Gage County
1115 West Scott St.
Beatrice NE 68310
Phone: (402) 223-1384
FAX: (402) 223-1370

News Column

Paul C Hay, Extension Educator

SCOTCH PINE UNDER ATTACK

Pine wilt disease was first identified in the United States in 1979 in Columbia, Missouri. The symptoms of pine wilt disease usually appear from August through December. The trees can wilt and die quite rapidly, or in some cases survive for a year in a very sick condition. Pine wilt disease has been identified in Scotch or Scots pine, Austrian Pine, White Pine, and Ponderosa Pine. Scotch pine are the most susceptible and the pine wilt could potentially do to Scots pine what Dutch elm disease has done to the American Elm, the former Nebraska State tree.

Pine sawyers are wood borers which lay eggs on pine trees and then bore into the tree to feed. The pine sawyer does some damage to the pine, but is not a major pest and we would rarely recommend any treatment for the insect. Pine sawyers tend to be more active in trees stressed by drought, root injuries, age, diseases insects, etc. Pine wilt disease is caused by the pinewood nematode which is carried from tree to tree by the sawyer beetles. The pinewood nematode enters the tree through feeding wounds of the sawyer beetle. The microscopic wormlike nematodes multiply and reproduce into tremendous numbers. As populations buildup they block the resin canals which blocks the flow of water and nutrients to the tree.

Pine trees just like other plants and animals needs water for cooling. Plants use most of the take up for transpiration, to keep the plant cool. Once the vascular system is partially or fully blocked by the pinewood nematodes, death is almost a certainty. The pinewood nematode will feed for several months on the dead tree and on fungi which begin the decay process. The sawyer beetles active at this time will have the nematode crawl under their wing cover and fly them to a new victim.

By promptly identifying the problem, then cutting and removing the tree you can reduce the chance the nematodes will infest other trees in the area. This will at least slow down the progression of the disease. The wood of Scotch pine killed by the pinewood nematodes will have purple stains in the wood. Samples of this wood can be tested for conformation of pine wilt disease. Submit a three inch slab of the main stem to the University of Nebraska Plant Diagnostic Lab, 406 Plant Sciences, Lincoln, Nebraska 68583. Enclose a check for $10 and make sure the sample arrives at the lab as quickly as possible. Cutting and mailing on Monday through Wednesday is best.

One of the biggest uses of Scots Pine is in Christmas tree production. This may not be a problem, as the sawyer beetles rarely bother trees for the first six to seven years. It may mean that Christmas tree producers will be wise to sell trees before they get too old, fertilize for quicker growth, and cut remaining culls for wreaths. I would recommend that Scots pine not be used in windbreak or landscape plantings in Southeast Nebraska. Will the disease get to Halsey National Forest and kill trees that haven't burned, it's likely, but time will tell.

View other Gage County News Columns & News Letters: http://gage.unl.edu/news/news.htm

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