by the fact that Bt is exempt from any requirements for a maximum residue limit when applied to crops (BC MOH 1992 and NZ Food Regulation 275 ⁽³¹⁾).

Bt is related to the B. cereus bacterium which can cause food poisoning. However, there is no evidence linking the use of Bt to food poisoning.

3.6.2 Cumulative Effect in the Food Chain

Btk is unlikely to have any effect in food chains because it has not been found to replicate or accumulate in predators (BC MOH 1992).

3.6.3 Likely Effect in New Zealand

The New Zealand situation is likely to be similar to that found in Vancouver, that is, the population is exposed to sources of Btk in food other than aerial spraying. A number of Bt formulations are registered in New Zealand for use on kiwi fruit, citrus trees, grapevines and berry fruit. Bt is also approved for use in organic agricultural regimes and is relatively widely used on organic crops ⁽³²⁾. It is therefore unlikely that an aerial spray programme for tussock moth would have any significant effects on Btk residues on food.

3.7 Does spraying with Btk have any effects on human health?

Humans may be exposed to Btk from sources other than tussock moth eradication programmes (see Section 3.6). The most likely routes for exposure as a direct result of an eradication programme are through direct contact with the formulation on skin or eyes (eg, sprayers may be splashed with the formulation), or direct contact with spray droplets on the skin, in the mouth or eyes, or through inhalation.

3.7.1 Summary of Available Data

All the studies carried out in North America to date on Btk health effects show no public health concerns, despite long term, large scale and intensive use of Btk in aerial eradication programmes (USDA 1995 & BC MOH 1992). Some workers applying Btk in ground-spraying operations may experience some transitory irritant health effects (Noble et al 1992) and label information indicates that Foray 48B may cause eye irritation. No evidence of vegetative growth (ie, pathogenic activity) of Btk in non-insect species has been found in any laboratory studies (BC MOH 1992). This is because Btk is activated only by the specific conditions which exist in the insect gut. The acidic gut of humans and other animals prevents any activation of the pesticide.

No mammalian LD50 has been established because of the low level of toxicity ⁽³³⁾. In experimental situations, humans have been exposed to >109 (one thousand million) spores Btk/kg by inhalation and >1010 spores Btk/kg orally with no adverse effects (BC MOH 1992). These levels of exposure are much higher than the levels that members of the public would be exposed to during an aerial spray programme. No ADI (Acceptable Daily Intake) for Btk has been assessed by Canadian authorities, the US EPA or WHO (World Health Organisation) (USDA 1995). No vapour pressure level or odour threshold has been set (BC MOH 1992) and there is no withholding period (ie, time before which it is unsafe to enter the sprayed area) (Foray 48B label information).

3.7.2 Effects on Workers

A major study of workers in the Vancouver spray programme (using Foray 48B sprayed at a dose rate of 40 BIU/ha) found that some people working on Btk ground spray programmes, without protective clothing, developed minor irritations of the skin, eyes and respiratory tract. These health effects tended to be transient and irritant in nature: dry skin, chapped lips, itchy, red and burning eyes, runny nose and nasal stuffiness. The symptoms were reported two to three times more frequently among ground spray workers than among the control group during the trial period. However, the ground spray workers studied in Vancouver were exposed to up to 500 times the amount of Btk that a member of the public standing outside during the spray operation would be exposed to ⁽³⁴⁾.

Factors which were found to be statistically significant influences on the symptoms reported by ground spray workers were whether the worker had a pre-existing history of asthma, seasonal allergies or eczema and the degree of exposure to Foray 48B. Both of these factors increased the reported incidence of symptoms. The sex of the worker and whether the worker smoked were found not to influence the reported symptoms. The study also found that Btk persisted in the nasal cavities of workers for up to four weeks (or longer in a minority of cases). No significant or serious health problems in spray workers resulted from Foray 48B exposure and no days of work loss could be attributed to Btk (Noble et al 1992).

The researchers were unable to determine what proportion of the observed symptoms arose from exposure to the Btk organism, and what, if any, was attributable to the other components in the Foray 48B formulation (Noble et al 1992).

Ground workers are likely to have greater levels of exposure to Btk than aerial workers. A US study found that ground workers using spraying equipment had low levels of cumulative exposure to Btk during the spray period ⁽³⁵⁾, and aerial workers had levels of exposure only slightly higher than those of the general public (USDA 1995).

3.7.3 Public Health Effects

Two detailed epidemiological studies have been carried out on exposure of the general public to Btk. One of these studied the use of Foray 48B to spray large areas of urban Vancouver (see above). US authorities have concluded that "on the basis of both the available epidemiological studies as well as the long history of use, no hazard has been identified for members of the public exposed to Btk formulations" (USDA 1995).

Hospital studies carried out as part of the Vancouver study found that (Noble et al 1992):

complaints of asthma or other respiratory diseases, or complaints of eye, nose or throat irritation were not more common in people living inside the spray zone, nor were they more common in people who were found to be culture positive with Btk (ie, people who had Btk present in their bodies);
there was no evidence of an increase in people attending hospital emergency departments during the time of the spray; and
no cases of serious infection with Btk were identified in any hospitalised patients.

The researchers found that while some of the reported symptoms may have been attributable to the spray, it was not possible to distinguish these from identical complaints that regularly occur during spring due to environmental factors such as dust and pollen (Noble et al 1992).

The Vancouver study did not examine the psychosocial effects of Btk spray programmes (ie, health effects caused by stress and fear associated with aspects of the spray programme). These matters are addressed in Section 3.11.1.

3.7.4 Effects on Sensitive Population Groups

Among members of the general public (as opposed to ground sprayers working with Btk), no groups have been identified who may be more sensitive to the effects of Btk. The Vancouver study found that people with asthma or other respiratory diseases did not turn up to emergency departments more frequently during or after spraying with Foray 48B as compared to before spraying (Noble et al 1992).

Another Canadian publication advises that the elderly and children are at no more risk to the effects of Btk than other members of the population (Agriculture Canada c.1992).

The Vancouver study also examined whether HIV positive people or people with immunosuppressive diseases may be vulnerable to infection with Btk, and found no cases of a Btk pathogen causing an infection (Noble et al 1992). Canadian authorities have also reported that concerns that people with immune system conditions may be at higher risk of infection when exposed to Bt are not supported by studies or scientific publications (BC MOH 1992).

No allergic response to Btk has ever been documented (USDA, 1995 ⁽³⁶⁾).

In spite of these assurances, studies of human populations cannot identify every potentially sensitive individual. There is very little information on potentially sensitive individuals, particularly people from groups not widely represented in the areas studied in North America (eg, Maori and Pacific Islanders). There is always a possibility that some individuals may have particular chemical sensitivities which make them sensitive to either Bt spores or other ingredients in Btk formulations. In particular, people who have already developed an allergy to one of the components in Foray 48B, or who have asthma of a type that could be initiated by irritants such as tobacco smoke or pollens may be affected by exposure to Btk formulations ⁽³⁷⁾, although it must be stressed that epidemiological studies do not support this possibility.

3.7.5 Chronic Effects

No chronic effects of Btk (ie, effects which occur either after prolonged exposure, or an extended period after initial exposure) are known (USDA 1995). However, most studies of the potential health effects of Btk have concentrated on short term effects.

3.7.6 Unusual or Controversial Results

In studies of the human health effects of Btk there have been some unusual or controversial results which could indicate some adverse effects. The following cases have been examined in the preparation of this EIA:

a farmer splashed a Btk formulation in his eye and developed a corneal ulcer (Samples and Buettner, 1983). Btk was recovered from the eye and this is sometimes cited as evidence of pathogenic Btk infection in humans. However, it can also be interpreted as a severe eye irritation accompanied by the recovery of incidental viable Btk, which was known to have been splashed into the farmer's eye (USDA 1995); and
a nine-year-old boy walked across a lawn after the application of Foray 48B and developed symptoms of rashes, vomiting, fever and diarrhoea. A strain of Bt (different from the strain used in the preparation of Foray 48B) was isolated from the boy's blood and he was diagnosed as having Kawasaki disease (a disease which he was also diagnosed with at age two). The US EPA concluded that there was no direct correlation between the occurrence of Kawasaki syndrome and spraying with Foray 48B (Schaffer 1992).

A number of other reports of possible pathogenic activity of Btk in humans have been recorded (eg, see STOP 1995), but these tend to be anecdotal and not conclusively linked to the use of Btk formulations.

None of these cases appears to alter the findings presented above relating to the safety of Btk formulations.

3.7.7 Likely Effect in New Zealand

It is not possible to predict precisely how much Btk a member of the population standing outside during a spraying operation would be exposed to. However, it can be said with certainty that even at exposure levels hundreds of times higher than those anticipated for the general population, no significant adverse health effects have been experienced overseas. It is therefore concluded that spraying with Btk will have no adverse effects on public health in New Zealand, including members of the population with asthma, other respiratory diseases or immunosuppressing diseases.

Health effects on ground spray workers will be similar to those documented in the Vancouver study above - that is, effects will be irritant and transient. The types of health effects workers may experience are milder than the effects experienced by those working with most other agrichemicals and may be reduced by the use of appropriate protective equipment (see Section 4.6).

Health-related nuisance effects (eg, noise and odour) are addressed in Section 3.10.

3.8 What effects may Btk have on non-target invertebrates?

Non-target invertebrates are any invertebrates (ie, animals without backbones such as insects, spiders, crustaceans, molluscs) other than the target organism (tussock moth). These organisms may be exposed to Btk either directly by encountering it in the environment (eg, by eating leaves, litter, or the uppermost layer of the soil) or indirectly, by eating caterpillars which have been infected with Btk. Aquatic invertebrates may also be exposed to Btk through direct application of the spray to water, but very few studies have been done on this possibility (USDA 1995). Although Btk has a half life in the environment of 12-32 hours, it has an insecticidal activity of a week or longer (USDA 1995). Btk is therefore not expected to affect caterpillars other than the generation which is present when the Btk is sprayed.

