Posted 25 March 2011. PMN Crop News.
Destroy Dead Pines Now
Source: Kansas State University Press Release. www.ag.ksu.edu
Manhattan, Kansas (March 22, 2011)– The only sure way to halt the spread of always-fatal pine wilt disease is to destroy dead pine trees by April – preferably by the first week.
That means removing the trees and immediately chipping or burning their wood. Firewood cut from a pine wilt victim can still serve as a reservoir for the disease’s spread, said Megan Kennelly, plant pathologist with Kansas State University Research and Extension.
The central U.S. pines commonly infected are the Scots and Austrian, although mugo pines occasionally fall victim, Kennelly said. The disease has been in the eastern half of Kansas for decades. Last year, however, confirmed cases extended the state’s "front line" communities to include Beloit, Great Bend, Hays, Medicine Lodge and Pratt.
"This winter, K-State’s diagnostic lab detected cases from even further west," she added. "We’re really hoping they’re isolated -- that appropriate sanitation will prevent further spread."
The disease travels by way of pine sawyers – a type of flying, longhorn beetle. The actual tree killers, however, are microscopic worms known as pinewood nematodes. The beetles and nematodes both overwinter in dead pine wood. They get together when the new beetles emerge from their pupal case and pause to harden. That’s when nematodes can enter the beetles’ breathing chambers in great numbers.
The adult beetles leave their winter home (around May 1 in Kansas) to find a healthy pine host. There, they bore a feeding hole -- which also serves as the entry for their wormy passengers. Once inside, pinewood nematodes are so prolific they often can clog a tree’s water and nutrient flow in a matter of months.
"Usually, the first symptom is off-color, gray-green needles -- wilt. Those needles then turn brown, but don’t fall off. Typically, that happens in late summer or early fall, and the trees is dead within a few weeks or months," Kennelly said.
More information about pine wilt and about diseases that may be affecting pine trees that "look bad, but aren’t dead," she said, is at www.plantpath.k-state.edu/DesktopModules/ViewDocument.aspx?DocumentID=943.