Repellence of Boophilus microplus larvae in Stylosanthes humilis and Stylosanthes hamata plants

Abstract

The aim of the study was to investigate the repellence of B. microplus larvae by the tropical legumes Stylosanthes humilis and S. hamata, and to identify some of the chemical compounds presents in both legumes. The effect was evaluated by a repellence bioassay in an olfactometer using extracts from stems, leaves and whole plants treated with diverse organic solvents such as hexane, acetone, chloroform and methanol. The identification of chemical compounds was done by gas chromatography -mass spectrometry on whole plant extracts. This study demonstrated that both legumes had repellence properties. Repellence ranged from 68% to 92% in S. humilis and from 70% to 82% in S. hamata. Sixteen compounds were identified in S. humilis, with ferrocene and beta sitosterol being the most abundant (18.3% and 14% of the total, respectively). Seventeen compounds were identified in S. hamata, with linolenic acid being the highest relative abundance (17.6%). The compounds identified may be considered as potential candidates for explaining the repellence effects.