In May or June, adult pine sawyers emerge from pine trees and fly to new trees and feed under the bark of young pine shoots. If the beetle is carrying the pinewood nematode, the tree may become infested with nematodes. As the adults feed on the new hosts, nematodes move from under the beetles' wing covers to the pine and enter the tree through feeding wounds. Once in the tree, nematode populations build up rapidly and block the resin canals. Within 4 to 5 weeks, the nematode has spread throughout the tree and there is a marked reduction in resin flow and transpiration.
Trees start showing initial signs of a wilt condition, including needle discoloration.
Trees infested with the pinewood nematode usually die within 3 months. Larvae develop beneath the bark and within woody tissue of dying trees and recently cut logs. The larvae produce somewhat oval shaped galleries filled with shredded wood. Newly formed adults emerge late in the spring and fly to new trees. After the tree dies, nematodes continue to reproduce for several months while they feed on fungi that invade the dead trees, principally blue stain fungi.