Control of Colorado Potato Beetle Larvae with Foliar Insecticides, 1985

Abstract

Abstract Potatoes were planted 6 May, at the University of Minnesota Northwest Experiment Station, Crookston, MN and at the Red River Valley Potato Growers Association Research Farm, Grand Forks, ND. Plots were of variable length with 38-inch row spacing, randomized in complete blocks with 3 replications. Pretreatment counts were made by counting all 2nd through 4th instars on sufficient plants to yield a minimum of 200 larvae per plot. At Crookston, most larvae were 3rd and 4th instar, at Grand Forks, most larvae were 2nd or 3rd instar. Insecticide sprays were applied using a CO2 powered hand-sprayer delivering 36 gal of water at 35 psi. At Crookston, beetle counts were made 9 Jul, 10 Jul and 15 Jul; foliar sprays were applied 9 Jul immediately after the pretreatment count. At Grand Forks, counts were made 1 Jul, 8 Jul, 10 Jul and 16 Jul; Bacillus thuringiensis and the insect growth regulators were applied 1 Jul and 9 Jul, the conventional insecticides were applied on 9 Jul only. Two untreated controls were included at both locations. Percent control was based on pretreatment and posttreatment counts for each plot.