3.8.1 Caterpillars

As Btk is specific to Lepidoptera larvae, it is expected to kill all exposed early instar caterpillars (ie, caterpillars which have hatched relatively recently) located within the target area and in adjoining areas that are exposed to spray drift.

In the US, Btk spraying commonly resulted in an 80% reduction in the number of caterpillars, with population recovery taking up to two years (Abbott 1994). Other US reports indicate that, although data are sparse on the effects of multiple applications of Btk within one year, it is reasonable to expect that both the numbers and types of non-target caterpillars may be reduced and that these effects could persist for one year or longer (USDA 1995). One study that did address multiple applications of Btk within a year was carried out in Oregon in 1986-88. It found that the number of species of leaf eating Lepidoptera was significantly reduced for three years after spraying with Btk, and the number of individual non-target caterpillars in the trial area was significantly reduced for two years. Factors which influenced the ability of non-target species to recover included the stage of larval development at the time of spraying, the number of generations in a year (species with a single generation take longer to recolonise), and the insect's ability to disperse (Miller 1990).

Permanent changes in non-target caterpillar populations do not appear likely except, possibly, in habitats that support small isolated populations of Lepidoptera that are highly vulnerable to Btk. This is particularly so if there may be physical or biological barriers which prevent the insect from moving back into the sprayed area (USDA 1995).

In some studied species (namely gypsy moth), caterpillars which are exposed to Btk but do not die, grow more slowly and remain in the larval stage longer, and therefore may be more susceptible to parasites (USDA 1995).

3.8.2 Bees

Many studies have been carried out on the effect of Btk on honeybees. The overall conclusion of these studies is that Btk is non-toxic to bees, even at high levels of exposure (Ellis 1991, Lehnert & Cantwell 1978).

3.8.3 Other Insects and Spiders

Studies have shown that Btk does not affect the overall abundance of beetles, sucking insects such as aphids, leaf hoppers, cicadas or spiders. Neither are immature and adult stages of mayflies, caddisflies, dragonflies, damselflies, midges or dobsonflies generally affected (USDA 1995). However, a blackfly (known as sandfly in New Zealand) and a stonefly species were affected by Btk in a laboratory study and a mayfly population decreased after Btk was applied in a field study (USDA 1995).

A number of field studies have shown no appreciable adverse effects on the abundance and composition of aquatic invertebrates following Btk application (USDA 1995), even at dose rates more than 100 times greater than those which would occur during normal Btk treatments (Perrin & Richardson 1993). However, there have been no studies specifically on aquatic Lepidopteran caterpillars (USDA 1995). Invertebrates in marine and estuarine environments are also reputedly unaffected by Btk (USDA 1995).

Invertebrate parasites and predators which feed on Btk-infected insects may experience temporary drops in population numbers. This drop would be due to lack of food supply, rather than Btk toxicity. The fact that Btk does not affect natural caterpillar predators and parasites is one reason why it can be successfully used in integrated pest management programmes (Ellis 1991).

3.8.4 Earthworms

Experiments involving earthworms and the Btk formulation Dipel found no significant difference in worm density between treated and untreated plots, even when the Btk was applied at a rate 100 times greater than the recommended dose for field application (Ellis 1991).

3.8.5 Other Invertebrates

Other invertebrates which field studies show to be unaffected by Btk include planaria, flatworms, nematodes, roundworms, leeches, crustaceans, crayfish, water mites, snails ⁽³⁸⁾, clams and mussels (these were studied in a stream in Ontario) (Ellis 1991). Further studies indicate that Btk is not toxic to shellfish (including oysters, mussels and periwinkles) and shrimp (Ellis 1991).

3.8.6 Insects Reared for Scientific, Domestic or Commercial Purposes

Any business involved in rearing moths and butterflies commercially, for example butterfly farms, would carry a heavy risk of damage if located within or near a spray area. Scientific institutions with insect rearing facilities for biological control work or study of Lepidoptera species would similarly be at risk.

School biology classes or private individuals rearing caterpillars, such as monarch butterflies on swan plants, could expect caterpillar mortality if they were exposed to the spray. Because there is a residual population of these insects there will be a gradual return of the natural population once spraying operations have been completed.

3.8.7 Likely Effects in New Zealand

North American studies confirm that members of Order Lepidoptera (moths and butterflies) are the only invertebrates that are susceptible to Btk. Commercially important species such as honeybees are not at risk from Btk. Similarly, there is no reason to suspect that other insects, including New Zealand species for which no overseas data exists, or other invertebrates, including earthworms, snails and crustaceans (eg, crayfish) will be affected by Btk.

New Zealand has 1761 species of Lepidoptera. This figure includes 63 vagrant species (recorded in New Zealand only occasionally) and 73 species introduced since European settlement (Dugdale 1988). Of these, it is estimated that 295 indigenous species in 22 families could be at risk from Btk (Faulds 1994 ⁽³⁹⁾). This figure is an estimate only, and is based on a number of assumptions ⁽⁴⁰⁾. As the estimate pertains only to indigenous species, it may give a misleadingly low impression of the effect of Btk on Lepidoptera diversity, particularly in urban areas such as Auckland where over half of the moths and butterflies present may be introduced species.

None of these 295 species is considered to have a restricted distribution (Faulds 1994 ⁽⁴¹⁾). However, if an area to be sprayed contained indigenous Lepidoptera species with restricted distributions, Btk may have an adverse impact on those species. Further detail of species likely to be affected cannot be provided except on a case-by-case basis, depending on the location and time of spraying. If there were Lepidoptera species present in an area to be sprayed which were:

rare or endangered; or
an isolated population (ie, could not be re-established from nearby populations) or
at a vulnerable developmental stage; or
poor dispersers;

then these species could be absent from the sprayed area for a number of years unless active steps were taken to re-introduce them (see Section 4.10)

3.9 Does spraying with Btk affect animal health?

The two main issues considered in this section are first, the effects of Btk formulations on animal health (this includes direct effects of contact with Btk as well as indirect effects as a result of feeding on insects treated with Btk), and secondly, the effects of other aspects of the spray programme on animal health.

Animals may be exposed to Btk through ingesting Btk on plants, ingesting insects infected with Btk, inhaling Btk spray, or through skin (dermal) contact with the spray. The mode of action of Btk (ie, it is activated by the specific conditions in the insect gut) means that there are no concerns about dermal contact and inhalation in animals (USDA 1995).

3.9.1 Effects of Btk on Mammals

There are many references dealing with the possibility of toxicity or pathogenicity of Bt spray products, and all of the references consulted during the preparation of this EIA suggest that Btk is of no risk to mammals. Laboratory experiments have confirmed that Btk does not grow in warm blooded animals (Hayes & Laws 1991) and US authorities state that in all evidence submitted to US EPA as part of the registration process for Btk (and this included studies on many different mammals and several routes of exposure), there was no indication of pathogenicity in experimental animals (USDA 1995).

The effects of Btk on mammalian predators feeding on Btk-treated insects have not been well studied, but available literature suggests that there are no adverse effects. Btk is unlikely to have any effect in food chains because it has not been found to replicate or accumulate in predators (BC MOH 1992).

It is possible that bats which feed on night-flying moths in the summer may have to expand their foraging territories and adjust their foraging habits temporarily if their food sources are affected by Btk (USDA 1992).

3.9.2 Effects of Btk on Reptiles and Amphibians

There is little information on the toxicity of Btk to reptiles and amphibians, but the information that does exist suggests that they are at no risk from Btk (USDA 1995).

3.9.3 Effects of Btk on Birds

There have been no significant reductions in bird populations noted in areas treated with Btk (BC MOH 1992). Studies in Manitoba and Ontario of 74 bird species representing 21 families showed no significant reductions in bird numbers (Ellis 1991). An assessment of the potential impacts of the Vancouver spray programme on songbirds concluded that there would be negligible mortality of adult birds and the most severe potential effect would be a localised decrease in breeding success of a few species which are most highly dependent on Lepidoptera for food. This was not considered to produce any detectable change in bird numbers the following year (Weber 1993). The USDA concluded that field studies show the effects of Btk spraying on insectivorous birds to be "subtle"(USDA 1995).

Other studies indicate that Btk has no effect on domestic birds such as chickens, even if they are fed Btk directly (Ellis 1991).

3.9.4 Effects of Btk on Fish

Most fish are unlikely to be affected by Btk. There is some suggestion, but no evidence, that fish which have alkaline digestive systems such as carp or koi may be adversely affected by Btk (USDA 1995).

A trial conducted with Foray 48B in British Columbia found the formulation to be lethal to rainbow trout at high concentrations (26 600 ppm). At the specified rate of application, or in a worst case over-spray scenario, rainbow trout were not affected. However, the researcher expressed concern at the potential adverse effect that the acidity of the product (pH 4.3, regardless of the level of dilution) could have on fish populations in the event of a spill into a waterway (Watts 1992).

There has been no documented evidence of any fish kills as a result of the many forestry, agricultural and urban spraying programmes involving Btk in Canada and the US in the last 20 years. This suggests that sources of fish food are not significantly affected by Btk (Ontario Ministry for the Environment 1989). Field studies have found that Btk-contaminated water has no observable effects on fish behaviour and reproduction, and there is no evidence that consumption of Btk-treated insects has adversely affected fish to any noticeable degree (USDA 1995 and Ontario Ministry for the Environment 1989).

No references were found which indicated any adverse effect on marine fish.

3.9.5 Other Effects of the Spray Programme on Animals

Perhaps the greatest effect of the spray programme on animals will be through aircraft noise. Animals particularly sensitive to this type of effect are pets, horses and stock.

3.9.6 Likely Effects in New Zealand

Mammals

New Zealand's two species of native bats (the short tailed bat and the long tailed bat) both include Lepidoptera in their diet (Nowak 1994). The short tailed bat has a very broad diet and so would not be affected by any temporary reduction of Lepidoptera populations caused by Btk. The diet of the long tailed bat consists of mosquitoes, moths and midges, so it may be affected to a greater extent by low Lepidoptera population levels.

No information was found during the preparation of this EIA on the effects of Btk on marine mammals, but there is no reason to believe that there would be any adverse effects on whales and seals.

