Repellent and Insecticidal Efficacy of Leaf and Stem Powders of Mimosa diplotricha C. Wright ex Sauvalle (Mimosaceae) Against maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae).

Abstract

Studies on the repellent and insecticidal potential of the invasive alien plant, Mimosa diplotricha C. Wright ex Sauvalle (Mimosaceae) (commonly known as the giant sensitive plant) are non-existent, hence this study evaluated the repellent and insecticidal activities of the leaf and stem powders of the against the maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) under laboratory conditions. Maize grains infested with the adults of S. zeamais were exposed to three concentrations viz. 1.5, 2.5 and 3.5 g of M. diplotricha leaf and stem powders for 3 hours after which percentage repellency was calculated. Also, adult weevils were exposed to grains treated separately with three different concentrations (1.5, 2.5 and 3.5 g) of the leaf and stem powders of M. diplotricha at different exposure periods. Percentage survival was recorded every 24 hours over a 120-hour period. The leaf and stem powders of M. diplotricha exhibited some degrees of repellency against S. zeamais, although, the repellent activity was a function of both concentration and exposure time. Following a 3-hour exposure period, the 3.5 g of the leaf (53%) and stem (58%) powders exhibited the highest repellent activity against S. zeamais. Although, the leaf and stem powders of M. diplotricha plants exhibited some degrees of mortality against S. zeamais, it was observed to be concentration and exposure time dependent. At the highest concentration (3.5 g), the leaf and stem powders of M. diplotricha accounted for only 28% mortality (72% survival) of S. zeamais after a 120-hour exposure period. This study reports the repellent and insecticidal activities of the leaf and stem powders of M. diplotricha against S. zeamais, for the first time, it however, suggests that the phytochemical constituents of the plant be analyzed first before further use.