California Forest Pest Council

Status:  Uncertain, however thought to be native throughout North America

Hosts (in California):  Found in trees or logs of over 30 conifer species including Abies (fir), Pinus (pines), Cedrus (cedars), Larix (larch), Picea (spruce) and Pseudotsuga (Douglas-fir).  Most trees are resistant except when seriously water stressed.  Primarily exists as a problem in landscape plantings.  Main landscape trees impacted are exotic pines including Japanese black (P. thunbergii), Japanese red (P. densiflora), Scots (P. sylvestris) and Austrian (P. nigra) pines.

Management: No major management options exist for pine wood nematode.  Individually infected branches can be trimmed.  Infected landscape trees can be replaced with non-hosts or native species.

Highlights:  Nematodes are microscopic eel-like organisms.  The pine wood nematode lives within the cells of its host plants or within its insect vector.  Insects, primarily longhorn beetles in the genus Monochamus (wood boring long horn beetles), vector the nematodes when they attack dead or dying trees or when feeding or laying eggs on new hosts.  Within the tree the nematodes move first to the resin ducts and then to xylem cells.  Toxins produce cause the cells to break down, fill with air and become unable to conduct fluid resulting in a wilting of living trees.  The pest is also known to spread blue stain fungi into healthy trees. The nematodes reproduce rapidly (the lifecycle can be completed in as little as four days when conditions are best).  Damage to healthy living trees is rare in California and occurs primarily on non-native pines in landscaping settings.  However, the nematodes have become a major pest causing extensive damage when introduced to Japan and other parts of East Asia.