Origin:
This is a native of Asia.
Biology:
There are 4 species of ambrosia beetles in this genus in North America, 3 of which are foreign invaders from Asia. These exotic species, in particular, may attack and damage healthy trees, and the species X. crassiusculus is now found commonly from North Carolina south and west to Florida and Texas. It also has been found in Oregon, Virginia, and Indiana. It appears capable of infesting most kinds of trees and shrubs other than conifers. Typical of “ambrosia” beetles the females bore through the bark of smaller trees or shrubs and into the wood to create a system of galleries, in which they then introduce a fungus which they actually cultivate, and the emerging larvae then feed on this fungus. Within any gallery there may be eggs, larvae, and pupae, all of which are tended by the female beetle. Males are rarely found. While living plants are the normal hosts there have been incidents of logs in lumberyards also infested by the beetles.
Identification:
Entry holes are typically close to the ground on smaller stems, and there may be stringy frass within this hole and symptoms of wilting foliage on the plant. The female adults are less than 3 mm long and are a smooth reddish brown color with few hairs on their wings or thorax. Typical of the bark beetles the head protrudes downward from the prothorax and is hidden from view from above. The antennae are typical of bark beetles with several very small and short segments and a much larger, rounded terminal club.
Characteristicts Important to Control:
Control is only preventive, using residual insecticides applied to the bark of the susceptible plants prior to female entry into that plant, or shortly after when bore holes are noticed but no frass has yet been pushed into the holes to close them. If plants are known to be infested no insecticide applications are known to be effective at killing them inside the wood, and these plants may need to be removed and burned.
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