Gypsy moth is known as a forest defoliating insect. It is an invasive species that was brought over from Europe to North America in the 1800s, although it widespread defoliation did not occur until the 1980s in Ontario.
The gypsy moth is a threat to Ontario’s forests because of the damage it does to tree canopies. The moths lay eggs on tree bark in the winter and when they hatch, the caterpillars chew holes in leaves during the spring and early summer. Depending on the population, they can chew through an entire canopy. If caterpillars feed on a tree’s leaves for two seasons, the tree will likely die.
Identifying Gypsy Moth
The Gypsy Moth is found on a variety of tree species, such as oak, birch, beech, sugar maple, aspen, spruce, and pine.
The first sign of a Gypsy Moth infestation is the egg mass. Each spongy, beige coloured egg mass about the size of a loonie, can hold up about 600 to 700 eggs. These egg masses can be seen on the trunks and branches in late July until the following May when they start to hatch. The eggs hatch into hairy caterpillars about 50 mm long. They are darkly coloured, with a double row of five pairs of blue spots and six pairs of red spots down the back. After pupation, the moths are either light brown or white, depending on if they are male or female.
The caterpillars will chew holes through the leaves on a tree and are capable of defoliating an entire tree, even with regrowth during the summer.
In the early stages, Gypsy Moth infestations are particularly hard to diagnose, because feeding occurs primarily at night. It’s important for you to inspect your trees each spring and summer for egg masses, as well as monitor the health of the leaves on your tree for empty patches and holes.
What do I do if my tree is infested?
If you believe your tree is infested by the Gypsy Moth, you have a few options for maintaining your tree’s health.
First, if you notice egg masses on the bark, you can remove these by removing them gently with soap and water, vacuum with portable or hand held unit with extensions, or scrap them off with a putty knife depending on the bark condition. After collecting the egg masses in a container, you must either destroy them by burning or crushing them. Do not compost them as they will hatch and defoliate plants nearby.
To help monitor for Gypsy Moth caterpillars, you can place a band of burlap or cloth around the trunk of the tree. If present, caterpillars will hide under it in the heat of the day and you can easily find them and remove them. The caterpillars, while not poisonous, can cause irritation for some people. Always handle insects with gloves.
There are insecticides available to stop infestations. The small wasp and the fungus Entomophaga maimaiga are both biological controls of the Gypsy Moth.
If you suspect your tree is infested with Gypsy Moth, contact P & A. We can diagnose an infestation and make professional recommendations for treatment.
You should always report sightings of an Invasive Species. Report sightings to the toll-free Invading Species Hotline at 1-800-563-7711 or email info@invadingspecies.com.
Recently, the Government of Canada updated the regulated zones for Gypsy Moth. It’s important that you know these zones and follow the bylaws associated with them. Don’t move wood in or out of the regulated area to help prevent the spread of this invasive species.