Insect (and other) Invaders

Three people in a forest, one looking up into a tree

Bugs that are a Bother

In July, it can seem like there’s nothing worse than being caught in a storm of black flies or mosquitoes. But it’s sometimes the insects that don’t bug us that can cause the most harm. There are a number of invasive insects that appear harmless to humans but threaten forest and field health across the watershed. These are a few that you should watch for.

Brown Marmorated Stink Bug

Brown Marmorated Stink Bug
Photo: Gary Bernon, USDA APHIS,

Until recently, the brown marmorated stink bug (BMSB) has kept a fairly low profile in Ontario. But increasing reports of crop damage have raised the alarm in agricultural communities. BMSB feeds on many plants, but they also pose a threat to fruit crops like apples, grapes, peaches and plums, as well as corn and soy.

Farmers are encouraged to report any sightings and landowners should remove and dispose of crushed beetles found in residential or commercial buildings.

Read more about BMSB.

Emerald Ash Borer

Emerald Ash Borer
Photo: Debbie Miller, USDA Forest Service,

This small, glossy beetle destroys up to 99 per cent of the ash trees in any region it infests. Assumed to have been unintentionally imported with wood packaging materials in the 1990s, the emerald ash borer (EAB) has devastated ash trees across Manitoba, Ontario, Quebec, Halifax and New Brunswick. As of 2019, 41 per cent of the ash trees within CVC woodland monitoring plots have been affected.

You can help stop the spread by only burning local firewood and monitoring your ash trees for symptoms.

Read more about EAB.

Jumping Worm

Photo: Michael McTavish, University of Toronto, Invasive Species Centre.

Although researchers suspect jumping worms have been in North America since the late 1800s, they’re relatively new to Ontario. Spread primarily through the horticultural trade, jumping worms (which are invertebrates, not insects) reduce soil organism diversity and degrade soil quality, making it difficult for plants to grow.

Avoid buying mulch, compost or other gardening products that come from areas with known populations, such as the eastern and southern United States. Report any sightings to EDDMapS.

Read more about jumping worms.

Spongy Moth

Spongy moth
Photo: John Ghent, John Ghent,

You’ve likely already heard about the spongy moth (formerly LDD moth). For the last few years, spongy moth caterpillars have been feasting on the leaves of local trees across the watershed. Healthy trees can withstand the initial impact, but persistent yearly feeding on leaves can eventually weaken and kill trees.

Although monitoring data suggests natural controls are starting to lower the population, landowners still need to remain vigilant and protect their trees from damage.

Read more about spongy moth

Success Story: Asian Longhorned Beetle

Photo: Kenneth R. Law, USDA APHIS PPQ,

The successful efforts to control an infestation of Asian longhorned beetles (ALB) in Toronto, Vaughan and Mississauga proves how critical early detection and rapid response are for protecting our forests. Monitoring and reporting were critical for control efforts. First detected in 2003, ALB has been officially eradicated from the region. These beetles are destructive to hardwood trees, like maples. 

Early detection is the best defense

Reporting sightings of invasive species is critical to preventing new infestations and controlling existing threats. The Canadian Food Inspection Agency’s quick response to the appearance of the Asian longhorned beetle in Ontario helped prevent its spread and reduce what could have been devastating effects on Ontario’s hardwood forests. Report any sightings of invasive species to EDDMapS and help researchers track and respond to threats.

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