By Ann Robinson—Iowa State University Extension and Outreach
Honeybees are facing tough times. Colonies of these pollinators are being lost at an unprecedented rate, and some are blaming farming practices, in particular, the intensive corn and soybean production systems in the Midwest. New research by Iowa State University and University of Illinois scientists offers a more nuanced view of the role of agriculture in honeybee health than what has been previously known.
Scientists placed honey beehives next to soybean fields in Iowa and tracked how the bee colonies fared over two growing seasons. The bees did well for much of the summer, they found. The colonies thrived and gained weight, building up their honey stores.
But in August, the trend reversed. By mid-October, most of the honey was gone, the team discovered, and the bees themselves were malnourished. The researchers moved some of the affected hives to reconstructed prairie sites with a lot of late-flowering prairie plants. Those hives rebounded to healthier levels and were better prepared for winter. “We saw a feast or famine kind of dynamic happening, where in the middle of the summer the hives in ag fields were doing great. In fact, the hives in the most highly agricultural areas out competed hives in areas with less row-crop production,” said Amy Toth, professor of ecology, evolution, and organismal biology at Iowa State. “But then they all just crashed and burned at the end of the season,”
Toth was part of a collaborative team that included ISU entomology professor Matthew O’Neal and University of Illinois entomology professor Adam Dolezal. Dolezal performed the work while a postdoctoral researcher at ISU, along with two graduate students, Ashley St. Clair (in ecology and evolutionary biology and entomology) and Ge Zhang (in entomology). Their findings, published this week in the Proceedings of the National Academy of Sciences, offer new insights into the role of agriculture on honeybee survival, according to the report’s authors.
Overall, the results show that intensively farmed areas can provide a short-term feast, but such landscapes are unlikely to sustain the long-term nutritional health of colonies. However, reintegration of biodiversity into such landscapes may provide relief from late season nutritional stress. “There’s been a lot of interest in how bees respond to agriculture,” Dolezal said. “There’s been work on pesticides, and predictions that intensively farmed landscapes have lost a lot of floral resources important for pollinators.”
On the other hand, there have been studies that found honeybees do well in agricultural areas, Dolezal said. “One hypothesis has been that bees near agricultural zones have more access to flowering crops and weeds like clover than those near forests, which can have fewer flowering plants,” he said.
This article was developed in cooperation with the University of Illinois News Bureau.