ABSTRACT
The effects of lambda-cyhalothrin on aquatic ecosystems has been studied under field conditions in the Philippines, USA and UK. In the Philippines, lambda-cyhalothrin was applied at field rate and 2× field rate to rice paddies and the effects on Tilapia nilotica in rice-fish culture studied. There were no effects on fish survival, growth rate or production. Lambda-cyhalothrin was applied directly to replicated pond mesocosms in trials in the USA and UK. USA mesocosms (450 m3) were treated at 3 rates. The mid-rate, representing the typical maximum estimated entry rate (from aerial applications to US cotton), was multiple applications of simulated spray-drift at 0.38% of field rate and simulated run-off applications at 1.1% field-rate. High and low-rates were 10× and 0.1× the mid-rate, respectively. The UK mesocosms (25 m3) were treated with 4 applications of simulated spray-drift at 0.38% and 3.8% field rate. Mesocosms were monitored prior to and for up to 6 months after application. In the US mesocosms there were no effects, at any treatment rate, on hydrosoil microbes, phytoplankton, periphyton or filamentous algae. At the low rate there were negligible effects on macroinvertebrate populations. The mid-rate had transient effects on some groups, notably the Hemiptera and Ephemeroptera, and the high rate showed more severe effects on macroinvertebrates and also reduced zooplankton populations. UK mesocosms gave similar results with little or no effects at the lower rate and more pronounced effects on certain sensitive groups at the high rate.
