Vegetative Barriers to Prevent Soil Erosion and Increase Biological Pest Control in Agricultural Landscapes
Midland, Bay, and Tuscola Counties, MI

Grantee: Michigan State University, Department of Entomology
Basin Program Funds: $14,860
Non-federal Funds: $13,301
Project Duration: 12/1997 - 01/1999
Status: complete

Problem Statement
Soil erosion and sedimentation from crop lands has been identified as a major source of nonpoint source pollution in the Great Lakes basin. The U.S. Department of Agriculture – Natural Resources Conservation Service (NRCS) identified vegetative barriers as an effective measure for reducing sedimentation and nonpoint source pollution. Recent Michigan State University, Department of Entomology research has demonstrated that vegetative barriers also provide habitat for weed seed and crop pest predators. The relative influence of this benefit, however, has not yet been quantified.

Background
In addition to creating a significant source of nonpoint source pollution, agricultural land-use disturbs habitat, overwintering sites, refuge from pesticide application and food resources for arthropods which prey on crop pests. The lack of these habitats has been linked to increased crop losses which can, in turn, lead to increased pesticide use and an attendant rise in nonpoint source pollution. Including adequate habitat management in agricultural land-use planning is the key to an ecosystem-based approach to managing these problems. Properly managed vegetative barriers, such as cross wind trap strips within fields and filter strips bordering fields, may serve multiple purposes including wind and water erosion control and increased habitat for beneficial life forms.

In the Saginaw Bay region, high crop and tillage intensity combined with inherent soil and landscape characteristics make soil erosion and associated nutrient and pesticide loading in surface waters an acute problem. Annual soil erosion into the Saginaw Bay watershed is estimated at nine million tons. Under the Great Lakes Water Quality Agreement the watershed has been designated an Area of Concern and become the focus of the U.S. Environmental Protection Agency's first National Watershed Initiative Program. Under this program, the NRCS is developing vegetative barriers as a component of a Conservation Management System. These include technical guidelines for cross wind trap strips to induce soil deposition and trap pollutants before they are deposited downwind. At the same time the reduction in non-crop habitats, such as fence and hedgerows, wood lots and riparian buffers has limited the abundance and diversity of crop pest predators. One means of reintroducing the required habitat into the landscape is through vegetative barriers. Michigan State University research has developed natural enemy resource habitats comprised of perennial grasses, legumes and flowering herbs most of which have also been approved for use in vegetative barriers.

Activities
Three field test plots of varying composition, legume, switch grass and crops (soybean in 1997 and corn in 1998), were established in Midland County, Bay County and Tuscola County. At each site, researchers conducted bi-weekly pitfall trapping for carabid ground beetles which are important insect and weed seed predators. In addition, researchers conducted seed predation studies at the Midland County site.

Results
The research demonstrated that filter strips can contain a more diverse and abundant carabid (ground beetle) community than the adjacent field. A total of 36 species of carabids and 3360 individuals were found in the crop strip, 43 species and 4330 individuals in the legume plot and 50 species and 5247 individuals in the switch grass test site with corresponding abundance following similar trends. Carabids and other invertebrates were responsible for a significant removal of weed seed. For instance, in one week they removed 84% of foxtail seeds in the switch grass filter strip compared to 42% and 17% in the legume and soybean filter strips respectively. An unexpected finding was that crickets also consume large quantities of weed seeds.

The project team produced the following articles:

Additionally, project personnel hosted three field days which attracted approximately 100 farmers, extension agents, and highschool students. Midwest Biological Control News is received by all county extension offices and extension entomologists in the 11 state north-central region meaning more than 2,000 people saw the article. Another 2,000 people received the USDA —NRCS conservation information sheet as well.

Contact: Douglas Landis, (517) 353-1829

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