Evaluation of susceptibility status of Culex quinquefasciatus larvae to few organophosphorus insecticides based on logistic regression analysis.

A laboratory trial was carried out at Pune to evaluate the effectiveness of five types of larvicides viz. Malathion, Temephos, Fenthion, Dichlorvos and Fenitrothion against Culex quinquesfasciatus larvae. The expected number of mortality at various dose levels for the five types of insecticides were estimated separately using logistic regression model. Based on the fitted model, the estimated dose level corresponding to the 90 percent mortality (LC90) was obtained for each insecticide. Approximate 95 percent confidence intervals for the LC90 dose, in each case, has been provided. The analysis revealed that out of all the five types of insecticides included in the study, fenthion was the most effective. The estimated value of LC90 in this case was the lowest and is equal to 0.007 mg/L. The effectiveness of temephos, dichlorvos and fenitrothion was found to be approximately same and malathion was the least effective. The results were found to be comparable with that obtained under probit method.