Honeybees used to pollinate crops have been exposed to fungicides which impair their ability to fight off a potentially lethal parasite, according to a University of Maryland news release.
A study by the University, joined by U.S. Department of Agriculture, was published on Thursday in the online journal PLOS ONE. It is the first analysis of "real-world conditions" encountered by the pollinating insects.
"The researchers collected pollen from honey bee hives in fields from Delaware to Maine. They analyzed the samples to find out which flowering plants were the bees' main pollen sources and what agricultural chemicals were commingled with the pollen," the University said in a news release.
"The researchers fed the pesticide-laden pollen samples to healthy bees, which were then tested for their ability to resist infection with Nosema ceranae - a parasite of adult honey bees that has been linked to a lethal phenomenon known as colony collapse disorder."
The pollen samples obtained for the study had an average of nine different agricultural chemicals, including fungicides, insecticides, herbicides and miticides, according to the news release.
There was also a presence of lethal agricultural chemicals in every sample, with one specifically contained 21 different pesticides
The most common pesticides found in the honeybee's pollen were the fungicide chlorothalonil, and insecticide fluvalinate.
"We don't think of fungicides as having a negative effect on bees, because they're not designed to kill insects," University of Maryland researcher Dennis vanEngelsdorp, the study's senior author, said in a news release.
According to the University, there is a federal regulation prohibiting the use of pesticides while pollinating insects are foraging.
"But there are no such restrictions on fungicides, so you'll often see fungicide applications going on while bees are foraging on the crop. This finding suggests that we have to reconsider that policy," vanEngelsdorp said.
The findings did not offer an explanation to colony collapse disorder, a unexplainable natural occurrence where honey bee colonies suddenly die. However, scientists hope the study helps shed light on what causes stress on honeybee populations.