What are the symptoms of pine wilt?
The first symptom of pine wilt disease is the discoloration of needles, which turn from yellow to green then to brown. The entire tree eventually turns brown and dies. Diseased trees die in two waves. The first wave spans late fall to early winter.
The second wave starts in early winter and ends in late spring. Discoloration of needles starts from the base and moves to the tip, while small twigs and branches become very brittle.
What species of pine are affected?
This disease affects mostly non-native pines, including Austrian, Japanese black, Japanese red, Scotch and Virginia. Some native pines have also been reported as hosts, but are seldom killed by the disease. Older, weaker trees are more prone to injury and may die within 30-90 days of the onset of symptoms.
What causes pine wilt disease?
Small worms called nematodes multiple in the tree's branches, causing tree decline. As the trees begin to die, they are attacked by insects known as sawyers. These beetles emerge in spring to feed on the developing tree. They attack weakened trees, thus transmitting the harmful pine wilt nematode.
Solutions and Treatments
Trees killed by the pine wilt nematode should be removed and disposed of by chipping, burning or de-barking. It is important to remove diseased trees in the winter or early spring before growth resumes and nematode is spread to healthy trees. Maintain trees in healthy condition by proper watering and fertilizing. Also, when planting pine trees, choose types that are adapted to your area.