We received a lot of great questions about Gypsy Moth caterpillars, which seemed to be everywhere in late spring. Gypsy Moths are an introduced species that go through three- to four-year population booms, and we are currently in year two of a boom. We asked CVC ecologist Laura Timms for more information on Gypsy Moths. Here are her top seven things to know about this species:
- Gypsy Moth caterpillars were introduced to the Boston area in 1869, by a man named Étienne Léopold Trouvelot. He thought that he would be able to use them to start a North American silk industry. He kept them in cages in his backyard and unfortunately, they escaped. Since then, Gypsy Moths have spread across the northeastern United States and eastern Canada.
- They eat the leaves of many different types of plants, but prefer hardwood trees like maple, spruce, elm, birch and poplar. They love oak the best. They also feed on garden shrubs and flowering plants.
- One year of Gypsy Moth feeding won’t kill a healthy, mature tree. Healthy hardwood trees will regrow their leaves. Small, diseased or stressed trees due to pests, pollution, drought or root compaction are more vulnerable. Back-to-back years of Gypsy Moth feeding can weaken a tree, making it susceptible to disease and damage from other insects. After two or more years of feeding, Gypsy Moths can kill a tree.
- Some people find exposure to Gypsy Moth caterpillars irritates their skin or throat. This is because caterpillars have small hairs on their bodies that can be dislodged into the air. If you find that you’re sensitive to these hairs, wear gloves if handling Gypsy Moths or avoid touching them altogether.
- As part of their ongoing Gypsy Moth control programs, the cities of Brampton and Mississauga are carrying out a combination of ground sprays, tree injections, scrapping egg masses off trees and using pheromone traps, which are milk cartons that have female Gypsy Moth sex hormones inside the carton to attract males. The males get stuck to the carton, giving researchers a rough estimate of population density.
- CVC does not currently manage Gypsy Moth infestations in our conservation areas. Unlike Emerald Ash Borer (another introduced forest pest), Gypsy Moths rarely cause large-scale damage and management programs are very expensive. In addition, insect outbreaks play an important role in forest ecology. They create habitat for wildlife that use tree cavities and eat decaying trees, such as woodpeckers and the insects they feed on. Small gaps in the forest caused by a few dead trees can also make room for new plants and trees to grow.
- There are a few things you can do to reduce the number of Gypsy Moth caterpillars on your property. You can hand-pick caterpillars off of leaves, wrap burlap bands around tree trunks to collect caterpillars, and scrape egg masses off trees and destroy them. Check out the City of Mississauga’s resources for managing Gypsy Moth caterpillars on your property.
Learn more about insects of the Credit River Watershed here.
*Header image credit to Melissa Esposito
By CVC’s Kimberley Laird