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Pine wilt. Causal Agent

The nematode Bursaphelenchus xylophilus  



The most common hosts in Oklahoma are Scotch, Austrian, and Japanese Black Pines, although other pines can become disease. The disease is more common in the eastern half of Oklahoma.



/programs/digital-diagnostics/plant-diseases/site-files/pine-wilt-or-pine-wood-nematode/pinewilt1.jpgPine wilt on tree. Pine wilt is a lethal disease of pines that can suddenly appear in pines that are usually at least 15 years old, although occasionally in trees as young as 7 years. Pine wilt is most common in the fall when the needles of the entire tree begin to turn light green or brown. Within 1-3 months, the trees are usually dead and brittle. 


The disease is spread by the pine sawyer beetle, genus Monochamus, which lays eggs in the dying or dead tree. When the adult beetles emerge from the pine in the spring, they carry the nematode that causes pine wilt to healthy pines. As the beetle feeds, nematodes are deposited in the plant, which causes pine wilt to develop in the pine tree.


The symptoms of pine wilt closely resemble damage caused by environmental factors, primarily drought stress. It is important to sample trees and have them tested for pine wood nematodes to confirm that pine wilt was the cause of death. Branches near the trunk that measure at least 1 inch in diameter should be sampled. Contact your local county extension office about submitting samples for testing. 



Examples of pine wilt damage on trees. Preventative injections of insecticides are available, but they are expensive and can only be applied by certified applicators. The insecticides are expensive and they are not 100% effective. There is no cure for a tree once it is infected with the nematodes. Prevent spread to nearby trees by removing the diseased tree. If able to do so, burn the wood to reduce the chance of disease spread to nearby trees. Stumps should be ground down and buried under 6 inches of soil. Please contact your local county extension office for current information.

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