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

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Platypus spp. and Xyleborus spp.

Importance. -- These ambrosia beetles are best known for their damage to fresh-cut logs and unseasoned lumber. They also readily attack weakened, stressed, and dying trees and healthy trees with bark injuries. Damage is largely in the form of degrade.

Identifying the Insect. -- Adult beetles are black to brown; .1 to .2 inch (3 to 6 mm); elongate and cylindrical with a wide head in Platypus and cylindrically compact in Xyleborus species. Larvae are white, slightly curved to curculiform, legless, and .1 to .2 inch (3 to 6 mm) long.

Identifying the Injury (figure 26a). -- White to light brown boring dust in small piles in bark crevices is good evidence of attack. Numerous round holes about .1 inch or less (1.5 to 3mm) in diameter give entry to branched or unbranched tunnels which are stained black and extend into the wood. The lower trunk may sustain hundreds of attacks (figure 26b).

Biology. -- The beetles are attracted to wood with a moisture content above 48 percent. They do not feed on the wood, but instead feed upon ambrosia fungi which they culture within the galleries. In the Gulf States, beetles are active most of the year. There are two or more generations per year.

Control. -- Maintain tree vigor. Salvage infested timber immediately. Promptly use logs during summer months. Store logs under water or water spray. Green lumber is often kiln dried or chemically dipped to prevent attack.


Figure 26a
Figure 26b
Figure 26. -- (a) Pin-hole borer attacks indicated by frass on bark; (b) numerous holes made in wood by pin-hole borers.
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