Effects of Carbaryl, Trichlorfon, and DDT on Collapsing Douglas-Fir Tussock Moth Populations in Oregon

摘要

Carbaryl, trichlorfon, and DDT were tested on collapsing field populations of Douglas-fir tussock moth in eastern Oregon. DDT applied at the rate of 0.75 lb a.i./1.0 gal/acre (340.20 g a.i./3.78 1/0.404 ha) was the most effective treatment in reducing tussock moth (DFTM) populations and preserving tree foliage. Trichlorfon applied at the rate 1.0 lb a.i./5.3 pt/acre (453.59 g a.i./2.51 1/0.404 ha) was not significantly different from DDT in preserving foliage, but was less effective in reducing DFTM populations. Carbaryl applied at the rate of 1.0 lb a.i./0.25 gal/acre (453.59 g a.i./0.95 1/0.404 ha) was not as effective as DDT in preserving foliage and reducing DFTM populations. Differences in volumes of the insecticides applied, droplet sizes, and spray distribution affected their coverage of the study plots and the test results. Virus played a major but unmeasured role in reducing tussock moth populations. Data also indicated that virus-infected larvae survived the insecticide treatments better than healthy larvae.