Larvicidal and knockdown effects of some essential oils against Culex quinquefasciatus Say, Aedes aegypti (L.) and

Efficacy of 25 essential oils was screened against fi-larial vector, Culex quinquefasciatus, for their lar-vicidal and knockdown effects in a preliminary study. Of these, 8 oils viz. calamus oil, cinnamon oil, citro-nella oil, clove oil, eucalyptus oil, lemon oil, mentha oil and orange oil exhibited 100 % larvicidal activity at 1000 ppm and 100 % knockdown effect at 10% concentration. These 8 oils were screened further against Cx. quinquefasciatus, Aedes aegypti and Ano-pheles stephensi for their larvicial and knockdown effects at different concentrations. Mentha oil was the most promising against An. stephensi and Ae. aegypti recording LC50 and LC90 values of 39.74 and 115.67 ppm and 46.23 and 165.36 ppm, respectively for lar-vicidal activity. Calamus oil was the most effective against Cx. quinquefasciatus with LC50 and LC90 val-ues of 40.40, and 140.07 ppm, respectively for lar-vicidal activity. Orange oil showed the most potent knockdown effect with the KT50 and KT95 values of 27.44, 26.22 and 29.91 and 70.81, 65.33 and 68.57 min, against An. stephensi, Cx. quinquefasciatus and Ae. aegypti, respectively. The results clearly indicated that mentha oil and calamus oil were the most prom-ising larvicides and orange oil had potent knockdown effect against the tested mosquito species. These oils could be used to develop a new formulation to control mosquitoes