Investigating the Long-Held Concerns About Blueberry Pollination on Honey Bee Health.

Research team led by Dr. Marta Guarna in Canadian high-bush blueberries during the 2018 field season.

​Many of us know blueberries as the tart and sweet fruit that is mixed into yogurt or made into muffins. Beekeepers know blueberries as a source of pollination income year after year, often right on the heels of almond pollination. If the blueberry bushes bloom early, as they did this year in some areas, there can be a rush to get the bees there to pollinate in time.

Blueberries are native to North America and while they can grow anywhere, some climates are better suited for commercial production than others. According to the United States Highbush Blueberry Council,98% of all commercial blueberries grown in the U.S. come from just 10 states: California, Florida, Georgia, Indiana, Michigan, Mississippi, New Jersey, North Carolina, Oregon, and Washington. In Canada, blueberries are the number one fruit export, relying on honeybees to increase yields and meet demand.  Beekeepers know that bringing their bees to the blueberries will certainly improve fruit yields, but they are less certain about the impact that blueberry pollination will have on their bees. 
 
For many years, some beekeepers have been concerned about the condition of their bees after they come out of the blueberry barrens. They have reported decreased populations and an increase in signs of European foulbrood(EFB) or other diseases. Anywhere the blueberries grow, questions about honey bee health seem to follow. 

Late-stage European foulbrood in honey bee brood. Note the poor brood pattern and dehydrated larval “scales” at the bottom of the cells. Photo credit: Rob Snyder, 2013. For more information on EFB look for Rob’s blog on beeinformed.org

​Researches have wondered if the fungicides used in blueberries are harming the bees? What about the blueberry plants themselves? It is known that blueberry flowers are difficult for honey bees to access, but is there something else about the plant or these conditions that is not good for the bees? PAm has worked to funnel your donations into applied research to help answer these questions. 
 
Current work led by Dr. Priya Chakrabartiand Dr. Ramesh Sagili is looking into the impact of sterol-biosynthesis inhibiting fungicides (SBI’s) on blueberry plants, and the implications that may have for honey bee nutrition. Plant sterols are recognized as an important plant compound for bees, but their exact role is not well understood. 

Collecting blueberry pollen for the study at Oregon State University.

​Former PAm Costco Scholar,  Sara Wood, who is a PhD candidate at the Western College of Veterinary Medicine,  also plans to continue her bee research in the area of pesticides, blueberries, and honey bees. She plans to study the virulence of field-collected EFB strains in honey bees, and whether some pesticides impact disease development. 
 
What is clear about blueberry pollination is that agricultural practices and nutrition are closely interwoven in how honey bee health is impacted.  

Honey Bee Colonies placed in Blueberries in the Pacific Northwest in Early April 2020. Photo provided by George Hansen.

​Early research by Gordon Wardell, who serves on the PAm board of directors, identified some characteristics of blueberry pollen that might be a factor, such as pH. Between that early work and now, questions still remain. Utilizing funds provided by Costco Canada, PAm was able to provide a grant for one of the biggest collaborative blueberry-focused projects to date, coast to coast in two countries, with many participating beekeepers, blueberry growers and bee research labs. 
 
This ongoing study led by Dr. Marta Guarna, a research scientist with the Canadian government, will wrap up at the end of 2020. Beginning in 2018, Guarna set out to follow hundreds of colonies, some involved in blueberry pollination and some not. Her team compared the health status of the two groups by looking at the colony size, brood pattern, and disease symptoms. In addition to recording observations, they took samples from the colonies so that they could be definitively diagnosed with EFB and the frequency of infection compared between the groups. Pesticide analysis may also be performed on some samples at a later date. 
 
Preliminary results, reported in a Canadian honey council publication, HiveLights, clearly show that among colonies involved in the study, there was an increased occurrence of EFB infection in colonies that pollinated blueberries compared to colonies that did not pollinate blueberries.  Building on Wardell’s early work, future findings hope to shed light on the effectiveness of pH adjusted pollen patties in mitigating infection. 
 
By reporting these findings before completing the study, Guarna is giving beekeepers a better understanding of this system in real-time. Her team’s work could lead to ways to manage any negative health effects without resorting to avoiding blueberries, a crucial fruit for local economies.