Managing field borders for weed seed predators

Project Overview

Project Type: Graduate Student
Funds awarded in 2010: $9,856.00
Projected End Date: 12/31/2011
Grant Recipient: North Carolina State University
Region: Southern
State: North Carolina
Graduate Student:
Major Professor:
Dr. S. Chris Reberg-Horton
North Carolina State University

Annual Reports


  • Agronomic: corn, soybeans, grass (misc. perennial), hay


  • Animal Production: feed/forage
  • Crop Production: crop rotation
  • Education and Training: extension
  • Natural Resources/Environment: biodiversity, habitat enhancement
  • Pest Management: biological control, cultural control, weed ecology
  • Production Systems: agroecosystems, organic agriculture, transitioning to organic


    Despite great potential for weed seed eating organisms (i.e. 'weed seed predators') to contribute to ecological weed management programs, there are very few dependable strategies that farmers can reliable use to conserve and enhance these organisms. We conducted a large, field-scale experiment to determine if increasing vegetative diversity along the borders of crop fields increases weed seed predator abundance and enhances the ecosystem service these organisms provide. Our results definitively show that manipulating field border vegetation along the borders of crop fields is not a viable strategy to conserve weed seed predators. However, crops that provided greater overhead cover did see increased weed seed predation and greater numbers of native weed seed predators. Approaches to accomplish this denser cover in the fall, when summer annual weeds are being shed, may enhance weed seed predation services and contribute to an ecological weed management program.


    Preventing weed seeds from entering the soil is an important weed management strategy because the weed seedbank is the main source of new weeds in agricultural fields. Increases in the weed seedbank lead to greater management costs in subsequent seasons. Weed seed predation accounts for greater losses to seedbanks than aging, microbial decay or even disturbances like cultivation. Estimates of annual weed seed losses due to granivory by epigeal vertebrates and invertebrates typically range from 33 to 90%.

    Despite the potential benefits of weed seed predation, the literature is not conclusive on how to best conserve weed seed predators to create a consistent and dependable weed management strategy. Increasing vegetative diversity surrounding crop fields through set aside programs may enhance this ecosystem service.

    The conditions in the humid subtropical climate of the Southeast United States (i.e. the warm temperate zone) raise particular issues for how weed seed predators will respond to increasing vegetative diversity in the agricultural landscape. Although an earlier study confirmed carabid beetles are the predominant weed seed eating invertebrate in the Southeast (Brust & House 1988) a more recent study found the invasive fire ant, Solenopsis invicta Buren, is now the dominant weed seed predator in the region (Pullaro et al. 2006). These non-native, diurnal, social ants will not respond to conservation strategies the same way as native, nocturnal, solitary ground beetles.

    This study was undertaken to examine how field border management in the southeastern U.S. affects seed predator abundance and field type. Managed habitats along fields are increasingly present in this region due to cost share programs designed to enhance wildlife habitat in the region, particularly for quail. Multiple field border types were tested, varying in vegetative diversity and management practices. This project was part of a multidisciplinary effort to find a crop field border conservation strategy that maximizes ecosystems services.

    Project objectives:

    1.) Determine the effects four different field border vegetation communities have on levels of weed seed predation in adjacent crop fields by invertebrates and vertebrates.

    2.) Identify the specific predators responsible for this weed seed predation.

    3.) Disseminate the results of this project to organic growers.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.