Discouraging news for pine tree owners has emerged under the microscopes at Kansas State University and the Kansas Department of Agriculture. Over the last few weeks, their labs have confirmed cases of pine wilt disease in 11 western Kansas counties.
The always-fatal disease first showed up in 1979 in both Missouri and eastern Kansas. Since then, scientists have identified cases from Canada to Mexico. Until now, however, western Kansas has harbored no signs of a true pine wilt invasion, said Jon Appel, State of Kansas plant pathologist.
"From the first, of course, one problem was the possibility that people in a wilt-free area might choose not to use local trees and wood. As part of that, infested nursery stock can be a risk. The apparent trigger at one of our new western sites was infested firewood, brought in from eastern Kansas," said Megan Kennelly, plant pathologist with K-State Research and Extension and its Plant Disease Diagnostic Lab.
Pine wilt symptoms generally appear in late summer to late fall. First, needles turn an "off," gray-green color. Then they brown, but don't fall off. In many cases, the disease progresses so quickly that infected trees are dead within weeks. With late fall infections, however, trees may lose some sections or branches in fall, but wait to collapse the following spring.
The western Kansas counties with newly confirmed cases of the disease are Barber, Finney, Hodgeman, Meade, Osborne, Pawnee, Phillips, Rooks, Rush, Seward and Smith. The state's "front-line" communities now include Beloit, Great Bend, Hays, Medicine Lodge and Pratt.
Each dead pine can host several hundred nesting pine sawyer larvae, Appel warned. In turn, each adult beetle that emerges in spring can carry tens of thousands of the nematodes that actually cause pine wilt.
More about pine wilt in the Midwest is at http://www.ksre.ksu.edu/library/plant2/MF2425.pdf. The bulletin is a cooperative effort of the land-grant universities in Iowa, Kansas, Missouri and Nebraska. The publication is available for purchase by contacting Mandy Wilson at the K-State Research and Extension Bookstore at 785-532-5830.
More information about pine wilt scouting and prevention of its spread will be in the January Kansas Farmer magazine.