CORVALLIS. Ore. — Ramesh Sagili, Oregon State University’s honeybee researcher, has long believed nutrition is key to fighting off colony collapse disorder, the mysterious ailment that wipes out hives and threatens crop pollination.
So when he and graduate student Cameron Jack carried out a study in which sets of bees were given various levels and a variety of pollen, they expected a logical result. They assumed the bees that received the most wildflower pollen — a source of protein — would be best able to stave off parasites that weaken bees.
That turned out to be true: Bees fed a high-pollen diet had a higher survival rate. But, surprisingly, they also had higher rates of a pathogen called Nosema ceranae — the opposite of what the researchers expected. They thought better-fed bees would have lower infection rates.
“Even though (Nosema) spore intensities were higher in bees that received more pollen in their diet, the bees in these treatments had greater survival, which appears to be counterintuitive,” the researchers said in a study published in Journal of Insect Physiology.
Better nutrition, they concluded, allowed the bees to compensate for the effect of the pathogens. They survived longer, and examination showed they had higher levels of protein in the head glands that produce food for larvae.
Sagili said the study raises questions about the use of antibiotics, used by many beekeepers to control the Nosema pathogen. Broad-spectrum antibiotics may be causing other problems for bees, such as disrupting the gut structure that helps them digest food.
Sagili said beekeepers have asked him whether they should stop using antibiotics, and he urges a cautious approach. Large-scale keepers, who transport thousands of hives to pollinate crops up and down the West Coast, can’t afford the risk of halting antibiotic use all at once. He suggests trying it with 5 percent or 10 percent of hives and monitoring what happens.
Many observers worry a mono-crop diet may weaken bees as they feed on only one crop at a time while doing their pollination work each year, beginning with almonds orchards in California and working north as other nuts, fruit and berries come into season. Sagili said a “polyfloral” diet provides better nutrition for bees; some keepers give bees a break from mono-crop work to forage naturally and add variety to their diet.
The research work at OSU began in June 2014. Bees for the study were taken from “sister queen” colonies to control any variation in Nosema infection that might be attributed to genetics of the bees. They were divided into five groups, fed varying amounts of wildflower pollen, then exposed to the Nosema pathogen.