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Oak Pests - A Guide to Major Insects, Diseases, Air Pollution and Chemical Injury

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Arrhenodes minutus

Importance. -- The oak timberworm is a major cause of defect and degrade in the red and white oaks in the East. Attacks are most commonly associated with wounds on mature trees.

Identifying the Insect (figure 24a). -- Adults are brownish black, brentid weevils about 1 to 1.4 inches (25 to 35 mm) long. The female has a narrow snout, while the male's mouth-parts are broad and flattened. The larvae are white, elongate, cylindrical, and curved (figure 24b).

Identifying the Injury. -- Attacks usually occur at blazes, around other borer entrances, and other wounds that expose the sapwood. White, powdery frass at egg sites on exposed wood is good evidence of infestation. Winding tunnels .1 inch or smaller (0.2 to 3 mm) in diameter, characterize damage in lumber.

Biology. -- During spring and early summer, females chew cylindrical holes into the sapwood and lay single eggs. Eggs hatch in a few days and the larvae bore almost through the tree then "U-turn" back across the grain to the point of origin. Pupation occurs in the gallery, and adults emerge through circular holes near the egg site. The life cycle requires 2 to 3 years.

Control. -- Trees should be protected from wounds and injuries, including other borer attacks to largely prevent infestation by the oak timberworm.

Figure 24a

Figure 24b

Figure 24. -- (a) Oak timberworm adult female; (b) oak timberworm larvae and galleries in wood.
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