Have you seen these fellows munching away at the trees or plants in your yard? 

What Are Gypsy Moths?

You may not have come across a Gypsy Moth until this summer, but in other parts of Ontario, they have had some devastating effects on trees and understory plants over the years. Gypsy Moths are invasive and destructive during the caterpillar stage, ravaging tree and plant leaves. As adults, they only live to reproduce; they don’t eat, they don’t pollinate flowers, and they die after fertilizing and laying their eggs.

Originating from Europe, Gypsy Moths are an invasive forest defoliating insect first discovered in Ontario in 1969. Since then, their population in our province has grown rapidly. Their preferred host trees include oak, birch, aspen, sugar maple, beech, and even eastern white pine and Colorado blue spruce. 

gypsy moth caterpillar

Why should this pest be controlled?

A single Gypsy Moth caterpillar can eat an average of one square meter of foliage. It’s difficult for trees and other plants to recover from large spread defoliation caused by Gypsy Moth caterpillars, and some stressed and weakened trees will die from defoliation. 

Why should this pest be controlled?

A single Gypsy Moth caterpillar can eat an average of one square meter of foliage. It’s difficult for trees and other plants to recover from large spread defoliation caused by Gypsy Moth caterpillars, and some stressed and weakened trees will die from defoliation. 

How to ID a Gypsy Moth?

Adult male moths are light brown with slender bodies, and females are larger and white. 

Mature larvae are long, dark-coloured, and hairy, with a double row of 5 pairs of blue spots, followed by a row of 6 pairs of red spots down the back.

Life Cycle:

  • In winter, the moths survive as partially developed larvae in eggs. Females lay masses of 100 to 1000 eggs on tree hosts. The egg masses are covered with fine brown hairs. 
  • In spring, eggs hatch and the larvae travel from the bark of the tree to feed on the new foliage by cutting small holes in the surface of leaves. 
  • As the larvae grow, they then move to continue to feed on the edge of the leaves. 

How to ID a Gypsy Moth?

Adult male moths are light brown with slender bodies, and females are larger and white. 

Mature larvae are long, dark-coloured, and hairy, with a double row of 5 pairs of blue spots, followed by a row of 6 pairs of red spots down the back.

Life Cycle:

  • In winter, the moths survive as partially developed larvae in eggs. Females lay masses of 100 to 1000 eggs on tree hosts. The egg masses are covered with fine brown hairs. 
  • In spring, eggs hatch and the larvae travel from the bark of the tree to feed on the new foliage by cutting small holes in the surface of leaves. 
  • As the larvae grow, they then move to continue to feed on the edge of the leaves. 

What you can do:

May to July: Hand-pick Caterpillars

  • Hand-pick caterpillars off your plants, and then soak them in soapy water. Understory shrubs and plants may also be affected, so check those as well for caterpillars.
  • Gently shake smaller trees and plants to knock the caterpillars off the leaves. Collect and soak them in soapy water. 

Late May to Early June: BTK Application

  • For larger infestations, BTK can be applied to the foliage when caterpillars are beginning to feed. The caterpillars must ingest the product for it to be effective.  

May to September: Burlap Banding

  • Wrap burlap banding & fencing around the trunk of possible host trees to trap and prevent the caterpillars from climbing the tree to reach the foliage. Check trees daily and continue to remove the caterpillars and place in soapy water. 

Late July to End of August: Gypsy Moth Traps

  • Install a Gypsy Moth trap when moths are most visibly active. Female moths can’t fly and send out pheromones to attract male moths. Male moths are attracted to the trap by the bait, which smells like the female Gypsy Moth pheromone.

Late July to September: Egg Mass Removal

  • Remove spongy egg masses from the bark and branches of trees and place in soapy water for a day or two before disposing.

We found these articles helpful in learning about the Gypsy Moth: