Bronze Birch Borer is another insect that had not been seen commonly in Calgary but has shown up in greater numbers over the past few years due to the added stress that erratic weather has caused the trees in Calgary.
The adult female bronze birch borer is an elongate beetle with a metallic greenish black sheen. She seeks weakened birch and lays her eggs in cracks in the bark. Upon hatching, the grubs burrow into the living tissue below the bark and begin feeding on living trunk tissue. After the grabs mature as adult beetles, they emerge from the birch stem through D-shaped exit holes.
Key Points
- – Dead tops on birch may reveal the presence of bronze birch borer, but drought stress and root damage alone are far more likely to be responsible for top die-back on birch.
- – Bronze birch borer is more likely to attack trees already stressed by other factors.
- – D-shaped exit holes at the base of the dead stem show where the beetles have left their feeding galleries beneath the bark
Tree Damage
Tree show damage in mid-July when tops can dry out and die-back. It starts as yellowing and leaves eventually turn brown. The tunnelling of the grubs under the bark completely encircles the stem, and the stem dies.
Control Measures
- The best control for this insect is prevention by keeping your tree healthy, which for Birch means lots of water, keeping the roots cool and avoiding root damage.
- Trees that are already affected should be pruned to remove the dead and heavily infested branches. Ensuring the galleries of the previous years infestation are completely removed.
- Trees may be injected with a biological pesticide which has shown some promise in controlling this insect.
For more information on keeping you Birch well watered see this link:
Watering Landscape Trees in Calgary
