As much as 30 percent of the American diet is a direct result of animal pollination, the majority of which is provided by bees. This bee pollination equates to more than $18 billion worth of crops annually in the United States alone. Despite their significant economic value, bees — both honey bees and native bees — are facing severe population pressures from multiple factors including habitat loss, pathogens, pesticides, climate change, and increase monoculture. These pressures can lead to severe population declines. Recently, providing pollinators with augmented habitat as a conservation method has become an increasingly popular trend. Much of this effort has been centered around adding habitat into the agricultural landscape to promote floral resources for beneficial arthropods and pollinators. Building on this trend, the NC Department of Agriculture and Consumer Services (NCDA&CS) has recently implemented an initiative called “Protecting NC Pollinators,” that mandates the planting of pollinator habitat at all Experimental Agricultural Research Stations across the state — which is the focus of this study. Despite the increasing popularity of augmented habitat, there are still many gaps in the empirical research documenting the impact of this tool. This study fills this gap by documenting the bee communities found on NCDA&CS research stations across the state — resulting in the most detailed survey of native bees in the state to date — measuring the pathogen ecology of the bee communities in this habitat to ensure that pollinator health is supported, and finally, measuring the impact habitat has on crop output.
- Screen bee samples for pathogens;
- Document pollinator networks at the plots and a nearby crop;
- Measure the impact of the plots on crop output.
All sampling was conducting at official NCDA&CS research stations. When selecting sites from across the state we first focused on selecting stations distributed amongst the different ecoregions. Second, we selected sites with the highest quality pollinator habitat – for this study high quality habitat meant high seed take and high bloom as well as high floral diversity – in order to minimize variation at the plot level. And third, sites that already regularly plant soybeans were prioritized. This resulted in 8 out of the 18 research stations being selected for this study: Peanut Belt Research Station (upper coastal), Caswell Research Farm (central coastal), Horticulture Crops Research Station – Clinton (central coastal), Border Belt Tobacco Research Station (lower coastal), Horticulture Crops Research Station – Castle Hayne (lower coastal), Piedmont Research Station (piedmont), Mountain Research Station (mountain), and Mountain Horticulture Crops Research and Extension Center (mountain).
At each of the 8 sites, sampling occurred at 3 fields. The first field, the pollinator habitat, was an established sampling plot that has been maintained since 2016. The second field, the near soybean field, was the closest field as possible to the habitat where soy was to be grown in order to measure the impact the presence of habitat has on yield. And the third field, the far soybean field, was the furthest field as possible to the habitat where the soy was to be grown in order to act as a control as the presence of the habitat should not directly impact yield. There was variation between sites with how close the near and far fields were to the habitat, but there was no overlap between the near and far field distances between the sites. All near fields were within 270 meters from the habitat, with the closest being 9 meters away. All the far fields were more than 320 meters from the habitat with the furthest being 3700 meters away. This gradient allowed us to evaluate distance from habitat in several different ways while also being field realistic. All soybean fields selected grew indeterminate plants, although variety varied across the state. Only two of the eight sites used seed treated seeds (Mountain Horticulture Crops Research and Extension Center and Peanut Belt Research Station). All stations applied either an insecticide, an herbicide, or both to the fields, but they were all applied before bloom, at first bloom, at late bloom, or after bloom. No pesticides were applied during peak bloom of the crop.
We used two sampling methods in all 3 fields, visual surveys and netting surveys. Both survey methods were conducted using haphazard transects through the fields. In all 3 fields, only floral visitors were documented in order to truly document the community of flower visiting pollinators. Any insect found on leaves, the ground, or air was not documented. We spent 30 minutes total in each field, during which time both survey methods were used. We surveyed each field twice per day, once in the morning and once in the afternoon, in order to account for any temporal variation. The order in which we visited each field was randomly determined, for both the morning and afternoon sampling, to make sure the order in which we sampled the fields was not repeated. We sampled the fields 2 – 3 times over the bloom period depending on bloom longevity of the soybean fields (pollinator plot surveys were only conducted during the same day as soybean surveys, so once the soybean had senesced, we stopped sampling). Surveys were conducted when the soybean fields were between the R2 and R5 stages.
During the visual surveys one person documented the bee visitors and one person documented all non-bee visitors. Identifications were made down to the family, genus, or species depending on the level of absolute certainty capable for each insect. The plant that each insect visitor was found on was also documented. After 20 minutes, the visual surveyors switched to conducting netting surveys.
For the entire 30-minute sampling time, one person collected plant visitors using a hand net in order to have an identification verification collection. This collection also allowed individuals unable to be identified visually in the field to be identified later under a microscope. Each visitor was stored in individual 1.7 ml microcentrifuge tubes and stored on ice. The plant that each sample was collected on was documented. After 20 minutes, the visual surveyors also collected samples by net using the same methods. Once the 30 minutes was up, all samples were stored on dry ice until transported back to the lab where they were stored at -80C.
Plant were collected for yield analysis once they reached R8 and then had sufficient time to dry in the field. Plants were collected as close as possible to when the research stations were harvesting the field in order to have realistic harvest conditions and data. 30 plants from both the near soybean field and the far soybean field were removed by walking a haphazard transect and randomizing the distances between each plant selected. Plants were either processed by hand in the field or brought back to the lab for processing depending on impending weather conditions. To process each plant, each node was removed from the plant individually. The number of pods per node and the number of beans in each pod was documented. Any variation in a particular bean – such as deformity, abortion, herbivory damage, or mold – was documented. Once an entire plant was processed, all of the beans from that plant were weighed together. Thus, for every plant we documented the total number of beans, total number of pods, number of pods per node, number of nodes, average bean weight, number of deformed beans, number of aborted beans, number of aborted pods, number of beans damaged from herbivory, and number of beans with mold growth. Beans and pods that were aborted or experienced herbivory damage were not included in the total bean or pod count for the plant.
Educational & Outreach Activities
The presentations counted above include 1 presentation to a local garden club, 1 presentation during a pollinator conference at Montgomery Community College, 1 presentation at the annual national Entomological Society of America conference, and 1 presentation at a local scientific conference (Southern Appalachian Honey bee Research Consortium). The preliminary data on pollinators in soybeans was very well received and sparked a lot of interest. Conversations started by these presentations have resulted in Hannah Levenson, the graduate student on this project, developing a “pollinator in soybean network” with other scientists across 4 different states. Hannah recently worked with two of the scientists in this unofficial network to submit a proposal for a new symposium focused on pollinators in soybean at the next ESA conference.
Hannah also participated in a Pollinator Field Day that was coordinated by the North Carolina Pollinator Conservation Alliance. At this field day she ran a station where she talked about her research to attendees and demonstrated how to survey bees in the field. Attendees also learned a few way to ID different species of bees on the wing.
Currently, Hannah and David Tarpy are in the beginning stages of writing up this project for publication. Hopefully in the next few months it will be ready for submission.