Evaluation of a Biological and a Botanical Insecticide for Colorado Potato Beetle Control, Rosemount, 1990

Natural product insecticides used in this experiment were B. thuringiensis var. tenebrionis (BK-102) and azadirachtin (RH 0000 and RH 9999) from the neem tree, Azadirachta indica. Es-fenvalerate (Asana XL) was used as a conventional insecticide. Certified B-size seed potatoes were planted 23 May at the Plant Pathology Farm, Rosemount Agricultural Experiment Station, University of Minnesota. Plots were 1 row wide, 7.6 m (25 ft) long, with 102 cm (40 in) spacing between rows and 30 cm (12 in) between plants. A completely randomized plot design with 4 replications was used. Potatoes were scouted daily for CPB egg masses beginning 18 Jul. When egg masses were found these were flagged and checked daily for hatch. Timing of first spray application was based on egg hatch. Two basic spray schedules were used: first application at 30% hatch of flagged egg masses and subsequent applications on a 7 d schedule, or first application at 30% hatch of all eggs (unflagged) laid on or before that sampling date and subsequent applications on a 7 d schedule. Plots were sprayed 1-4 times for second generation of CPB larvae. Spray dates were: 20 Jul (30% hatch of flagged eggs—2nd generation), 25 Jul (30% total hatch—2nd generation), 27 Jul, 1, 3, 8, 10 and 15 Aug. Insecticidal sprays were applied in 935 liters water/ha with a CO2-powered handsprayer. CPB larvae were counted on 20 whole plants per plot on 1, 8, 15, and 22 Aug. Two way analysis of variance was used to test for differences in CPB densities.