Fungicidal Effect of Some Plant Extracts against Tuber Dry Rot of White Yam (Dioscorea Rotundata Poir) Caused by Aspergillus Niger

Abstract

In vitro study was carried out to test the efficacy of Azadirachta indica A. Juss. (Neem), Nicotiana tabacum Linn. (Tobacco), rhizomes of Zingiber officinale Rosc. (Ginger) leaves of Carica papaya Lam. (pawpaw) and seeds of Piper nigrum Linn. (Black pepper) and a chemical fungicide (mancozeb) at three concentrations of plant extracts (30, 60 and 90 g/L) and mancozeb (4, 8 and 12 g/L). The concentrations were amended in potato dextrose agar (PDA). A. Niger was isolated from rotted tissues of yam tubers obtained from Kadarko in Keana Local Government Area of Nasarawa State, Nigeria. The research was conducted at Advanced Plant Pathology Laboratory, Federal University of Agriculture, Makurdi, Nigeria. Results revealed that P. nigrum and Z.officinale were the best in fungi toxicity against A. niger at their respective concentrations throughout the period of incubation. This was followed by C. papaya, A. indica and N. tabacum respectively. Mancozeb gave 100 % inhibition at all concentrations tested throughout the period of incubation. Though all the extracts at all concentrations produced significant inhibitory effect (P ≤ 0.05) on mycelial growth of A. niger; the concentrations of 60 g/L and 90 g/L of the plant extracts and 4 g/L of mancozeb were considered more effective and are therefore, recommended for the control of A. niger. This has shown that there is high potential in these natural plant products for the control of yam disease if properly harnessed to replace chemical fungicide which are often harmful to the environment, toxic to man and very costly to purchase. Keywords: A. Niger; Concentrations; Fungitoxic; Inhibition; Mancozeb; Plant extracts;