Use of Tank-mix Adjuvants to Improve Effectiveness and Persistence of Chlorpyrifos and Cyhalothrin Formula tions

Abstract

The use of adjuvants enhances the insecticide effic iency and increases the persistence of insecticides. In this study, the effect of adjuvant s on the toxicity of chlorpyrifos and cyhalothrin formulations were investigated under la boratory and field conditions. The comparative toxicity of two chlorpyrifos [(48% Emulsifiable concentrate (EC)] formulations (Dursban and Pyrifos El Nasr), two cyh alothrin (5% EC) formulations (Halothrin Gold El Nasr and Lambada Mox) and two ad juvants (Top Film and Tritone K) were examined against the second and the fourth larval stages of Spodoptera littoralis . The effect of adjuvants on the toxicity of chlorpyr ifos and cyhalothrin formulations were investigated under laboratory and field conditions. The results showed that Dursban exhibited the highest toxicity against the second a nd fourth larval stages of S. littoralis with LC 50 values of 0.2 and 1.11 mg L -1 , respectively. In contrast, Pyrifos El Nasr had th e lowest toxicity against both larval stages. The res ults of joint toxic effect between adjuvants and insecticides indicated that adjuvants revealed potentiating effect on the toxicity of four insecticide formulations as co-tox icity factor values were greater than +20. Mixing the adjuvants with chlorpyrifos and cyhaloth rin formulations in spraying tank before application of insecticides in field strongl y increased the toxicity and the persistence of insecticides. Cyhalothrin formulatio ns mixed with adjuvants gave continued significant mortality through 21 days, wh ile chlorpyrifos gave continued significant mortality through 15 days of treatment. However, chlorpyrifos and cyhalothrin formulations without mixing with adjuva nts gave significant mortality through 3 to 4 days of treatments. These results in dicated that adjuvants increased efficiency and residual effect of chlorpyrifos and cyhalothrin commercial formulations. Therefore, the adjuvants can be used for reducing t he number of applications in the season and the application rates of insecticides. Keywords: Insecticides, Pesticide application, Spodoptera littoralis , Toxicity of insecticides.