Scientists test alternate pollination methods for cranberries

Around this time every year, cranberry flowers blossom for a about four-week period during which pollination needs to occur. To make sure this happens, cranberry producers often rely on bringing in beekeepers with honeybees to get the job done.

However, with the occurrence of colony collapse disorder — an unknown phenomenon causing honeybee colonies to die or disappear — the future of the honey-producing insect is far from stable. The U.S. Department of Agriculture estimates that, since the 1940s, the number of managed honeybee colonies has dropped from 5 million to 2.5 million.

"We've been concerned for quite some time about the honeybee population," said Tom Lochner, executive director of the Wisconsin State Cranberry Growers Association.

In an effort to address this growing concern, scientists at the University of Wisconsin-Madison are researching alternative methods by which growers can pollinate their cranberries. But what's a good substitute for honeybees?

Well, according to the leader of the group conducting the research, Claudio Gratton, wild bees are a possibility.

In the absence of honey bees, wild bees can conduct 30 percent to 50 percent of the occurring pollination, said Gratton, who also is a professor of entomology at UW-Madison. According to the Wisconsin Department of Natural Resources, there are about 500 bee species found in the state.

Gratton hypothesizes that if growers plant wildflowers on the edges of crop fields, the diverse plants and shrubbery will attract native bees that will, in return, pollinate the crops.

This larger variety of plants — instead of just one crop, such as cranberries — will help to attract more bees, Gratton said.

"Imagine going to McDonald's every day," Gratton said about trying to attract wild bees with one plant. "It's just not enough diversity of food."

However, some cranberry growers are skeptical of this method, worrying that bees will pollinate the new plants and not their cranberry crops. After all, cranberries aren't the most appealing fruit to honeybees.

"Cranberry flowers, themselves, don't have a lot of nectar or pollen, so one of the challenges is getting the bees in there," Lochner said.

"Bees like it — but they don't love it," Gratton said about cranberries, also citing the plant's specialized structure and unappealing shape as reasons for the bees' distaste.

Lochner said growers also are anxious about any resulting weeds that could possibly migrate into the cranberry marshes and affect the crops' yield.

Despite this, Gratton hypothesizes the presence of wildflowers and other plants will not have a negative effect on cranberries. He anticipates new wildlife in areas surrounding the crops will ultimately enhance pollination for the intended harvest.

Still, unlike honeybees — which are easier to domesticate — native bees are more difficult to manage and predict, said Mary Brown of Glacial Lake Cranberries Inc. She said honeybees are a much more reliable method of pollination for her company's cranberries. She noted the turnout of native bees depends on weather conditions.

She said she expects honeybees will be her cranberries' main source of pollination in the future. However, native bees will help to fill in the gaps.

"They will always complement what we're doing," Brown said about the wild bees.

Lochner echoed a similar line of sentiment. Although he said cranberry growers are interested in new pollination methods — for example, some producers are experimenting with commercial bumblebees, rather than honeybees — he still expects producers to use beekeeping services.

"Growers are still going to look to supplement the native population with commercial honeybees," Lochner said.

Melanie Lawder can be reached at 715-423-7200. Find her on Twitter as @mel_lawder.