Pesticides in Norwegian agriculture. Their effects on benthic fauna in lotic environments. Preliminary results

Predicting the Effects of Insecticide Mixtures on Non-Target Aquatic Communities

“…The highly significant declines in abundance of different taxa and guilds due to chlorpyrifos treatment, and the lack of similar findings due to dimethoate treatment are troubling because this study determined the appropriate doses from standard bioassays of the same genera from public databases of the published literature. For instance, according to a Norwegian study by Baekken and Aanes [5], the 96-hr LC 50 for Baetis rhodani exposed to dimethoate was ~ 7 µg/L. In this study Baetis not only survived but emerged as adults (37 females and 26 males, not shown) in the 0.8 TU treatment where the dimethoate concentration was in the range of 19.93 -22.96 µg/L.…”

“…Chlorpyrifos and dimethoate are also highly toxic to non-target, aquatic species. According to van Wijngaarden et al [4], the 48-h LC 50 (median lethal concentration to affect 50% of the population) for chlorpyrifos on the non-target mayfly, Cloeon dipterum is approximately 1 µg/L and similarly, Baekken and Aanes [5], report that the 96-hr LC 50 for the mayfly, Baetis rhodani, is in the range of 7 µg/L for dimethoate. The third insecticide, imidacloprid (1-((6-Chloro-3-pyridinyl)methyl)-N-nitro-2-imidazolidinimine), is also highly toxic to non-target aquatic species (e.g., the mayfly, Epeorus longimanus 24-h LC50 = 2.1 ± 0.5 µg/L, see [6]).…”

Understanding Perturbation in Aquatic Insect Communities under Multiple Stressor Threat

“…Test conditions manipulated concentrations of insecticides (imidacloprid, dimethoate, and chlorpyrifos), fungicides (chlorothalonil), nutrients (oligo-, meso-, and eutrophic gradients) and predation pressure (stoneflies and dragonflies). In brief, the chemicals tested were chlorpyrifos (O,O-Diethyl O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate) and dimethoate (O,O-Dimethyl S-[2-(methylamino)-2-oxoethyl] phosphorodithioate) both organophosphorus insecticides that are among the top 10 most commonly used in North America as well as being highly toxic to nontarget aquatic species [26,27]. Imidacloprid (1-((6-Chloro-3-pyridinyl)methyl)-N-nitro-2-imidazolidinimine) is a neonicotinoid insecticide, while chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile) is a widely used fungicide in Atlantic Canada [28,29].…”