Gypsy moth (Lymantria dispar dispar or LDD) infestations are ravaging trees in many communities across the province, and this year, it’s been particulary noticeable.
Kristyn Ferguson, Ontario program director with Nature Conservancy of Canada says what we’re seeing now is the species going through its natural cycle.
“It goes through these massive population cycles every 10 to 12 years where we see a big boom in their numbers and they catch our attention every time that happens,” said Ferguson. “They are going through this natural population ‘boom and bust’ cycle and we’re on the second year of the ‘boom.’ We expect the ‘bust’ to happen soon. When they are in these really high densities, they’re not going to last this way.”
She says a number of things will eventually take the caterpillar numbers down, like a virus, or a moth fungus, but for now, just know that it’s not going to last forever.
These caterpillars have a voracious appetite and are devastating many plant and tree species, such as oak, maple, birch and elm.
The Nature Conservancy says one caterpillar can eat one square metre of leaves in one season. While hardwood trees may survive up to three years of severe defoliation, coniferous trees would not survive one bad infestation.
Ferguson says there are things you can do to protect your favourite trees and plants, but don’t handle the caterpillars with bare hands as some people can develop an itchy rash from touching the tiny hairs on the caterpillars, which contain histamines.
Create caterpillar traps by wrapping trees with burlap bands (May to August). Secure the burlap to tree trunks at chest height with a piece of rope or twine. Fold the material above the rope or twine down over itself to create a trap. This should stop caterpillars from climbing your trees.
Check your burlap band traps in the afternoon, when caterpillars are likely to seek shelter from the mid-day sun inside the burlap.
Scrape caterpillars into a bucket of soapy water and let sit for a day or two. Wear gloves to avoid direct contact with the caterpillars.
Continue to check your traps throughout the day and season.
Scrape egg masses from trees (August to early May). Use a scraper tool (e.g. a butter knife or spent credit card) to scrape off egg masses into a bucket of soapy water. Let sit for a day or two and dispose in the garbage.
Do not use adhesive tape around the tree to trap caterpillars as this can be a death trap for birds and other insects.
Photos courtesy of Nature Conservancy of Canada