Effects of the insect growth regulator methoprene and organophosphorus insecticides against non-target aquatic organisms in urban drains

Abstract

The effects of Altosid 10F (10% methoprene slow-release formulation) and organophosphorus insecticides (dichlorvos 2%+fenthion 3%) on non-target aquatic organisms were evaluated in both the field and the laboratory. The aquatic non-target organisms of Syrphidae, Asellus hilgendorfii (Crustacea), Cloeon dipterum (mayfly), Chironomidae, and Hermetia illucens survived in urban drains after treatment with Altosid 10F (1ppm methoprene). On the other hand, treatment with 2.7ppm emulsion of dichlorvos 2%+fenthion 3% greatly decreased the population of these non-target aquatic organisms in drains. The toxicity of methoprene and some insecticides against Physa fontinalis (Mollusca) and A. hilgendorfii, which cohabit urban drains, was assessed in the laboratory. Significant difference in the toxicity against P. fontinalis was found between methoprene and the other insecticides tested : 48hr LC_<50> values were 1.9ppm for fenitrothion and dichlorvos, 2.5ppm for diazinon, but 10.6ppm for methoprene. Meanwhile, the 48hr LC_<50> values of fenitrothion, dichlorvos, diazinon, methoprene and fenthion to the young nymphs of A. hilgendorfii were 0.018,0.035,0.25,0.3 and 0.65ppm, respectively.