Bumble bee nest density in diversified farms to ensure pollination services

View the project final report

• 2011 annual report

Commodities

• Vegetables: cucurbits

Practices

• Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, workshop
• Farm Business Management: whole farm planning
• Natural Resources/Environment: habitat enhancement, wildlife
• Production Systems: holistic management, organic agriculture

Native bumble bees of the northeast region have the capacity to provide essential pollination services to crops of diversified farms. The utilization of native and wild bees, instead of managed bees, for pollination services reduces costs for growers because they do not need to be rented or maintained. Efforts to conserve and promote native bees require knowledge of population density. Previous studies, limited to Europe, have used population genetics to determine nest density of bumble bees. We propose to use similar methods in diversified Pennsylvanian farmscapes. We will use molecular markers (microsatellites) to assess the numbers of colonies of bumble bees from pumpkin fields and from floral provisioning, which are areas designed for promoting and sustaining bee populations. We will use these genotyping techniques to determine relatedness among individual foragers by coupling population genetic methods with mathematical fits to statistical distributions. These methods will estimate a range in the number of nests in the surrounding landscape that are pollinating a target crop, and the degree to which bees visiting that crop utilize resources from nearby floral provision areas. Given the success of previous efforts in Europe, we expect that we will be able to quantify nest density of our native northeastern bumble bees. The purpose is to understand resource utilization of native pollinators in the agroecosystem, which are providing an essential ecosystem service. The results will provide a better understanding of native pollinators and allow decision-makers to improve farm productivity, reduce costs and improve the functioning of sustainable agriculture.

Objective 1: Measure nest density by estimating how many nests are providing foragers to a specific field, from pumpkin fields in Pennsylvania that vary in surrounding landscape and farmscape patterns.

Purpose: Learning about the nesting density of the unmanaged native B. impatiens will provide new information about nesting and how native bees use resources from the surrounding landscape, (which includes floral provisioning fields- which links to Objective 2), and can be expanded in future work to develop effective management programs designed to ensure resilient pollination ecosystem services in our northeastern agro-ecosystems.

Expectations: We expect to determine the number of nests that are providing pollination services to a field by utilizing population genetics methods to compare microsatellite markers among sampled bees and determining the number of related (sister) bees present in the sample. The number of sister-hoods present will allow us to estimate the number of nests that are providing bees to that field.

Objective 2: Determine if colonies that are utilizing floral provisioning plots are also utilizing nearby horticultural crops.

Purpose: The management tactic of planting floral provisioning resources near target crops is for the purpose of supporting native bee populations with additional resources. However, little is known if bee populations that visit crop fields actually utilize the resources- if populations overlap their use with the floral provisioning resources and pollination of target crops, or if there is resource partitioning, and the same populations of B. impatiens do not visit both floral provisioning and target crops. This can be determined with the tools of population genetics, and testing whether sisters from the same nest can be found in both the floral provisioning flowers and the target crop bloom, which would indicate whether or not there is an overlap in use.

Expectations: Using population genetics tools, we expect to find sisters (related bees) visiting nearby floral provisioning plots and as well as pumpkins because bumble bees are generalist foragers and forage from a variety of resources.