More kinds of bees means better crop yields, research suggests

By Joshua Learn, E&E reporter
Greenwire: Monday, May 12, 2014

Pollination works best and leads to more productive crop yields when several kinds of bee species are involved, new research suggests.

Researchers from North Carolina State University found that blueberries produced more seeds and grew larger when visited by a diverse variety of bees -- a revelation that could add fuel to recent worries over dwindling populations of the insect because of pesticides, habitat loss and other threats.

"It shows the importance of bees in general and that we really need to do as much as we can to promote pollinator health," said David Tarpy, an associate professor of entomology at the university and a co-author of the research paper, published Friday in the journal PLOS ONE.

He said farmers and scientists need to think of the entire pollination system rather than single species groups like honeybees. "There's no one species that optimizes this ecosystem pollination," he said. "It takes a community."

The research, which included five groups of bee species, focused on blueberries because the fruit relies on insect pollination and is a valuable, well-understood crop.

Shelley Rogers, a former graduate student and lead author on the report, worked for two blueberry seasons. When flowers blossomed, she would lift off special nets and wait until a single bee showed up to pollinate the flower. Once the bee finished, she put the net back on. Rogers later returned to measure the blueberry's size by dissecting it and counting the number of seeds inside.

"Bigger blueberries have more and larger seeds," Tarpy said.

The results showed that when it comes to pollination, honeybees tended to provide quantity over quality, while other bees did a better job pollinating in individual trips. "You can't just rely on honeybees," Tarpy said. He pointed out that some larger farms truck in whole colonies of honeybees to pollinate their crops.

Native species like bumblebees, carpenter bees and southeastern blueberry bees also put in extra work by foraging for nectar when the weather isn't as nice. "Relying on one type, either managed bees or nonmanaged bees, does not optimize the system," Tarpy said.

He said single blossoms also needed to be visited multiple times to get the maximum amount of pollination. "Sometimes you need dozens of visits for a marketable fruit or vegetable."

"Coach" Mark Smallwood, executive director of the nonprofit Rodale Institute, which focuses on pioneering organic farming practices, agreed that "the more diversity, the better."

"It's just like anything," he said. "We wouldn't want to mono-crop blueberries, so we wouldn't want to mono-crop the pollinators, either."

Smallwood said honeybee hives in the United States are down to 2 million from 7 million in the 1940s. Because the honeybees were introduced into the United States, they need stewardship from beekeepers, he said. "The honeybee needs the beekeeper; the indigenous bees do not."

He said honeybees and native bees "tend to work very well together and will actually move each other around in a blueberry orchard or an apple orchard."

A separate study released Friday in the journal Bulletin of Insectology found that neonicotinoids -- insecticides applied to corn and soybean seeds -- are killing entire honeybee colonies as bees exposed to the chemical abandon their colonies and die during the winter (Greenwire, May 9). However, earlier research by Chensheng Lu, a professor in Harvard University's School of Public Health and the study's lead author, has faced criticism from the insecticide industry and some bee experts.

A U.N. report released in 2011 said that the "potentially disastrous decline in bees ... is likely to continue unless humans profoundly change their ways, from the use of insecticides to air pollution."

"The fact is that of the 100 crop species that provide 90 percent of the world's food, over 70 are pollinated by bees," Achim Steiner, executive director of the U.N. Environment Program, said in a release on that report.

Tarpy said climate change could affect crop pollination as well considering that honeybees are often finicky with weather. He said that although the colonies self-regulate their temperature, honeybees often won't pollinate crops when it rains, while others such as carpenter bees or bumblebees will.

"More rain would place more of a need on native bees if climate were to change that way," Tarpy said, adding that some species that don't live in colonies could be more affected by temperature changes.

Reprinted from Greenwire with permission from Environment & Energy Publishing, LLC., 202-628-6500.

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