A Survey of Dwarfmistletoe of Ponderosa Pine in South-Central Oregon

Abstract A survey of ponderosa pine dwarfmistletoe was made on 49,000 acres in south central Oregon. Data on dwarfmistletoe infection were collected during the course of a survey designed primarily to determine stand volumes. The main objective was to determine the location and intensity of dwarfmistletoe infection and the volume infected. The survey data were acquired by means of a wedge prism at a series of point samples in each timber type and analyzed by machine methods. Timber-type maps were developed showing the location and intensity of dwarfmistletoe infection. The timber types on approximately 71 percent of the land area essentially were free from dwarf-mistletoe. The timber types on over half of the 29 percent had less than 20 percent of their cubic volume infected. For the unit as a whole, 8 percent of the cubic volume of ponderosa pine larger than 6 inches d.b.h. was infected. By present standards, 46 percent of the infected trees and 12.4 percent of the infected cubic volume are unmerchantable. This plus the increased prevalence of dwarfmistletoe in all-aged timber types presents special problems in silvicultural control.