Twolined chestnut borer
July 31, 2015
Twolined chestnut borer is primarily a pest of oaks. Adults, found from mid-June through September, are rarely seen. They lay their eggs in bark fissures and cracks around late June or early July. Larvae burrow into the bark and feed in the phloem. Larval development may take up to two years. Emerging adults chew a D-shaped exit hole in the bark. Injury symptoms begin in the upper part of the crown and proceed downward.
Trees exhibit sparse foliage, chlorotic leaves and dieback. D-shaped exit holes (about 1/8 inch in diameter) may be visible in the upper part of the tree. Long, winding galleries packed with frass can be found under the bark in areas where larvae are present.
Stressed trees are much more prone to injury. Help keep trees healthy through proper site selection and watering; protect from construction injury. Once injury occurs, damage may be pruned out if it isn’t too extensive.
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