Control of Colorado Potato Beetle, Potato Leafhopper, and Green Peach Aphid, 1991

Abstract

Abstract Potatoes were planted 15 Mayat the University of Minnesota, Agricultural Experiment Station, Rosemount. Plots were 4 rows wide, 10.6 m (35 ft) long, with 102 cm (40 in) spacing between rows and 30 cm (12 in) between plants. Plots were separated on all sides by 2.0 m (6.7 ft) of cultivated soil. Eight experiments were planted in the same field. For each experiment, a completely randomized plot design with 4 replications was used. In all eight experiments, CPB control was the primary objective. Experiment 1 was to evaluate neem (Margosan-O) alone or in combination with other insecticides. Experiment 2 was to evaluate several conventional insecticides and Kryocide. Experiment 3 was to compare several commercial Bacillus thuringiensis insecticides at 3 rates each. Experiment 4 was to evaluate neem (RH-999) alone or in combination with other insecticides. Experiment 5 was to compare 3 Bacillus thuringiensis insecticides from Ecogen Inc. at 2 rates each. Experiment 6 was to evaluate application of Furadan 4 F applied as a systemic spray at drag-off Experiment 7 was to compare performance of several insecticides when first sprays were applied at different stages of egg hatch or larval development. Experiment 8 was to compare different insecticide rotation schedules. Plots were scouted daily for CPB egg masses beginning 8 Jun. When egg masses were found they were flagged and checked daily for hatch. Timing of first spray application (except in Experiment 6) was based on egg hatch. Five treatment schedules were used: 0 = untreated control (UTC), 1 = Furadan 4 F applied as a spray 6 Jun just prior to drag-off, 2 = first application at 30% hatch of flagged CPB egg masses (i.e., first eggs to hatch for that generation), 3 = first application at first appearance of 2nd instar, 4 = first application at first appearance of 3rd instar. Spray applications for schedule 2 were applied 17-18, 24 Jun, 23 (second generation), 29 Jul, 6, and 13 Aug. Spray applications for schedule 3 were applied 19, 27 Jun, 24 Jul (second generation), 31 Jul, 7, and 14 Aug. Spray applications for schedule 4 were applied 22 Jun, 26 Jul (second generation), 8, 12, and 16 Aug. Insecticidal sprays were applied using a tractor-mounted boom sprayer, with drop nozzles. Sprays were applied in 739 liters of water/ha (79 gal/acre) at 620 kPa (90 psi). CPB larvae (small = 1st and 2nd instar, large = 3rd and 4th instar) were counted on 8 randomly selected whole plants, PLH nymphs and GPA apterae were counted on 35 mid-plant leaves. Leaf loss to defoliation by CPB feeding was estimated visually as percent foliage lost. CPB were counted on 21, 26 Jun, 25 Jul, 1, 9, and 15 Aug; defoliation was estimated on 28 Jun, 3, 10, 17, 22, 30 Jul, 5, and 19 Aug; PLH were counted 30 Jul and 29 Aug; GPA were counted 29 Aug. Data were expressed as mean insect numbers or plant injury.