Effect of Acicnemis variegatus Fairmaire (Curculionidae) on some Ludwigia spp. in Ile-Ife, Nigeria

Abstract

This study investigated the effect of Acicnemis variegatus on reproductive and growth parameters of five Ludwigia spp [L. octovalvis var brevisepala (Jacq.) Raven, L. decurrens Walter, L. hyssopifolia (G.Don)Excell, L. erecta (Linn) Hara and L. leptocarpa (Nutt.) Hara]. The larva of Acicnemis variegatus significantly reduced the fruit length and the total number of seeds per fruit but increased fruit diameter in L. octovalvis, L.erecta and L. hyssopifolia. The number of primary branches, number of flowers and fruits were significantly reduced in L. hyssopifolia and L. erecta suggesting abortion of flowers due to presence of larva. Total numberof larva per fruit ranges from one to two in fruits of affected exposed Ludwigia species in which they pupate and make a tiny hole which serve as exit. Adult A. variegatus were only found on Ludwigia species duringflowering, often mounted on each other or singly on flower buds, bloomed flowers and developing leaves of affected Ludwigia species. A. variegatus did not affect exposed L. decurrens and L. leptocarpa. The resultsuggests that adult A. variegatus do not feed on the Ludwigia spp. studied. The significant reduction in number of seeds due to the presence of larva in fruits of affected plants could be an important agent in reducing plant densities.