Pesticide-Ridden Pollen Kills Honeybee Larvae Within Hives, New Regulations Urged

A group of scientists is urging the US Environmental Protection Agency to change its pesticide regulations after a new study revealed that four pesticides commonly used on crops to kill insects and fungi also kill honeybee larvae within their hives.

Honeybees are vital to to flowering crops and recently their numbers have been declining worldwide as disease and the mysterious colony collapse disorder take their toll.

"Our findings suggest that the common pesticides chlorothalonil, fluvalinate, coumaphos and chloropyrifos, individually or in mixtures, have statistically significant impacts on honeybee larval survivorship," said Chris Mullin, a professor of entomology at Penn State University. Mullin, Penn State entomology professor Jim Frazier, and colleagues from the University of Florida, published their research in the journal PLOS One.

"This is the first study to report serious toxic effects on developing honeybee larvae of dietary pesticides at concentrations that currently occur in hives," Mullin said.

The team also discovered that N-methyl-2-pyrrolidone (NMP) - an inactive chemical often used as a pesticide additive - is highly toxic to honeybee larvae and its presence corresponded to increased larval mortality, even at the lowest concentration tested.

"We found that four of the pesticides most commonly found in beehives kill bee larvae," Frazier said. "We also found that the negative effects of these pesticides are sometimes greater when the pesticides occur in combinations within the hive. Since pesticide safety is judged almost entirely on adult honeybee sensitivity to individual pesticides and also does not consider mixtures of pesticides, the risk assessment process that the Environmental Protection Agency uses should be changed."

An average of six insecticides is present on pollen bees bring back to their hive, the researchers found. The pollen is used to feed bee larvae.

To study the effects of these insecticides on bee larvae, the researchers reared honeybee larvae in the lab, applying the chemicals to larvae food alone and in combination with others.

"Chronic exposure to pesticides during the early life stage of honeybees may contribute to their inadequate nutrition or direct poisoning with a resulting impact on the survival and development of the entire bee brood," Mullin said.

In the course of their research, Mullin and his colleagues documented the adverse effects common "inactive" ingredients in pesticides were having on honeybees.

"Multi-billion pounds of these inactive ingredients overwhelm the total chemical burden from the active pesticide, drug and personal-care ingredients with which they are formulated. Among these co-formulants are surfactants and solvents of known high toxicity to fish, amphibians, honey bees and other non-target organisms. While we have found that NMP contributes to honeybee larvae mortality, the overall role of these inactive ingredients in pollinator decline remains to be determined," Mullin said.

"There is a growing body of research that has reported a wide range of adverse effects of inactive ingredients to human health, including enhancing pesticide toxicities across the nervous, cardiovascular, respiratory and hormone systems," Mullin added. "The bulk of synthetic organic chemicals used and released into U.S. environments are formulation ingredients like NMP, which are generally recognized as safe. They have no mandated limits on their use and their residues remain unmonitored.