Nematodes carried by adult sawyer beetles start the infestation inside pine tree branches through spring feeding activities. After the introduction, the nematodes rapidly reproduce into tremendous numbers, eventually clogging the tree’s vascular system. This disrupts the plant’s water flow and stops branches from producing resin, a substance trees produce in response to injury. By mid-summer, needles will have turned brown and the entire tree eventually becomes brittle and dies. As the tree declines, sawyer beetle pupae inside the declining trees become infected with nematodes. After overwintering inside the tree, the pupae produce nematode infected adults in the spring that spread the disease to new trees.