Effect of 3 Pyrethroid and 4 Suggested Synergist Combinations on Pyrethroid-Resistant Colorado Potato Beetle, 1987

A trial was established at the Northwest Experiment Station at Crookston, Minn. Plots were 2 rows × 25 ft long, replicated 3 times, and arranged in a randomized complete block design. 5.3 cc of detergent (Ivory Liquid dish soap) and 10.5 cc of the appropriate vegetable oil was used per liter of material when each was added. Applications were broadcast with a hand-held CO2 sprayer using 40 psi pressure and 15 gal total material/acre. Treatments were applied 27 Jun, and surviving larvae/5 plants were counted 24 h later. Counts were converted to percentages, transformed using ARCSINE, and compared. Defoliation estimates were made at the time of larval counts 17 days later. Temperature on the day of application was 86°F.