A number of other pine species are also susceptible. The first visible symptom is discoloration of needles from green to yellow to brown. These symptoms are accompanied by a marked decrease in resin flow that is apparent when a branch is cut and resin does not flow from the wound. Death of affected trees may occur gradually or very rapidly. Trees infected in the spring ultimately wilt and die by late summer.
Nematodes enter pines through feeding wounds left by the beetles.
They migrate into resin canals where they rapidly multiply. A recently wilted or killed pine can be sampled by removing a piece of sapwood from the trunk or main branches using a hatchet or an increment borer. The part of affected branches -inch or more in diameter closest to the trunk also makes a good sample. It is best to submit several samples from various portions of the tree. Put the wood samples in a plastic bag and take them to your county Extension office.