Decreasing Economic and Environmental Costs through Reduced Area and Agent Insecticide Treatments (RAATs) for the Control of Rangeland Grasshoppers: Empirical Results and Their Implications for Pest Management

Abstract

-Reduced area and agent treatments (RAATs) for management of rangeland grasshopper infestations were compared with blanket applications of 2 standard compounds at traditional rates (100% of infestations treated with carbaryl applied at 16 oz/ac or malathion applied at 8 oz/ac) in southeastern Wyoming during 1995-96. Two RAATs applications of carbaryl (12 oz/ac applied in alternating swaths to 66% of infestations [12-66] and 8 oz/ac applied in alternating swaths to 50% of infestations [8-50]) were essentially indistinguishable from the standard treatment, with 80 to 90% grasshopper mortality. A carbaryl 8-33 treatment resulted in only 40 to 60% control. Mortality following application of 4 oz/ac of malathion in alternating swaths to 80% of an infestation (4-80) was indistinguishable from the standard application, with 75 to 90% control. However, a malathion 4-50 treatment resulted in only 55 to 65% control. Fipronil (14 oz/ac) applied to 25% of an infestation resulted in 80 to 90% control, comparable to the highest rates of mortality with the other RAATs. The greatest benefit: cost ratios (>2.8: 1) were seen with the carbaryl 8-50, malathion 4-80, and fipronil 14-25 treatments. The RAATs strategy appears to depend on movement of grasshoppers from untreated to treated swaths and on the conservation of natural biological control agents. Had RAATs methods been used during the 1986-88 outbreak in the western US, pest managers would have saved $38 million and used 34 million metric tons less insecticide [