The greatest impacts of the Btk spray programme on mammals in New Zealand appear to be the effects of noise from low-flying aircraft on vulnerable domesticated mammals.

Reptiles and Amphibians

A study of New Zealand frogs (native species and the introduced whistling frog) found that 0-5% of their diet consisted of Lepidoptera (Kane 1980). New Zealand's native lizards (geckos, skinks and tuatara) also eat a combination of insect species and other small invertebrates and Lepidoptera would form a small (if any) part of their diet. Frogs and lizards are therefore unlikely to be affected by reduced Lepidoptera populations resulting from a Btk spray programme.

Birds

Although the North American studies on bird toxicity did not include bird species native to New Zealand, there is nothing in those studies to indicate that there could be any long term adverse effects on native birds.

There may be some effects on birds which rely heavily on Lepidoptera or Lepidopteran larvae in their diet, but these effects are likely to be temporary and behavioural rather than significant. Native birds that feed on caterpillars (along with other invertebrates) include grey warbler, silvereye and to a lesser extent, tui and kingfisher. Following a Btk spray programme, these birds may have to increase their foraging range (possibly to include areas outside the spray zone) and the time spent looking for food. Other native species, such as fantail, catch their insect prey on the wing. The effects of reduced Lepidoptera numbers are likely to be greatest on birds such as fantails, as Lepidoptera make up a large proportion of their diet, and the birds are territorial and do not forage far for food. If spraying occurred in spring, it is likely that at least some of the species mentioned above (particularly, grey warbler, silvereye and fantail) would be unable to breed successfully in the sprayed area that season due to reduced food supply. However, these effects will be temporary and the bird population should recover as soon as food supplies return to normal levels (DOC 1996 ⁽⁴³⁾).

Fish

Similarly, there is nothing in the American studies to indicate that New Zealand fish may be affected by spraying Btk. However, the unconfirmed suggestion that fish with alkaline digestive systems, such as carp, may be affected by Btk is of potential concern, as grass carp are sometimes used in lakes and ponds to control weed growth (see Section 4.11). The main risk to fish in New Zealand is posed by an accidental spill of Btk formulation into a waterway. This possibility, and means for preventing it, are discussed in Section 4.4.

3.10 What are the likely effects on amenity values?

Amenity values are "those natural and physical qualities and characteristics of an area that contribute to people's appreciation of its pleasantness, aesthetic coherence, and cultural and recreational attributes" (Resource Management Act 1991). Effects on amenity values are often known as "nuisance effects". The WHO defines nuisance as "occurring when life is less pleasant than it would otherwise be without affecting health in the medical sense".

The main potential effects of a Btk spray programme on amenity values are the visual effect of the spray from aircraft, noise from aircraft, and odour. There are also positive effects on amenity values which arise from eradicating a pest which is able to defoliate urban trees and bushes.

3.10.1 Likely Effects in New Zealand - Visual Effect of Spray

The Btk sprayed from aircraft would be perceived as a very fine mist for a short duration (approximately 10 minutes). The spray would be seen (if spraying takes place in daylight) and felt in the area of direct application and, to a lesser extent, in any area affected by off-target spray drift. The area affected by off-target spray drift would depend on the height of the aircraft, windspeed and droplet size, but is unlikely to be greater than 300m from the downstream edge of the sprayed area .

3.10.2 Likely Effects in New Zealand - Noise and Other Effects of Low-flying Aircraft

The physical effect of aircraft flying at low altitudes over urban areas is likely to be the most significant effect of the spray programme on people.

The level of noise impact will depend on:

the type of aircraft used in the spray programme;
the height and speed at which the aircraft fly; and
the time of day at which spraying takes place.

It is possible to apply the spray using either helicopters or fixed wing aircraft. The helicopter of choice is the Bell 205 (Iroquois); the fixed wing aircraft of choice is the Cresco.

The Bell 205 helicopter is powered by a single 1,250 shaft horsepower (shp) Lycoming turboshaft. The rotor diameter is 48 feet (14.63 metres). In an aerial spraying operation, the Bell 205 would be flown at approximately 65 knots.

The Cresco is a fixed wing aircraft commonly used for agricultural spraying. It is fitted with a single 700 horsepower turbine engine manufactured by Pratt & Whitney. This engine is also used in Air New Zealand Banderiante passenger aircraft. The Cresco is capable of operational spray speeds of up to 120 knots.

The Bell 205 helicopter is susceptible to the "bladeslap" effect, which results in impulses of sound of high intensity. The noise levels from the Cresco would be similar to the noise created by the same type of aircraft making an approach to an airport. Higher noise levels could be expected at transect ends as the aircraft banks and turns.

Indicative maximum noise levels for these aircraft, flying at a range of speed and heights, is given in Table 4.

Table 4: Comparison of Indicative Maximum Noise Levels Produced by Aircraft Operating at a Range of Heights

	Airspeed (knots)	Flying height 10m (30ft) ⁽⁴⁵⁾	Flying height 30m (100ft)	Flying height 90m (300ft)
Helicopter - excluding bladeslap (Bell 205)	65	105 - 110 dBA	98 dBA	84 dBA
Fixed wing aircraft (Cresco) ⁽⁴⁶⁾	110 - 120	95 dBA	85 dBA	75 dBA

Background noise levels vary depending on the time of day and the nature of the target area. In residential areas, the background noise levels at the most likely spraying time (ie, very early morning) are approximately 30-40 dBA. Aircraft noise of 90-100 dBA would therefore be experienced as a very significant intrusion of limited duration. At these noise levels, people would be woken from sleep.

However, if noise levels reach 110 dBA, the effects could become more significant. A period of three seconds of exposure to a level of 110 dBA represents the maximum daily exposure permitted at this level in an industrial setting. Child hearing could suffer initial damage at this level and, as the onset of the noise is likely to be very rapid, at levels of 110 dBA some heart conditions could be aggravated ⁽⁴⁷⁾ (Ministry of Health 1996 ⁽⁴⁸⁾).

In addition to noise effects, some helicopters, when flown at very low heights (10m), can cause significant negative effects from downwash. At higher flying heights these effects become unnoticeable. If the spraying takes place outside of daylight hours, the aircraft will be fitted with spray lights. Each aircraft would have two 28 volt, 600 watt lights, which can be aimed vertically down or horizontally straight ahead or anywhere inbetween. These lights may result in a flickering effect, and be experienced as a nuisance, particularly by motorists.

The final decision on which aircraft to use, and the speeds and heights at which the aircraft will operate, will be to a large extent determined by the need to minimise the negative effects of the operation. Where Btk is to be applied in a populated area, the operation will be managed so that the major effects described above (ie, noise levels of 110 dBA and significant downwash effects) do not occur.

3.10.3 Likely Effects in New Zealand - Odour

It is highly unlikely that any odour from Foray 48B could be detected on the ground during or after a spray operation.

3.11 Have any other potential social, economic or cultural impacts been identified?

3.11.1 Public Concerns About Spray Programmes

When agrichemicals are sprayed from aircraft in urban areas, there is always a degree of public apprehension and anxiety (California Department of Food and Agriculture 1992).

Surveys of public opinion carried out as part of the US environmental impact assessments on the management of gypsy moth identified that people were (USDA 1995 & California Department of Food and Agriculture 1992):

anxious and fearful about the appearance of helicopters and planes used to spray insecticides;
anxious about the safety of insecticides and distrustful of government claims about insecticide safety or government actions to control insect pests;
concerned and angry about "involuntary exposure" to pesticides;
concerned about possible effects on their physical health;
concerned about the risks of insecticide spills, plane accidents and car accidents related to the spray programme;
concerned about workers being exposed to traffic, power lines, dogs, and rough neighbourhood conditions;
affected by disruptions to their normal routines;
worried about government expenditure on eradication programmes; and
concerned about the potential environmental effects of spray programmes.

Other potential causes of stress or fear are lack of understanding of the reasons for spraying and lack of information on the substance being used and its possible effects on human health. For some people, the sound of helicopters approaching may be deeply distressing if it recalls memories of living or serving in combat zones (MOH 1996 ⁽⁴⁹⁾).

Authors of the EIA on the Californian gypsy moth programme noted that "anxiety will never be eliminated entirely. Many individuals feel threatened because, if impacts they are concerned about materialise in the future, serious consequences might result. Regardless of how much data has been collected which does not show these theoretical impacts, some would prefer not to allow the use of any pesticide in the public sector..." (California Department of Food and Agriculture, 1992).

In general, people in rural agricultural areas are less likely to be concerned about spraying to control insect pests because of their familiarity with the spraying of agricultural crops (USDA 1995).

3.11.2 Likely Effects in New Zealand - Social Concerns

It is likely that the concerns identified in Section 3.11.1 above will be felt by some people in New Zealand. Steps to address these concerns are covered in Section 4.3.

3.11.3 Likely Effects in New Zealand - Issues of Particular Concern to Maori/Treaty of Waitangi Issues

No issues of particular concern to tangata whenua have been identified during the preparation of this EIA. Potential issues which were considered include effects on water quality, effects on native plants used for cultural purposes, effects on kaimoana (sea food) or other food resources, and health effects which may have a greater impact on the Maori population. The information provided in Sections 3.3-3.10 above indicate no significant adverse effects from Btk in any of these areas. It is therefore unlikely that Maori would be affected to any greater extent or in any extra ways than other members of the population.

As a partner to the Treaty of Waitangi, the Government is obliged to consult with iwi on matters which may affect them (see Section 4.3).

3.11.4 Likely Effects in New Zealand - Other Cultural Effects

No issues of particular concern to any other cultural groups in New Zealand have been identified during the preparation of this EIA. However, as noted in Section 3.11.1 above, some cultural groups in New Zealand, because of previous exposure to helicopter noise in war situations, may find the noise associated with a Btk spray programme particularly distressing.

3.11.5 Likely Effects in New Zealand - Economic Activity

No significant adverse effects on economic activities arising from the spraying of Btk have been identified during the preparation of this EIA apart from potential effects on commercial butterfly-rearing operations (see Section 3.8). It is not considered that there would be any adverse effects on tourism or agricultural, horticultural or viticultural activities (including organic agriculture) as a result of the spray programme. If anything, positive economic effects are expected as a result of the eradication programme, as the presence of tussock moth in the New Zealand environment has a significant economic cost (see Section 5.2).

