Timing Applications of SIR 8514 for Control of the Colorado Potato Beetle (Coleoptera: Chrysomelidae) on Potatoes

SIR 8514, 2-chloro-N-[[[trifluoromethoxypheny1];-amino]carbonyl]benzamide, a chitin synthesis inhibitor, was evaluated for control of Leptinotarsa decemlineata (Say) on potatoes. A series of plots was treated with SIR 8514 25% WP at times coinciding with the appearance of specific life stages. Numerical thresholds of adults and larvae per plant were also used. Counts of egg masses, larvae, and adults were made, and plots were rated for defoliation. Treatment effectiveness was rated based on yield and seasonal mean of larvae per plant. Optimal control and yields were obtained when spray application coincided with peak egg hatch. In the laboratory, adults were fed potato leaves dipped in a water suspension of SIR 8514 25% WP before mating to test for induced sterility or egg mortality induced in vivo. Eggs collected from these adults showed no significant difference in percent hatch compared with those of control adults. Egg masses were dipped in a series of concentrations, and an LC50 for eggs was determined. Instars 1 to 4 were fed dipped leaf discs, and an LC50 was determined for each instar. First instars were most susceptible, and 4th instars were least susceptible. Some feeding inhibition was observed for 2nd and 4th instars.