When bees from commercially run hives go out looking for food, they're basically limited to eating nectar and pollen from the crops farmers want pollinated. That can be problematic for the insect's diet — and their long-term survival amid the mass die-off of honeybees over the past decade.
That's what Penn State entomologist Christina Grozinger discovered while in the middle of a recent bee research study. She and her colleagues originally set out to look at the effects of pesticides on bee genes, but when they started seeing the consequences a restricted diet had on bees, they were intrigued.
Soon, they changed course and set out to find out what a bad diet means for the health of commercial honeybees, who pollinate a third of the world's food supply.
In a study published Friday in The Journal of Insect Physiology, Grozinger and her colleagues gave test bees a soy-based diet, a no-protein diet, or a natural, varied diet of pollen. At the same time, the bees were given a lethal dose of the pesticide chlorpyrifos, an insecticide frequently used on agricultural crops. After 16 days, they counted which bees survived the longest.
What did they find? Nature does it best.
Bees who ate the natural diet of varied pollen sources survived longer — an average of four days longer — than the bees on artificial diets. While that may not sound like much, Grozinger said it's actually significant.
"When you think of a whole colony of 50,000 bees, during those four extra days they can contribute to the good of the colony," she said.
The researchers still aren't quite sure why diet has such a big effect on the bee's mortality. It could be that a healthier diet helps them detoxify pesticides better.
Still, it looks like the best diets for bees are the most diverse.
"Different pollens have different nutritional profiles," Grozinger said. "Bees need a complex diet to get all the nutrients they need — just like humans."
That's the opposite of what commercial bees get. Their diets typically come from a single pollen source — supplemented seasonally with a non-pollen source of protein like soy or egg yolks.
The researchers' next study will examine what an optimal diet is for bees, and if bees go out in search of the exact macronutrients they need.
"Anything we can do to improve bees' survival is important, and having better and more diverse forage sources is important," Grozinger said. She pointed out that bees face multiple threats: pesticides, poor nutrition, pathogens, and parasites. "Good nutrition can help bees handle multiple stressors," she said.