No abstract

Fifteen insecticide treatments were tested at the MSU Montcalm Research Farm, in Entrican, MI, for their control of Colorado potato beetles (CPB). ‘Snowden’ potatoes were planted 12 inches apart with a 34 inch row spacing on 10 May. Treatments were replicated four times and assigned to plots in a RCB design. The plots measured 40 feet long and were three rows wide. There were at least two rows of bare ground between plots and five feet of untreated potatoes between plots in the same rows. The Admire and Mocap treatments were applied in furrow at planting. The first foliar treatment was applied, at 25% CPB hatch, on 18 June using a tractor-mounted sprayer (30 gal/acre, 40 psi). Subsequent first generation sprays were applied on 29 June and 7 July. Light rain occurred on 7 July before the insecticides had a chance to dry. Insecticide effectiveness was determined by counting the various stages of CPB on two randomly chosen plants from the middle row of each plot. Counts were done on 12 and 23 Jun and 3 and 12 July. Second generation methods were the same as for the first generation with sprays occuring on 19 July, 26 July and 2 Aug and counts on 18, 24 and 31 Jul. All plots other than the two Trigard treatments were sprayed with a maintenance spray of Imidan and PBO. Each plot was assessed for percent defoliation on 3 July and 9 August. The middle row of potatoes from each plot was harvested on 22 August, separated by size and weighed.

‘Spartan Banner 80’ onions were direct seeded on 13 May at the Michigan State University Muck Research Farm, Laingsburg, MI. Plots were 3 ft long non-adjacent sections of single rows (16 inch spacing between rows), separated by 8 untreated rows, with five replications in a randomized complete block arrangement. A natural population of thrips present in the field was augmented with thrips introduced on onion tops from a heavily infested commercial field. For each plot, five onion tops were inverted and placed in close contact with the hearts of the onions for 3 days and removed just prior to spray application. Treatments were applied with a hand-held CO2 sprayer with a flat fan nozzle at 40 psi and 50 gal per acre on 18 Aug. Due to a rain, heavy winds and the stage of the onions, plants had begun to lay down by 26 Aug when post-treatment sampling was done. Five standing plants were randomly selected in each plot and thrips were counted. Data were log transformed before analysis.

Seven insecticides were tested at the MSU Montcalm Research Farm in Entrican, MI. Potatoes were planted 12 inches apart with a 34 inch row spacing on 6 May. Plots 45 feet long by three rows wide were arranged in a randomized complete block design with four replications. Plots were separated by at least 6 feet of bare ground. The Admire in-furrow treatment was applied with spray bottles on 6 May. Foliar treatments were applied on 23, 30 Jun/2 and 7 Jul using a tractor-mounted sprayer at 30 gal/acre and 45 psi. Light rain interrupted spraying on 30 Jun; remaining treatments were applied on 2 Jul AC303.630 at 5 gal/acre was applied with a CO2 sprayer with a 3-nozzle hand-held boom. Two plots of Cryolite received additional sprays on 4 and 12 Aug. These plots were removed from yield analysis, but were included in analysis of beetle numbers. Two randomly selected plants from the middle row of each plot were sampled for CPB on 28 Jun, 6 and 12 Jul. An outer row was sampled in 5 plots because the middle row had few plants. A visual defoliation assessment was done on 6 and 12 Jul. Potatoes were harvested on 14 Sep, separated by size and weighed.

Two fields in Bay Co., MI, were selected for trials using the insect growth regulator Trigard against CPB. ‘Onaway’ potatoes were planted on 17 Apr 1991, and 3 May 1991, respectively, and were managed by growers Brian Hugo and Jim Kryszak. Plots measuring 14 rows wide by 60 feet long were established in each field on 7 Jun in a randomized complete block design with 4 replications. Treatments were: 0.125 lb (AI)/acre (low rate); 0.25 lb (AI)/acre (medium rate); and 0.375 lb (AI)/acre (high rate; and an untreated control. The fields were sprayed on 7 and 19 Jun using a tractor mounted boom sprayer at 25 gal/acre and 40 psi. A maintenance spray program using insecticides effective against adult beetles was started on all plots the second week of Jul, after the summer adults had emerged. A pre-spray count of CPB egg masses, adults, and small and large larvae from one or two plants per plot was taken on 7 Jun. High numbers of large larvae were already present in the Hugo field at this time. Four plants per plot were sampled on 13, 20, 27 Jun and 2 Jul. On 2 Jul a qualitative defoliation rating was given to each plot based on the percent of plants in each of five defoliation categories. Potatoes were harvested from two 10-ft sections of row per plot in 19 Aug, sized and weighed.