干旱区生态环境知识资源中心

Relative susceptibility of three important mosquito vector larvae viz., Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus, prevalent in the arid region was determined against four organophosphates (malathion, fenitrothion, fenthion, temephos) and three synthetic pyrethroid (alphamethrin, deltamethrin and fan valerate) compounds. Studies were carried out on late 3(rd) or early 4(th) instar larvae of these species using standard WHO technique. Based on concentration mortality data LC50 and LC90 values along with their fiducial limits, regression equation, chi-square (chi(2))/heterogeneity of the response have been determined by log probit regression analysis. LC50 values as observed for the above seven insecticides were 0.8097, 0.0398. 0.0432, 0,0035, 0.0025, 0.0092, 0.1006; 1.2370, 0.0531, 0,0655, 0.0076, 0.00004, 0.00004, 0.0046 and 1.4980, 0.0719, 0.0817, 0.0056, 0.00021, 0.00073, 0.0112 mg/l for the above three mosquito species respectively. Among the four organophosphates tested temephos was the most effective followed by fenitrothion, fenthion and malathion, In general, Anopheles was found more susceptible as compared to the other two culicines to the above four compounds. The results also showed that larvae of Ae. aegypti were most susceptible followed by Cx. quinquefasciatus and An. stephensito all the three pyrethroids tested. Among the three compounds tested alphamethrin was found to be the most toxic followed by deltamethrin while fanvalerate was the least toxic. The study would be of great importance while planning use of these insecticides for the control of different vector species in this area.