Gypsy Moth

May 20, 2020 Update -  City monitoring gypsy moth populations and tree health. Learn More...

What is Gypsy Moth?

European Gypsy moth, Lymantria dispar, is an introduced pest that impacts trees when larvae emerge in spring and the caterpillars feed on leaves causing defoliation. Oaks are the preferred host species of tree.

As part of Burlington's Integrated Pest Management (IPM) program, Forestry staff assess sites annually across the city and conduct egg mass surveys to determine areas where natural processes can no longer keep pest population levels down on their own. Although healthy trees can generally withstand repeated defoliation, trees which are already in distress from problems such as acute drought, compacted soils, diseases or other pests may die. Generally, healthy trees which are defoliated in spring, will leaf out again by fall. Gypsy moth populations tend to be cyclical, with peaks every 8-12 years, followed by dramatic population decline of the pest

Treatments are only used when populations exceed accepted thresholds. Treatment of the insect populations below threshold levels. The treatment option commonly used is BtK (Bacillus thuringiensis var. kurstaki), a bacterium found naturally in soils. BtK works only against larva of the target species of insect; it does not affect plants, animals or people. BtK is one of the few organic treatments acceptable to organic growers as it is a naturally occurring biological organism.