Use of a Monitoring System to Evaluate Pesticide Efficacy and Residual Activity Against Two Pine Root Weevils, Hylobius Pales and Pachylobius Picivorus (Coleoptera: Curculionidae), in Christmas Tree Farms

Abstract

Hylobius pales, the pales weevil, and Pachylobius picivorus, the pitch-eating weevil, comprise part of a weevil complex which affects plantation pine production in the Lake States. Common control practices on Christmas tree farms include calendar applications of persistent insecticides. The resulting environmental risks could be minimized by repeating applications only when needed. A sampling method using ethanol-and turpentine-baited pitfall traps was used here to assess the efficacy and monitor persistence of chemical sprays. Trap catch in lindane-treated field plots and untreated controls were compared over two years. Unsprayed controls had significantly higher weevil populations than treated plots. Spray efficacy continued for three years following application. Weevil population growth in relation to insecticide efficacy and degradation is discussed.