Postharvest Management of Fungal Rot Agents of Groundnut (Arachis hypogea L.) Using Leaf Extracts of Neem (Azadirachta indica)

Abstract

This study was carried out to manage groundnut seed rot in Mubi, Adamawa State Nigeria. Groundnut Rot was reported in all the three location surveyed and the average rot incidences in the market was 21%. Mubi New Market showed 25% as the highest percentage, followed by Mubi Old Market with 20% and MubiKuturu Market with 18%. Four organisms were isolated from the lesions on Potato Dextrose Agar (PDA) as follows; Aspergillus niger, Fusariumsolani, Rhizopus stolonifer and Aspergillus flavus. The pathogen most frequently occurring was Rhizopus stolonifer (67.22%), followed by Aspergillus niger (15.56%), Aspergillus flavus (15%) and the least was Fusarium solani (2.22%). Pathogenicity test confirmed that all four fungal isolates from groundnut seed were pathogenic and the level of severity was assessed with Aspergillus flavus being most severe with 83.3%, followed by Aspergillus niger with 50%, Rhizopus stolonifer 50% and Fusarium solani 33.33%. Plant extracts employed to control the vegetative mycelial growth was from aqueous and ethanolic leaf extracts of neem at 20%, 40% and 60% concentration. In vitro application of extracts for the control showed that neem aqueous controlled the mycelial growth better as compared with neem ethanol extracts. There was complete inhibition at 60% on Rhizopus stolonifer and Fusarium solani while neem ethanol on Aspergillus flavus and Aspergillus niger showed progressive inhibition on mycelial growth. There was a significant difference on vegetative growth of the fungi on both neem extracts with increase in concentration at p= 0.0001 as compared with the control. It is recommended that the use of antimicrobials commonly found in populated areas of rural areas can be used to reduce chemical costs and smallholder farmers' over-reliance on agricultural chemicals reduce.