Asian ambrosia beetle, Xylosandrus crassiusculus (Motschulsky) (Coleoptera: Scolytidae), frass tubes produced by Asian ambrosia beetle. Photo by W. O. Ree, Jr.
Common Name: Asian ambrosia beetle
Scientific Name: Xylosandrus crassiusculus (Motschulsky)
Order: Coleoptera
Description: The Asian ambrosia beetle is about 1/16 inch long, stout bodied and reddish brown. The males are much smaller, have a more hunch-backed appearance and are flightless.
Unlike the shothole borer where each individual emerges from a separate hole, Asian ambrosia beetles emerge from the tree via the parental entrance hole. The shothole borer, Scolytus rugulosus (Muller) and the peach tree bark beetle, Phloeotribus liminaris (Harris) also leaves bark appearing as if it had been shot with a shot gun. These beetles attack a wide variety of weakened and dying fruit and ornamental trees. The galleries produced by these beetles are produced just underneath the bark. The shot-hole effect is produced when newly emerged beetles leave the host plant.
Life Cycle: Female beetles excavate galleries deep into the wood of twigs and branches, pushing out strings of boring dust which will resemble tooth picks. These protrusions can be up to an inch in length, often with several hundred on an individual tree. Afterwards, the beetles cultivate an ambrosia fungus which has been carried into the gallery by the adult. Females then lay eggs which hatch into legless larvae that develop through several stages (instars) before pupating. Both the adults and the larvae feed on the fungus rather than the host plant. Female beetles remain with their brood until they mature. Newly emerged adult beetles mate with their offspring before leaving the gallery. Flight activity apparently occurs throughout the year, with higher activity in March.
Habitat and Food Source(s): Mouthparts are for chewing. This beetle attacks 126 plant species including pecan, peach, plum, cherry, persimmon, golden raintree, sweet gum, Shumard oak, Chinese elm, sweet potato and magnolia. Infestations start with a female beetle boring in to a twig, branch or trunk of a host plant. Host material can range from approximately 0.8 inch to 11.8 inches in diameter. This beetle will attack seemingly healthy trees. Attacks generally occur on the trunk of the host plant. Immature stages can be found by splitting open infested twigs and branches. Adults can also be obtained this way, reared from infested wood or trapped using a flight intercept trap – a pane of glass with a trough underneath it baited with ethanol.
Pest Status: A minute beetle that has been attacking pecans and ornamentals in east Texas since the mid 1980’s; medically harmless.
For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.
Literature: Johnson & Lyon 1988; Ree 1994.