Feeding honeybees a diet of natural pollen makes them significantly more resistant to pesticides than feeding them an artificial diet, according to Penn State University research.

"Our study demonstrates that exposure to non-lethal doses of at least two of these pesticides causes large changes in the expression of genes involved in detoxification, immunity and nutrition-sensing," Christina Grozinger, professor of entomology and director of the Center for Pollinator Research, Penn State, said in a news release.

"This is consistent with results from previous studies that have found that pesticide exposure compromises bees' immune systems. Furthermore, our study reveals a strong link, at the molecular level, between nutrition, diet and pesticide exposure."

Further work found that diet significantly affects how long bees can survive lethal pesticide doses.

To determine the effects of pesticide exposure on gene expression, the researchers first fed one of two miticides—coumaphos or fluvalinate—to the bees for seven days.

On the seventh day, they extracted RNA from the bees, attached fluorescent markers and examined the difference in gene expression.

They noticed a change in patterns between the treated bees and the untreated control bees.

A subsequent trial examined bees fed a pollen diet compared to an artificial diet of either soy protein or a no protein diet.

They were then fed a lethal dose of chlorpyrifos, and the researchers recorded bee mortality for 16 days.

The researchers found that bees fed a pollen-based diet had less sensitivity to chlorpyrifos compared with the bees fed an artificial diet.

They published the results in the online issue of the Journal of Insect Physiology.