EVALUATION OF ANTIMICROBIAL POTENTIALS OF SELECTED BOTANICALS AGAINST KOLANUT STORAGE ROT PATHOGEN (LASIODIPLODIA THEOBROMAE) IN NIGERIA

Abstract

Stored kolanuts are predisposed to infection by Lasiodiplodia theobromae sequel to infestation and/or attack by kolanut weevils (Sophrorhinus spp. and Balanogastris sp.) from field to store. The effectiveness of varying aqueous/ethanolic leaf extracts concentrations of Azadirachta indica, Piper guineense, Lantana camara, Eucalyptus sp. And fruit peels of Citrus sinensis against mycelia growth and pycnidia production of L. theobromae (causative agent of kolanut storage rot) was determined using poisoned food technique. Percentage mycelia inhibitions by extracts of A. indica, P. guineense, L. camara, Eucalyptus and Citrus peels within 24 hours of incubation ranged between 26.09-33.05%, 33.05-51.31%, 45.22-60.87%, 55.65-64.35%, and 52.18-67.83%, respectively. Contrary to observations in other extracts, higher percentages of the pathogen’s mycelia inhibition were generally recorded for concentrations of Eucalyptus, Citrus and the standard check/positive control (mancozeb) after 48 hours of incubation. However, the mycelia inhibitions noticeably reduced at 72 hours of incubation. The study also revealed a decrease in the number of pycnidia produced by the pathogen as the extracts’ concentrations increased. The reduction in the number of pycnidia produced by the pathogen varied with individual treatments in the following order, Eucalyptus>Citrus peel>Lantana>Piper>Neem. Lantana, Eucalyptus and Citrus extracts competed favourably with the standard check in the inhibition of the pathogen’s mycelia growth. P. guineense and L. camara extracts which were comparable to mancozeb, induced higher inhibitory effects on both mycelia growth and pycnidia production. Hence, could be used for effective control of kolanut storage rot.