The US-based research team “detected 35 different pesticides in the sampled pollen, and found high fungicide loads”. Individual crops were contaminated with up to 21 different chemicals, with an average of 9 contaminations.

The study, published in journal PLOS One, found that eight of the chemicals led to increased risk of bees being infected with the deadly Nosema ceranae gut parasite. Furthermore, the researchers conclude “while fungicides are typically seen as fairly safe for honey bees, we found an increased probability of Nosema infection in bees that consumed pollen with a higher fungicide load”.

The risk of infection is amplified when the bees are subject to a chemical blend of multiple pesticides and fungicides that may be relatively harmless on their own. Speaking to Quartz, lead researcher Dennis vanEngelsdorp suggests “the pesticide issue in itself is much more complex than we have led to be believe. It’s a lot more complicated than just one product, which means of course the solution does not lie in just banning one class of product”.

Another problem for both bees and farmers is that honeybee populations are collecting pollen from weeds and wildflowers rather than the crops reliant on pollination. These plants have also become contaminated through agricultural spraying practices, with the side-effect that crops are further denied pollen supplies.

CCD - which sees the populations of worker bees from colonies abruptly disappear - has become a major mystery and concern for scientists, farmers and government. In the US and some European countries, CCD is estimated to have wiped out between 33% and 50% of colonies in recent years, with an estimated 10 million colonies wiped out in the US over the last six years. The EU has introduced a two-year ban on neonicotinoids pesticides after research identified them as a potential factor in CCD.