Field and Economic Evaluation of Operational Scale Reduced Agent and Reduced Area Treatments (RAATs) for Management of Grasshoppers on South Dakota Rangeland, 1997-1999
R. Nelson Foster¹, K. Chris Reuter¹, K. Fridley², D. Kurtenbach², R. Flakus², R. Bohls³, B. Radsick⁴, J. B. Helbig⁵, A. Wagner² and L. Jech⁶
 

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Abstract

 Strategies that utilize lower than traditional doses of insecticides in combination with swaths of applied insecticide that leave untreated areas between each swath are one way to significantly reduce the cost of controlling grasshoppers on rangeland. By leaving untreated areas, this strategy provides reserves for naturally occurring biological control agents and facilitates an economical integrated management approach for dealing with damaging populations of grasshoppers on rangeland. This three year study was conducted in different locations and years to develop and demonstrate on a large scale operational level, the utility of  reduced area / agent treatments (RAATs) for significantly reducing costs to manage damaging populations of grasshoppers. In 1997 these reduced agent/area treatments (RAATs) resulted in about 15% lower mortality than traditional treatments while reducing pesticide use and cost by 60% with malathion and 75% with carbaryl. Total treatment costs were reduced by 38% with malathion and 66% with carbaryl. Economic analysis showed the greatest benefit/cost ratio in 1997 was obtained with RAATs malathion (1.14) followed by RAATs carbaryl (1.05), traditional malathion (0.84) and traditional carbaryl (0.51). In 1998, RAATs treatments resulted in about 10% to 15% lower mortality than traditional treatments while reducing pesticide use and costs by 60% with malathion and 62.5% with carbaryl. Total treatment costs were reduced by 38% with malathion and 58% with carbaryl. Economic analysis showed the greatest benefit/cost ratio in 1998 was obtained with RAATs malathion (1.25), followed by RAATs carbaryl (1.05), traditional malathion (1.04) and traditional carbaryl (0.65). In 1999 RAATs treatments resulted in about 2% to 7% lower mortality than traditional treatments while reducing pesticide use and costs by 60% with diflubenzuron and 67% with carbaryl. Total treatment costs were reduced by 56% with diflubenzuron and 59% with carbaryl. Economic analysis showed the greatest benefit/cost ratio in 1999 was obtained with RAATs diflubenzuron (2.09), followed by RAATs carbaryl (1.84), traditional diflubenzuron (0.97), and traditional carbaryl (0.90). In these economic analyses, values greater than one indicate a positive return on the treatment investment in the year of treatment. The implementation of these kinds of treatments will provide excellent opportunities for dramatically changing the way that grasshoppers are managed on rangelands. Additional development and refinement will further improve the economics and natural biological control base of such integrated management strategies.

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