The focus of this NebFact is to describe symptoms, sampling procedures, and disease management. A Fatal Disease of Exotic Pines in the Midwest , EC00-1878 . Symptoms Pine wilt typically kills Scots pine within a few weeks to a few months after the pine sawyer introduces the nematode to the pine. The needles initially turn grayish green, then tan, then brown. Resin flow from the wood ceases as the tree declines and the wood may appear dry when it is cut.
Needles remain on the dead tree for a year or more.
Scattered branches of the crown may be affected initially, but the symptoms soon spread to the remaining branches. The entire tree may turn brown all at once. In the Midwest over 90 percent of the trees killed by pine wilt have been Scots pine. Other pine species are occasionally killed by pine wilt and display a similar pattern of symptoms. As pines age, their susceptibility to pine wilt increases.