March 18, 2015
University of Maryland
The world’s most common insecticide does not significantly harm honey bee colonies at real-world dosage levels, a new multiyear, field-based study shows. “Imidacloprid is the most widely used insecticide in the world. It’s not restricted because it is very safe–an order of magnitude safer than organophosphates,” an author said, drawing a comparison with a class of chemicals known to be highly toxic to nearly all living things.
Colony declines are a major threat to the world’s honey bees, as well as the many wild plants and crops the bees pollinate. Among the lineup of possible culprits–including parasites, disease, climate stress and malnutrition–many have pointed the finger squarely at insecticides as a prime suspect. However, a new study from the University of Maryland shows that the world’s most common insecticide does not significantly harm honey bee colonies at real-world dosage levels.
The study, which was published March 18, 2015 in the journal PLOS ONE, looked at the effects of the insecticide imidacloprid on honey bee colonies over a three-year period. To see significant negative effects, including a sharp decrease in winter survival rates, the researchers had to expose the colonies to at least four times as much insecticide encountered under normal circumstances. At 20 times the normal exposure levels, the colonies experienced more severe consequences.
The study does not totally absolve imidacloprid of a causative role in honey bee colony declines. Rather, the results indicate that insecticides are but one of many factors causing trouble for the world’s honey bee populations.
“Everyone is pointing the finger at these insecticides. If you pull up a search on the Internet, that’s practically all anyone is talking about,” said Galen Dively, emeritus professor of entomology at UMD and lead author of the study. “This paper says no, it’s not the sole cause. It contributes, but there is a bigger picture.”