Scientists from the Purdue University found out that the large part of pollen gathered by bees in Midwestern regions is contaminated by pesticides. The list of dangerous compounds includes both agricultural compounds and insect repellents.
The study was undertaken by Christian Krupke and Elizabeth Long. Experts chose three Indiana sites to place honeybee hives and gathered their pollen during 16 weeks. Their goal was to find out the location of the pollen source and its level of contamination by pesticides.
“We put hives beside fields of treated corn, untreated corn and also a meadow environment,” said professor Krupke. “A more natural setting.”
Scientists discovered that insects almost didn’t use crops, even in regions with large fields of soybeans or corn. According to Krupke, bees use these plants’ pollen, but only if other sources aren’t available. However, this selectivity didn’t protect bees. Researches identified residues of dangerous compounds of different types. Among them were neonicotinoids – products that are often used in agriculture and are harmful to bees. Scientists also detected high levels of pyrethroids, which are common compound for insect repellents.
Krupke started to worry about bees’ health in 2012, when he noticed that many insects are dying for some unknown reason. The project demonstrated tolls were caused by contamination of pesticides. Researches found 29 pesticides in pollen from the meadow site, 29 pesticides in pollen from the treated cornfield, and 31 pesticides in pollen from the untreated cornfield.
“These findings really illustrate how honeybees are chronically exposed to numerous pesticides throughout the season, making pesticides an important long-term stress factor for bees,” Long said.
The most common chemical products found in pollen from each site were fungicides and herbicides, typical crop disease and weed management products. Pollen from all three sites also contained DEET, the active ingredient in most insect repellents.
Both Krupke and Long, who is now an assistant professor of entomology at The Ohio State University, were surprised by the diversity of pesticides found in pollen. Professor mentioned they don’t know what consequences this variety of dangerous compounds can have for bees. Some fungicides are harmless to them, but they can raise the toxicity of insecticides, when products combine.