Swiss Needle Cast

The 1998 Forest Health Note released by the Oregon Department of Forestry concerning Swiss Needle Cast was most interesting. The report covered the disease's known history, cycle, distribution and effects and some suggestions to combat it. There seems to be evidence of genetic tolerance. The spread of the disease does, also, seem to be greater in the Northwest coastal mountains of Oregon than any place else. The disease is endemic and has coexisted with Douglas Fir (Pseudotsuga taxifolia) since before it was first noticed in the early part of this century. The current increase of the disease apparently can be traced to the use of seed stock gathered from outside of the infected topographic area and at a differing altitude.

The original aerial survey of 1996 showed some 130,000 acres of Douglas Fir to have the typical discoloration of the disease (Phaeocryptous gaeumannii). A follow-up ground survey revealed a greater area of infected trees not visible from the air. The 1997 aerial survey showed a three fold increase of infected Douglas Fir showing the symptoms had spread to nearly 400,000 acres. And the range now extends at least twenty-four miles in from the coast.

The report puts forth the hypothesis that the forest management practices and a shift to a wetter climate are responsible for the current epidemic. The current practices mentioned are those of the single tree plantations that presently exist across the nation not just in the Pacific Northwest. I personally do not believe that the weather is as much to blame as we think. And that the use of seed stock from outside of the local area is more of the problem than has been explored.

What this disease means to the public at large is higher prices for timber products. The predictions of timber growth in the area of greatest infestation shows a 22% decrease in growth volume. That is to date and if (while) the disease continues, the decline of a marketable product will increase. Since Douglas Fir is planted and grown in plantations of hundreds of thousands of acres precisely for its fast growth and true straight grained wood, one can see why the single tree plantation is both desirable and the root of the problem.

There was one revelation in this year's report. It was the repeated concession in dealing with the "problem". Put quite simply it is "plant something else" or at least reduce and spread out the population of Douglas Fir that is planted. The natural order in the coastal range was Spruce, Cedar, Hemlock and then Douglas Fir considered both in dominance and numbers. But, again because of the properties of fast growth and true straight grained wood, the subsequent plantings have favored the huge plantations of Douglas Fir. This of course is the real base problem and, as listed in the report, the best single way to solve the problem is to reduce the number of Douglas Fir.

A complete copy of the report can be obtained from Dr. Greg Filip at Oregon State University 541-737-6567. Or go to the original Swiss Needle Cast story and click on the Oregon State University link.

Michael Sherer