The use of pesticidal plants as environmental friendly Practice for field and storage pests’ management in Common beans and cowpeas
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Infestation caused by insect pests on legumes has been witnessed to cause losses in the fields during cultivation as well as during storage. Use of pesticidal plants is seen as an alternative option although it is not used widely. Fresh leaf extracts of Tephrosia vogelii, Vernonia amygdalina, Tithonia diversifolia and Lantana camara were evaluated for their efficacy against field insect pests (Aphids (Aphis fabae), Bean leaf beetle(Ootheca bennigseni), Flower (blister) beetles (Mylabris sp), Caterpillars (Anticarsia gemmatalis and Pod suckers) and beneficial insects (Spiders (Araneae), Lady Bird beetles (Coccinella septempunctata), Lacewings(Chrysopidae) and Robbefly (Asilidae)) in common beans (Phaseolus vulgaris L) and Callosobruchus maculatuson stored cowpeas (Vigna unguiculata). Pesticidal plants extracts were prepared in concentrations of (0.1%, 1% and 10% w/v). Weekly spraying of the extracts was done preceded by insects’ assessment one day before each spray. Yield of common beans and persistence of compounds from plants solutions was also evaluated. Pesticidal plants powders were tested on stored cowpea against C.maculatus. The pesticidal plants showed a significant (P ≤ 0.05) ability to reduce insect pests as well as favouring presence of predators and natural enemies in the field. Leaf extracts of T.vogelii was found the most active in the control of field as well as storage insect pests and again contributing to the growth and yield of common beans. Effectiveness of T.vogelii was the highest against C.maculatus by exhibiting less infestation by adult insects, less oviposition and low damage. In this study pesticidal plants were observed to be active against common insects’ pests when compared with untreated. Their effects against beneficial insects and natural enemies were observed to be lower compared with synthetic pesticide treatment.