Aerial Tests of Organophosphate Insecticides Against the Sitka Spruce Weevil, 1983

Abstract

Abstract A 15-year-old, 38 ha Douglas-fir/Sitka spruce plantation within the upper Hoh River valley in western Washington was the test site for aerial spray trials of Orthene and Metasystox-R against the Sitka spruce weevil in 1982 and 1983, respectively. A helicopter equipped with a 15.25-m spray boom with 64 nozzles along its length (#325 and #228, alternated; #46 swirl plates) was used for both tests; only the #325 nozzles were used in 1983. Four 1.6 to 2.0-ha rectangular treatment plots were established at random within the plantation. Spruce stocking density was ca. 900 trees/ha, and trees ranged 2-12 m in height in 1982. In the 1982 acephate test, Kromekote spray cards recorded droplet deposition, and weevils plus spruce material from sprayed and unsprayed areas were collected subsequent to treatment for mortality and oviposition assessment. Efficacy evaluations were carried out in August of both years by scoring all spruce within 10-m radius subplots for presence or absence of visible, weevil-induced leader damage. Three subplots were randomly located at least 15 m inside each of the 4 treated plots; an equal number of subplots were similarly located in unsprayed areas.