Lethal effects of pyrethrins on spruce budworm (Choristoneura fumiferana)

Abstract

Spruce budworm (Choristoneura fumiferana (Clemens)) is one of the most serious forest insect pests in North America. Laboratory bioassays were performed to determine the lethal doses and lethal time of pyrethrins (a botanical insecticide) on 4th instar larvae of spruce budworm using larval dip assay. Results show that the LT50 values (time of 50% larval mortality) for spruce budworm at the pyrethrins concentrations of 12.5, 25, 50, 100, and 200 μg·L−1 were 94.78, 45.54, 20.36, 14.39 and 11.37 h, respectively. The percentage of cumulative mortality at the pyrethrins concentrations of 12.5, 25, 50, 100, 200 μg·L−1 was approximately 50%, 67%, 93%, 100% and 100% within 120 h, respectively. The LC50 value (concentration of 50% larval mortality) for the 4th instar larvae was 16.1μg·L−1. Thus, larval mortality of spruce budworm increased in a concentration-dependent manner, and lethal time decreased with increasing pyrethin concentrations. These findings suggest that pyrethrins have a potential in controlling spruce budworm populations.