Released: March 01, 2006

Scout Now for Pine Diseases

MANHATTAN, Kan. – Pine trees are at risk in the High Plains – as much as anything because most owners don’t know the difference between natural pine behavior and disease symptoms.

Late winter before St. Patrick’s Day can be a good time to learn, however, said Ward Upham, horticulturist with Kansas State University Research and Extension. That’s one of the important times for pine owners to scout for disease symptoms. Plus, it’s just before the beginning of each year’s “calendar” for controlling pine diseases.

“What tree owners need to learn first is that all pine needles turn yellow and eventually drop. But, it’s a natural process only if all of the affected needles are on the inside of the tree, close to the trunk,” Upham said. “That’s where the oldest needles are.

“Natural needle drop isn’t always as simple as it sounds, though. Pines may shed their old needles gradually or all at once. They may do so after those needles have been on the tree from one to three years. It can depend on the variety or even the individual tree.”

Natural needle drop is not at work, however, if needles are yellowing on the tips of branches, Upham warned. Another disease symptom can be needles with discolored spots or bands.

“In that case, the sooner you identify the problem, the better off you’ll be – even if it means taking a sample to the local Extension office and asking for help,” he said. “Some pine problems have very similar symptoms, but no two call for exactly the same treatment.”

Upham said problems for pines in the High Plains include:

* Pine wilt - an always-fatal disease that’s most serious among Scots pines, but may infect Austrians and whites. In fall, trees with pine wilt typically turn yellow-brown with brittle branches. The needles do not drop. The only way to prevent the disease’s spread is to remove the dead tree and chop or burn it by spring. * Dothistroma needle blight - most serious for Austrian and Ponderosa pines, but also can affect Mugos, causing a loss of vigor that over time can kill. First symptoms appear in late summer and can include dark green bands, yellow-tan spots and yellow needle tips, often followed by red bands and brown needle tips. The disease usually affects one- to three-year-old needles in the lower part of the crown. In late winter or early spring, the small black fruiting structures of the blight-causing fungus rupture through the dead needle parts.

* Brown spot – mostly affects Scots pines, but can attack Ponderosas. Symptoms can look much like those for Dothistroma needle blight. A major difference is that the black fruiting structures for brown spot erupt in fall. Even so, the disease-carrying spores disperse the following spring during rainy weather.

* Winter desiccation – any pine dried out by winter conditions. Needles turn yellow and may exhibit bands, but won’t develop black fruiting structures. The damage may be on one side of the tree.

* Sphaeropsis tip blight – most likely in Austrian pines and most severe in older ones, but can affect Mugo, Ponderosa and Scots pines. Black fruiting structures are visible on needles and cones in fall and winter. After that, spring’s new needle shoots won’t elongate properly. They’ll turn yellow or tan, but normally won’t drop. The infection usually starts in the lower part of the crown, but repeated infections can spread upward and kill whole branches or the entire tree.

Upham has more in-depth descriptions of these problems – as well as photos and recommended treatments – on the Web at http://www.oznet.ksu.edu/dp_hfrr/extensn/hortprob.htm  in an alphabetical list of “Common Plant Problems in Kansas.”

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News