Effectiveness of the Powders of <i>Securidaca longepedunculata </i> (Fres.) as Bioinsecticides against Cowpea Beetle, <i>Callosobruchus maculatus </i> (Fab.) (Coleoptera : Chrysomelidae)

Abstract

Insect pests cause a great deal of post-harvest losses of stored food products worldwide and especially in the tropics where food products are usually susceptible to attack by insects between the periods of harvest, storage and consumption. In the present study, powders obtained from different parts of Securidaca longepedunculata (Fres.) (leaf. Stem bark and root bark) were tested against the cowpea beetle, Callosobruchus maculatus in the laboratory at ambient tropical conditions of temperature and relative humidity. The powders were applied at 0.0 (control), 0.2, 0.4. 0.6. 0.8 and 1.0 g. Insect mortality was observed for four (days). The result obtained showed that mortality of the insect increased with increased in concentration and exposure time. The powder obtained from the root bark recorded the highest insect mortality of 71.25 % within 96 h of exposure at the highest dosage of 1.0 g this was followed by the stem bark causing 65 % at the same level of concentration. The LD50 revealed the root bark powder to be the most effective as 3.17 % was required to obtain 50% insect mortality within 96 h of application as reflected by the regression probit analysis. The least toxic powder on C. maculatus was leaf powder. It was also observed that the tested powders significantly (P<0.05) reduced oviposition and percentage adult emergence when compared with the control. The results obtained from this research work showed that root bark of S. longepedunculata contains components of higher toxicity potential.