When bugs attack: the 5 most destructive insects for trees

While most insects are beneficial, the worst culprits destroy trees. These are the five most destructive insects and the signs you may have an infestation.
Asian long-horned beetle

Mainly found in Ontario, the Asian long-horned beetle attacks several hardwood species such as maples, oaks, poplars, mountain ash and birch trees.

  • This is a borer insect, which means that its larvae digs tunnels into the trunk of the tree. Adults, meanwhile, hollow out oval furrows in the bark, which sometimes cause resin to flow.

The only way toeffectivelyeliminate this insect is to clear-cut all the hardwoods near the infected trees.

Brown spruce longhorn beetle

This beetle targets weakened and distressed trees; however it has been known to attack healthy spruce trees.

Even though brown spruce longhorn beetles have only been found in Nova Scotia, they've already done a lot of damage.

  • Just like the Asian long-horned beetle, infestation of a spruce tree can be evidenced by the presence of holes in the bark and flowing resin.The larvae of this beetle dig an "L" shaped tunnel under the bark of infested trees.

Spruce budworm

The spruce budworm is the brown caterpillar of a small North American moth. It targets the needles of fir and spruce trees, thereby slowly weakening the tree.

Not only is this caterpillar creating havoc across Canadian forests, but it might be found in your own backyard.If you see larvae on the needles of a tree, shake the branch, use water to remove them or pick them off by hand.

  • The tips of the needles of an infested tree have a reddish colour and will fall off in the autumn season. At this point, the tree will begin to display a greyish hue.

Beech scale

The beech scale is a small, sucking insect that uses its piercing mouthpiece to penetrate the bark of the tree to suck its sap. The holes it makes never close up, making the tree vulnerable to fungal infections and other diseases.

  • The presence of beech scale insects can be detected by the appearance of a white wax either on or beneath the surface of the bark.

They are mainly found in beech trees in Nova Scotia but are quietly making their way to other provinces. Studies are under way to find a solution to inhibit its spread. One option is to introduce a fungus to known to target the beech scale.

Emerald ash borer

This tiny beetle has caused widespread tree damage across Ontario and Quebec. Ash trees make up a large part of our forests, but are especially abundant in cities. The larvae dig an "S" shaped groove under the bark that kills ash trees in as little as one to five years.

  • An infected ash tree will have distinctive "D" shaped holes on the trunk, new shoots at the base, and the crown will begin to lose its leaves.

Local and Canadian government authorities currently have rigorous programs under way to stop the emerald ash borer in high-risk areas.

When bugs attack: the 5 most destructive insects for trees
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