Risk assessment of etofenprox (vectron (R)) on non-target aquatic fauna compared with other pesticides used as Simulium larvicide in a tropical environment

Within the rotational scheme developed by the Programme to fight the resist ance of Simulium damnosum to chemical larvicides, there was an operational gap at discharges between 5 and 70 m(3) s(-1) for the treatment of rivers w here resistance to organophosphates was present. The use of permethrin and carbosulfan was precluded because of risk of environmental impact and, Baci llus thuringiensis ser. H-14 treatments were not envisageable due to cost a nd logistics constraints. Among the possible complementary groups of larvic ides tested, the pseudo-pyrethroids, held promise, because of a mode of act ion similar to that of pyrethroids, but along with a usually lower toxicity for fish. Etofenprox, one of the pseudo-pyrethroids tested, shows a global detachment of non-target insects in 24 h close to that of pyraclofos, an o rgano-phosphorus compound (27 against 23%). In laboratory conditions, six t imes the operational dose which is 0.03 mg l(-1) 10 min, is needed to cause 50% mortality of Caridina sp. (a small shrimps species) and 30 times this same dose for 95% mortality. For fish species, a safety margin of 400-800 t imes the operational dose is observed for Oreochromis niloticus and 200-400 times for Tilapia zillii. (C) 2001 Elsevier Science Ltd. All rights reserv ed.