Asian Ambrosia Beetles

Xylosandrus crassiusculus (Motschulsky)

Order Coleoptera:  Family Scolytidae

Description: Adult females are minute (2 to 3 mm), stout bodied, dark reddish brown, and have a hunched-back appearance.  Males are smaller, about 1.5 mm long.  The head of adults is completely hidden when viewed from above.  Larvae are white, legless, C-shaped, and indistinguishable from other scolytids.

Hosts: Entered the United States at Charleston, South Carolina about 1974.  Now known to attack various trees and shrubs, including pecan, peach, plum, cherry, persimmon, oak, elm, sweet gum, magnolia, fig, buckeye, and sweet potato.  It probably will attack other plants on which it has yet to be found. 

Damage: Adults and larvae bore into twigs, branches or small trunks of woody host plants, excavate a system of tunnels in the wood or pith and introduce a symbiotic ambrosial fungus on which they feed.  The boring and introduced fungus damage and clog the xylem, ultimately killing all or part of the plant.  Infestations normally can be identified by toothpick-like spines of boring dust protruding from holes made in the host plant by females excavating their galleries.  The strings or spines of boring dust may be up to 2 to 3 inches long but are fragile and easily broken off by wind or rain.  Unlike other scolytids, which normally attack only stressed or damaged plants, Asian ambrosia beetles attack apparently healthy plants.  Individual plants may host up to 50 beetles.  It is almost impossible to save heavily infested plants.

Life Cycle: They are active year-round during warm periods but most adult activity has been observed in March.  They mate, lay eggs and rear young within the galleries excavated by the females. They breed in host material from 2 to 30 cm in diameter, although smaller branches are most commonly attacked first.  All life stages can be found inside the galleries.  When mature, females leave infested plants and fly to new host plants.  Males do not fly.  There are several generations per year.

Control: Infested plants or plant parts should be removed and burned.  Insecticide applications to the trunks of surrounding plants may help reduce infestations.  Up to four applications of a residual chemical, repeated ever six to eight weeks, may be necessary to stop an infestation.

Asian ambrosia beetle larvae and eggs in gallery
Photo by: Dr. Beverly Sparks,
UGA Extension Entomologist

Asian ambrosia beetle in crape myrtle
Photo by: Dr. Will Hudson,
UGA Extension Entomologist

Asian ambrosia beetle on confederate rose
Photo by: Dr. Will Hudson,
UGA Extension Entomologist