Flatheaded appletree borer
Chrysobothris femorata (Olivier)
The adult is a short-horned beetle, flattened above, with short antennae and large conspicuous eyes (A). The upper surface of the body is dark metallic brown with slightly patterned wing covers. Underneath the wing covers (as seen in flight), the body is a bright metallic blue. The beetle's undersurface is coppery bronze. The larva (B) is light yellow and has a characteristic enlargement of the thoracic segments (just behind the head), which gives this insect its common name.
Most fruit-growing states and provinces in eastern North America.
Attack apples mainly, but most deciduous tree fruits are susceptible. The larvae dig tunnels along the extent of the trunk. Injured spots are slightly depressed and darker (C). These depressions may split over time and can be enlarged every year by succeeding generations that attack the dead wood on the border of the injured area. The borers will often girdle a small tree, and a single larva can kill the tree.
Flatheaded borers are attracted to diseased or weakened trees and newly transplanted nursery stock. Trees suffering from sunscald are particularly susceptible. An insecticide can be applied to the trunk against egg-laying adults in early to midsummer.
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