Does roundup® affect worker bees (Apis mellifera) that inhabit areas of high agrochemical pressure?

Abstract

Glyphosate-based herbicides (GBHs) find wide application in conventional agroecosystems due to their effective mode of action. The impact of herbicides on bees may be underestimated due to the scarcity of studies assessing various exposure routes to GBHs, including contact and ingestion of contaminated food. This study evaluated the survival, food consumption, and body weight of honey bee populations in three different locations, characterized by different degrees of exposure to GBHs. In bioassays, honey bees were exposed to diets containing sucrose solutions infused with glyphosate, with dosages ranging from 0 to 14 mg (a.i./bee). During the experiment, the honey bee population had a period of exposure (6 h) to the syrup infused with glyphosate. Mortality counts and feeder weight measurements were performed to assess the effects. A significant reduction in syrup intake was observed in all three bee populations during the Roundup® exposure phase, leading to a decrease in GBH intake. Notably, the decrease in syrup consumption emerged as the main factor contributing to the lower body weight observed among honey bees from low- and high-impact locations, persisting into the post-exposure period. Overall, the results demonstrate that honey bees in the high-impact region are more sensitive to Roundup®. However, studies using biochemical biomarkers are still necessary to unravel how glyphosate interferes with the acquisition and expenditure of energy during periods of exposure of honey bees and which physiological changes allow them to adapt to inhabited places with high agricultural pressure.