Diagnosing Borers

Symptoms Of Borers
Trees and shrubs with borers usually signal problems when the foliage on certain branches suddenly droops and turns brown in mid season. You might spot a small hole in the bark of affected stems or a telltale sprinkling of sawdust which the insects leave at their entrance holes or at the base of the tree or shrub.

Eventually affected stems and branches die or become so weakened that they break off in a storm. Some borers attack trees and shrubs near the ground, weakening them so much that they can be pushed over easily. Close examination of the broken stems or branches usually reveals tunnels under the bark or in the wood, confirmation that borers are present.

Borer damage weakens plants and makes them vulnerable to disease. Their straight or serpentine tunnels are often black from fungus that has entered plant tissues through the tunnels. Other pest insects gain access to the interior of the plant through the tunnels. However, damage is difficult to detect until part of an infested plant starts to die.

If you have large, valuable specimen trees on your property, consider hiring a certified arborist to examine them for borers. Take steps to remove even a single borer.

Some Trees and Shrubs Affected By Borers

Trees Vulnerable To Borers
American HollyHemlock
BirchJapanese Maple
Black WalnutLondon Planetree
Blue SpruceMaple
Callery (Bradford) PearOak
English HollyWeeping Willow
Flowering CrabappleHawthorn
Flowering Dogwood

Shrubs Vulnerable To Borers
Bigleaf HydrangeaMeserve Holly
BoxwoodMountain Laurel
Japanese BarberryYew

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