By ROBERT PIERCE
• Leader & Times
First identified in the United States in 1979 in Columbia, Mo., pine wilt disease made its way to southeast Kansas that same year, and recently, officials with K-State Research and Extension identified six cases of the ailment in the local area.
Seward County agent Mike Hanson said two of the trees were in Beaver County, Okla., near the Ponderosa, and the remaining were found in Liberal.
Hanson said he visited Kismet this week, and he believes there may be some cases of pine wilt in that community.
“So far, it’s been found in Meade, Pratt and Seward County this year,” he said. “It’d never been seen in Meade and Seward County before this year.”
Hanson said he has taken many samples. He said a lot of trees have environmental stress, and the tests were taken simply to make sure which trees had pine wilt.
“We have found some negative samples that we’ve got to resubmit because two weeks ago, they looked a lot better than they do now,” he said. “We’re thinking it that maybe it would’ve been a false negative sample. We’re just going to make sure we’ve got the correct diagnosis on that.”
Pine wilt is caused by a pine wood nematode from the Sawyer beetle. Hanson said the beetles carry as many as 80,000 of the nematodes in their throats.
“While its eating on the tree, those nematodes get into the tree, and it basically cuts off the resin flow in the pine tree,” he said. “It’ll kill the tree. There’s no stopping it.”
Hanson said a healthy tree will not acquire pine wilt as easily as one that is stressed.
“Making sure you have plenty of water and nutrients to your tree will help,” he said. “As far as any chemical control taking care of that, there’s nothing that’s 100 percent effective. They’ve got a treatment that cost between $100 and $150 per tree that they say is about 60 to 65 percent effective that needs to be done every year.”
Hanson said as soon as a confirmed diagnosis is made of the tree, experts can let the residents or owners of the property know about it. He said if there is pine wilt in a tree, the tree needs to be destroyed before April 1.
“That’s when you start seeing the Sawyer beetles come out of dormancy,” he said. “They say you can find in a tree 200 to 300 of those Sawyer beetles. You need to make sure you get it before they come out of dormancy.”
Hanson advised homeowners to fertilize their trees as well as their lawns. He said pine wilt only affects non-native pine trees to the U.S.
“Some of them that we’re seeing it in are the Austrian,” he said. “Scots and Mugo also get it, but Ponderosa and Pinyon pines are maybe a good replacement around here for those. It can take care of a tree pretty quick.”
In general, when pine wilt occurs, trees wilt and die rapidly within a short period of time.
“Occasionally, trees may survive for more than one year,” Hanson said. “The needles turn yellow/brown and remain attached to the tree. The early stages of the disease are subtle and may vary. The pinewood nematode is transmitted from pine to pine by a bark beetle, the pine sawyer.”
Hanson said three to four weeks following infestation by the Sawyer beetles, transpiration of foliage decreases and resin production is reduced.
“Needles initially show a light grayish-green discoloration, then turn yellow and brown,” he said. “The disease may progress uniformly through a tree or branch by branch, depending upon the size of the tree and the environmental conditions during the growing season.”
Hanson said needles remain attached for up to six to 12 months after the tree has died.
“The rapid death of a tree contrasts with other pine problems such as fungal diseases, insects or environmental stresses,” he said.
In addition to rapid wilting and yellowing of the foliage, another important symptom is reduced resin production.
“When branches of a healthy tree are cut, a thick, sticky resin will be produced at the site of the wound; on a diseased tree, resin may be absent,” Hanson said.
Branches and twigs become brittle and dry and will break easily. Trees yellow from winter burn may appear similar but will have flexible branches and good resin production.
Hanson said if someone suspects they have pine wilt, they need to call the Extension office. That number is 624-5604. If a new tree is desired, he recommends planting non-susceptible varieties.
Southwest Kansas and the Oklahoma Panhandle have a drier climate than many regions, and Hanson said this causes a higher level of stress in trees, which in turn leads to the higher likelihood of pine wilt.
“It just keeps moving west,” he said. “There’s been big areas over in Eastern Kansas taken down by pine wilt. We probably won’t have that big of problem because we don’t have that many pine trees out here. We don’t want it to continue to move westward, so that’s why we want to get those trees destroyed.”