The challenges of predicting pesticide exposure of honey bees at landscape level

This Belgian study sought to better understand pesticide contamination pathways by evaluating honey bee pollen pellets, the botanical origin of the pollen as well as the landscape around the bee hives. The pellets were collected late in the growing season (July – October).

About half of the pollen samples analyzed were contaminated with at least one pesticide. In total, five fungicides (boscalid, pyrimethanil, trifloxystrobin, kresoxim-methyl, and cyprodinil) and two insecticides (dimethoate and thiamethoxam) were found. The pesticides found most frequently in pollen pellets from apiaries were the fungicides boscalid (31.7%) and pryamethanil (16.7%) and the organophosphate insecticide dimethoate (16.7%). The researchers attempted to pinpoint exposure pathways for the three most commonly found pesticides. For boscalid and dimethoate, the researchers were able to predict exposure probability but were unable to identify precise contamination sources. For pyrimethanil, they were not able to build any model to explain contamination.

The study’s findings did however indicate that pesticide use on non-pollinator attractive crops can be a source of exposure through drift, contaminated wildflowers and succeeding plants. This finding indicates that current pesticide risk assessment processes for registering pesticides, based on a crop’s attractiveness to bees, fail to respond risks from pesticide use on non-attractive crops.

The research also showed how a pesticide’s properties can affect the potential exposure routes. More specifically, dimethoate, a relatively short-lived insecticide, was only found in pollen pellets but not in bee bread, which undergoes processing by adult workers before being fed to larvae.

Authors: 
Simon-Delso, N., G. San Martin, E. Bruneau, C. Delcourt, and L. Hautier
Journal: 
Scientific Reports
Year published: 
2017