Predicting pine sawfly population densities and subsequent defoliation with pheromone traps

Field in Finland to develop a monitoring and prediction trials were conducted from 1989 to 1993 method using pheromone traps for European pine sawfly (Neadiprion sertifer Geoffr.) population densities and needle defoliation. Three traps per site were baited with 100 mug of(2S,3S,7S) - 3,7 - dimethyl - 2 - pentadecyl acetate (diprionyl) at sites representing advanced pine stands. The number of overwintering eggs per sample branch was used to evaluate the effectiveness of using pheromone traps to estimate sawfly populations. The relationships between the number of males in traps, the number of eggs per branch in the subsequent generation, and the number of needle-year classes after the subsequent growing season were highly correlated. The risk threshold for moderate to heavy defoliation was around 1,000 males/trap. Our results suggest that after some minor improvements, a pheromone-based monitoring system for the European pine sawfly would provide an effective tool for integrated pest management programs and successful forest management in coniferous pine-dominated forests.