Acute and chronic toxicity of neonicotinoids to nymphs of a mayfly species and some notes on seasonal differences

Abstract

Mayfly nymphs are among the most sensitive taxa to neonicotinoids. The present study presents the acute and chronic toxicity of 3 neonicotinoids (imidacloprid, thiacloprid, and thiamethoxam) to a mayfly species (Cloeon dipterum) and some notes on the seasonality of the toxicity of imidacloprid to C. dipterum and 5 other invertebrate species. Imidacloprid and thiamethoxam showed equal acute and chronic toxicity to a winter generation of C. dipterum, whereas thiacloprid was approximately twice as toxic. The acute and chronic toxicity of imidacloprid was much higher for the C. dipterum summer generation than for the winter one. The acute toxicity differs by a factor of 20 for the 96-h 50% effective concentration (EC50) and by a factor of 5.4 for the chronic 28-d EC50. Temperature had only a slight effect on the sensitivity of C. dipterum to imidacloprid because we only found a factor of 1.7 difference in the 96-h EC50 between tests performed at 10 °C and 18 °C. The difference in sensitivity between summer and overwintering generations was also found for 3 other insect species. The results indicate that if the use and environmental fate of the 3 neonicotinoids are comparable, replacing imidacloprid by another neonicotinoid might not reduce the environmental impact on the mayfly nymph C. dipterum. The results also show the importance of reporting which generation is tested because sensitivity values of insects in the summer might be underestimated by the experiments performed with neonicotinoids and an overwintering population.

Effects of insecticides on aquatic ecosystems in Bangladesh

“…To date no study seem to have been undertaken to investigate the sensitivity of imidacloprid on the aquatic organisms in the sub-tropics and tropics. Van den Brink et al (2016) found that a reproducing, summer generations of several arthropods were more sensitive to imidacloprid than their non-reproducing, winter generation. Earlier studies demonstrated that higher temperature also might increase the sensitivity of arthropods (Camp and Buchwalter, 2016;Van den Brink et al, 2016).…”

“…Van den Brink et al (2016) found that a reproducing, summer generations of several arthropods were more sensitive to imidacloprid than their non-reproducing, winter generation. Earlier studies demonstrated that higher temperature also might increase the sensitivity of arthropods (Camp and Buchwalter, 2016;Van den Brink et al, 2016). Hence, a difference in sensitivity between tropical and temperate communities to imidacloprid can be hypothesised.…”

“…The aquatic contamination by pesticides used in agriculture may constitute potential (eco)toxicological risks to non-target aquatic organisms of different trophic levels in a food chain i.e. primary producers (Daam et al, 2008a;Malev et al, 2012;Liu et al, 2013;Kumar et al, 2014), invertebrates (Maltby et al, 2005;Palma et al, 2009;Rubach et al, 2011;Roessink et al, 2013;Van den Brink et al, 2016), and fish (Tillitt et al, 2010;Marimuthu et al, 2013;Manjunatha and Philip, 2016;, when exceeding the threshold levels.…”

“…In addition, insecticides like imidacloprid may adversely affect arthropods (e.g. insects like the mayfly Cloeon dipterum) (Roessink et al, 2013;Van den Brink et al, 2016).…”

“…Both single species laboratory tests (Alexander et al, 2007;Stoughton et al, 2008;Roessink et al, 2013;Cavallaro et al, 2017;Van den Brink et al, 2016) and model ecosystem studies (Hayasaka et al, 2012a;Mohr et al, 2012;Colombo et al, 2013) using imidacloprid, were all conducted in temperate regions. To date no study seem to have been undertaken to investigate the sensitivity of imidacloprid on the aquatic organisms in the sub-tropics and tropics.…”