Problem Identifier Unit Screen//v.w/ RR Template

Problem Identifier Unit Screen//v.w/ RR Template Bronze Birch Borer

Problem
Leaves are yellowing and the foliage is sparse at the top of the tree. There is increased side growth on the lower branches. Twigs and branches may die. The leaves on these branches turn brown but don't drop. There are D-shaped holes and ridges on the trunk and branches. Swollen ridges are packed with sawdust. Weak, young, or newly transplanted trees may be killed.

Analysis
(Agrilus anxius)

The birch borer is the larva of an olive brown beetle about ½ inch long. For about six weeks in summer, adult beetles lay eggs in bark crevices, usually around a wound. The larvae that hatch from these eggs are white and have flat heads. They bore into the wood just beneath the bark. The feeding and tunneling of the larvae stop the flow of water by cutting the conducting vessels; branch and twig dieback result. If the tree is healthy, sap flow acts as a defense against borers; when the insect burrows into the wood, tree sap fills the hole and drowns the insect. Factors that weaken the tree such as poor growing conditions, transplanting, and mechanical injuries make it more attractive to female beetles.

Solution
Cut out and destroy all dead and dying branches. Severely infested young trees should be removed. In spring, spray or paint the trunk and branches with an insecticide containing lindane to kill young larvae before they burrow into the wood. Repeat 3 more times at intervals of 2 weeks. Maintain tree vigor by watering and fertilizing regularly. European white birch and cutleaf ornamental varieties are most susceptible. If possible, plant native species such as paper birch or river birch.

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