WEST LAFAYETTE, Ind. — Life is fragile for Apis mellifera, the Western honeybee. In nature, there are many ways a honeybee might die, including starvation, bacterial and fungal diseases, viruses, parasites and being wolfed down by predators such as skunks.

In recent times, the list has been expanded to include toxic demise from exposure to pesticides. CCD, or Colony Collapse Disorder, has received much press in recent years as a blanket explanation for the noticeable decline in honeybee populations worldwide.

In December 2011, the U.S. Environmental Protection Agency (EPA) published an article called “Pesticide Issues in the Works: Honeybee Colony Collapse Disorder.” The article stated when most or all of the bees in a hive are killed by exposure to pesticide, the EPA terms it a beekill incident resulting from acute pesticide poisoning.

The EPA determines such deaths to be different from CCD because they are usually avoidable, the article said. One source of beekill incidents has been found to be the insecticides Clothianidin and Thiamethoxam, which are found in seed coatings on corn and soybeans.

A Purdue University News Service article from January, “Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields,” described research by its Department of Entomology and was published in the scientific journal PLoS ONE.

That article said analyses of dead bees found in and around the hives of test apiaries over a two-year period showed the presence of neo-nicotinoid insecticides. Low levels of Clothianidin and Thiamethoxam were also found in the soil.

Researchers and professors Greg Hunt and Christian Krupke of the entomology department at Purdue, Krispn Given, an agricultural technician for the department, and Brian Eitzer of the Connecticut Agricultural Experiment Station in New Haven collaborated to publish the research paper.

Hunt, a professor of behavioral genetics and a honeybee specialist, said the United States is losing about one-third of its honeybee hives each year. He said there are many factors working against these bees.

According to him, during the study of test apiaries in Indiana, toxic insecticides were found in waste talc stuck on farm machinery that was used to plant nearby cornfields. Krupke said such talc dust is exhausted from farm machinery during planting and routine cleaning. The material then enters the environment. This is one potential route for exposure.

The exposure to the bees could have come by direct contact when flying through the dust plume, or from contact to dust on flowers or other areas that the bees visited. Krupke said the insecticides Clothianidin and Thiamethoxam are applied to all corn seed, as a chemical slurry containing insecticide, fungicides and polymers which attach to the seed.

Hunt said neo-nicotinoidal pesticides are designed based on the structure of nicotine. They bind to the nicotinic acetycholine receptors in the synapses of nerves. Symptoms of contamination seen by researchers during the study were bees lying dead in front of their hives and living bees twitching and showing symptoms of neurotoxicity.

He said the research team did not want to cause widespread panic among growers but wanted them to be aware of the problem. “Pollen consumed by nurse bees to make royal jelly to feed larvae can be contaminated,” he warned.

The researchers’ report may be found online at www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0029268