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Asian Long-horned Beetle

By Lauren McVittie

What is it?

The Asian long-horned beetle is a large invasive insect that feeds on hardwood trees, eventually killing them. 

Where did the beetle come from? 

These insects are native to China and the Korean Peninsula. Although no one knows for sure how the beetles arrived in North America, they likely arrived in shipment packaging such as crates and pallets.The Canadian Food Inspection Agency (CFIA) and the Canada Border Services Agency has intercepted the beetle at ports and warehouses since 1982.

Where has the beetle appeared in Ontario?

In 2003, the first infestation in Ontario was found close to Vaughn and Toronto. Infested as well as susceptible trees were removed. In April 2013, after five years of monitoring with no beetles reported, the infestation was declared eradicated.

A few months later, in August 2013, the Asian long-horned beetle reappeared in Mississauga and Toronto near Lester B. Pearson International Airport. Trees were removed in 2013 and 2014. According to the government of Ontario, surveys are ongoing to ensure all instances of the beetle and infected trees have been identified.

What does the beetle look like?

The beetle is 20-35 mm long and 7-12 mm wide, with long antennae. Its body is shiny black with up to 20 white dots.

How does it affect trees?

Female adult beetles chew a hole in the bark and lay one egg inside the hole. After 1-2 weeks, the larva hatches and feeds on the tree just beneath the bark. The larva then burrows deep into the tree and feeds there throughout the winter. 

The beetle feeds on the tree’s nutrients and water supply, and eventually prevents the tree from accessing nutrients. Without access to nutrients and water, the tree slowly dies.

Which tree species are affected?

In Ontario, the beetle has been observed affecting the following trees:

  • Maples
  • Birches
  • Poplars
  • Willows 

What are the signs of infestation?

  • Holes chewed by female beetles to lay larvae are oval shaped, 10-15 mm wide, light in colour when recent, darker when older
  • Bees, wasps, and butterflies as well as other insects are attracted to foaming sap caused from larvae feeding on tree beneath bark
  • Once the tree has been cut off from nutrient supply, it will die from the top down with leaves wilting and canopy becoming sparse
  • Adult beetles emerge from trees beginning in May through July

What is their wider impact?

According to Natural Resources Canada, the Asian long-horned beetle poses a significant risk of widespread urban deforestation.  The risk of tree loss affects more than the health of our environment; tree loss from the beetle will also affect the tourism and recreation industries, hardwood forest industry, and maple syrup production.

Because there is no pesticide or natural predator to control the beetle, affected trees as well as susceptible trees must be removed. Natural Resources Canada reported that 531 infested trees were cut down and chipped between September 2003 and March 2004. An additional 12, 500 trees susceptible to the beetle were also destroyed during this period.

What can I do?

Monitor the trees on your property for signs of the beetle, and report any findings by calling the Invading Species Hotline at 1-800-563-7711 or report online at