Larvicidal activities of five Kotschya species against Culex quinquefasciatus Say (Culicidae: Diptera)

Abstract

Resistance of mosquito vectors to the commonly used chemical insecticides is posing threats to human health. It is becoming necessary to identify safe, eco-friendly and effective alternative sources of larvicides in order to reduce mosquito menace. HPLC profiling of the chemical constituents in the stem and root bark ethanol extracts had similar pattern of chemical constituents except for K. aeschynomenoides which indicated to have large quantity of polar compounds compared to others. In this study, the ethanolic extracts and powders of five Kotschya species were tested against Culex quinquefasciatus Say. Chemical profiling of the stem and root bark ethanol extracts from K. speciosa, K. thymodora, K. platyphylla, K. aeschynomenoides and K. strigosa did not show any major differences in terms of their chemical composition. At 0.5 mg/ml, the root and stem ethanol extracts from K. speciosa, K. thymodora and K. strigosa exhibited high larvicidal activity (≥ 70%) on the 8^th day post treatment. Stem powder of K. thymodora and root powder of K. speciosa and K. strigosa had activity comparable to their respective extracts at 0.2% w/v and 0.4% w/v at the same exposure time. This suggests that Kotschya species contain same or related compounds in varying quantities that are responsible for larvicidal activity.

Keywords: Fabaceae, Kotschya strigosa, K. speciosa, K. thymodora, K. platyphylla, K. aeschynomenoides, Larvicidal, Culex quinquefasciatus