Some Native Bees May Be Valuable for Commercial Pollination Services

LAWRENCEVILLE, Georgia -- Orchard crop producers who rely on the honeybee for fruit production can potentially look to alternative native pollinators for their pollination services.

Researchers with Georgia Gwinnett College are using a Southern Sustainable Agriculture Research & Education (SARE) grant to evaluate native bee populations in northern Georgia apple orchards to determine if any species can carry the pollinating workload in situations where the honeybee may not always be the answer.

"Most farmers of big orchards are highly reliant on the honeybee for pollination, but the cost to bring hives to the orchard may be expensive for farmers, and the honeybee continues to decline across Georgia. Anecdotally, farmers who raise honeybees lost an average of 40 percent of the hives last year," said zoologist and project coordinator Mark Schlueter. "The goal of our project was to determine what native bee pollinators exist in the environment and if their populations are high enough to be a force for commercial-scale pollination. Could we boost the native populations to supplement or even replace the honeybee in pollinating apple orchards?"

Schlueter, along with taxonomist Nick Stewart, are conducting their assessment at four orchards across northern Georgia: Mountain View Orchards, Mercier Orchards, Hillside Orchards, and Tiger Mountain Orchards. In their initial work, supported by the Southern SARE On-Farm Research Grant, “A Measurement of the Pollination Success of Native Bees in North Georgia Apple Orchards: Is there a need for commercial European honeybees?” (OS11-061), Schlueter and Stewart documented nearly 100 different kinds of native pollinators, including moths, beetles, flies and bees.

"We wanted to know what native bees are there and when because only certain bee species are relevant to apple pollination," said Schlueter.

Of the native pollinators documented, the one that was naturally present in large numbers at all 4 orchard locations at the time of apple blossoming were the mining bees, specifically Andrena crataegi -- a species about the size of honeybee.

Stewart describes it as the "perfect apple bee."

A mining bee (Andrena crataegi) looks out its burrow in a sand patch under an apple tree. Photo courtesy of Mark Schlueter.

“Most Andrena species are solitary, but this species is communal,” said Stewart. “They are most abundant in the spring when the apple trees are blooming, and then they disappear for the rest of the season.”

Andrena crataegi lives in enormous systems of underground burrows close to its food source. Both males and females are pollinators, and research has documented males even sleeping on apple blossoms.

“Their behavior is conducive to making it a more valuable bee for potential commercial pollination services,” said Stewart.

Georgia Gwinnett College student Nick Stewart sampling native bees at a northern Georgia apple orchard. Photo courtesy of Mark Schlueter.

Another documented bee species that may have pollination potential is the mason bee of the genus Osmia. The mason bee may be small, but its pollinating efficiency is 10 times that of the honeybee.

“Efficient pollination occurs when bees pollinate all ten ovules in a flower. This results in large, sweet apples with 10 seeds,” said Schlueter. “Inefficient pollination of the flower results in smaller apples with fewer seeds – often referred to as ‘bag apples’.”

Stewart sees the mason bee as a backup to the mining bee when apple trees blossom earlier than normal. In 2011, apple orchards across northern Georgia bloomed three weeks early. This year, they bloomed five weeks early.

“The mason bee emerges even earlier than the mining bee, so they are available to pollinate early-blossoming apple trees,” said Stewart.

In a newly funded Southern SARE On-Farm Research Grant, “Native Bee Assessment in North Georgia Apple Orchards: Measuring diversity and devising methods to boost abundance (OS12-066),” the researchers are studying best methods to provide artificial habitats for the mining bee and mason bee.

Since the mining bee requires exposed, sandy soils close to their food source as a habitat, Schlueter said that sand-filled boxes placed near the apple trees are being evaluated as a potential artificial habitat.

For the mason bee, which is a cavity nester, the researchers are using bundles of hollow bamboo as reed nests and hanging them in various places in the orchard.

The native bee assessment will continue for the next two years, which also will include how effectively the native bees pollinate the apple orchards.

“Preliminary data seems to suggest that the native pollinators are more effectively pollinating the apple trees than the honeybees,” said Schlueter. “Unlike the honeybee, which rapidly flies from one flower to the next, the native bees are spending more time at each flower and carrying away more pollen.”

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Published by the Southern Region of the Sustainable Agriculture Research and Education (SARE) program. Funded by the USDA National Institute of Food and Agriculture (NIFA), Southern SARE operates under cooperative agreements with the University of Georgia, Fort Valley State University, and the Kerr Center for Sustainable Agriculture to offer competitive grants to advance sustainable agriculture in America's Southern region.