Glyphosate based herbicides (GBH) are worldwide one of the most widely used agrochemicals. This includes their application in combination with genetically engineered crops and in non-agricultural environments such as industrial or urban landscapes. Despite decades of widespread use and environmental contamination, ecotoxicological assessments of GBHs on non-target arthropods (NTAs) remain limited, particularly regarding oral exposure. To address this gap, we tested the effects of the GBH ETISSO® on two ant species, Camponotus maculatus and Cardiocondyla obscurior (Hymenoptera: Formicidae). Sub-colonies containing workers and larvae were orally exposed to test field-relevant test solutions containing 0.5%–10% GBH in 7.5–10% honey-water solutions for 21 days. GBH concentrations exceeding 7.2 g/L for C. maculatus and 3.6 g/L for C. obscurior led to significantly reduced food acceptance. Hence, starvation in combination with the toxicity led to a significantly increased mortality at those and higher concentrations. At lower, readily consumed concentrations, up to 32% C. maculatus larvae exhibited development impairments, in the form of pupal malformation and the absence of the pupal cocoon while C. obscurior workers, exposed to GBH solutions during larval stages, showed altered morphological robustness. Thus, the GBH ETISSO® leads to significant disruptions of developmental processes in both species already at sublethal doses. Our study demonstrates for the first time, that sublethal GBH exposure in ant workers can negatively affect larval development, with potential long-term effects on colony maintenance and survival. Therefore, testing toxicity on adult workers only may be misleading for ants or social insects in general, as larvae appear more sensitive than adult workers. This is especially concerning since larvae may experience cumulative effects due to constant feeding by workers. Our study contributes to a better understanding of potential adverse effects through oral exposure of GBHs for non-target arthropods (NTAs). It also highlights the need to re-evaluate common testing schemes in particular when testing social insects that are key species for many terrestrial ecosystems. Our results challenge the widespread assumption that GBHs are non-toxic to terrestrial arthropods. • Oral uptake of GBHs negatively affect ant survival and development. • Food acceptance behaviour needs to be checked for GBH test solutions. • Field-realistic concentrations of GBH cause malformations during metamorphosis. • Toxicity testing of social insects needs to include adults and developmental stages. • GBH effects on non-target insects deserve more attention.
Pohl et al. (Sun,) studied this question.