Control of Colorado Potato Beetle with Natural Product Insecticides, 1991

Abstract

Abstract Potatoes were planted 15 May at the University of Minnesota Agricultural Experiment Station, Crookston. Experimental plots were 4 rows wide, 36.6 m (120 ft) long, with 91 cm (36 in) spacing between rows and 30 cm (12 in) between plants. The two center rows of each plot were planted with certified 'Red Pontiac' seed pieces cut the previous day. Plots were separated on all sides by 1.8 m (5.9 ft) of cultivated soil. A completely randomized plot design was used. Plots were scouted daily for CPB egg masses beginning 19 Jun. When egg masses were found they were flagged and checked every 2 - 3 days for hatch. Timing of first spray application was based on egg hatch; first application was made at 30% hatch of flagged egg masses and subsequent applications on a 7 d schedule. All treatments were applied 3 times for each CPB generation: 27 Jun, 5, and 11 Jul for first generation CPB larvae; and 18, 25 Jul, and 8 Aug for second generation. Natural product insecticides used in this experiment were Bacillus thuringiensis var. son diego (MYX-1806), and neem (Margosan-O). Sprays were applied using a tractormounted boom sprayer, with a single hollow cone nozzle over each row. Spray volume was 655 liter water/ha (70 gal/acre) at 827 kPa (120 psi). All data were collected from the two center rows of each plot. CPB larvae (small = 1st and 2nd instar, large = 3rd and 4th instar) were counted on 20 randomly selected whole plants per plot. Leaf loss to defoliation (from feeding by CPB) was estimated visually as percent foliage lost. Data were expressed as mean CPB larvae or plant injury (defoliation) × number of days elapsed = Area Under the Curve (AUC).