Sustainable Management of Insect Herbivores in Grassland Ecosystems: New Perspectives in Grasshopper Control

G ecosystems cover 30% to 40% of the earth’s terrestrial surface, provide critical habitat for large numbers of species, and support extensive grazing economies on every continent except Antarctica (Coupland 1979, Samson and Knopf 1996). In the United States alone, there are approximately 312 million hectares of rangeland (NRC 1994). Fire, grazing, and climate combine to act as the primary ecosystem drivers in grasslands. In combination with local species interactions, these processes set the stage for the unique local structure and function of the system (Coupland 1979). Grasslands that are used to support grazing activities are renewable natural systems, requiring management practices that capitalize on appropriate natural feedbacks and constraints (Fuhlendorf and Engle 2001). This need contrasts significantly with high-input, intensely managed row-crop agriculture, in which many of the natural feedbacks found in grazing systems have been irrevocably altered. Against this backdrop of grasslands as a renewable system, we address the underlying assumptions and strategies for managing grasshopper populations—models of economically significant insect pests in rangeland—to assess and highlight the importance of natural feedbacks in developing appropriate ecologically based strategies. Insect grazers such as grasshoppers, locusts, and Mormon crickets are common native components of grasslands worldwide. Major plagues of these insects periodically affect the livelihoods of people on six continents and have been reported throughout recorded history (figure 1). Because they feed on plants, their presence in large numbers often puts them in direct competition with livestock and other grazing herbivores.