Response of Fungal Rot Pathogens of Sweet Potato (Ipomoea Batatas (L) Lam. in Storage to Aqueous Extracts of Some Tropical Plant Materials and Benomyl

Abstract

Sweet potato is ranked amongst the seven most important tropical tubers in the world. Its production in sub-Saharan Africa is however deeply constrained by poor shelf life due in part to microbial deterioration during storage. This study evaluated aqueous extracts of some plants (Ocimum gratissimum, Curcuma longa, Azadirachta indica, Ficus exasperata and Achornea cordifolia) and benomyl as possible low-input bio-pesticides for the control of storage rot of the crop. The experiment was laid out in a Completely Randomized Design (CRD) made up of 7 treatments, replicated 4 times. The results revealed that Rhizopus stolonifer (70.01%) and Botryodiplodia theobromae (67.9%) were the most frequently occurring fungal isolates from the rotted samples; that virulently initialed rot development in the healthy tubers. Exposure of these pathogens to test extracts-impregnated medium showed that aqueous extracts of Cucuma longa, Azadirachta indica and Ficus exasperata significantly (P≤0.05) reduced the mean spore germination and radial growth of the pathogens by 77.22 and 89.04 %; 76.51 and 85.29 %; and 61.93 and 75.69 % respectively over the control experiment: and these results thus compared well with 91.37 and 90.37 % recorded for benomyl treated samples. Therefore aqueous extracts of the test plants (Cucuma longa, Azadirachta indica and Ficus exasperata) in this order could be used for the control of rot development in sweet potato due to these fungal pathogens. However determination and characterization of the active principles of the plant materials is strongly recommended.