Assessment of the Curative Potency of Some Plant Materials on Cowpea seeds with Established Infestation of Callosobruchus maculatus (Fabricus)(Coleoptera: Chrysomelidae: Bruchinae)

Abstract

An investigation into the possibility of plant materials affording quick and practicable control where pest populations are approaching economic threshold was carried out in the laboratory. The leaves, barks or seed powders of ten locally available plants, which have been reported to have insecticidal activity on storage pests, were screened to evaluate their curative efficacy relative to a conventional storage chemical, Actellic 2 % dust (Pirimiphos – methyl), as protectants of stored cowpea with established infestation. The cowpea was infested with bruchids 5 weeks before the administration of the test materials and after the emergence of the first filial generation. Each plant material was tested at three rates (2.5, 5.0 and 10.0 g/100.0 g seed). Actellic was applied at the rate of 1.0, 2.0 and 3.0 g/100.0 g seed. The treatments were replicated thrice. Seeds not treated with the test materials served as the control. Data were collected weekly over a 10 – week period on adult emergence, percentage adult mortality and seed damage. The seed damage data were used to estimate the weevil perforation index (WPI). The most effective materials and Actellic 2 % dust only gave marginal protection. At week 10 of the experiment, Moringa oleifera, Piper guineense and Ocimum gratissimum had WPI of 46.7 %, 46.7 % and 50.0 %, respectively at their highest rates of application. Though Actellic dust effected higher mortality of the insects, it could hardly protect seeds that were already heavily infested with only 50% WPI at the highest rate (3.0 g/100 g seed).

Key Words: Callosobruchus maculatus, Curative, Plant Materials, Progeny, Weevil Perforation Index (WPI).