Relative susceptibility of some common mosquito vector larvae to synthetic insecticidal compounds in northwestern Rajasthan.

Abstract: 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 fanvalerate) 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 LC 50 and LC 90 values along with their fiducial limits, regression equation, chi-square (x 2 )/ heterogeneity of the response have been determined by log probit regression analysis. LC 50 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. stephensi to 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. Key words: Organophosphates, Pyrethroids, Vector mosquitoes, Desert Rajasthan PDF file of full length paper is available with author Introduction Vector control, which includes both anti-larval and antiadult measures constitutes an important aspect of any mosquito control programmes. Mosquitoes, the best known group among dipteran insects, are of great importance to man as vectors of many communicable diseases such as malaria, filaria, dengue/dengue hemorrhagic fever (DHF) etc. Among the anophelines, Anopheles stephensi and An. culicifacies are the important vector of malaria while among the culicines, Culex quinquefasciatus and Aedes aegypti are the vectors of filaria and dengue/DHF respectively. All these mosquito species have been identified as primary vectors of the above communicable diseases in this region of Rajasthan (Bansal and Singh, 1993