SYSTEMIC INSECTICIDE IMPLANTS FOR PROTECTION OF WHITE FIR SCIONWOOD FROM DOUGLAS-FIR TUSSOCK MOTH (LEPIDOPTERA, LYMANTRIIDAE)

White fir, Abies concolor (Gordon & Glendinning) Lindley ex Hildebrand, is an important tree species along the western slope of the Sierra Nevada in California. In 1989 and 1990, the ability of implanted applications of acephate, dimethoate, and carbofuran to protect potential scionwood from damage by the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), was evaluated. Dimethoate was not effective during either the first or the second year, carbofuran was effective only during the second year, and acephate was effective for two successive years after implantation. One application of acephate increased the availability of usable scions from 1 to 99% during the first year of treatment with similar results the year after treatment application.