Old Dominion researchers eye mason bees for duty

4/26/2014 7:00 AM
By Associated Press

VIRGINIA BEACH, Va. (AP) — The brand-new posthole digger made barely a dent in the ground outside the strawberry patch.

Necessity being the mother of substitution, Lisa Horth abandoned the tool and instead used a hatchet to whack a hole in the turf deep enough to plant the wooden post of a bee house.

The assistant professor of biology at Old Dominion University abandoned the hatchet for a moment, too, when a small, blue-black insect flew past to hover in front of another house, freshly planted a few feet away.

"Oh, oh, ohh! That was a mason bee!" Horth exclaimed.

So far, so good.

Mason bees resemble flies. They live alone. Only females sting, and it's mild.

Plus, they're native to America.

They're not much like honeybees, the quintessential bee-looking bee, which live in colonies and sting.

Honeybees are European, imported to Virginia in the early 1600s by English colonists who wanted a familiar insect to pollinate crops. Since then, they have spread across the country, making themselves indispensable to the agriculture industry. Trucking honeybee hives from state to state has become big business.

But in the early 2000s, honeybee colonies started to vanish. Overnight, an active hive could empty out — abandoned, apparently — with few or no dead bees around. Beekeepers found themselves losing up to 90 percent of their colonies for no apparent reason. The problem has been named Colony Collapse Disorder, and although various culprits have been suspected — neonicotinoid pesticides, mites, viruses — no cause has yet been determined.

The U.S. Department of Agriculture says mass honeybee disappearances also occurred in the 1880s, 1903, 1920s and 1960s. No one knows the cause of those, either. Whatever the reason, pollinator loss affects food production.

"One in three bites of food is produced by a flying insect," Horth said. "Most of those are bees. Bees are a multibillion-dollar industry in itself. And bees are dying."

All of which led her to wonder whether native mason bees could step up to the plate.

Horth has set up research plots at six strawberry farms in Pungo. At half of them, she and her students have installed bee houses and stocked them with mason bee cocoons.

Marked strawberry flowers will be tracked through the growing season to see whether mason bees can supplement honeybees and make a difference in the size, quality and quantity of fruit.

"It's native bees with a plant that they've evolved with," Horth said. "The whole idea that we could pollinate crops with native bees instead of bringing in honeybees is, to me, a great idea."

Strawberries can actually pollinate themselves. But fruits that develop from self-pollinated flowers, or from flowers that are visited only once by an insect, tend to be smaller and misshapen.

"Farmers say people want bigger and more symmetrical fruit," she said. "Repeat pollination makes them that way."

Short strings have been tied around individual flower stems, and those flowers will be monitored for maturation and fruit development. Because some are U-pick fields, the researchers placed three times as many strings as needed for the study, to allow for loss.

In early April, many of the strawberry blooms were nearly open or already being visited by mason bees.

"That's good," Horth said, tying a string around flower stem No. 20-27. "Good for us, good for the farmers, good for the bees. So everybody's happy."

Mason bees will never replace honeybees because the native species doesn't make honey. But they are efficient workers.

Crown Bees, a Washington-based business that provided cocoons for Horth's study, says a female mason bee can pollinate as efficiently as 100 honeybees.

So why haven't mason bees naturally filled the gap left by Colony Collapse Disorder?

Horth said it's because of monoculture — large fields planted in a single crop. Mason bees venture only about 100 feet from where they hatch, compared with the 5-mile radius flown by a honeybee from its hive. They also need a variety of plants so flowers are available from early spring to fall.

"How are you going to get enough bees on your property when you're surrounded by farmland?" Horth said. "So people have sort of created this problem."

To get enough bees at the strawberry fields in Pungo, more than 100 bee houses were installed. Made of bamboo, wood or phragmites — a hollow reed — the houses feature myriad narrow tunnels. Female mason bees stock the tunnels with pollen, lay eggs inside, then seal the opening with mud, which is why they're called "mason" bees. Once the eggs hatch, the larvae eat the pollen and spin cocoons in which they overwinter.

The bee houses perch on posts, which had to be sunk into the ground. While Horth hatcheted postholes, a grad student went in search of a narrow shovel.

"We want this to be a stable system for the farmers, so the bees will keep coming back year after year," Horth said. "So it's a cycle that doesn't involve me anymore, because I'm not very good at digging holes."

___

Information from: The Virginian-Pilot, http://pilotonline.com


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