Pine wilt is a disease caused by the pinewood nematode, Bursaphelenchus xylophilus. This nematode is spread by the pine sawyer beetle. By itself, the beetle does little damage to a tree beyond some minor stress, but it is the primary vector of this nematode, which enters the trachea of the insect at larval stage and is spread during feeding after the insect spreads to other trees as an adult. This disease is established in Eastern Kansas but has yet to establish in most of Western Kansas at this point.
Pine wilt disease usually kills pine trees relatively quickly, within a few weeks to a few months. Mature pine trees (10+ years old) are more susceptible than young ones. Because of this, it is not a serious threat to Christmas tree farms. However, this makes it a prime threat to windbreaks as pine trees are frequently used as windbreaks across the state.
How do I recognize it?
Symptoms include color change in needles from green to grayish green, then to brown. If you remove a limb, it is usually characterized by a lack of resin, as the nematodes multiply and clog up the xylem which stops resin flow. Needles do not drop immediately but may stay on a dead tree’s branches up to a year.
What to do if I find it?
To prevent the spread of pine wilt, it is imperative to remove dead pines promptly. They must be burned, buried, or chipped, as they may harbor insects and promote spread of the nematode. Do not use the wood for firewood, as the insects may still emerge from firewood logs. When planting evergreens, select resistant trees, such as white pine, spruces, firs, and junipers. Susceptible pines include Scots pine, Austrian pine, Mugo pine, jack pine, and red pine. No effective nematicides exist at this time.
If you suspect a pine tree of having pine wilt, a sample of wood is necessary. Take a disk of wood or branch at least 1 inch thick and 3 to 4 inches wide and submit it to the Kansas State University Plant Disease Diagnostic Lab in Manhattan, Kansas. If a pine tree dies it is important to know whether pine wilt was the cause, as it is important to dispose of the tree properly to avoid spread of the nematode.


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