By Doug Graves
LONDON, Ohio – According to the American Bee Journal, the 10 best flowers for attracting honey bees are lavender, black-eyed Susan, zinnia, sunflower, rosemary, lilac, white wild indigo, marsh blazing star, purple coneflower and goldenrod.
There’s no documentation that the flowers from soybeans crack the top 20, but research shows that bees are foraging on them in droves and most farmers and beekeepers are unaware they’re out there.
“Most people don’t associate honey bees with soybeans, but our studies show that honey bees have been visiting these soybean fields for a long time,” said Dr. Chia-Hua Lin, research scientist at the Rothenbuhler Honey Bee Research Laboratory at Ohio State University. “It’s just that we haven’t paid attention to this fact. The flowers of the soybean plant are very small and most people haven’t noticed the flowers nor the bees around them. However, beekeepers have begun to take notice. I’ve been in conversation with beekeepers in Ohio and those who have kept their hives near soybean fields say they’ve had big honey flows come in around the time when soybean plants are at their peak.”
Lin’s research began six years ago when she and her associates set up observation hives at the Molly Caren Agricultural Center in Madison County prior to the soybean bloom in 2016. The purpose was to study the bees’ waggle dances (or movement) and foraging behavior around the soybean fields. The bee waggle patterns were recorded once a week on fair-weather days from 11 a.m. to 3:30 p.m. During each session, hives were recorded for one hour using Canon Vixia HF G20 video cameras. This research was done from July 14 to Aug. 8 each year.
Videos showed that worker bees discovered the tiny soybean flowers and returned to the hive to inform other bees of their discovery. Lin and her staff learned that these foragers preferred soybeans over other habitats between 0.5-1.5 kilometers from the hives, as indicated by a higher percentage of foraging activity in soybean fields than landscape makeup would predict.
“Our results suggest that the soybean plant is an important floral resource for honey bees in Ohio’s agricultural landscape,” Lin said, “and the honey bees prefer soybean flowers over other blooms.”
Lin said her lab is currently performing two other bee/soybean-related studies.
“First, we’re studying how much of the honey production in Ohio comes from the soybean blooms,” Lin said. “In another study, we’re looking at how much honey bee pollination contributes to the soybean yield.”
Soybean fields, with their large expanses of uniform green plants, seem an unlikely habitat for bees and other pollinator insects. The tiny white or purple flowers of soybeans are self-pollinated, so they technically don’t need assistance from friendly insects for the seed-development process. These attributes have steered most soybean research projects toward yield-robbing pests like bean leaf beetles, aphids and stink bugs.
Kelley Tilmon, an entomologist at Ohio State, helped spearhead a recent Pollinator Diversity Study, a multi-year project funded by the Ohio Soybean Council and the North Central Soybean Research Program that investigates the diversity of pollinator insects in soybeans.
Tilmon said pollinators play a positive role in soybean yields.
“For many years, people didn’t worry very much about whether there were pollinators in soybeans,” Tilmon said. “However, there is some evidence now that, even though soybeans are self-pollinated, having a good pollinator community might actually enhance yields.”
Pollinators include wasps, ants, butterflies, flies, moths and beetles. Performing the most work, though, are bees.
“We’ve found close to 48 different pollinator species in Ohio soybeans and bees are the majority,” said Tilmon, referring to mining bees, leaf cutter bees, plasterer bees, sweat bees and honey bees.
Tilmon and her colleagues used a special insect trap called a bee bowl to monitor the insect populations in eight different Ohio soybean fields during the flowering through pod-filling growth stages. Out of all the bee species collected, sweat bees were the most abundant, but the honey bee numbers are not far behind.
“The extent to which honey bees forage on soybean flowers has been hotly debated among beekeepers and soybean growers for decades,” Tilmon said. “The soybean is not considered an attractive nectar source because honey bees are only occasionally observed on soybean flowers. However, because soybean flowers grow inconspicuously under the leaf canopy, foraging activities of bees in a soybean field can easily go unnoticed.”
Lin and her researchers say the soybean is potentially valuable to pollinators as a nectar source, as an individual soybean flower can produce up to 0.5 microliters of nectar with mean concentrations from 37 to 45 percent. A soybean plant produces an average of 200 to 800 flowers.
“I have yet to hear of soybean farmers renting honey bee colonies, but it makes sense to have soybean farmers and beekeepers working together to improve the crop’s yield,” Lin added.