Pine trees are a beautiful and practical addition to any yard, farm or community, but they are now under attack by pine wilt disease, said Hays-based Lauren Walz, Cottonwood Extension District horticulture agent.

“This summer pines have struggled to stay alive because the area has gone from one extreme (rain) to another (hot temps),” she said. “Now to add to that mix, I am starting to see a lot of pine trees fall to pine wilt.”

This is not new to western Kansas; it merely went dormant over the last several years and hasn’t been seen as often. In 2010 and 2011, an onslaught of pine wilt decimated trees in Great Bend and across the state.

Now, “I’m getting a lot of calls,” Walz said. “I’ve been making a lot of home visits.”

What is pine wilt?

“Pine wilt is a very serious disease,” Walz said. It is considered to be a problem in Scots pine trees in landscape settings, windbreaks, Christmas tree farms, and recreational plantings. Pine wilt has also been reported on Austrian and white pines. 

In Kansas, the symptoms for pine wilt usually appear from August through December. In general, the trees wilt and die rapidly within a short period of time, but occasionally, trees may survive for more than one year. 

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 (a tiny worm) is transmitted from pine to pine by the pine sawyer beetle, she said. The bugs bore into the tree, killing it.

Needles initially show a light grayish-green discoloration, then turn yellow and brown.

“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,” Walz said. The 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.

How to fight it

“Once a tree shows signs of pine wilt, it can’t be saved,” Walz said. Any treatments would be preventative on non-infected trees.

There is one option to potentially save unaffected Scots, Austrian, and white pine trees from pine wilt, she said. According to the Colorado Extension, two compounds are labeled for the prevention of pine wilt. 

These products are directed toward killing/immobilizing the nematode and not for killing the pine sawyer beetle.

Several commercial injection systems are available, but pine injections are almost always done by professional arborists, Walz said. Yearly injections provide the greatest protection, but the cost and potential damage associated with the injection process are issues to consider. 

“These can be quite expensive,” she said. It is up to the tree owners to decide how much they are willing to spend.

It is important to confirm the presence of the pinewood nematode if pine wilt is suspected to be the cause of a tree death. Early confirmation will allow the owner to act quickly to prevent the spread of the nematode to nearby pine trees.

In established pine plantings, the only control measure is to remove affected trees and burn, bury or chip the wood before April 1. Trees should be removed to ground level and no stumps should be left. This prevents further spread of the nematode and its host beetle before they emerge from the trees in the spring.

“It definitely works,” said Jeremy Elliott of myLawn! Turf & Tree in Great Bend, who is certified to administer the injections. “It is definitely a good option.”

But, it is pricey, he said, with the cost depending on the diameter of the tree. And, it takes time with each tree requiring multiple injections, and the fast-flowing resin in the trees can clog and ruin injector needles.

“Prevention is better,” Elliott said. He outlined precautions folks can take to help mitigate the chances of infection.

The sawyer beetles that carry the nematodes are attracted to dying wood, he said. “It is critical to keep all deadwood out of pine trees.”  

“Also, it is extremely important to water the trees in the winter,” he said.  

It may not be pine wilt

“There are several other pine tree issues,” Walz said. “We just don’t want people to go cut down their trees because they become discolored.”

There are two blights making the rounds in pine circles:

• Tip blight. This impacts new growth and shows up on the “candles” on branch tips.

• Needle blight. This shows up on the previous year’s growth.

There can be red bands on the needles and a yellowish color to the tree, but it will not turn brown as it does with pine wilt.

“But, it needs to be diagnosed by a professional,” Walz said. It can be hard for an untrained eye to distinguish the difference.

Elliott noted these blights are basically fungus. Just like removing deadwood and maintaining watering, treating for these conditions must be part of preventative care.

“Taking care of the your trees is so important,” Elloitt said.

He said that a tree owner can take a sample of a tree in to have it tested. It needs to be a branch about 6 to 8 inches long, about as big around as your wrist and have been attached at the tree’s trunk.

That can be taken to the Extension Service office. It will be sent to Kansas State University for testing and the results will be emailed to the tree owner.