In vitro evaluation of leaf extracts on the growth of Aspergillus niger infecting maize grains

Mycotoxin producing fungi are important pathogens affecting stored maize grains. Conventional management strategies using synthetic chemicals are expensive, hazardous and environmentally unfriendly. This has necessitated the search for alternatives in botanicals. Market sampling of maize grains were carried out in five markets in Port Hartcourt, Nigeria, namely; Choba-main and Choba junction, Rumuosi, Aluu and Ozuoba, to evaluate the occurrence of mycotoxin-producing fungi. Studies were then carried out in the laboratory to evaluate the efficacy of water leaf extracts of Azadirachta indica, Garcina kola, Moringa oliefera, Ocimium gratissimum, Gongronema latifolium and Vernonia amygdalina at three different concentrations (2.5, 5.0 and 7.5% w/v) on the prevalent fungus. Result from the market sampling showed that Aspergillus niger, Aspergillus flavus and Pennicillin sp were commonly isolated from the maize grains with Aspergillus niger having the highest occurrence. Choba markets were observed to have the highest percentage occurrence of Aspergillus niger (66-100%). Laboratory studies showed that Gongronema latifolium, effectively reduced the growth of A. niger on PDA media and leaf extract concentration at 7.5% was the most effective.