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FS ShieldForest Health Protection, Southern Region

PINEWOOD NEMATODE,

caused by Bursaphelenchus xylophilus


Importance. - The importance of the pinewood nematode as a forest disease agent in the United States is unknown. It may be native to our country. In Japan, where the nematode may have been introduced, as many as 20 percent of the trees in some stands have been killed. In this country, the disease has been found more often in shade trees. The disease occurs mostly on species of pine, particularly the nonnative species. It is rare on some other species of conifers.

Identifying the Parasite. - The pinewood nematode can be identified only through microscopic examination of a specimen.

Identifying the Injury. - Affected trees show symptoms of wilting, coupled with a significant reduction in resin flow. Wilted trees will turn from yellow to brown within 3 months after becoming infested.


Virginia pine infested with pinewood nematode

Virginia pine infested with pinewood nematode. (Click for detail. JPG 45K)


Biology. - The nematode is carried from previously colonized dead pine by woodboring beetles in the genus Monochamus. The young adult beetles feed on young tissues of healthy trees and, in the process, inoculate them with nematodes.

Control. - At the present time, no control for nematodes is known in the United States. In Japan, chemical control for the beetles is being tested.