How to Manage Pests

Pinewood nematode—Bursaphelenchus xylophilus

Pinewood nematodes are tiny eel-like roundworms. They are so small that they cannot be seen without a microscope. To confirm the presence of nematodes, take samples of roots and some surrounding soil to a diagnostic laboratory.

Damage

Pinewood nematodes feed in the vascular tissue of twigs, stems, and trunks. Pines are most seriously affected, but other conifers including cedar, larch, and spruce are also hosts. Pinewood nematodes are spread primarily by juveniles "hitchhiking" on adult roundheaded borers or longhorned beetles. The beetles feed as larvae beneath bark and pupate in wood, then emerge from dead or dying trees as adults contaminated with nematodes. Before laying their eggs in unhealthy trees, adult beetles may fly to other pines to feed on foliage; nematodes can then leave the beetles and infect the new tree. If beetles feed on the foliage of healthy plants, the introduced nematodes may eventually contribute to the decline of that plant as they reproduce within the tree. Branch dieback is the most common symptom in native pines infested with pinewood nematodes. The unhealthy trees in which they are found have typically been damaged by other causes, such as root disease or improper care, and the nematodes may be a secondary invader.

Solutions

No management practices are available except for removal of infested limbs or trees. Replace with nonhost species.

For more information, see the Nematodes Pest Note.

Adult pinewood nematode