One of the greatest threats to trees in Ontario is the spongy moth.

Previously called the European gypsy moth, the invasive pest lays eggs in tree bark. Caterpillars hatch from the eggs and eat the leaves of trees, often stripping them bare. When this happens repeatedly, trees become weak and are more likely to die.

In 2021, Ontario experienced the biggest outbreak of spongy moth ever recorded. The pests defoliated 1.8 million hectares of trees.

How to protect your trees

You can minimize damage to trees and shrubs from spongy moth and other caterpillars.

How? Apply Safer’s BTK Caterpillar Killer twice to trees in late spring, advise experts at Pest HQ, Ontario’s leading source for DIY pest control supplies.

BTK or Bacillus thuringiensis kurstaki is a natural, soil-based bacteria. It affects the digestive system of caterpillars. After eating a treated leaf, caterpillars stop feeding within hours and die within a few days.

Apply BTK to leaves in early May, when caterpillars are emerging and before trees are in full leaf. Apply again in early June, when caterpillars are still small and susceptible to BTK.

Mix the concentrate with water per label directions and use a sprayer to apply. Do this in the morning when winds are calm.  

Professional-grade products ordered from Pest HQ ship fast or can be picked up at our headquarters.

What else you can do: 

 In late July, look for spongy moth egg masses on tree trunks and squash them. They look like tan, fuzzy lumps about 3 to 6 cm long.

 Inspect RVs, campers, trailers, tarps, outdoor furniture, toys and equipment before moving items to a new location. Do not transport firewood.

Questions? Contact Pest HQ.