PEST MANAGEMENT OF DOUGLAS-FIR TUSSOCK MOTH, <i>ORGYIA PSEUDOTSUGATA</i> (LEPIDOPTERA: LYMANTRIIDAE): MONITORING ENDEMIC POPULATIONS WITH PHEROMONE TRAPS TO DETECT INCIPIENT OUTBREAKS

Abstract

Abstract The numbers of Douglas-fir tussock moths ( Orgyia pseudotsugata ) (Lepidoptera: Lymantriidae) caught in sticky, delta-shaped pheromone traps baited with different concentrations of synthetic lures were compared with egg-mass densities and subsequent defoliation throughout a population cycle. A lure containing 0.01% pheromone by weight in the form of a 3 × 5-mm polyvinylchloride rod provided more consistent catches than pheromone concentrations of 0.0001, 0.001, 0.1, or 1.0%. Trap saturation occurred when &gt;40 moths per trap were caught. To achieve a standard error of 30%, 6 traps were required at each site. There was a poor correlation between numbers of moths caught and egg-mass density or defoliation estimates in the following generation, but a threshold density was found that provides a warning of an incipient outbreak. Ground surveys for egg masses are recommended to confirm suspected infestations after continuous increases in moth catches for 2 to 3 years or if an average of 25 moths or more per trap has been caught.