Pollinators are essential for optimizing yields of specialty crops such as blueberry. Both managed honey bees and wild bees provide this service by visiting crop flowers and transferring pollen between plants, which eventually leads to fruit. Wild bees are particularly efficient at moving pollen, which is one reason growers have increasingly been trying to attract wild bees to their farm. One way to do this is to put in pollinator habitat. In blueberry, this often means a small parcel of land adjacent to the crop is seeded with wildflowers attractive to wild bees. And presence of these plantings has been shown to increase wild bee diversity and abundance. However, the proximity of these wildflower plantings to active pest management (pesticide sprays) could put bees at risk of increased pesticide exposure. In this project, we will determine if presence of these plantings on farms leads to elevated pesticide exposure, and where on the farm pesticide exposure is the highest (wildflower plantings, weeds adjacent to the crop, etc.). Finally, we will be testing some strategies growers can use to decrease pesticide residues in wildflower plantings, such as use of drift reduction technology, or changing the placement of these plantings.
Managing crop pests during the bloom of bee-pollinated crops, such as blueberry, can be particularly challenging. Growers must strike a balance between effective suppression of pests, and limiting risks to pollinators. This project will better understand the risks pesticides pose to managed bees during blueberry bloom, and test strategies for mitigating these risks.
Pesticide exposure - The project will identify and quantify pesticides found in bee collected pollen from managed bumble bees (Bombus impatiens) and honey bees (Apis mellifera) brought into blueberry fields for pollination. We will also identify the source of the pollen (what plants the bees are visiting). This will help us determine if managed bees are being exposed to pesticides through pollen and if so, where exposure is coming from.
Disease risks - Beekeepers often find that their hives have elevated rates of European foulbrood (EFB) disease after blueberry pollination. Therefore, we are testing strategies for reducing EFB rates in honey bees by exploring some of the potential stressors that could be leading to high rates of infection, such as poor nutrition, and pesticide exposure. We are also testing beekeeper strategies for mitigating these stressors.
Best management practices - Finally, we are testing grower best management practices, such as night spraying and use of drift reduction technology, to reduce risk to bees while suppressing pest populations.
Alternative managed pollinators, such as leaf-cutter bees (Megachile) and bumble bees (B. impatiens), have increased in use for pollination of specialty crops. It's thought that one way to support these alternative pollinators is to provide them with a wider diversity of flowering plants. One way to do this is by establishing wildflower plantings adjacent to crop fields. This project will test if presence of pollinator plantings adjacent to blueberry and cherry fields improves the health of these target pollinators.
Highbush blueberry is pollinated both by managed bees (mostly honey bees) and wild bees. In fact, wild bees account for between 10-80% of pollination provided to highbush blueberry in Michigan. But there have been recent concerns about declines in wild bee populations around the world. Given that wild bees are so important for this crop, we wanted to evaluate changes in wild bees in blueberry fields over time. Therefore, we are comparing the diversity and abundance of wild bees found in blueberry fields over a 14 year period (2004-2018), using consistent repeated sampling methods.
Additionally, Very little is known about the current status and trends of most wild bees. Therefore, using museum specimens, and contemporary collections, we are comparing current wild bee diversity to historic rates around the state of Michigan.
Michigan is a leading producer of highbush blueberries, with a record ~110 million pounds harvested from the 22,000 bearing blueberry acres in 2016. However, despite high flower density and strong bush health in the spring of 2018, growers harvested only 66 million pounds, causing significant economic loss and financial hardship to the blueberry industry. This 50% crop loss came after a short period of extreme heat experienced at the end of May 2018, when many areas of the states’ blueberry fields were in bloom. While these things happened in the same year, we do not know enough about the effects of extreme heat on pollination form the plant or insect side of the interaction to be able to make recommendations on how to mitigate heat effects on pollination. Extreme spring weather in this region is expected to intensify with climate change, but the lack of previous experience under these conditions helps to explain the limited information on the degree to which these abiotic stressors affect blueberry pollination. For example, there are no published reports on threshold temperatures that inhibit key steps in the blueberry pollination process. Building on our recent preliminary research, this project will investigate the effects of extreme heat on blueberry pollination, provide insight on future cooling strategies to help ensure yields of this valuable crop, and determine whether extreme heat affects the nutritional value of pollen for bees. Our results will form the foundation of future interdisciplinary proposals to USDA-NIFA Foundational and USDA-SCRI.
Land managers face challenges that may limit their ability to support bees using wildflower plantings. This research seeks to determine the best strategies to establish these plantings to optimize pollinator abundance. This ongoing experiment at the Clarksville Research Center is designed to determine the best combination of 1) land preparation methods, 2) seeding rates, and 3) post-seeding management methods to improve pollinator habitat establishment.