Chronic High Glyphosate Exposure Delays Individual Worker Bee (Apis mellifera L.) Development under Field Conditions
Institute for Bee Protection, Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, 38104 Braunschweig, Germany
Institute for Bee Protection, Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, 14195 Berlin, Germany
Odemer Apiaries, 73765 Neuhausen auf den Fildern, Germany
Author to whom correspondence should be addressed.
Present address: Institute for Apiculture, Lower Saxony State Office for Consumer Protection and Food Safety, 29221 Celle, Germany.
Received: 12 September 2020 / Accepted: 25 September 2020 / Published: 27 September 2020
Glyphosate-based herbicides (GBH) can be found worldwide throughout conventional agroecosystems due to their unique and effective mode of action. Their use is generally not considered harmful to honey bees, and, consequently, foragers may encounter food sources that are potentially contaminated with GBH residues. However, recent studies found GBH to cause sublethal effects in bees, and therefore give rise to concern. While most related research has addressed such effects under laboratory conditions, field-realistic approaches under free-flying conditions are scarce. Here, we explore if GBH influences several important performance parameters at the colony level using standard and modified regulatory testing methods. Colony conditions (i.e., colony weight gain, individual worker bee survival, and overwintering) were not affected when subjected to chronic GBH exposure in a realistic range (high and low). In line with previous laboratory results, the high range of treatments revealed a delayed brood development of workers and reduced hatching weight of adults when compared with the control group. However, we concluded that more drastic effects on honey bee health did not seem to appear, as a broad range of performance parameters remained completely unaffected. In future research, the underlying mechanisms of the developmental delay that was confirmed here should be carefully investigated.