Evaluation of botanicals as biopesticides on the growth of Fusarium verticillioides causing rot diseases and fumonisin production of maize

Abstract

Partially (Pp) and completely purified (Cp) methanolic extracts of leaves of Cassia alata,Cymbopogon citratus (lemongrass), Mangifera indica (mango), Carica papaya (pawpaw),Citrus limon (lemon), fruits of Xylopia aethiopica, seeds of Aframomum melegueta (alligator pepper), Citrus aurantifolia (lime), Garcinia kola (bitter kola), Piper guineense (brown pepper), and rhizome of Zingiber officinale (ginger) were tested for antimicrobial activity using the poisoned medium and disc diffusion assay techniques on maize mycotoxigenic fungus:Fusarium verticillioides. The Pp extracts of P. guineense, G. kola and A. melegueta showed consistent higher growth inhibitions at 2, 5 and 7 days after incubation, while C. papaya and M. indica had the least activities. It was observed that these extracts completely inhibited the mycelial growth of the fungus at 2 days after incubation and produced growth reduction of 82, 80 and 73% respectively. The Cp extracts of P. guineense, G. kola, and A. melegueta also exhibited consistently higher inhibitions at 3, 5, and 7 days after incubation, while C. papaya andM. indica had no inhibitory activity. The three extracts produced reduction of mycelial growth of 76, 54 and 43% respectively. CP extracts of the plant material showed minimum inhibitory activity against F. verticillioides at 10 to 250 mgml-1 concentration level. The thin layer chromatographic analysis of the plant extracts showed different fractions, while 4 and 1 fractions of P. guineense and A. melegueta showed bioactivity respectively, which may be the important factor in causing the inhibitory effect. P. guineense, G. kola and A. meleguetashowed potential and could be successfully used as environmentally-friendly, cheap, available, effective and sustainable alternative biopesticides. Key words: Alternative pesticides, antifungal, Fusarium verticillioides, maize, medicinal plants