DEFOLIATOR SITUATION IN THE FIR STANDS OF EASTERN OREGON AND WASHINGTON
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Buckhorn, W. J. 1948. Defoliator situation in the fir stands of eastern Oregon and Washington.
Abstract: Early in the spring of 1947, control of a tussock moth outbreak on the Umatilla National Forest near Troy, Oregon was being considered. Since the outbreak had been discovered but not delineated in the fall of 1946, information was needed about its extent and intensity. The only feasible way to obtain that information in time to consider a control project was to make an aerial survey. A survey was completed on March 24 and 25, 1948 by the author and District Ranger W. W. Ward. Delineation of the infested area was difficult because of problems distinguishing defoliated fir from dormant western larch. The principal infestation area was mapped from the air and then checked from the ground later in the season. A control project was completed on 14,000 acres of heavily-infested, economically-valuable timber. Some 41,000 acres were not treated due to unmerchantability or a light infestation of tussock moth. The treated area was sprayed as a portion of the north Idaho control project with a C-47 airplane carrying 1000 gallons of spray per trip and operating out of Moscow, Idaho, located 65 miles from the project area. The spray was a solution of DDT in fuel oil applied at the rate of one pound of insecticide in one gallon of diluent per acre. The results were "phenomal" with practically 100 percent control resulting. On the unsprayed areas in the Umatilla NF, a polyhedral virus disease appeared near the end of the feeding period and caused widespread mortality of the larvae and pupae. In some instances, as on four small areas to the north and east of Troy, the virus in combination with natural predators virtually wiped out the tussock moth population. Later in the season, the tussock moth infestation developed to a greater extent than anticipated in untreated stands, and in other localities such as one eight miles south of the project area near Promise, Oregon. Other reports came in regarding tussock moth defoliation that ultimately turned out to be western spruce budworm defoliation. In order to help sort out this confusing situation, it was finally decided to make an aerial survey of the 7,755,000 timbered acres of the Blue Mountain region, and to make supplementary ground surveys in the Blue Mountains and elsewhere. This turned out to be the first aerial survey conducted in Region 6 to determine the extent and severity of insect damage. An aerial survey has been conducted every year since then. This report, which describes the results of that first-ever aerial survey, contains the following sections: introduction; Douglas-fir tussock moth (history, situation by forests); spruce budworm (history, situation by forests); summary and discussion; recommendations; tables (summary of survey flights, summary of defoliator situation in fir stands of eastern Oregon and Washington – season of 1947); and maps (Blue Mountains, northern Washington, southern Oregon). Not all of the maps were copied, but the color map showing the Blue Mountains situation (tussock moth – sprayed, tussock moth – unsprayed, spruce budworm) was copied although in 8½" x 11" pieces since the original map was larger than letter size. With respect to western spruce budworm, the most severe defoliation anywhere in the region was on parts of the Umatilla NF near Dale in the Meadow Creek-Desolation Creek drainages. Another large area of budworm infestation on that Forest was a 160,000-acre center near Wall Creek, ranging from Swale Creek on the east to the Spray-Heppner highway on the west. A small infestation center near Battle Mountain State Park was causing considerable public attention. On the northern half of the Umatilla NF, the largest center embraced some 67,000 acres near the headwaters of Phillips Creek, Umatilla River, and Willow Creek.

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