3.11.6 Likely Effects in New Zealand - Safety

Traffic Safety

There may be an increased risk of traffic jams and road accidents due to sunglare from spray on windshields and distraction by low-flying aircraft ⁽⁵⁰⁾. This risk will be addressed as part of the communications strategy preceding any eradication programme and through liaison with traffic control authorities.

Aircraft Safety

The safety of low-flying aircraft is addressed in the conditions placed on low level operations by the Civil Aviation Authority (see Section 4.2.4). Potential hazards for low-flying aircraft include power lines, trees and television aerials.

3.12 Are any particular environments more sensitive to the effects of spraying with Btk than other environments?

This EIA has been prepared so that it is relevant to any area of New Zealand. However, there are some receiving environments (ie, areas in which Btk may be applied) that may be more sensitive to the effects of a Btk spray programme than others. Some of these sensitive environments have been identified in preceding sections of this chapter. Environments which may be particularly sensitive to Btk formulations include:

biologically sensitive environments (eg, environments which contain rare or isolated populations of sensitive insects, or environments which contain rare or threatened populations of species which are heavily reliant on vulnerable insect species as a food source);
socially sensitive environments (eg, hospitals, schools, marae); and
economically sensitive environments (eg, butterfly-rearing operations).

Environments which may be particularly sensitive to noise associated with the spray programme include hospitals and businesses involving noise-sensitive animals (eg, stud farms, zoos).

All environments (particularly waterways) are potentially sensitive to adverse effects arising from an accidental discharge of Btk (ie, a spill). These effects are of low probability but high potential impact.

Means for reducing potential impacts on sensitive environments are addressed in Section 4.10 and means for reducing the occurrence and effects of Btk spills are addressed in Section 4.4.

3.13 Could there be any cumulative or long term effects?

3.13.1 Genetic Stability of Btk

A common concern with biological pesticides is their genetic stability (ie, whether they remain true to their parent strain). Btk is a living organism, and although the potential exists for mutagenic changes, the chances of mutation are exceedingly low. The chances that a mutation may cause Btk to infect species other than Lepidoptera are even lower. This conclusion is based on the observations that:

pathogenic mutations of Btk have not been demonstrated (BC MOH 1992);
widespread Btk-induced epizootics are very rare (BC MOH 1992); and;
an early study which attempted to induce harmful mutations in Bt by serial passage through mammals, found no increase in virulence to mammals (Ellis 1991).

3.13.2 Resistance of Tussock Moth to Btk

There appear to be very few studies of the potential for insect pests to become resistant to Btk. Some resistance in crop pests has been observed ⁽⁵¹⁾ and there are also reports of resistance in the diamond back moth (a pest in North America) (STOP 1995). One study of gypsy moth found significant variation in susceptibility to Btk among the populations studied, suggesting the potential for resistance to develop through natural selection. The fact that spray dosage rates necessary for successful control have increased over the years suggests that there may be some selection pressure for resistance in gypsy moth (Rossiter et al 1990).

However, no documented cases of major gypsy moth resistance were found during the preparation of this EIA. It is even less likely that resistance would be an issue for tussock moth in New Zealand, as tussock moth does not have the same history of exposure to Btk and, if the eradication programme is successful, neither will tussock moth be subjected to selection pressure for Btk resistance in the longer term.

3.13.3 Cumulative Effects of Btk Treatments

Potential cumulative effects of Btk include residual exposure to Btk formulations after a single exposure, multiple applications in a single season, and multiple applications over several years.

Btk is not persistent in the environment as it is rapidly inactivated by UV radiation and other micro-organisms (see Sections 3.3 & 3.4). Neither is it bioaccumulating. For these reasons it is not anticipated that there would be any cumulative effects arising from residual exposure to Btk.

Multiple applications in a single year are likely to have greater impacts on vulnerable non-target insect populations than single applications, but are still unlikely to prevent recolonisation by those species within three years (see Section 3.8).

Cumulative effects from spray programmes conducted over several years are not anticipated due to the lack of persistence of Btk in the environment. This assumption has been backed up by monitoring of the Oregon spray programme which was carried out over several years (California Department of Food and Agriculture 1992). There is some potential for cumulative effects on non-target organisms if a spray programme is repeated over a number of years (USDA 1995) but again, the Oregon study indicates that many sensitive insect populations return to roughly pre-treatment levels in three years (Miller 1990).

4. Preventing or Reducing Any Adverse Effects

4.1 Introduction

This section of the EIA sets out measures that will be used to help prevent or mitigate the actual and potential effects of spraying Btk identified in Section 3 of the EIA.

4.2 Legislation and other requirements

The provisions in legislation, plans and policies can be used to help manage the environmental impacts of Btk spray programmes. Several different types of approvals and consents are required in order for the eradication programme to proceed. These approvals are summarised in this section. The Acts, plans and policies of relevance to the proposed tussock moth eradication programme are:

the Forests Act 1949 and the Forest Disease Control Regulations 1967 made under that Act;
the Biosecurity Act 1993;
the Resource Management Act 1991 and plans prepared under it;
the Pesticides Act 1979 and its replacement, the Hazardous Substances and New Organisms Act 1996;
the Civil Aviation Act 1990; and
the Environmental Protection and Enhancement Procedures.

4.2.1 The Forest Disease Control Regulations and the Biosecurity Act

This Act and set of regulations provide the Ministry of Forestry with the power to carry out an aerial spraying programme to eradicate tussock moth. It is most likely that the eradication programme will be carried out under the Forest Disease Control Regulations of the Forests Act. These regulations require an eradication programme to be authorised jointly by the Ministers of Forestry, Conservation and Health. Alternatively, the eradication programme may take place under the biosecurity emergency provisions of the Biosecurity Act. A biosecurity emergency must be declared by the Governor-General.

4.2.2 The Resource Management Act

Resource Consent Requirements for the Discharge of Contaminants

Section 15 of the Resource Management Act (RMA) requires a resource consent to be obtained from a regional council to discharge any "contaminant" (this would include Btk) into water, or onto land in circumstances where it may enter water, unless the discharge is allowed by a rule in a regional plan. Section 15 also places restrictions on the discharge of contaminants into air. The requirements of section 15, together with the requirements of regional plans prepared under the RMA, mean that regional councils would normally require a resource consent to be obtained for the aerial spraying of Btk.

However, the process for obtaining a resource consent can become protracted, particularly if there are public submissions and appeals. If the process was still unresolved when the tussock moth eggs hatched, it could jeopardise the effectiveness of an eradication programme. As an eradication programme involves considerable amounts of planning and expenditure, the Government needs to be certain that, should an eradication programme for tussock moth prove necessary, the programme will be able to proceed. The Government has therefore decided to use the regulation-making powers of section 360(1)(h) of the RMA to write a new regulation exempting the discharge of Btk in any spraying programme authorised under the Forest Disease Control Regulations of the Forests Act, or the emergency provisions of the Biosecurity Act, from section 15 of the RMA.

The new regulation does not bypass the environmental protection provided by the Act. Rather, matters of potential environmental concern were considered by the Government at the time of drafting the regulation instead of being considered by regional councils in the process of assessing a resource consent application. The Government is therefore, in effect, acting as the consent authority in place of the regional council. In addition, an eradication programme will still be subject to approval under either the Forest Disease Control Regulations or the Biosecurity Act (see Section 4.2.1 above).

Hazardous Substances

The new regulation will not exempt the Btk spray programme from any other provisions of the RMA, including provisions in plans relating to the storage, transportation or use of hazardous substances ⁽⁵²⁾. It should be noted that provisions on these matters may be included in regional or district plans and may or may not cover Btk, depending on the definition of "hazardous substance" adopted by the local authority in question. It is unlikely (but not inconceivable) that Btk would be included in any definitions of hazardous substances adopted by local authorities. It is also unlikely that any provisions of this type would require a resource consent to be obtained, provided that the storage, transportation and use of Btk complied with any relevant rules in any relevant plans. These matters will be checked on a case-by-case basis depending on the area in which any eradication programme takes place. Any relevant provisions in plans may help to prevent or mitigate any adverse effects arising from the storage, transportation or use of Btk.

Aircraft Noise

District plans and regional coastal plans normally address any adverse effects of noise arising from activities. However, overflying aircraft are exempted from the noise control provisions of the RMA. The only noise emission controls that local authorities may set for aircraft are in relation to the use of airports ⁽⁵³⁾.

4.2.3 The Pesticides Act

The Btk formulation Foray 48B has recently been registered by the Pesticides Board under the Pesticides Act for use in New Zealand. The registration process includes an assessment of any adverse effects that the pesticide may have and the circumstances in which it may be safely used.

4.2.4 The Civil Aviation Act

The three main requirements of the Civil Aviation Authority under the Civil Aviation Act and related provisions are:

approval for low level operations ⁽⁵⁴⁾;
standard operational requirements of the Civil Aviation Safety Orders, Regulations and Rules; and
"agricultural rating" requirements for pilots.

4.2.5 The Environmental Protection and Enhancement Procedures

The Environmental Protection and Enhancement Procedures (EP&EP) derive from a Cabinet directive, rather than legislation. The EP&EP oblige all government departments to assess the environmental impacts of their programmes and policies and compare, where possible, the environmental impacts of alternative courses of action. The preparation of this EIA is part of that process.

4.3 Public communication and information programme

If it is decided to eradicate tussock moth using Btk, the Ministry of Forestry will implement a public communications strategy as part of the eradication programme. The aim of the strategy will be to provide the public with information on the need for the eradication programme, the effects of Btk, and steps that people can take to reduce their exposure to Btk if they wish to. The communications strategy will include press releases, advertising, publications, direct mail, specialist meetings for the public, surveys to monitor public opinion, presentations, and an 0800Êenquiries line.

In addition to general widespread publicity, the strategy will also cover liaison with key organisations (local authorities, health authorities, iwi and urban Maori groups, educational authorities, the police, environmental groups, industry groups etc.) before, during and after the spray programme.

