As commercial pollinators, bumblebees may fly to the rescue in Delaware

Honeybees have long been used in agriculture to help pollinate crops. But with populations declining due to the devastating colony collapse disorder, it seems more farmers are looking elsewhere for pollination help.

Now, University of Delaware researchers are studying how the honeybees’ larger cousins — bumblebees — work as pollinators on Delaware farms.

Kevin Evans, a third-generation farmer from Bridgeville, Delaware, had always used honeybees to help pollinate his crops. So had his father, and grandfather before him. But several years ago, he made a switch in his watermelon fields.

“Seven or eight years ago, there was some concerns with the health of some bees. There was the bee decline, and some harsh winters on ’em in the local area,” Evans said.

He heard it was getting hard for beekeepers to meet demand.

“I just was proactive, and started to look into another pollination source at the time,” Evans said. “And looked into bumblebees, and it looked like it could be a fit.”

Testing bumblebees in the field

According to the Delaware Department of Agriculture, there have been no documented cases of colony collapse disorder in the First State. However, both a department spokesman and Evans said that, anecdotally, they have seen more and more local growers using commercial bumblebee hives.

Unlike honeybees, bumblebees are an annual species — they die and new hives start each spring. A few years ago, some growers approached University of Delaware professor Deborah Delaney with a bumblebee problem:

“They would get them into the field and (the hive) wouldn’t even last through the flowering of one of their first crops,” Delaney said. “So they’ weren’t even lasting through the bloom time in some instances.”

Bumblebees are larger and hairier than honeybees and, as their name suggests, don’t create much honey. Commercial bumblebees have been available and used in the U.S. for years, but Delaney said much of the academic research surrounding bumblebees has studied them in the wild or greenhouses.

So, Delaney launched a project looking at how to best use bumblebees in the field.

On a recent morning, the project took her to the University of Delaware cooperative extension in Georgetown.

Determining where hives will thrive

Thirty medium-sized cardboard boxes filled with bees were stacked high in an outbuilding, waiting to be sorted. They arrived the night before in a refrigerated truck from Michigan.

Jackie Marchese, the graduate student overseeing the project, removed each of four smaller, ventilated plastic boxes from the larger artificial hive, releasing the sound of a heavy buzz. She labeled and weighed each hive.

“As the season progresses, they collect pollen, collect nectar, and it’s a way of measuring how productive they’re being throughout the season,” Marchese said.

The team loaded the boxes up onto a pickup truck and took them to three different fields.

Some go in direct sun, others in the shade where field meets forest, while a third group nestles under a little cardboard tent that provides shade in the middle of the field.

Marchese will come back weekly throughout the summer to weigh the hives, to see which bees are living longest, and to test what kind of pollen the bees bring back

“Are they collecting watermelon pollen or are they going in and getting some sort of random flower in the forest?” Marchese said.

Bumblebees are not immune

Bumblebees are not suffering from the same widespread devastation as honeybees. But select species of bumblebees have seen staggering declines in recent decades.

Some scientists believe pesticides are the culprit. Others suggest a link between new pests and pathogens that commercial bumblebee hives bring with them to native populations.

The Delaware Department of Agriculture is monitoring the issue this summer, and Deborah Delaney said the idea does worry her.

“Any scientist who is looking at bumblebees as potential pollinators, especially in this type of system, is worried about the possible spread of pests and pathogens,” Delaney said. “But I think the overall trend of bumblebee decline, at least nationally, we don’t know all the causes. But that’s definitely a concern.”

The team is testing the bees for some common pests and microscopic organisms, and for genetic diversity, hoping to tease out some answers.

“Growers are using them, and we need to know what the ramifications are,” Delaney said.

Farmer Kevin Evans says bumblebees do just as well, if not better, than honeybees in his watermelon fields.

But if the University of Delaware team could figure out a way to make his bees live longer, he could get more use out of each bee box, which cost him well over $200 each.