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Research Highlights

Research Highlights
Soybeans could be a link to boost honey bee life

Photo by Adam Varenhorst, South Dakota State University

By Carol Brown, USB database communications 

A field of soybean plants chock-full of blooms may look like an all-you-can-eat buffet for pollinator insects. But are bees — which have declined in population over the last two decades — coming to the feast?  

A study, funded by the United Soybean Board (USB), was conducted in Iowa soybean fields to find out whether bees, in particular honey bees, would benefit from soybean production. 

Bee-ology 101 

“Both managed honey bees and wild bees are suffering declines in numbers due to a parasitic mite introduced in the 1990s, but they are starting to recover now,” said Adam Dolezal, assistant professor of entomology at the University of Illinois, who conducted post-doctorate work at Iowa State University (ISU). 

To help bees regain their numbers, they need sources of nectar and pollen. Soybean fields have both. 

 “There’s about 4,000 species of bees found in North America. When we use the term ‘wild bee,’ I’m referring to those,” said Matt O’Neal, lead project investigator and ISU entomology professor.  “When we think about honey bees, we don’t think of them as wild: they’re kept, they’re managed, you might even say they’re domesticated. But when they get loose, they’re like feral horses.” 

A lack of forested areas in Iowa and other agriculture-centric states means there aren’t many natural habitats, such as a hole in a tree, for feral honey bees. Humans need to manage honey bee populations in colonies of hives. But to get the bees to take advantage of all the soybean nectar, they need to be placed near the fields. 

Enter the bee team at ISU. They placed 20 honey bee hives adjacent to soybean fields in central Iowa for two growing seasons. Their results produced some answers and created a path for further study. 

Soybeans and bee diets 

“We saw the colonies all grew during the early part of the summer, reaching maximum weight,” Dolezal said, “Then starting about mid-August, almost all the colonies just crashed. They started to eat all their honey stores and they lost the weight they had gained throughout the summer.” 

They found the switch point where bee weight loss began. The end of soybean bloom was at the same time as the end of clover bloom, the other main pollen source for the bees.  

“The bees had this feast available in the early part of summer when both soybeans and clover are blooming. But once those blooms end, there’s really nothing out on the landscape for them to eat,” Dolezal said. 

The researchers were able to reverse this by moving the bee hives near fields of restored prairie. The bees did well near the prairie as they found flowers after the soybeans and clover finished blooming. In a prairie there are different plants in bloom throughout the summer and into fall. The research team saw a strong reversal of the honey bee weight declines in this situation. 

Expanding on findings 

Based on their results from the USB study, the researchers secured a nearly $1 million, three-year grant from the United States Department of Agriculture (USDA). They are continuing to explore how honey bees use soybeans and how farming practices, such as spraying for aphids, affect the honey bee.  

“The USB-funded project laid the groundwork for us to expand this research,” O’Neal said. “This was a big project that got even bigger because of the checkoff money that started it all. It continues to help us understand the factors contributing to honey bee health.” 

Through the USDA project, the research team is further studying honey bees when hives are placed in annual crop fields that also have prairie strips. They are also looking at best management practices that benefit the combination of corn and soybean production, prairie establishment and honey beekeeping.      

Recently, O’Neal and the research team authored a paper on the USB-funded project for the PNAS Journal. 

Other resources:

New Insights on Honey Bee Health in Ag Landscapes from Iowa Study – Iowa State University

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.