Due to the short time frame for making a decision on whether or not to eradicate tussock moth, opportunities for public consultation (as opposed to provision and discussion of information) on the favoured means of eradication are limited. However, the communications strategy will provide opportunities for local public consultation over some operational aspects of any eradication programme that may be undertaken.

The availability of information and the opportunity to discuss concerns should help to reduce levels of public fear or anxiety about the spraying programme (as identified in Section 3.11).

4.4 Contingency plan

The Ministry of Forestry will prepare a contingency plan to address any emergency situations that may arise during the use, transportation (aerial and ground) or storage of Btk. The plan will have the twin aims of:

reducing the potential for any unplanned spills or other accidents involving Btk to occur; and
in the event of a spill or accident, preventing, minimising or cleaning up any adverse effects.

The plan will include information on responsibilities and actions in the event of an emergency.

4.5 Storing and transporting Btk

It is likely that the Foray 48B Btk formulation will be imported, stored and transported in the form of 1000 litre bulk containers or 200 litre drums, appropriately sealed and secured. One of the risks identified in Section 3.9 of this EIA is the possible adverse effects of a spill of Btk formulation, particularly if Btk is able to enter waterways. Another concern is that the stored Btk does not become contaminated, either deliberately, as a result of sabotage, or accidentally.

Storage

The manufacturer's instructions for Foray 48B state that it is to be stored in a cool, dry place ⁽⁵⁵⁾, and that containers should be kept closed when not in use.

Prior to and during the programme, Btk will be stored at a single site selected and designed for its:

security from human interference (the site would have 24-hour security);
ability to prevent any spills from entering the environment (eg, by way of barriers or moats);
location in relation to potentially incompatible land uses (eg, schools, sensitive ecosystems);
vicinity to transport routes and loading points for aircraft; and
compliance with any relevant provisions in regional or district plans.

Transportation

As Btk is not infectious or otherwise hazardous to humans or animals, it is not covered by any requirements relating to the transportation of hazardous substances ⁽⁵⁶⁾ . Btk is not included in either the alphabetical listing of hazardous substances or the listing by UN number appended to New Zealand Standard 5433:1988 (the Code of Practice for the Transport of Hazardous Substances on Land). Nevertheless, the transportation of Btk prior to and during the eradication programme will be consistent with the Hazardous Substances and New Organisms Act 1996 and follow the general principles for transporting hazardous loads, that is:

Btk containers will be segregated (ie, they will not be carried with any dangerous substances or foodstuffs); and
the load will be properly labelled and appropriate documentation relating to Btk will be carried.

4.6 Safeguards for people working with Btk

The Health and Safety in Employment Act 1992 places a general obligation on employers to provide a safe working environment for employees. For the use of pesticides, this responsibility is normally fulfilled by following the manufacturer's instructions regarding safe use of the product. The occupational health precautions listed on the Foray 48B label are to avoid skin and eye contact, and to wash hands and exposed skin before meals and after work.

Section 3.7 of the EIA identified that people working with Btk may experience some adverse health effects which are likely to be irritant and transient in nature. These effects will be reduced by:

ensuring that all people working on the programme are fully trained in the safe use of Btk;
ensuring that all equipment used during the programme is properly calibrated and maintained;
providing workers with appropriate protective equipment and ensuring that it is worn; and
following the manufacturer's instructions with regard to mixing and applying Btk.

4.7 Safeguards relating to the spraying operation

Potential concerns relating to the spray operation itself include:

ensuring that each application is effective so that a minimum number of spray treatments is required;
minimising off-target spray drift;
accurately identifying the area to be sprayed; and
minimising noise associated with the operation.

Maximum efficacy of each spray application will be assured by:

using dose rates which are high enough to kill the insects;
timing the applications precisely;
spraying only during favourable weather conditions;
using well-maintained equipment and trained applicators; and
using appropriate technology to ensure adequate spray coverage.

Spray drift will be managed by:

selecting nozzle sizes and calibrating equipment to achieve the recommended droplet size and spray swath path; and
spraying only when meteorological conditions are favourable.

All aircraft will follow pre-determined flight transects using DGPS for guidance and will be required to conduct spray delivery calibration flights before operating over a target area (see Section 2.5 for details). There are strong economic incentives on those managing the programme to ensure that Btk is not misapplied and that the programme is not extended to unnecessarily large areas.

Temporarily high local noise levels are an unavoidable effect of the spray programme. However, noise effects can be minimised by ensuring that pilots take standard flying precautions to minimise noise nuisance.

4.8 Disposal of surplus Btk

As far as possible, the Btk imported for an eradication programme will be used for the purpose for which it was intended or a similar approved purpose. The Btk containers and any remaining Btk formulation will be disposed of according to the manufacturer's instructions and any relevant local authority requirements. 200 litre Btk containers are able to be recycled. For containers that cannot be recycled, the label of Foray 48B states that they should be triple rinsed and burnt, if circumstances permit, or otherwise buried in a landfill.

4.9 Safeguards for sensitive individuals

Sections 3.7 and 3.11 above identified that some people may be extra sensitive to or concerned about possible exposure to Btk.

Although there is no evidence linking Btk to any adverse health effects on members of the public with allergies, respiratory conditions, or immune disorders, people with pre-existing allergies or conditions which may make them sensitive to Foray 48B may feel more comfortable if they take reasonable precautions to avoid exposure to Foray 48B. These precautions would be no different from precautions, for example, that people with asthma may take to avoid exposure to pollen or other airborne materials that could aggravate their condition. The public information programme referred to in Section 4.3 above should provide people with sufficient information to take such action if they so desire. Staying indoors with windows and doors shut during the spray operation would reduce Btk exposure to minimal levels.

4.10 Safeguards for sensitive environments

Potentially sensitive receiving environments identified in Section 3 above include water supply areas, hospitals, schools, marae, businesses involving butterfly rearing or noise-sensitive animals and biologically sensitive areas (eg, areas with rare insect populations).

With regard to water catchments and water supply reservoirs, should any area for which spraying is planned include or be adjacent to these areas, the Ministry of Forestry will liaise closely with local health authorities and water supply authorities to determine the most appropriate means of eradicating tussock moth from the water supply area.

Hospitals, schools, marae and potentially sensitive businesses will be among those contacted as part of the communications strategy outlined in Section 4.3.

For each area to be sprayed, the Ministry of Forestry will liaise with the Department of Conservation to identify any biologically sensitive areas (ie, areas where there may be vulnerable insect populations present which would not be able to recolonise the sprayed area within one to two years). Should any such areas exist within the area to be sprayed, steps will be taken to either protect the insects from the effects of the spray or to facilitate recolonisation of the area after spraying. Examples of ways in which vulnerable non-target insect populations may be reintroduced following spraying include:

removing individual insects before spraying and reintroducing them once Btk is no longer active in the environment; and
encouraging schools to rear native moth and butterfly species for release into sprayed areas.

4.11 Monitoring the environmental effects of the spray programme

The Ministry of Forestry, in consultation with other relevant agencies including the Ministry of Health and the Department of Conservation, will co-ordinate the design and implementation of an environmental monitoring programme for Btk. The application of Btk to eradicate tussock moth represents an opportunity to gather information specific to New Zealand about the environmental effects of Btk. Environmental factors can be monitored before, during and after the spray programme or alternatively, treated and non-treated areas can be compared. The advantages of a monitoring programme are:

it helps to identify any actual adverse effects arising from the spray programme and to determine whether any remedial action is required;
it increases public confidence that the potential environmental and health consequences of the programme are being addressed;
it provides information should further spray programmes for tussock moth be necessary; and
it provides information should gypsy moth or any other exotic Lepidoptera pests ever establish in New Zealand and require eradication.

The monitoring programme will focus on assessing impacts on:

non-target Lepidoptera species; and
human health, including physical and psychosocial effects.

Secondary effects which may also be monitored include:

possible effects on carp populations; and
possible effects on native bird species with high proportions of Lepidoptera in their diets.

The monitoring programme will be based on overseas monitoring programmes (eg, the surveys of hospitals and GPs carried out by Noble et al in Vancouver in 1992) and will involve a number of agencies, including universities.

5. Comparison Between the Proposed Means of Eradication and Alternative Options for Responding to Tussock Moth

5.1 Introduction

This section of the EIA considers alternative options for responding to tussock moth in New Zealand, and compares these options with the proposed Btk spray programme. The main options are to:

do nothing (ie, allow the tussock moth to spread and establish in New Zealand if it is able to);
use a chemical insecticide to eradicate tussock moth (the chemical Dimilin (diflubenzuron) is the main alternative);
eradicate the eggs by mechanical or chemical means;
use biological control to reduce (rather than eradicate) tussock moth populations ⁽⁵⁷⁾; or
use other means to reduce tussock moth populations, such as mass trapping, mating disruption, or sterile insect release.

5.2 What may happen if no action is taken to eradicate the tussock moth?

It is difficult to predict with any certainty what may happen if tussock moth were to spread and establish in New Zealand. Little is known about how the moth is likely to behave in New Zealand because of differences in climate, day length, daily temperature rhythms and food choices between New Zealand and the moth's natural range. The information presented in this section is therefore the most likely scenario of what could happen, as assessed by scientists of the New Zealand Forest Research Institute (Bain 1996 ⁽⁵⁸⁾) and officials from the Ministry of Forestry and other agencies.

5.2.1 How Well Could Tussock Moth Spread and Establish?

The tussock moth is likely to disperse well in New Zealand because:

the early season females can fly;
young caterpillars can disperse by "ballooning" on silken threads; and
plant material and inanimate objects (vehicles, garden furniture etc.) carrying larvae, egg masses or cocoons may be transported out of the infected area.

There appear to be no obvious barriers to tussock moth establishing throughout New Zealand. Its life cycle is influenced by standard factors such as photoperiod, temperature and food availability, but none of these should be limiting in New Zealand.

The absence of natural parasitoids and predators of the tussock moth in New Zealand should allow populations (and therefore damage) to be greater here than in its native range ⁽⁵⁹⁾. Competition with other species is very rarely a limiting factor for defoliating caterpillars. Their main source of competition is themselves when numbers are very high. All these factors suggest that tussock moth could establish well in New Zealand.

