PROTECTION OF DOUGLAS-FIR FOLIAGE FROM WESTERN SPRUCE BUDWORM (LEPIDOPTERA: TORTRICIDAE) DAMAGE BY EARLY APPLICATIONS OF ACEPHATE (ORTHENE 75S)

Abstract

Acephate (Orthene 75S) was applied to Douglas-fir (Pseudotsuga menziesii Mirbl. [Franco]) in spring 1976 to determine its efficacy for protecting current year’s foliage from western spruce budworm (Choristoneura occidentalis Freeman). Results showed budworm mortality for both treatments exceeded the checks by at least 91% at all sample periods. A significant degree of foliage protection was also achieved as measured by mean twig length and mean number of missing needles per twig. Samples of new growth were analyzed for residues of acephate and methamidophos (an active metabolite of acephate) by gas-liquid chromatography. Results showed that high levels of insecticide persisted for about 10 days, then dropped over a 5-day period to lower levels for the rest of the study, about 35 days.