Energy crops could be answer to increased insecticide use

| July 14, 2011

The link between increased insecticide use and landscape simplification has now been documented by a team of researchers from the Great Lakes Bioenergy Research Center. The team has released a study it completed by utilizing publically available USDA data on insecticide use by county, Doug Landis, Michigan State University professor of entomology and landscape ecology, told Biorefining Magazine. The data was then coupled with USDA cropland data layers derived from satellite mapping of crop production. “Using a geographic information system (GIS), we were able to associate the patterns of the insecticide use to those of landscape simplification.”

The term landscape simplification, Landis explains, “is the result of converting noncrop habitats within a landscape to croplands. In the Midwestern U.S., the conversion of prairie, woodland, streamside and fencerow habitats to cropland has resulted in a more simplified landscape composed primarily of just a few crops.” Each year, he said, “Landscape simplification results in application of insecticides to an extra 3.5 million acres, with direct costs between $34 and $104 million.” The findings of the study suggest that an extra 10 square miles in a typical Midwestern county each year will require the application of insecticide. The implications of this continued practice, he added, will come at a price to farmers who bear the financial cost, and to the general public who have to deal with pollution and pesticide resistance.

But, while the research showed the upwardly trending use of insecticides with a decrease in the number of crops planted in a large geographic region, the research team did provide a solution. For fewer bugs, plant more grass. “Strategically diversified agricultural landscapes with perennial bioenergy crops like switchgrass and mixed prairie (grasses) could temper the negative environmental effects,” he said. “These crops could be grown on more marginal farmlands (lower productivity soils or more sloping areas), or used to buffer streams and rivers to reduce soil, nutrient and pesticide runoff.”

The two main factors that result from continued landscape simplification are the concentration of insect resources, and the reduction of habitat for enemies of those insects. For example, Landis said, previous studies have shown that populations of the soybean aphid—the major insect pest of soybeans in the Midwest—are increased in more simplified landscapes. “This occurs because ladybeetles and other key aphid predators are less abundant and less able to suppress aphids in annual crop-dominated landscapes,” Davis said.

Farm landscapes with little diversity make it easier for pest population to increase, he also said, which logically leads to farmers using more insecticides. “Policies aimed at promoting sustainable bioenergy cropping systems should consider all the ecosystem services or disservices that these systems produce,” he said. The study showed that annual insecticide use in the Midwest resulted in an additional 5,400 square miles, an area roughly the size of Connecticut.

Claudio Gratton, University of Wisconsin-Madison professor entomology, and member of the team said that “we are at a junction right now.” For Gratton, the increased demand for renewable energy provides the one big, constant question—where will it all come from? “We hope that these kinds of studies will help us forecast,” he said, “the impacts that bioenergy crops may have on agricultural landscapes.”