This project addresses native bee populations on 12 small mixed vegetable farms including ten from across the state of Maryland, one in Pennsylvania and one in West Virginia. The purpose of the project is to census native bees (non-Apis) in agroecosystems and provide baseline data so that research on declines and recovery efforts have benchmarks for comparison. Additionally, the research investigates bee presence within vegetable gardens as compared to adjacent habitats around the farms. The results will provide information that farmers can use to guide the management of adjacent lands for pollinator foraging and nesting habitat thereby improving pollination visitation and crop productivity.
It has been suggested that the promotion of native pollinators on agricultural lands can bridge the conservation and food sectors of society because their presence and associated habitat directly benefits both agricultural productivity (through pollination of crops) and ecosystem services (through providing pollination services for uncultivated plants and as members of diverse ecological communities and food webs). Certain pollinator populations are threatened globally due to habitat fragmentation and alteration, misuse of pesticides, infestations of parasites, and disease. Localized population declines in managed and wild bee populations have prompted interest on the part of various stakeholders in restoring and maintaining pollinator-friendly habitat on working landscapes, particularly private agricultural lands. This research evaluates opportunities for promoting pollinators, in particular, wild bees (non-Apis), on agricultural lands. Land use change, introductions of nonnatives and misuse of pesticides will continue to threaten native pollinators in the short term. Before decline can be assessed and restoration efforts can be evaluated as successes or failures, however, an understanding of the present status of native pollinator populations is required. The proposed project will contribute to that understanding by way of measuring native bee diversity on several CSA farms in and around the state of Maryland.
- To census wild bee populations on 12 mixed vegetable farms in and around Maryland in order to gain an understanding about the diversity of bees available to farmers for pollination.
To determine what habitats in and around vegetable gardens support wild bee populations on small mixed vegetable farms.
The study sites are on 12 small mixed vegetable farms including ten from across the state of Maryland, one in Pennsylvania and one in West Virginia. Eleven of the farms are Community Supported Agriculture (CSA) farms with customers receiving produce and cut flowers throughout the growing season. Five of the farms had managed honeybees (Apis mellifera) either onsite or on neighboring lands. During the summer of 2005, we surveyed the 12 farm sites in each of June, July and August for bees and other insects using transects of painted fluorescent pan traps. We surveyed in several habitats including vegetable crops and cut flowers, shrubs, forest edges, meadows, grass lawns and wetlands.
Among the 12 study sites we collected more than 3200 individual bees representing four families, 22 genera and more than 47 species. Abundance of bees increased from June to July 2005 in both crop habitats and in all other habitats combined (forest, shrub, meadow, lawn, wetland) indicating an overall greater abundance in bee populations in mid-summer. Coincidently, number of species also was greatest in July among all habitats. Significantly more bee species were collected in crops than in lawns, meadows and wetlands (p=0.002, 0.002, 0.001, respectively) although there was no difference between crop habitats and shrub or forest habitats signifying that crop fields provide adequate foraging resources for bees on farms. Wild bee abundance measures suggest a temporal shift in foraging from forest edge flowers to cucurbit crops as the season progresses. On farms with both shrubs and forest edges, bee abundance measures indicate a preference for shrub foraging over forest foraging most likely due to the differences in density of flowers between the two habitats. Among bees sampled in crop habitats, including habitats on farms with managed hives, more than 96 percent were non-Apis (i.e., non-honeybee), indicating a heavy reliance on wild bee populations for pollination services at these sites. Among all habitats, sweat bees (Family Halictidae) were most abundant comprising more than 80 percent of all bees collected (n=2626). Within crop habitats, halictids accounted for 85 percent of the bee counts (n=1964). There were significantly more halictids in crop habitats as compared to all other habitats combined during the months of July and August 2005. Even though halictids dominate throughout the growing season, a closer look at the species level reveals that different species of halictids dominate at different times. For example, female Agapostemon virescens, a bee we collected in large numbers (n=441), dominated crop and forest habitats in June while female Halictus ligatus (n=128) dominated in July. Our results demonstrate that species richness and abundance of wild bees on farms changes throughout the growing season. This has tremendous management implications since different species of bees are pollinating at different times and at different rates. Therefore, to enhance crop productivity in vegetable gardens farmers can provide floral resources and nesting habitat before, throughout and after the growing season to ensure the presence of a suite of bees that can provide pollination services for their crops instead of only focusing efforts during mid-summer when bee species richness and abundance is greatest and most crops are in bloom.
The results of this research project demonstrate that a suite of bees, not just a few species, provide pollination services to farmers and that providing foraging resources and nesting habitat is essential before, during and after the growing season in order to capture the maximum effort of pollination services from wild bees. The results of the study are provided to the 12 participating farms in the form of a summary report and a detailed description of the findings at their individual farm. Additionally, other farmers that I am interviewing for a related project also receive this information. Once these results are compiled into a manuscript for a peer-reviewed journal in the field of agriculture/entomology, the information will be available to a wider audience.
Education & Outreach Activities and Participation Summary
Over the last two years I have been involved with the Farm Bill Task Force with the North American Pollinator Protection Campaign. This task force is working with NRCS to include pollinators in the text of broader conservation programs available to farmers within the upcoming Farm Bill. At the October 2006 meeting I will be sharing my results with the task force in order to inform some of those efforts. In August 2006 I gave a presentation on the results of the project in Memphis at the annual Ecological Society of America conference and in June 2006 I presented this information at the Blandy Experimental Farm colloquium. Additionally, I presented posters describing this research project at the Ecological Society of America’s International Conference on Ecology in an Era of Globalization: Challenges and Opportunities for Environmental Scientists in the Americas, at the University of Maryland’s Bioscience Day, and at the Marine Estuarine Environmental Science Program Annual Symposium. I shared findings with individual participants at the Pennsylvania Association for Sustainable Agriculture annual meeting. During the summer of 2005 I presented my research to the public at two of my farm study sites on public field days. A local boy scout troop (#746) has been involved in learning about wild bees and helping to create bee boxes for farms which I will deliver to my 12 participating farms once completed. Additionally, at the completion of my doctoral degree, each of the farms will be provided with a specimen box of the bees collected at their individual farms along with an information sheet explaining the research and the role of wild bees in vegetable production. The results of this research have been included in my semi-structured interviews with farmers under a related project, and will also be incorporated into a survey that will be delivered to local sustainable agriculture farmers.
Areas needing additional study
This bee census research is part of a larger ongoing interdisciplinary project that incorporates ecological and ethnographic methodologies to investigate opportunities for improving agricultural productivity via pollinator promotion on farms. Initial interviews with local vegetable farmers indicate a strong interest in promoting pollinators via habitat manipulation on-farm, however, respondents request evidence of a direct link between native bee diversity and increased crop production and/or quality. Additional experiments to evaluate the contributions of wild bees to vegetable crop pollination are underway currently at Blandy Experimental Farm.