By Jesse Lee
What does it look like?
Photo by L.D. Dwinell, USDA Forest ServicePine wilt nematode, also called pinewood nematode (Bursaphelenchus xylophilus), is a microscopic pest with a worm-like appearance. The male pine wilt nematode features a distinctive, stirrup-like spicule.
Host material and range
Pine wilt nematode attacks a range of pine trees throughout the United States, and most commonly affects Scots pine (Pinus sylvestris). The pest is thought to be native to the United States.
Pine wilt nematode is spread from tree to tree by the pine sawyer beetle or longhorned beetle (Monochamus carolinensis). The nematode attaches itself to the adult beetles shortly after the beetles hatch from their pupal stage deep within the pine wood.
The beetles then emerge and fly off to find other healthy pines on which to feed, often miles away, and carry with them up to tens of thousands of the pine wilt nematodes.
The nematode feeds on the cells that line the resin canals of the pine, cutting off the flow of resin and disabling the tree from moving water throughout. This leads to pine wilt, in which the needles turn from green to brown, resin flow completely stops and branches begin to die, eventually killing the entire tree.
Trees infested with the nematode and affected by pine wilt can die off very quickly, often in as little as three weeks. The disease and pest are widespread, affecting stands of trees from landscapes to Christmas tree farms.
Healthy, resistant stands of pine trees can survive a pine wilt nematode infestation; the pest simply can’t take hold and dies before any lasting damage is done. Planting resistant pines instead of Scots pines and other susceptible trees can help prevent infestation.
To prevent spread of the disease after a tree has been affected, the dead trees should be removed and destroyed prior to mid-summer when the sawyer beetles emerge and begin to spread the nematode.
Treating pines with a fertilizer application can increase vigor to help fight off or withstand infestation, but once a tree is infested, there are few options for treatment.
Micro-infusion applications of abamectin have been found to prevent nematode infestation, while treatment with Metasystox-R is effective for control of the beetles. Trees that have been killed by the disease should be removed.
What can you do?
Plant resistant pines instead of Scots or Austrian pine; maintain vigorous, healthy trees through fertilization; and inspect pines, especially recently dead or dying trees, for signs of pine wilt, pine wilt nematode and sawyer beetles.
Jesse Lee is with Epic Creative, Wis. Article provided by Mauget, a leader in micro-injection and micro-infusion tree care. Contact Mauget or visit www.Mauget.com to learn more about the pine wilt nematode and pine wilt disease, steps taken to prevent and control it, and proper pesticide application and use.