Abstract

EVALUATION OF LARVICIDAL ACTIVITY OF THE ALCOHOLIC EXTRACT OF THE PLANT COLEUS VETTIVEROIDES K.C. JACOB FAMILY: LABIATAE AGAINST THE HUMAN FILARIASIS VECTOR CULEX QUINQUEFASCIATUS

*Beesha S. Kamal, Dr. Sudharmini S., Dr. Padmaja V., Dr. Kumari Jayageetha P.B.

ABSTRACT

Mosquitoes transmit many serious human diseases like malaria, dengue fever, yellow fever, filariasis etc and the use of chemical insecticidal agent result in insecticidal resistance and environmental pollution. Recently plant extracts are found to be one of the alternative solution to solve this problem. The present study is aimed to assess the larvicidal activity of alcoholic extract of dried whole plant of Coleus vettiveroides against the 1st, 11nd, 111rd and 1Vth stages of the larvae of Culex quinquefasciatus. The alcoholic extract in the concentrations of 100, 250, 500, 750 and 1000 μg/ml were used in this study. The data on mortality was subjected to probit analysis to determine the lethal concentrations (LC50 and LC90) to kill 50 and 90% of all the four stages of the larvae after 24 and 48 hours of exposure period. The percentage mortality of larval instars was found to be increased with increased concentrations of extract after 24 and 48 hours of exposure. The study revealed that plant extracts showed promising larvicidal activity in higher concentration. Decreased virulence, sluggish movement and colour variation of larval integument were remarkable observations noticed among all larval instars. The extract has affected the moulting process of larvae; hence they either failed to pupate or stopped during ecdysis. Long duration of exposure(48hrs)and high concentrations (228.6 μg/ml and 599.744 μg/ml)of the plant extract have produced 50% and 90% mortality among larval instars with statistically significant difference (p- value:0.011) in the values of LCL and UCL (44.07 and 1915.9) and toxicity (LC 50 and LC90). Hence the result of the present study help us to develop a new plant derived mosquito larvicidal agent instead of the currently used chemical insecticides.

Keywords: Alcoholic extract, Coleus vettiveroides, Culex quinquefasciatus, larval instars.