Commercially formulated glyphosate can kill non-target pollinator bees under laboratory conditions

Abstract

The use of glyphosate-based herbicides in agroecosystems has increased over the past few years because of the advent of genetically modified glyphosate-resistant crops and resistant weeds. This is alarming because of potential damaging effects on non-target organisms. In sub-Saharan Africa, for example Ghana, many rural farmers have not received training in the use of glyphosate-based herbicides, thus tend to apply higher than recommended concentrations on farms. Therefore, this study investigated the effect of glyphosate-based herbicides on beneficial insects under laboratory conditions, using Apis mellifera L. (Hymenoptera: Apidae, Apini) and Hypotrigona ruspolii (Magretti) (Hymenoptera: Apidae, Meliponini) as models. The bees were put in contact for 24 h with the recommended concentration of Sunphosate 360 SL, a glyphosate-based herbicide, 2× the recommended concentration, or distilled water as control. The effect of the herbicide on the bees was compared to the effect of a lambda-cyhalothrin insecticide. Generally, more bees died after contact with plants freshly sprayed with the herbicide than on herbicide-treated filter paper. In both cases, more bees died after contact with the higher concentration of the herbicide. These findings suggest that beneficial insects, specifically A. mellifera and H. ruspolii, may get killed if they are sprayed upon or come into contact with plants that have been freshly sprayed with (more than) the recommended concentration of glyphosate-based herbicides. Therefore, it is important to restrict access and use of such herbicides to trained personnel who will comply with spraying guidelines, that is, recommended concentrations and timing of spray. Spraying at a time when insects are flying about may be detrimental to beneficial insects such as pollinator bees, parasitoids, and predators.