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Description

Adult Description: Like other species of the tribe Xyleborini, the head of Xylosandrus crassiusculus is completely hidden by the pronotum in dorsal view. This beetle gets its name from the granulate surface on the declivity (hind end) which is smooth and shining in other species. Female Xylosandrus crassiusculus are small (2.11-2.9mm long), stout bodied beetles that are a dark reddish-brown when fully mature. Males are much smaller in length measuring only 1.5mm with a distinctive “hunch-backed” appearance from the reduced thorax.

Larvae Description: They are white, legless; “C” shaped and have well-developed head capsules. They are not easily distinguishable from other beetles in the subfamily Scolytinae.

Host Plant: Ornamentals and fruit trees up to 126 plant species; it is able to infest most trees except conifers. Preferred hosts are aspen, beech, cherry, Chinese elm, crape myrtle, white ash, dogwood, golden rain tree, hickory, magnolia, maple, mimosa, oak, peach, persimmon, sweet gum, and redbud, walnut, pecan and Bradford pear.

Ecological Threat

Is able to infest several important crop and ornamental trees. It destroys trees by constant boring into the bark and growing symbiotic fungi in the tunnels. The fungi paired with cankers formed from the tunneling in turn block the flow of nutrients throughout the tree and eventually cause death.

Biology

Ambrosia beetles are boring beetles that excavate tunnels in the bark of trees to grow ectosymbiotic fungi (an ambrosia fungus) to feed off of and in turn reproduce and excrete (frass) within the tunnels. Adults can overwinter with the tunnel galleries but eggs, larvae and pupae are all found together in the tunnel systems that are created by mature females. Initial flight usually occurs when daytime temperatures exceed 70^oF in the spring months. During the summer, the life cycle is 55-60 days long and there are typically 2 generations in the southern United States. Small branches and stems are most often attacked but attacks may occur on healthy, stressed of freshly cut host materials. High humidity is required for successful reproduction. Attacks on living plants are usually near ground level on saplings but can be at bark wounds on larger trees. Males are rare, reduced in size and flightless. Females mate before attacking a new host.

History

First discovered near Charleston, South Carolina in the mid-1970s on peach trees. More populations were found in Florida, Georgia and Alabama in 1983. In the mid-1980s it was found attacking pecan and ornamentals in Texas. In 1992 in Indiana adult beetles were collected and also that same year they were collected off of Weeping Higan Cherry trees in Oregon. The beetle was also found in Virginia that same year.

Native Origin

Tropical Asia

Current Location

U.S. Habitat: Anywhere with higher humidity levels and where the host plants are able to grow.

U.S. Present: AL, AR, CO, FL, GA, HI, IN, KS, KY, LA, MA, MO, MS, NC, OK, OR, TN, TX, VA, WV

Management

Pyrethroids have been found to provide control of attacking adults if applied prior to the closing of the tunnel galleries with frass. Once the beetles are in the tree and have frass packed in the entry holes they are isolated from the outside. If infestations occur, affected plants should be removed and burned and trunks of remaining plants should be treated with an insecticide labeled for this pest or site and kept under observation.

References

Text References

Anderson DM. 1974. First record of Xyleborus semiopacus in the continental United States (Coleoptera: Scolytidae). U.S. Department of Agriculture Cooperative Economic Insect Report 24: 863-864.

Deyrup MA, Atkinson TH. 1987. New distribution records of Scolytidae from Indiana and Florida. Great Lakes Entomologist 20: 67-68.

Mizell RF, Bolques A, Crampton P. 1998. Evaluation of insecticides to control the Asian ambrosia beetle, Xylosandrus crassiusculus. Proceedings of the Southern Nursery Growers Association 43: 162-165.

Internet Sources

http://edis.ifas.ufl.edu/pdffiles/IN/IN28800.pdf

http://www.in.gov/dnr/entomolo/files/ep-GranulateAmbrosiaBeetleFactsheet.pdf

http://entomology.ifas.ufl.edu/creatures/trees/asian_ambrosia_beetle.htm

https://insects.tamu.edu/fieldguide/bimg211.html