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

Abstract

The effects of Altosid 10 F (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 helgendorfii (Crustacea), Cloeon dipterum (mayfly), Chironomidae, and Hermetia illucens survived in urban drains after treatment with Altosid 10 F (1 ppm methoprene). On the other hand, treatment with 2.7 ppm 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: 48 h LC50 values were 1.9 ppm for fenitrothion and dichlorvos, 2.5 ppm for diazinon, but 10.6 ppm for methoprene. Meanwhile, the 48 hr LC50 values of fenitrothion, dichlorvos, diazinon, methoprene and fenthion to the yound nymphs of A. hilgendorfii were 0.018, 0.035, 0.25, 0.3 and 0.65 ppm, respectively.