Frequently Asked Questions - White Spotted Tussock Moth
What is white-spotted tussock moth?
Tussock moth, also known as Orgyia thyellina, is a member of the family Lymantriidae. It is related to gypsy moth (Lymantria dispar) which is a major forest pest in Eurasia and parts of North America.
Where does it come from?
Tussock moth is found naturally in Japan, Korea, Taiwan, China and the Russian Far East in both urban and rural areas. While not a serious pest in these countries, it may occasionally cause problems on certain tree species.
Why is it a risk in New Zealand?
The behaviour of exotic insects in new environments is unpredictable and affected by climate, new host plants, and the absence of natural predators and parasites. Feeding trials showed the white-spotted tussock moth to be a potentially serious pest to urban and garden trees and plants, and to have some impact on horticulture, trade, and exotic and indigenous forests, in particular the native beech forests.
Chris Scott, Senior Forest Health Officer
How was it found?
A resident of Auckland's eastern suburbs handed a suspicious looking caterpillar to Government scientists in April 1996. It is likely the moth had been in Auckland for at least a year before its discovery.
How did it get here?
Tussock moth could have arrived in many ways, including as an egg mass on plants, fruit, on an imported second-hand car, on machinery or in someone's luggage.
Is it a pest in other countries?
As far as we know, tussock moth has not been introduced to any country, apart from New Zealand, outside its natural range where it is not a serious pest.
How widespread was it?
Surveys immediately following its discovery showed it was confined to approximately seven square kilometres in the Auckland's eastern suburbs of Kohimarama, Mission Bay and St Johns.
What did we do about it?
The New Zealand Government decided to take the once-only opportunity to eradicate the tussock moth before it spread and became established as a pest. In its first year the eradication programme included a combination of aerial and ground spraying using the Btk spray. In all a total of 23 aerial sprays and 21 rounds of ground sprays took place. 
In its second year, the eradication programme was focused on high density trapping surveillance to find out if and where any tussock moths remained before a decision on what, if any, more action is needed. Approximately 6 500 pheromone-baited traps were placed on properties in and around the area where tussock moth were last found, in April 1997. This was the largest insect trapping programme ever undertaken in New Zealand.
Were tussock moths found?
During April 1997, six tussock moths were trapped within a small area at the centre of the original infestation. More than 300 properties around Kohimarama were searched in July 1997 but no new egg masses were found. There were no sightings of any stage of the life cycle of the white-spotted tussock moth after the last male moth was trapped on 27 April 1997.
How long did the tussock moth eradication programme last?
High density trap surveillance continued until June 1998, to cover three generations of any residual population. When traps were collected and checked for the final time, with still no sign of the pest, the decision was made to wind up the eradication programme.
However, the Ministry of Agriculture and Forestry carried out a much smaller trapping programme over the greater Auckland region in December 1998. Traps were checked once, in January 1999, and again when they were collected in April 1999 but no moths were found.
What did the eradication programme achieve?
The apparent success of the tussock moth eradication programme in Auckland is of international significance. It is believed that no other urban pest eradication programme of the scale and complexity attempted has succeeded. From a standing start in 1996, Operation Ever Green made science, health, operational and communications breakthroughs which will provide valuable guidance for future pest management programmes around the world.
Particularly noteworthy achievements of Operation Ever Green were:
- The rapid response by Government departments, within hours of the pest's discovery, to determine the exact extent and nature of the infestation
- The work of New Zealand scientists in determining the biology, behaviour and host range of the white-spotted tussock moth within months of its discovery - working from virtually nil scientific information
- The development and effective implementation of a highly complex eradication strategy all timed to the insect’s lifecycle
- The successful application of the biological spray Btk over a difficult urban terrain under unpredictable weather conditions,
- The collaboration between New Zealand and Canadian scientists that saw the previously unidentified white-spotted tussock moth pheromone synthesised, tested and commercially produced within 12 months
- The breeding in quarantine of the thousands of larvae and adult moths needed for plant host testing, developmental studies, field monitoring and pheromone development
- The major communication strategy which informed and ensured the support of the affected communities for the duration of the operation
- The considerable health initiatives undertaken to support the programme, including two formal Health Risk Assessments, and an ongoing programme of monitoring for any possible public health impacts
The vegetation controls
Controls remained throughout the trapping programme on removing plant matter from the area of east Auckland where moths were last found. The vegetation controls were imposed under the Biosecurity Act in September 1996.
Who was in the vegetation restriction zone?
Part or all of the following streets were in the zone: Allum, Archdall, Baddeley, Beere, Bongard, Codrington, Comins, Cruickshank, Dorchester, Dudley, Eltham, Geraldine, Godden, Godfrey, Gowing, Hawera, Hawkins, Hobday, Holgate, Hopkins, Houghton, Ipswich, John Rymer Place, Kempthorne Cres, Kepa, Kohimarama, Melanesia, Nihill, Palmer, Patteson, Piccadilly, Prebble, Rawhitiroa, Ripon, Rutherford, Selwyn, Siota, Southern Cross, Sprott, St John, Steele, Taranaki, Thatcher, Tipene, Tulagi, Worcester.
What did the 'restrictions' mean?
Garden vegetation which could not be composted or disposed of at home, could be taken only to the Operation Ever Green free disposal site in Morrin Road; or removed by an Operation Ever Green approved contractor. The controls did not apply to lawn clippings and plants bought from local nurseries.
The free site was open Saturdays, Sundays and public holidays between 8am and 5pm.
Residents in the restriction zone were advised to take proof of their address.
Vegetation was to be carried in a covered trailer or inside a vehicle.
Dealing with moths/eggs/caterpillars
What did they look for?
The young tussock moth caterpillar is black and very hairy and only about the size of an ant. As it grows, it develops an orange stripe down each side and two spots on its tail. The fully grown caterpillar has four distinctive fair-coloured tufts of hair on its back and is about 30 millimetres long.
This spectacular caterpillar with its huge appetite for our trees turns into a fairly ordinary moth. The male moth is generally grey/black, but can be lighter, with one spot on each wing. It is about 13 millimetres from tip to toe. The female moth is generally a creamy white colour with a dark spot on the wings, and is bigger.
She lays eggs which look like a tight cluster of white to buff-coloured pinheads, the whole mass about the size of a five-cent coin. From the eggs emerge the caterpillars and the whole cycle starts over again.
What should I do if I find a caterpillar or moth?
Call Exotic Disease and Pest Emergency Hotline - 0800 809 966.
If you wish you may scoop the moth or caterpillar into a jar with a screw-top lid but try to avoid touching the caterpillar in particular, as contact causes an allergic reaction in some people.
health monitoring
How was the Operation Ever Green spray programme been monitored for health effects?
Operation Ever Green's eradication programme for the white-spotted tussock moth used aerial Btk spraying between October and December 1996 throughout the eastern suburbs of Auckland, followed by continued spraying in a more limited area until April 1997. Also, properties in infested locations were ground sprayed with Btk. Three independent health risk assessments of the spray programme concluded there is no link between the spray and patterns of health reported in the area. The Government commissioned a health monitoring programme from 1997 to 1999 to monitor health in the area following spraying.
Page last updated: 30 April 2008