Control of Grasshoppers on Rangeland with Pydrin, 1982

Pydrin was applied at 0.025, 0.05, and 0.1 lb ai/acre to non-replicated square 10-acre plots near Broadus, MT on Jun 24. All dosages were diluted in water and applied in 8 oz of fluid/acre with a Bell helicopter at 40 psi pressure through Spraying Systems No. 80015 flat fan nozzles. Flight speed was 70 mph, flight height was 100 ft, and swath width was 95 ft. All nozzles were directed straight down. These treatments were compared to a standard treatment of 8 fl oz of 95% technical malathion/acre applied under identical conditions. Results were assessed by counting grasshoppers in 50 estimated 1-ydin2 quadrats along each of 2 diagonal transects through each treated plot, as well as in an untreated control plot. Counts were taken before treatment and at 1, 3, and 7 days post treatment. The above grasshopper species comprised about 60% of the infestation, and were predominantly 3rd stage nymphs at the time of treatment. Precount densities averaged 5.7/yd2, which was not an economical infestation but which was sufficient for experimental purposes. All post-treatment densities were expressed as a percentage control based on the precounts along the same transects and were subjected to an analysis of variance.