Growing Georgia
Native Bees Important Pollinators for Blueberries
By Allison Floyd
Wednesday, Dec. 11, 2013
Honey bees are vital to agriculture, pollinating most fruit and crops.
So, as many researchers try to figure out why the country has lost half its honey bees – from 5 million managed colonies in the 1940s to 2.5 million today -- North Carolina State University has been studying how farmers can maximize native bee species and minimize their need to ship in bee hives.
“Widespread concerns over the fate of honey bees and other pollinators have led to increased efforts to understand which species are the most effective pollinators, since this has huge ramifications for the agriculture industry,” said Hannah Burrack, an associate professor of entomology. “However, various research efforts have taken a wide variety of approaches, making it difficult to compare results in a meaningful way.
“We’ve developed a set of metrics that we think offers a comprehensive overview of pollination efficiency, which would allow researchers to compare data from different crops and regions.”
The research looked at four metrics. First is single-visit efficiency, which measures the number of seeds produced when one bee visits one flower. Second is abundance, which measures the number of each type of bee observed in a study area. Third is inclement weather behavior, which tracks how active a bee species is during cool, cloudy and/or windy weather. Fourth is visitation rate, or the number of flowers that a bee visits while foraging, and the amount of time it spends at each flower.
Specifically, graduate student and lead author Shelley Rogers assessed how well native bee species pollinated highbush blueberry crops in North Carolina. She found that small native bees were efficient in their first visits and were active during inclement weather. But the small native bees weren’t very abundant or appear to visit very many flowers.
“The perfect bee would produce a lot of seeds and visit a lot of flowers, even in poor weather – and there would be a lot of them,” Burrack says. “But as far as we know, the perfect bee doesn’t exist.”
That means a mix of bees might make up the best pollination plan, and the make-up of that group of bees would depend on conditions in the field. One day, extension agents or crop consultants might use data like the information collected at NC State to recommend a pollination plan for a farmer.
For instance, considering weather conditions during early spring and expected bloom date, a consultant might advise a farmer how to nurture certain native species, estimate how much of the crop those bees would pollinate and recommend how many other bees should be added to the mix to maximize yield.
“Honey bees are the work horses of pollination; no one is saying we don’t need them,” said David Tarpy, an associate professor of entomology and co-author of a recent NC State paper on the research. But 4,000 native species also can pollinate; studying those species strengths and weaknesses might allow farmers to rely more on native species.
“It is incredibly complicated because every crop is different, every region is different, every pollinator is different,” Tarpy said. “But this (research) is taking that first step to understand the different pollinators in a system and the pros and cons of each one.”
Experts have profiled individual bee species fairly well. They know how active individual bees are at certain temperatures, for example, but they still are learning how different species might work together in a community and how that would maximize pollination and yield.
“If it’s cold weather, bees don’t want to fly,” Tarpy explained. “So depending on the time blueberries are blooming, the farmer may need a mix of pollinators. The recommendation may be to foster ground-nesting bees and or supply wood for carpenter bees.”
“This highlights the importance of incorporating multiple metrics,” Tarpy said.
Researchers looking only at visitation rates or abundance might think the small native species are unimportant, but they actually appear to be important pollinators for blueberry growers, he said.