Remove dead trees to prevent pine wilt’s spread
April 15, 2009
LINCOLN, Neb. – Trees dead from pine wilt should be removed soon to prevent the disease from spreading to nearby trees, says a Nebraska Forest Service expert. Because trees infected with pine wilt die from the disease, it is important to take steps to prevent its spread.
“Removing dead trees is one of the best ways we have of preventing pine wilt’s spread,” said Laurie Stepanek, Nebraska Forest Service forest health assistant.
Pine wilt is caused by a microscopic, worm-like organism called the pinewood nematode. These nematodes live in pines and are carried from tree to tree by insects called pine sawyer beetles. Once inside the tree, the nematode disrupts the flow of sap, causing the tree to turn brown and die.
The pine sawyer beetle is active from May through September. If trees dying of pine wilt are discovered during the fall and winter, the deadline for safely removing and destroying them is the end of April.
Trees that die while the beetle is active should be removed within a month of the tree’s death to prevent the beetles from re-emerging and spreading the disease to new trees.
Once removed, trees should be disposed of by chipping, burning or burying to ensure beetles in the wood are killed. Chipped trees can safely be used as mulch in gardens or around trees, even pines. Because mulch resting against a tree’s trunk can trap moisture and lead to decay and diseases, mulch should be kept several inches away from the trunk.
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Additionally, research shows a slight risk of pine wilt spreading through infected mulch that comes in contact with trunk wounds on Scotch pine. Keeping the mulch away from the tree’s trunk can help prevent this.
Approximately 95 percent of the pines killed are Scotch pines, but Austrian pines occasionally are killed from the disease as well. While trees stressed by drought are slightly more susceptible to pine wilt, it easily can kill healthy trees, Stepanek said.
Ponderosa pine, eastern white pine, and spruce, fir, and juniper are resistant to pine wilt.
Pine wilt is very common in southeast Nebraska and is spreading to the west and north. The leading edge along which many trees are beginning to die extends from Holdrege in the west and Norfolk in the north. Outside Nebraska pine wilt is a problem in Iowa, Kansas, Missouri and Illinois.
More information about pine wilt is available on the Nebraska Forest Service’s Web site at http://www.nfs.unl.edu.