Tree board says now is the time to take action to reduce the threat of pine wilt disease

Stephen and Mary Kay Humber first noticed some branches of their 25-foot Scotch pine turning brown a few years ago.

Last year, during some routine pruning of the trees around their house on North Wilson Street, the pine was diagnosed with a beetle infestation.

By that point, it was far too late to save the tree, which dominates the corner of Wilson and First streets. This spring it is clearly dead and awaits removal.

The Humbers don?t know yet if the Scotch (also called Scots) pine on the other side of their front yard has been infected as well.

?It?s been a sad thing,? Mary Kay said.

Sad, but not uncommon.

Sharon Boese, chair of the Hillsboro Tree Board, estimates at least 50 Scotch pines have been removed within the city limits over the past few years because of a condition called ?pine wilt.?

An invasive disease in Kansas, pine wilt is gradually heading westward into areas it has not been known to occur, killing hundreds of trees in its wake.

To prevent the further loss of pine trees locally, the Hillsboro Tree Board is urging homeowners with affected Scotch pines to take action before May 1.

?You don?t see evidence of it, but it is spread by the sawyer beetle,? Boese said. ?To break that cycle, between April 1 and May 1, the (infected) tree needs to be removed.

?That means burned or chipped,? she added. ?You cannot store it for firewood because (the beetles) will stay in there and keep harvesting.?

Technically, the actual killer is a microscopic worm commonly called the pinewood nematode. The pine sawyer beetle spreads the nematode from tree to tree.

The only remedy against the disease is a radical one.

?If your pine is turning brown, cut it out?May 1 at the latest,? Boese said. ?If you cut it down, don?t leave a stump. I mean, cut it down to the ground.?

After May 1, the nematodes leave the respiratory system of the adult pine beetle as it feeds, and settle into the wound tissue, where the nematodes feed on resin canals and reproduce rapidly.

Dale Dalke, tree board member, said pine wilt first becomes evident as branches turn brown.

?It could be a branch or two, it could be the whole tree at once,? he said.

Complicating the issue is that brown branches don?t always indicate pine wilt.

?There are other diseases that have some of those same symptoms,? Boese said. ?Pine wilt is the most deadly. If people have question about what it is, you can send your branch into K-State or call the extension office.

?You don?t want to cut (the tree) down if it?s simply tipped light, which you could control,? she added. ?Find out for sure.?

Scotch pines are the most susceptible to pine wilt. It also has been reported in Austrian pines and more rarely on eastern white pines.

To some extent, homeowners can protect their undiseased pine trees from pine wilt.

Chemical applications can decrease the likelihood of pine wilt, Dalke said, but ?they don?t provide 100 percent control.?

In addition, the chemicals tend to be costly for the average homeowner, and need to be applied by a certified arborist.

Stressed trees are most susceptible to pine wilt.

?If you water your trees, especially during dry times in summer, that may help,? Dalke added.

At the same time, overwatering can stress a pine tree, too.

?A pine tree in your lawn that gets a lot of irrigation stresses it,? Boese said. ?They don?t like a lot of water.?

To help inform residents of the situation, the Tree Board has placed information about pine wilt at the Hillsboro Public Library.

Boese and Dalke stress that the time for action is now.

?There is a deadline,? Boese said. ?It?s not like you can say, ?I?ll do it in summer when I have time.??

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