Asian gypsy moth: How likely is it to establish in New Zealand?
An international collaborative research project involving scientists from New Zealand, the United States and Canada aims to estimate the risk of Asian gypsy moth (AGM) establishing in New Zealand. The work, which is based around egg phenology and climate, has been initiated by Dr David Gray, Natural Resources, Canada.
Asian gypsy moth (Lymantria dispar)
Photo: John H. Ghent, USDA Forest
Service, www.forestryimages.org 
Funding for the project is shared between the three countries, with actual research being carried out in North America.
At least two questions are fundamental to the issue of introduced exotic pests such as AGM:
- What is the probability that a given pest will become established in the event of an introduction?
- In the event of an introduction, and a measurable risk of establishment, can particular life cycle events (e.g hatching) be reliably predicted in order to plan an intervention such as eradication?
Estimating the probability that an exotic species will establish in a given locality is of interest for a number of reasons. For example, where the probability is near zero, the risk posed by an accidental introduction of the species is negligible. The contrary is obviously true if the probability of establishment is high.
Following an introduction, planning response action is problematic as there are no records of the insect’s life cycle patterns in the local region.
CLIMEX (climate modelling) addresses uncertainties on climatic parameters by estimating similarities between regions, but does not provide answers on life cycle events. A biological model that directly assesses how well the locality satisfies the species’ development requirements can help predict how likely an exotic insect is to establish in a novel environment.
Among the requisites of each species is the availability of food during the insect’s feeding stage(s) and suitable temperatures to complete its life cycle: a ‘predictable necessity of seasonality’.
For example, to survive, AGM eggs need to hatch when new foliage is growing, so that emerging larvae have a ready feeding source. On the other hand, the cold-hardy and low-temperature-requiring egg diapause phase (when the metabolism slows, delaying development) needs to coincide with winter. Finally, these events need to coincide sufficiently each year for the continual survival of the insect population.
The collaborative research will involve collection of gypsy moth strains from China, Japan, Russian far East and Germany, thus making the project truly international. The egg masses will be reared in quarantine facilities in the United States, where adults will be mated.
During rearing experiments, respiration measures will be used to determine the time-varying development responses in diapause and postdiapause in the four strains. The new parameters will be incorporated in to the gypsy moth life-stage model. This creates a population in each location with an egg hatch pattern estimated for the temperature regime of the location.
The gypsy moth life-stage model has been used successfully to predict egg hatch and peak second instar population of gypsy moth in British Columbia and New Brunswick. However, it is currently only properly described for the North American strain. There are differences in the hatch patterns of Asian and North American strains, so the research outputs will be useful to all three contributing countries.
As a final output, the risk of establishment of AGM in New Zealand will then be estimated and a graphical interface for the gypsy moth life stage model will be created for use by Biosecurity New Zealand. This information will allow New Zealand to further refine its surveillance and response to incursions of Asian gypsy moth.
The project is helping increase international linkages and has been made possible by funding through the MAF operational research fund, the USDA and Natural Resources Canada. MAF acknowledges the efforts of Dr David Gray in leading and organising the overall research.
- Mark Ross, Senior Adviser, Plant Response Team, Biosecurity New Zealand, phone 04 894 0535, mark.ross@maf.govt.nz
Page last updated: 30 April 2008