5.2.2 Which Plants Could Tussock Moth Feed On?

It is likely that the plant host range for tussock moth in New Zealand will be very wide. This is because:

its recorded host range to date is wide ⁽⁶⁰⁾;
past experience with new insect arrivals is that they often eat a range of plants;
wide eating habits are the norm for members of the genus Orgyia; and
the female is dimorphic (ie, has two forms - flying and flightless) and this suggests that it has two different egg-laying strategies, with different criteria for selecting host plants.

Native plants in the same family as, or in closely related families to, known hosts of the tussock moth occur in approximately 28 plant genera (about 40 species ⁽⁶¹⁾).

Extensive feeding trials are currently being carried out to get a better idea of the tussock moth's potential host range. Results from the first set of feeding trials (using mature or nearly mature larvae) showed that the caterpillar can feed readily on radiata pine and on red beech and silver beech. Later trials (using young larvae) indicated no feeding on radiata pine, but significant feeding on red beech and some Eucalyptus species. The results are a potential cause for concern as they indicate that these species might be at risk from tussock moth. However, the feeding trial results must be interpreted cautiously as they involve a "no choice" situation ⁽⁶²⁾. Tussock moth has not been found feeding on any pine species in Auckland, and the only native species that it has definitely been recorded feeding on in the field is kaka beak.

5.2.3 What Impacts Could Tussock Moth Have in New Zealand?

At this stage, the best available information suggests that tussock moth is likely to be a significant pest in New Zealand, although perhaps not such a problem as gypsy moth would be if it established here. The potential impacts of tussock moth include:

damage to amenity trees, bushes and other plants, including urban trees and home gardens;
reduction in the ability of forests to function as a carbon sink (part of New Zealand's strategy to mitigate the effects of climate change);
defoliation or mortality of indigenous vegetation, with various possible consequences including changes in the biological composition of forests, erosion of water catchments, downstream flooding, loss of recreational and amenity values, and loss of habitat for indigenous species;
costs of on-going control programmes; and
possible adverse effects on tourism.

5.3 How does the use of a chemical insecticide such as Dimilin compare with the use of Btk?

Although no specific information is available about the susceptibility of tussock moth to eradication using chemical sprays, there is no doubt that chemical sprays would be an effective means of eradication (Bain 1996 ⁽⁶³⁾). Chemical sprays have been used successfully on gypsy moth populations in North America, and another related species, O. pseudotsugata, can be well controlled with chemical sprays (Anon 1980, Neisess et al 1976).

5.3.1 What is Dimilin?

Dimilin (diflubenzuron) is a chemical insecticide which has been used to control gypsy moth in North America for a number of years. It intervenes in the formation of chitin (a substance found in the exoskeleton of insects) and thereby interferes with the moulting process of some immature insects. Of the available chemical insecticides, it is considered to be the best option for controlling tussock moth because of its extensive use in North America, its relatively narrow range of non-target organisms, and its low mammalian toxicity compared with other chemical insecticides.

5.3.2 Health Effects

No human health effects are likely from exposure to Dimilin at the dose rates used in eradication programmes. However, at very high exposures, increases in methaemoglobin (an abnormal blood pigment that reduces the oxygen carrying capacity of the blood) might be detectable. This effect may be additive if other compounds which reduce the oxygen carrying capacity of blood are present (cigarette smoke, other smoke, carbon monoxide, nitrates in air or water) (USDA 1995). A conservative estimate of cancer risk from exposure to Dimilin or its breakdown products is less than one in one million over a lifetime (USDA 1995).

5.3.3 Environmental Effects

Dimilin persists on vegetation throughout the growing season and may remain on leaf litter at least one year after spraying. Non-target organisms affected by Dimilin (even at low doses) include other caterpillars, other leaf and litter-eating immature arthropods, parasitic wasps, some beetles, spiders, sawflies, aquatic insects, bottom-dwelling crustaceans and immature free-floating crustaceans. At higher doses, more species are affected, especially aquatic organisms (USDA 1995). Vertebrates, adult beetles, earthworms, bees and molluscs do not appear to be affected. Neither does Dimilin have any toxic effect on plants (USDA 1995).

5.3.4 Advantages and Disadvantages of Dimilin Compared with Btk

The advantages of Dimilin (diflubenzuron) are:

it is persistent on foliage for much longer than Btk, so only one application is necessary;
its effectiveness is not restricted to the early stages of caterpillar development. Dimilin therefore has a wider application window than Btk, and the eradication programme would be at less risk of failure because of bad weather conditions; and
it requires only one application so the cost of eradication is less than it would be using Btk.

The disadvantages of Dimilin are:

it could have an adverse effect on some marine life such as freshwater crayfish;
it affects a wider range of invertebrates than Btk, and is therefore less desirable environmentally;
it has some documented adverse effects on human health; and
it is a chemical insecticide and is therefore likely to create greater public resistance to spraying in urban areas than would be created by spraying a naturally occurring bacterium such as Btk.

5.4 Could the tussock moth eggs be eradicated rather than using Btk to eradicate the caterpillar?

It may be possible to develop a control method that targets the eggs of the tussock moth before the caterpillars hatch. Research into this possibility is currently taking place. If such a method were feasible, egg masses would be located in the field and either removed by mechanical means (ie, crushing them) or sprayed with an appropriate chemical. While there is not enough information on this possible method of control to assess its advantages and disadvantages when compared with Btk, some immediate problems are apparent. Locating the egg masses in the field would be labour- and time-intensive, and it would be practically impossible to find all the egg masses. Egg masses are about the size of a ten-cent piece and are often laid in the canopies of trees. In the US, removing and destroying egg masses was found to be impractical and not effective in eradicating gypsy moth (USDA 1995).

5.5 What other means of eradication or control may be available?

Aerial and ground spraying with either Btk or Dimilin are the only known means by which the tussock moth population could be eradicated. (Of these two methods, Btk is the more environmentally acceptable.) The options discussed in this section relate to controlling the tussock moth population in an effort to reduce its impact. Most of these options have been developed for controlling gypsy moth populations and may or may not be transferable to tussock moth.

Methods designed to control tussock moth would only be considered if eradication is not the Government's preferred option, or if eradication failed and the moth became established in New Zealand.

5.5.1 Biological Control Agents

No biocontrol agents to reduce populations of tussock moth are currently available, either in New Zealand or overseas.

Parasites and Predators

If tussock moth is not eradicated from New Zealand, a certain amount of parasitism and predation will occur by indigenous and naturalised species. A New Zealand Pest Risk Assessment for Asian Gypsy Moth (Cowley et al. 1993) assumed a 10 percent rate of parasitism and predation under New Zealand conditions and five percent mortality from natural fungal, bacterial, and virus diseases. Similar estimates for tussock moth are not available. There may also be potential for heavy predation by birds if there is no other food available (based on a study by Whellan et al 1989 on gypsy moth predation ⁽⁶⁴⁾).

In the US, parasites have been introduced to control gypsy moth, but researchers do not believe that they play a major role in regulating populations. Similarly, predation has been found to help maintain sparse population numbers, but does not affect population densities if an outbreak occurs (USDA 1995). There are no parasites or predators currently known that could be introduced to control a New Zealand tussock moth population and maintain it at a non-damaging level. However, at least four natural parasitoids of tussock moth have been recorded (Herting 1976) and it is likely that there are more yet to be recorded (Bain 1996 ⁽⁶⁵⁾). There is no information available on the effectiveness of these parasitoids as biocontrol agents.

Entomophaga Maimaiga

The fungus Entomophaga maimaiga has been associated with gypsy moth larvae in North America and there has been research interest in its possible use for population control (Glare 1994). The fungus is host specific to Lymantriidae and so is likely to also infect tussock moth ⁽⁶⁶⁾. There are no species of Lymantriidae indigenous to New Zealand, so there would be no adverse effects on other insect species. However, the fungus appears to be difficult to use as a control agent as it is short-lived in storage, relatively expensive and sensitive to heat, humidity, sunlight and rainfall. Entomophaga maimaiga may eventually contribute to long term control of Lymantriidae species, but more research is needed.

Viruses

Another biocontrol option is the use of naturally occurring insect viruses. In North America, gypsy moth control programmes make use of the Lymantria dispar Nuclear Polyhedrosis Virus (LdNPV), which affects only gypsy moth (USDA 1995). The Canadian Forest Service has used another virus, the Orgyia Nuclear Polyhedrosis Virus (Orgyia NPV) to control other moths in the genus Orgyia (Jackson 1996 ⁽⁶⁷⁾). The advantages of viruses are that they are host specific and so do not affect other caterpillars. They provide good population control when moth population numbers are very high, but are not successful in eradicating moth populations (Bain 1996 ⁽⁶⁸⁾). Other recorded disadvantages of LdNPV are that it is expensive and is available only in limited supply.

The Orgyia NPV is said to infect a number of species in the Orgyia genus and has achieved good control of some members of the genus, but there is no information specific to its effect on tussock moth. However, if tussock moth is not successfully eradicated from New Zealand, Orgyia NPV, in conjunction with other methods, may prove to be an effective means of controlling tussock moth populations. Further research is needed.

5.5.2 Mass Trapping

Mass trapping method involves setting up large numbers of moth traps in the treatment area. The traps use a pheromone to attract male moths of the pest species. The moths are killed either on a sticky strip or on a strip impregnated with an insecticide in the trap. Male moths are therefore prevented from mating with females and population reduction results. Mass trapping is not seen as an eradication method, but may be used in conjunction with other control methods.

The disadvantages of this method for controlling tussock moth are:

a pheromone for tussock moth is not currently available;
there may be some human health risks associated with people tampering with insecticide-impregnated strips in the traps (USDA 1995);
non-target insects which inadvertently enter the traps may be killed (USDA 1995); and
traps must be extremely densely located in the target area.

