Control of Colorado Potato Beetle, 1996A

Abstract Potatoes were planted 21 May at the University of Minnesota Agricultural Experiment Station, Rosemount, MN. Plots were 4 rows wide by 50 ft long with 12 ft alleyways separating plots. Plant spacing was 36 inches between rows and 12 inches between plants. Four treatments and an untreated check plot were replicated 4 times in a RCB design. Early and late blight were controlled by seven applications of chlorothalonil. Foliar insecticide applications were made 10 Jul and 16 Jul. Treatments were applied with a tractor-mounted Brittonya boom sprayer delivering 40 gpa at 90 psi with 3 nozzles per row. Number of small (instar 1-2) and large (instar 3-1) larvae were counted on 5 randomly selected plants per row in each plot (20 plots per plot) on 11 Jul and 17 Jul. Percent defoliation estimates were made from whole plant inspection of 5 randomly selected plants per row in each plot (20 plants per plot) on 17 Jul. Analyses of variance were calculated following transformation of count and percentage data using log,0(x + 1) and arcsim/(x), respectively. Due to the very high CPB pressure in this location, some plots were completely defo-liated by the third week in July. No treatments were applied after 17 Jul due to near absence of a second generation of CPB.