Control of Pyrethroid Resistant Colorado Potato Beetle—Trial 1, 1986

Plots were planted in early May on the Northwest Experiment Station at Crookston, Minn., using B-size Norchip certified seed. Plots were 4 40-inch rows × 35 ft with 6 ft of fallow between plots. Treatments were replicated 4 times in a randomized complete block design. Soil systemics were applied over the top of the row within 4 days after planting and lightly incorporated. This location has very fine textured soil and had more than adequate moisture in 1986. Foliars were applied on 26 Jun, 10 and 28 Jul, and 12 Aug with a hand-held CO2 sprayer using 40 psi pressure and 17 gal total material/acre. Four applications of fungicide were made independent of insecticide applications. Larval counts were taken on 4 dates, as were defoliation estimations. The counts presented represent peak larval and defoliation numbers and late season defoliation levels. Yields were taken on the center 2 rows of each plot, graded as indicated, and weights were recorded.