5.5.3 Mating Disruption

Mating disruption is another method which relies on the availability of a pheromone capable of attracting male moths of the pest species. The method, which has been used on gypsy moth in North America, involves distributing pheromone flakes or beads by aerial application. This has the effect of confusing the male moths and preventing them from locating the females. Many females therefore remain unfertilised. Pheromones may have some toxic effects on people, but this risk is thought to be slight ⁽⁶⁹⁾ (USDA 1995).

There is no information on mating disruption specific to the tussock moth, as a specific pheromone for the species has not been isolated. However, the method may be promising for tussock moth control, as it has been found to successfully reduce gypsy moth populations in treated areas (Mastro 1994) and good results have also been shown on the related species O. pseudotsugata (Hulme & Gray 1994, Sower et al 1983 & 1990).

5.5.4 Sterile Insect Techniques

Sterile insect techniques involve the sterilisation by radiation of large numbers of reared moths of the pest species. The sterile insects are then released into the environment and mate with fertile adults, producing infertile eggs. The effect, in theory, is population reduction and eventual elimination. In small field trials with gypsy moth, the technique produced a significant decline in the hatching rate of eggs (Maksimovic 1972). In practice, the logistics of sterile insect programmes are immense, and operational problems can severely hamper their effectiveness (California Department of Food and Agriculture 1992).

This technique could not be used in New Zealand for tussock moth without considerable amounts of research.

5.6 What are the advantages and disadvantages of Btk compared with the alternative approaches?

The advantages of Btk in comparison with the alternative approaches discussed above are:

it has a history of successful use in the US for 30 years, for many years in Canada, and latterly also in Europe;
it is non-toxic to mammals, birds, fish, and most invertebrates other than caterpillars;
New Zealand currently has the technology and experience to organise and apply the Btk formulation for tussock moth;
it is effective against tussock moth larvae between their first and third instar stages of development. This gives a window of time for its application of between four and six weeks; and
there is a good chance that eradication can be successfully achieved.

The disadvantages of Btk are:

it will require multiple applications (between three and five) at regular intervals to cover the period when susceptible tussock moth caterpillars will be present;
it will need to be imported from overseas; and
it is removed from vegetation by rain, and given unfavourable climatic conditions (consistent high wind and/or rain) the programme may not succeed in eradicating the moth. (However this is also true of other eradication techniques because they rely on aerial spraying.)

6. Consultation

6.1 Public consultation

It is usual during the preparation of an EIA for those who may be directly affected by the proposed activity (eg, community groups, local residents), to be consulted directly. However, in this case, the opportunity to consult widely was constrained because of the need to act quickly in planning and implementing an eradication programme for tussock moth, should this prove necessary. Local public consultation was also constrained by the fact that the EIA applies to the whole country whereas, for any one spray programme, only a small part of the country would be affected. For these reasons, consultation during the preparation of the EIA has been confined largely to those agencies and individuals who would be able to provide specific technical comments on the draft EIA. Details of how local communities will be provided with information and consulted on any eradication programme are set out in Section 4.3 of the EIA.

6.2 Agencies consulted

The organisations listed below have been consulted in the preparation of this EIA. Those organisations marked with an asterix provided comments which have been incorporated, where possible, into the text of the EIA. The remaining organisations did not provide written comments, but in most cases, were able to discuss aspects of potential concern with Ministry of Forestry staff.

Ministry for the Environment*
Ministry of Agriculture
Te Puni Kokiri*
Ministry of Commerce*
Police Department*
Department of Conservation*
Ministry of Health*
Ministry of Transport*
Ministry of Research, Science and Technology*
Local Government Association
Parliamentary Commissioner for the Environment
Forest Health Advisory Committee*
Abbott Laboratories*
New Zealand Forest Research Institute*
Civil Aviation Authority*
Auckland Regional Council*
Auckland City Council
Regional Council Chief Executive Officers' Group* ⁽⁷⁰⁾

6.3 Environmental groups consulted

The views of the following environmental groups were also sought.

Royal Forest and Bird Protection Society;
Maruia Society;
Greenpeace; and
Environmental and Conservation Organisations (ECO) ⁽⁷¹⁾.

Forest and Bird commented that they strongly support the aerial spraying of Btk and agree with the conclusions of the EIA. The Maruia Society discussed the proposed spray programme with Ministry of Forestry staff, but had no technical comment to make on the EIA. Many of the comments provided by Greenpeace related to policy and operational matters which are beyond the scope of this EIA. Greenpeace's submission concludes (in part): "Greenpeace recommends a more thorough assessment of Btk's effect on the New Zealand environment be undertaken. This should include, as a priority, laboratory trials on native flora and fauna, including native birds and marine life. The intervening period should be used to physically search for, and remove, egg masses. This should reduce or even prevent the need for aerial spraying".

Notes

(1) Eradication involves a one-off cost rather than the ongoing costs of control and, if successful, means that there will be no ongoing adverse effects from the pest species.

(2) Gypsy moth is not found in New Zealand.

(3) pers. comm. to W.Faulds.

(4) John Bain, New Zealand Forest Research Institute (NZRFI) pers. comm. to N. Gibbs, June 1996.

(5) The number of generations is determined by daylength and temperature.

(6) An instar is the form an insect takes between moults.

(7) The fact that Bt occurs naturally in soils has no bearing on any potential adverse effects Btk formulations may have.

(8) The "half life" of a substance is the time taken to lose 50% of its activity.

(9) Some Bt varieties such as Bacillus thuringiensis var. thuringiensis contain exotoxins which can be toxic to mammals and are potentially mutagenic (BC MOH 1992).

(10) Ministry of Health (NZ) pers. comm. (comment on draft EIA, 17 June 1996).

(11) In 1992, Foray 48B samples were tested as part of a study on the health effects of Foray 48B, and no contamination was found (Noble et al 1992).

(12) Pheromones are chemicals produced by female tussock moths to attract male tussock moths.

(13) The potential adverse effects set out in the table are discussed in more detail in Section 3 of the EIA.

(14) Although fixed wing aircraft and helicopters would fly at the same speed, more helicopters can operate in a defined space and helicopters have a faster turn-around time at the end of a transect. This compensates for the narrower spray swath width of helicopters and leads to a shorter duration for each spray application.

(15) Spray swath width depends on type of aircraft and flying height, but is likely to be around 25-40m for helicopters, and wider for fixed wing aircraft.

(16) Further details of the potential adverse effects referred to in the Table can be found in Sections 3.10 & 3.11 of the EIA.

(17) 120 km/h. A minimum speed of 60 knots (111 km/h) is required for the spray equipment to function correctly.

(18) Within this range of wind speeds the most even spray distribution pattern is achieved.

(19) Higher temperatures increase the evaporation rate of the insecticide and thermal air currents may prevent the spray from landing on the target plants.

(20) Further information on the potential adverse effects referred to in the table is contained in Section 3 of the EIA.

(21) BIU/ha is an abbreviation for billions of International Units per hectare. International Units are a commonly recognised way of measuring Btk dose rates.

(22) This figure assumes the application of Foray 48B from aircraft flying at low levels (10-30m above rooflines). Significantly greater volumes of Foray 48B would be required to achieve the same dose rates when applying the formulation from a greater height.

(23) If the spray is applied by aircraft flying at heights greater than 30m, the spray equipment is set to a larger droplet size, and the formulation may be diluted.

(24) The British Columbia Environmental Appeal Board recently upheld an appeal against an application to carry out a gypsy moth eradication programme using only ground spraying of Btk. One of the reasons for declining permission to spray was that ground spraying alone was unlikely to successfully eradicate the gypsy moth population (Environmental Appeal Board 1996).

(25) These two documents are held in the library of the Ministry of Forestry in Wellington.

(26) This assumes that tussock moth is as susceptible to Btk as its relatives. There are no reasons to believe that tussock moth is not susceptible to Btk, as Btk is a specific Lepidoptera toxin, and is known to be toxic to gypsy moth and other related species. However, due to the short lead-time before the proposed tussock moth eradication programme, no tests have been able to be carried out to confirm this assumption.

(27) Spray programmes in the 1980s used the formulations Thuricide or Dipel applied at rates of 30 BIU/ha. In the 1990s, Foray 48B at rates of 40 BIU/ha has been used. Areas treated by aerial spraying ranged from 10 ha to 18 813 ha (Vancouver in 1992), and ground spraying was also used. Multiple applications (three times a year) were frequently used. Efficacy monitoring involved intensive pheromone trapping.

(28) Van Frankenhuyzen et al 1993. Canadian Entomologist 125, quoted in STOP 1995.

(29) In this and the following discussions of the persistence of Btk in the environment, please note the distinction between persistence (i.e., survival in the environment, usually in the form of an endospore) and pathogenicity (multiplication in an organism so as to cause a disease). Persistence does not necessarily imply any adverse effect.

(30) However, if Btk was to be sprayed in an area where attempts were being made to establish a Lepidopteran biocontrol agent, it would have to be assured either, that the control organism could be reintroduced once Btk was no longer present or, that the benefits of spraying outweighed the costs of not being able to reintroduce the agent.

(31) Reference to Bt in the NZ Food Regulations refers to its use as a "pre-harvest insecticide". This does not appear to cover its use on tussock moth. Residues on vegetables as a result of spraying Btk to eradicate tussock moth could therefore be considered the result of off-target application.

(32) To date the Foray 48B formulation has not been used in New Zealand on conventional or organic crops as it has only recently been registered by the Pesticides Board.

(33) LD50 is a standard toxicity measure. It refers to the does required to kill 50% of organisms in a trial.

(34) Mean exposure levels of groups of workers ranged from 3000 to 5.9 million organism spores per cubic metre of sampled air.

(35) Cumulative exposure is determined by multiplying the mean exposure value with the number of hours of exposure. The US study found workers were exposed to cumulative levels of 5.4 million - 100 million colony-forming units.

(36) However, a number of anecdotal cases (i.e., cases unsupported by rigorous scientific investigation and documentation) of possible allergic responses to Btk formulations have been noted during the preparation of this EIA. See, for example, STOP, 1995.

(37) Dr Jeremy Road, respirologist, University of British Columbia, quoted in STOP 1995.

