Influence of spray mixture rate and nozzle size of sprayers on toxicity of profenofos and thiodicarb formulations against tobacco budworm on cotton

Abstract

The toxicity of an encapsulated organophosphate, profenofos CS (CS = capsule suspension) was compared with an emulsifiable concentrate (EC), and a flowable carbamate, thiodicarb against tobacco budworm (TBW), Heliothis virescens (F.) eggs and neonate larvae on cotton using 650033 and 8002E flat fan nozzles in a spray table at 0.28 and 0.56 kg active ingredient (a.i.) ha −1. The 650033 and 8002E nozzles delivered spray solutions of 10.5 and 21.3 litre ha −1 with spray droplets averaging D v0.5, μm = 246 and 325, respectively. Regardless of formulations, the 8002E nozzle provided consistently greater mortality of H. virescens eggs and larvae than did the 650033 nozzle. Regardless of formulations, the lower a.i. (0.28 kg ha −1) rate produced egg mortality comparable to higher a.i. rate (0.56 kg ha −1). Contact toxicity of profenofos CS to H. virescens eggs was significantly higher than profenofos EC and thiodicarb. Residual toxicity of profenofos CS to TBW eggs was comparable to profenofos EC but residual toxicity of thiodicarb was significantly greater than profenofos EC and profenofos CS. Data indicate that encapsulated profenofos significantly increased efficacy against TBW eggs and neonate larvae but ovo-larvicidal activity of thiodicarb was significantly greater than profenofos CS and profenofos EC.