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Add selenium to the list of things that can be toxic to bees. Entomologists from the University of California, Riverside, have found that selenium can delay development and kill honeybees.

Selenium is a naturally occurring trace element. Low concentrations are beneficial to many animals, and in some regions, sheep and cattle are given selenium injections to prevent illnesses like white muscle disease.

But too much of a good thing can be toxic, especially to bees.

“Selenium occurs naturally in many places around the world, but it also is a byproduct of many industrial activities,” stated Kristen Hladun, postdoctoral entomologist at UC Riverside and lead author of a study focusing on the anthropogenic or man-made pollutant selenium and other heavy metals.

In mining and industrial activities like petroleum refining, coal-power production, and agricultural runoff, selenium can become concentrated in the soil.

The UCR study, published in the October 2013 journal Environmental Toxicology and Chemistry, found that soils high in selenium could contaminate pollen and nectar from plants grown in the contaminated soil.

“Metal pollutants like selenium contaminate the soil, water, can be accumulated in plants, and can even be atmospherically deposited on the hive itself,” Hladun said in a UCR news release.

Selenium enters the honeybee’s body when the bee ingests contaminated pollen and nectar. Hladun is unsure how selenium damages the insect’s internal organs, but organic forms of selenium can alter protein conformation and cause developmental problems, while inorganic forms can cause oxidative stress.

Honeybees at the larval stage were more susceptible to selenium than other insect species, she noted.

Hladun and other researchers involved in the project are also feeding honeybee colonies with selenium-laden food to look for changes in survival and behavior.

A three-year U.S. Department of Agriculture grant is funding the study that began in 2012. Researchers are studying the effects of other metal pollutants, including cadmium, copper, and lead.

Hadlun hopes the selenium information can help beekeepers avoid placing hives near contaminated areas and prevent bees from foraging on flowering plants and weeds with high selenium concentrations.