(38) Another reported study found that snails were affected by low concentrations of the Bt formulation Thuricide. A significant decrease in egg laying activity, size of egg masses and egg hatching was observed (Osman et al 1991, quoted in STOP 1995).

(39) Faulds, W., pers. comm. Indigenous Lepidoptera Susceptible to Control Measures Taken Against Asian Gypsy Moth, unpublished NZFRI report 1994.

(40) The estimate was obtained by deleting form the full list of NZ Lepidoptera any species which (i) are not native to NZ; or (ii) are confined to high altitudes (as it is assumed that tussock moth would be introduced at a port and establish in low lying areas); (iii) are not present at a vulnerable larval stage at the time of spraying (this assumes spraying in October/November. It also assumes a number of matters in relation to life cycles of NZ Lepidoptera, about which little is known in many cases); or (iv) have caterpillars which live under the soil, under bark, or otherwise would be protected from the spray; or (v) are leaf miners (which live inside leaves and therefore may be protected from the effects of Btk); or (vi) are confined to outer islands' or (vii) are recorded only from dense native forest; or (viii) have not been recorded since early historical times (Faulds 1994, pers. comm. (ibid)).

(41) pers. comm. (ibid)

(42) The length of time taken for recolonisation would depend, to an extent, on the size of the area sprayed (a larger area would take longer to recolonise).

(43) Department of Conservation, pers. comm. (comment on draft EIA, 21 June 1996)

(44) 300m is the likely range of off-target spray drift that may have some effect (e.g., insecticidal effect or visual effect). However, with sophisticated monitoring techniques, minute quantities of spray drift may be detected at distances considerably further from the target area.

(45) Flying heights for aircraft are normally given in feet.

(46) The Cresco is a particularly quiet aircraft commonly used in agricultural operations.

(47) A child's or elderly person's auditory reflex is unable to provide the level of protection afforded to other adults.

(48) Philip Dickinson, noise engineer, Ministry of Health, pers. comm. (comment on draft EIA, 17 June 1996).

(49) Ministry of Health (NZ) 1996, pers. comm. (comment on draft EIA, 17 June 1996).

(50) There are some anecdotal reports of effects of this type from spray programmes in Washington State (Washington State Department of Health Report of Health Surveillance Activities, Asian Gypsy Moth Control Program, March 1993. In STOP 1995).

(51) Anderson, C., Nature vol 355, Feb 1992, quoted in STOP 1995.

(52) The RMA gives regional councils responsibility for "the control of the use of land for the purpose of the prevention or mitigation of any adverse effects of the storage, use, disposal or transportation of hazardous substances" (s.30). Territorial authorities have a similar responsibility under s.31.

(53) See Sections 9(8) & 12(5) of the RMA. "Aircraft" includes fixed wing aircraft and helicopters.

(54) Under Civil Aviation Rule 137.61, pilots performing agricultural operations over a populous area may fly at low levels if they are operating on behalf of a government department or Crown entity, but the Director of the Civil Aviation Authority may set conditions and limitations on the operation.

(55) Optimum storage temperature is 5 degrees C.

(56) These requirements arise from the Transport Act 1962, New Zealand Standard 5433:1988, traffic regulations and various gazette notices.

(57) The use of the term "biological control" in this section refers to methods of biological control other than the use of Btk (which itself is a biocontrol agent).

(58) pers. comm. to N Gibbs.

(59) This situation is usual with introduced insects, providing other factors are not limiting.

(60) In Auckland it has been recorded feeding on plum, peach, cherry, roses, willows, kakabeak, grapefruit, Acer negundo, apple, birch, oak, wisteria, geranium and coral pea.

(61) Native species related to known host plants include mountain beech, black beech, silver beech, hard beech, red beech, bush lawyer, tree brooms, kowhai, kaka beak, mingimingi, dracophyllum, titoki, akeake, manuka, kanuka and rata (Department of Conservation 1996. pers. comm. (comment on draft EIA, 21 June 1996).

(62) Trials in which no choice is provided do not provide an indication of what a caterpillar would eat in a real-world situation where a choice of food plants is available. Trials using mature larvae have the additional constraint that mature larvae are usually tolerant of a wider range of foods.

(63) pers. comm. to N. Gibbs

(64) Note, however, that the hairs on caterpillars such as the larvae of gypsy moth and tussock moth are generally considered to act as a deterrent to bird predation.

(65) pers. comm. to N. Gibbs

(66) Studies reported by Hajek (1995) show that species of Lepidoptera other than gypsy moth can be infected, although usually at low levels. O. pseudotsugata (a North American species) is infected.

(67) Trevor Jackson, Agresearch, Lincoln, pers.comm. (comment on draft EIA, 10 June 1996).

(68) pers. comm. to N. Gibbs.

(69) USDA 1995 reports an interesting side effect of exposure to the gypsy moth pheromone disparlure. Exposed workers may attract male gypsy moths for years after working with disparlure(!) The USDA reports that this could be "annoying and particularly stressful for individuals with an aversion to insects".

(70) Response received from Taranaki Regional Council (not intended to reflect the views of the Regional CEOs).

(71) No comments were provided by ECO.

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Glossary

actinomycete
a type of soil microorganism

active ingredient
in relation to an agrichemical, is the ingredient which has a toxic effect on the target organisms.

ADI
abbreviation for Acceptable Daily Intake - the level of exposure to a toxic substance which is considered safe (set, for example, by the World Health Organisation).

agrichemical
any substance, whether inorganic or organic, manufactured or naturally occurring, modified or in its original state, that is used in any agriculture, horticulture, forestry, management of public amenity areas, or related activity, to eradicate, modify, or control flora or fauna.

arthropod
a large group of invertebrate animals with a segmented body and jointed limbs (eg, insect, spider, crustacean).

Bacillus thuringiensis
scientific name of a naturally occurring bacterium which is used to control populations of insect pests.

bioaccumulation
accumulation within the tissues of living organisms.

biocontrol
the managed use of an organism's natural parasites, diseases and predators to control pest populations of the organism.

BIU
abbreviation for Billions of International Units - the standard measurement for Btk dose rates. It is based on Btk activity against the cabbage looper larvae.

Bt abbreviation for Bacillus thuringiensis.

Btk
abbreviation for Bacillus thuringiensis var. kurstaki, a variety of the bacterium B. thuringiensis.

chitin
a strong, light-weight material which is a component of the exoskeleton of insects.

colony-forming units a measure of exposure to biological insecticides. A colony-forming unit may consist of one or more spores.

crustacean
a member of a group of hard-shelled, mainly aquatic, animals including crabs, crayfish, shrimps etc.

DGPS
abbreviation for Digital Global Positioning System. A satellite-based positioning or navigation system which provides extremely accurate measurements of the three-dimensional position, velocity and time of the receiver.

diflubenzuron a chemical insecticide.

Dimilin
a chemical insecticide (active ingredient diflubenzuron).

Dipel
a Btk formulation.

disparlure
a pheromone which has been isolated to attract male gypsy moths.

EIA
abbreviation for Environmental Impact Assessment - the process of evaluating the potential environmental effects of a proposal. This process may include preparing a written report.

endospore
a type of resting cell which develops within a bacterial vegetative cell under certain conditions. Endospores are extremely resistant to adverse environmental conditions.

endotoxin
a component of the walls of bacteria that is toxic to animals.

Entomophaga maimaiga
the scientific name of a fungus known to infect gypsy moth.

epidemiology
the branch of medicine concerned with the control of epidemics.

epizootic
occurrence of a disease in animals that is widely prevalent and spreads rapidly.

exoskeleton
the tough external skeleton of an insect.

exotoxin
a toxin that is secreted by a living organism.

Foray 48B
an agrichemical formulation with Btk as the active ingredient.

half life
the time taken for a substance to loose half of its activity (eg, radioactivity for a radioactive substance, insecticidal activity for an insecticide).

indigenous
belonging to a region, not introduced.

inert ingredient
those substances in an agrichemical formulation other than the active ingredients.

insecticide
an agrichemical which affects insects.

instar
the form an insect takes between successive moults.

invertebrate
an animal without a backbone.

iwi
tribe, people.

larva
stage in development between hatching and attaining adult form. For moths and butterflies, this stage is the caterpillar.

LD50
abbreviation for lethal dose - the dose of a substance at which 50% of the test animals die in a given test period. It is a measure of acute toxicity of a substance.

LdNPV
(Lymantria dispar Nuclear Polyhedrosis Virus), a virus used to control populations of gypsy moth.

Lepidoptera
moths and butterflies.

Lymantria dispar
the scientific name for gypsy moth, a relative of the tussock moth.

Lymantriidae
the scientific name for the family which includes tussock moth and gypsy moth.

microorganism
an organism not visible to the naked eye (eg, bacterium, virus).

mutation
a genetic change which, when transmitted to offspring, gives rise to heritable variation.

nematode
a type of slender, unsegmented worm.

non-target organism
any living organism that is not the target of a management practice.

Orgyia pseudotsugata
the scientific name for Douglas fir tussock moth, a relative of the tussock moth Orgyia thyellina.

Orgyia thyellina
the scientific name for the white-spotted tussock moth.

parasitoid
a parasite that lives inside an insect host.

pathogenic
disease-causing.

pH
a measure of the alkalinity or acidity of a substance. pH 1 is very acidic, pH 14 is very alkaline.

phagostimulant
a substance which encourages feeding.

pheromone
a substance secreted from an animal which influences the behaviour of other members of the species. Most commonly applied to sex attractant scents.

photoperiod
day length.

phytotoxicity
the ability of a substance to cause a toxic effect (destroying life or injuring health) on plants.

ppm
parts per million, a measure of concentration

protein crystal
in relation to Bacillus thuringiensis, is a substance produced by the bacterium at the time of sporulation. The protein crystal may contain toxins.

sporulation
spore-forming.

tangata whenua
literally, people of the land. Refers to the iwi or hapu of an area.

Thuricide
a Btk formulation.

UV
(ultra-violet) a form of radiation just beyond the violet end of the visible spectrum.

vegetative cell
an actively growing cell (as opposed to a cell that forms spores).

Page last updated: 19 June 2008

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