Control of Grasshoppers on Rangeland, 1978

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Abstract
A 75% water-soluable powder formulation of Orrhene 75S was applied at rates of 4 and 8 oz ai/acre to 4 square 40-acre plots and at a rate of 2 oz ai/acre to 3 such plots near Melville, Montana on July 12-14, 1978. All dosages were mixed with 2 qt of water per acre and applied at 36 psi pressure with a CessnaR Ag-wagon aircraft equipped with 26 D-6 nozzles and no. 45 course spinners. Flight speed was 125 mph, flight height was 100 ft, and swath width was 100 ft. These treat-ments were compared with a standard application of 8 fluid oz of ULV technical malathion/acre applied June 15 under similar conditions except that 8 no. 80015 flat fan nozzles were used. All nozzles were directed 45° down and back. Results were assessed by counting grasshoppers in 50 subsamples in each experimental plot and also in 4 contiguous untreated areas located outside the experimental area. The pretreatment counts utilized estimated 1-ft2 quadrats; the counts at 3 and 7 days posttreatment utilized estimated 1-yd2 quadrats. The species in the order listed above comprised 43, 33, 10, and 10% of the pretreatment infestation, respectively; the infestation was 53% adults. Precount densities averaged 20.3 grasshoppers/yd2. All posttreatment densities were expressed as percentage control based on the precounts in the same plot, were transformed to arcsin X, and were analysed as a randomized block design with 4 replications and one missing value. After analysis and determination of significant differences, means were retransformed back to percentages (see Table).

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