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Breaking the pine wilt cycle

 

 

Now you see it:

call-hall-2012-10-09_17-20-05_109

Now you don’t:

Call-Hall-now-gone-2012-10-25_17-20-32_596

This tree had pine wilt disease, and it was cut down and burned to reduce the risk of spread to other trees.

Pines have several disease and insect problems. One of them is pine wilt disease. It kills the entire tree quickly.

Pine wilt is caused by the pinewood nematode, a microscopic worm. The nematode is spread by the pine sawyer beetle. The nematode feeds and multiplies in the tree’s resin canals, causing wilting and death in several weeks to several months. The nematode and beetles spend the winter in the infected tree. In spring, the beetles emerge starting around May 1, carrying nematodes to new trees and continuing the cycle of infection.

The disease is common in the eastern half of the state, and it is spreading west around 10 miles per year. There have been pockets of infection in the western part of the state.

 In Kansas, new pine wilt infections are most visible from August to December. Trees wilt and die in a short period of time, from several weeks to a few months. In the first stages, the needles turn grey or green, then yellow and brown. The discoloration sometimes occurs branch by branch, sometimes all at once. With pine wilt, eventually the whole tree dies, within a few months. The brown needles stay on the tree for up to a year after the tree has died. Another key symptom is reduced resin. On a healthy tree, sticky resin bleeds from the site of a wound. In contrast, if a tree has pine wilt the resin is often reduced or absent, and branches become dry or brittle.

There is a website with color photos and descriptions at the following link:

http://muextension.missouri.edu/explorepdf/miscpubs/mx0858.pdf

There are images to compare and contrast pine wilt with other pine diseases here:

http://www.ksre.ksu.edu/bookstore/pubs/l722.pdf

With the other diseases (tip blight, needle blight) only parts of the tree turn brown. With pine wilt, the whole tree is brown and dead.

If you aren’t sure if your tree has pine wilt or something else, contact your local K-State Research and Extension Office or the K-State Diagnostic Lab (clinic@ksu.edu).

If a tree has pine wilt,  the tree should be cut down by  April 1  to make sure there is time to destroy the wood by May 1, when the beetles start to some out. Cut the tree to the ground—don’t leave a stump. Chip or burn the wood immediately to destroy the beetles and nematodes. Don’t keep pine wood around for firewood.

I’ll post information about some of the other pine problems soon. Are you pining for healthy pines?