Best management practices that promote sustainable crop pollination: the role of crop rotations and tillage depth

Project Overview

Project Type: Graduate Student
Funds awarded in 2013: $24,954.00
Projected End Date: 12/31/2015
Grant Recipient: University of California, Davis
Region: Western
State: California
Graduate Student:
Principal Investigator:
Neal Williams
University of California, Davis

Annual Reports


  • Vegetables: cucurbits
  • Animals: bees


  • Crop Production: conservation tillage
  • Natural Resources/Environment: wildlife
  • Production Systems: general crop production

    Proposal abstract:

    It is well documented that wild native bees can benefit many crops through increased seed and fruit set, thus providing sustainable pollination alternatives in cases of honey bee decline and increased honey bee rental prices. Yet it is unclear how to best manage crop systems to support wild native bees. Research on enhancing wild native bees has historically focused on field border management. However, to ensure the sustainability of a crop-pollination system, a comprehensive approach should also include within field practices. Promoting a whole-farm pollinator management strategy is especially important given that agricultural intensification is associated with practices that negatively impact wild native bees. Whole-farm strategies may provide effective alternatives for growers who are slow to adopt resource-intensive, border-management practices. The proposed project will contribute to our understanding of these strategies by determining the impact of tillage practices and crop rotations on a ground-nesting, native bee that is an important pollinator in a specialty crop system. Cucurbita crops (e.g. squash and pumpkin) rely on pollinators to set fruit. The specialist squash bee, Peponapis pruinosa, is an important pollinator of Cucurbita and can reduce grower reliance on rented honey bee colonies. In-field management is particularly relevant for this species given that it nests preferentially below its host’s vines. I will use observational surveys, manipulative experiments and a spatially explicit simulation model to identify crop rotation schemes and tillage practices that benefit P. pruinosa. Results from this study will be made available to growers and agricultural professionals through a set of communication channels including: grower presentations, fact sheets and videos summarizing best management practices, and an interactive web page demonstrating how crop rotations and tillage practices impact squash bee populations. These outreach activities will be accomplished via existing partnerships with the UC Cooperative Extension and California Resource Conservation Districts.

    Project objectives from proposal:

    Objective 1: Conduct a manipulative experiment to determine overwintering survival of P. pruinosa under different tillage depth treatments (summer 2013 and summer 2014)

    Objective 2: Conduct an observational survey to determine if crop rotations that promote between-year connectivity (i.e. how connected a focal Cucurbita field is to surrounding Cucurbita fields through time) have larger P. pruinosa populations than crop rotations that have low between-year connectivity (summer 2013 and summer 2014)

    Objective 3: Build a spatially explicit simulation model that uses crop rotations and tillage practices to predict P. pruinosa abundance and use this model to identify optimal management strategies (fall 2013 - spring 2014)

    Objective 4: Validate the model described in Objective 3 with data collected from squash fields in Yolo County (see Objective 1) and grower interviews (summer 2014)

    Objective 5: Communicate best-management practices using existing UC Cooperative Extension, Natural Resources Conservation Service and non-profit (e.g. Xerces Society for Invertebrate Conservation) partnerships (fall 2014)

    Objective 6: Develop an interactive website that can be used to show growers how crop rotation practices and tillage practices impact squash bee populations (winter 2013 - fall 2014)

    Objective 7: Publish the outcomes of Objectives 1-4 in three papers in peer-reviewed journals (fall 2014)

    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.