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Archive for Saturday, January 22, 2011

Garden Calendar: Protecting your trees against pine wilt

Pine wilt is the disease that is killing many of the Scotch and Austrian pines in our area, completely unrelated to the problems in the western part of the U.S. There's a new product out for control that is pretty ineffective.

Pine wilt is the disease that is killing many of the Scotch and Austrian pines in our area, completely unrelated to the problems in the western part of the U.S. There's a new product out for control that is pretty ineffective.

January 22, 2011

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Pine wilt is the disease that is killing many of the Scotch and Austrian pines in our area, completely unrelated to the problems in the western part of the U.S. There's a new product out for control that is pretty ineffective.

Pine wilt is the disease that is killing many of the Scotch and Austrian pines in our area, completely unrelated to the problems in the western part of the U.S. There's a new product out for control that is pretty ineffective.

One of my most exciting experiences as a County Extension Agent was the day a pine sawyer beetle emerged from a Scotch pine log in my office.

The pine sawyer beetle is unrelated to the mountain pine bark beetle that is causing problems in the western United States. Pine sawyer beetles are, however, partially responsible for much of the pine death in the Midwest.

Capturing the pine sawyer was exciting because the beetles are otherwise rarely seen. Pine sawyer beetles spend much of their life as larvae feeding deep in the wood of standing pine trees. They emerge only to mate, feed and lay eggs to continue the cycle.

Pine sawyer beetles also allow pinewood nematodes to hitchhike in their tracheas when they fly to new trees. Pinewood nematodes are the guys you really have to worry about. When pinewood nematodes get into the sapwood of the right kind of pine, they reproduce rapidly and can kill the tree in a few short months.

Although even I find it hard to imagine how worm-like organisms only one millimeter in length could kill a majestic old pine, it is true.

If you have a dead pine tree on your property, cut it down. Get rid of the beetle and nematode-infested wood by burning, burying or chipping it. Get rid of the wood by the beginning of March to lessen the spread of pine wilt. Dead pines are likely full of nematodes and pine sawyer beetles that will emerge this spring and carry the disease on to more trees.

Mulch made from infected pines is considered safe to use because pine sawyer beetles do not feed on the mulch and are typically destroyed in the mulching process.

A few years ago, a few products containing the active ingredient abamectin were labeled for preventative treatment of pine wilt. The products must be injected into the tree by a licensed applicator on an annual basis, are pricey, and offer no guarantees.

More recently, a product known as Organic Disease Control or ODC has been advertised for control of pine problems. Most importantly, this product is promoted for control of the mountain pine bark beetle rather than the pine sawyer beetle that is a problem in this area. Also, according to Kansas State University entomologist Raymond Cloyd, there is no quantitative scientific information supporting the claims of the ODC product.

Although Scotch pine are the most likely to die from pine wilt, the disease also kills Austrian pines and the nematodes have been identified in other pine species. Austrian pine also has problems with fungi that attack its needles and shoots.

Many resources on pine wilt suggest that native pine species are usually resistant. Since Kansas is the only one of the 48 contiguous states without a native pine, our options are limited. White pine and limber pine (commonly sold as “Vanderwolf”) show resistance but still may suffer some stress from Kansas weather and soil.

My suggestion if you really want an evergreen is to use eastern redcedar or upright juniper varieties. Baldcypress is a disease-free tree with a pine-ish look that drops its needles in the winter. Some large shrubs, including several species of viburnums are also suitable for windbreaks and screens. A few varieties of viburnums hold their leaves over the winter as well.

In case you are wondering, I burned my nematode-infested pine log. I really only wanted it because it also had a canker. The pine sawyer beetle is safely preserved for show-and-tell.

— Jennifer Smith is the Horticulture Extension Agent for K-State Research and Extension in Douglas County. She can be reached at 843-7058.

Comments

LogicMan 4 years ago

"without a native pine"

They are not native, so nature is solving the infestation problem.

All you hairless apes aren't native either, so watch out for Mother Nature!

Paul Decelles 4 years ago

Jennifer, that is an impressive looking beetle based on the images I've seen of it. Not as big as that borer found in willow but I can see why you were excited!

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