This wilt typically kills Scots pine within a few weeks to a few months. Pine sawyer beetles, also known as longhorn beetles, are attracted to the dying trees and the females lay their eggs under the bark. The grub-like larva hatch out and tunnel through the wood of the dying tree. When the beetle larva pupates into an adult and begins to emerge from the tree it is infected with thousands of the nematodes that enter its breathing holes. As the adult beetle flies to a new tree it carries the nematodes with it.
Nematodes enter the new tree through feeding site wounds made by the adult beetle.
The needles of affected trees initially turn grayish green, then tan-colored to brown. Resin flow from the wood also ceases as the tree declines and the needles may remain on the dead tree for a year or more. When Scots pine trees die rapidly, pine wilt should be suspected. To sample for the nematode, cut a piece of wood from the lower trunk or the base of the lower limbs. Place the sample in an air-tight, plastic bag and take it to your local Extension Office.