Can Wild Bees Meet Pollination Needs in Apples?: Determining the Efficacy of Native Bees and Their Contribution to Pollination

2012 Annual Report for GNC10-142

Project Type: Graduate Student
Funds awarded in 2010: $9,850.00
Projected End Date: 12/31/2014
Grant Recipient: University of Wisconsin
Region: North Central
State: Wisconsin
Graduate Student:
Faculty Advisor:
Claudio Gratton
University of Wisconsin, Dept. Entomology

Can Wild Bees Meet Pollination Needs in Apples?: Determining the Efficacy of Native Bees and Their Contribution to Pollination


To date, research on the SARE-funded project entitled, “Can wild bees meet pollination needs in apples?: Determining the efficacy of native bees and their contribution to pollination”, has 1) Documented the abundance and diversity of wild, native bee pollinators on 35 apple orchards covering a large geographic region of Wisconsin, 2) Compared fruit set at orchards with and without managed honey bees, and at orchards with varying abundance and diversity of wild bees, and 3) Obtained data and images that will be used to create a field identification guide to wild, native pollinators of apples. Frost damage in the spring of 2012 significantly affected fruit set and our ability to determine the contribution of both honey bees and wild bees to fruit set. Our data thus far show frost damage to be significantly, negatively correlated with fruit set, while the abundance of honey bees at an orchard has no effect on fruit set. The number of wild bee species found during bloom at an orchard is positively correlated with fruit set. Thus far, we conclude that most orchards can get adequate fruit set without managed honey bees, and that a high diversity of wild bees will increase fruit set. These research results were presented to apple growers at the 2013 Wisconsin Fruit and Vegetable Conference.

Objectives/Performance Targets

This research has three main objectives: (1) To assess which wild bees are most efficient in apples, (2) To determine whether wild bees alone, and in what numbers, can provide full pollination for apples, and (3) To develop a field ID guide to effective apple pollinators.

Outputs from this research include presentations to apple growers at grower meetings and networks. Outputs also include a pollinator ID guide that will be distributed to growers. Additionally, research results and the ID guide will be available online at extension websites. Furthermore, this research will be presented to other scientists and conservation organizations at entomology and ecology conferences, and will be published in peer-reviewed articles.


Objective 1: To address objective 1, we sampled wild bees at 21 apple orchards during the 2012 growing season and at 30 apple orchards in 2010, for a total of 35 different apple orchard study sites across both years. These study sites span a large portion of southern Wisconsin (Figure 1). With both sampling years combined, we collected approximately 9,500 wild bees representing 53 different species. From this collection, we were able to assess which bee species are the most abundant and universal across all study sites, as abundance will in part determine a bee species contribution to pollination. Andrena nasonii is by far the most abundant species across all study sites accounting for 1/3 of all bees collected. The genus Andrena, which consists of ground-dwelling, spring-emerging bees, is also the most abundant genus across all study sites. Other genera proposed to be important apple pollinators, such as Osmia spp., are present in very low abundance. This information will be used to determine the most effective wild bee pollinators of apples in southern Wisconsin.
In this upcoming year, we will continue to document the abundance and frequency of different wild bee species. Additionally, we will use field experiments and existing literature to measure or estimate rates of pollen deposition and pollination behavior in order to determine the pollination efficiency of different wild bee species.

Objective 2: To address objective 2, during the 2012 growing season, we compared fruit set at seven orchards that had honey bees colonies to fruit set at seven orchards without honey bees. We also measured wild bee abundance and diversity at all study sites. Since frost damage was significant during the 2012 growing season, we measured frost damage to flowers at all study sites. Frost damage (percent flowers damaged) was negatively related to fruit set (Figure 2). We also found that the number of honey bees captured in the orchard during bloom, which is an indicator of not only the number of honey bee hives but also of feral or neighboring honey bee colonies, was not associated with fruit set of apple blossoms (Figure 3). Specifically, many orchards without honey bees received fruit set equal to that of orchards with managed honey bee colonies. Combining 2012 data with data collected during the 2011 growing season, we found that the species richness of wild bees captured in the orchard was significantly, positively related to fruit set (Figure 4).
In this upcoming year, we will continue to measure fruit set at orchards with and without honey bees, and varying in wild bee abundance and diversity. We will also collect wild bees at all study sites to compare with measured fruit set.

Objective 3: Our work thus far on objective 3 has focused on gathering pictures and information that will be put into a native, wild bee identification guide. Sampling at 35 orchards during two growing seasons, and collecting 9,500 wild bees, has provided us with information as to the common wild bee pollinators and their distributions. We have taken numerous photographs for use in the guide (Figures 5, 6, 7) of bees visiting apple blossoms.
In the future, we will design a guide to native, wild bee pollinators of apples. We will take high resolution photographs of bees in the lab and in the field, and use our field experiments as well as existing literature to inform the guide. We have communicated with farmers and extension agents about the most useful format for the guide, and the consensus is that an App or Mobile Site, for use on a smartphone, tablet or computer, would be most used and appreciated. We have begun conversations with web designers and communications staff in our department about support for creating this guide.

Impacts and Contributions/Outcomes

The stated goal of this project is to help growers determine the contributions of wild bees to the pollination of apples, thereby decreasing their dependence on honey bees. Our research thus far shows that many orchards can achieve adequate fruit set with wild bees alone. Our research also indicates that having a diversity of wild bees is positively associated with total fruit set. Therefore, growers with a high diversity of wild bees may be able to rely on wild bees for their pollination needs, while growers with a lower native bee diversity may have to supplement with managed honey bees. Our previous research has showed that habitat diversity within a 1 km radius of the orchard strongly affects bee diversity. These findings may enable growers to predict whether they might have a diverse bee community based on the diversity of the landscape surrounding the orchard. These results were presented to growers at the 2013 Wisconsin Fruit and Vegetable Conference. Research results were also presented at the 2012 Entomology Society of America Meeting and the 2012 Ecology Society of America Meeting.


Dr. Claudio Gratton

[email protected]
1630 Linden Drive
Madison, WI 53706
Office Phone: 6082653762
Rachel Mallinger

[email protected]
Graduate Student
1630 Linden Drive
Madison, WI 53706
Office Phone: 2692674757
Bob Willard

[email protected]
31308 Washington Ave
Rochester, WI 53167
Deirdre Birmingham

[email protected]
7528 Kelly Road
Mineral Point, WI 53565
Thomas Griffith

[email protected]
3252 Vilas Road
Cottage Grove, WI 53527