Immature beetles develop beneath the bark and within woody tissue of dying trees and recently cut logs. Newly formed adults emerge late in the spring and fly to new trees. If the beetle is carrying the pinewood nematode, the tree may become infested with nematodes as they migrate from the beetle to the water-conducting tissue via feeding and oviposition wounds caused by the beetle. 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 oleoresin flow and transpiration.
Trees start showing initial signs of a wilt condition, including needle discoloration.
Trees infested with the pinewood nematode die within 3 months after becoming infected. 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. As the wood dries, the nematode switches from a reproductive phase to a dispersal phase. Larvae are transported to new trees by the pine sawyer adults, where the disease cycle starts over. In established pine plantings such as landscape settings and Christmas tree farms, the only control measure is to remove affected trees and burn the wood before May 1.