Evaluation of Efficacy of some Plant Extracts for the Control of Anthracnose (<i>Colletotrichum gloeosporioides</i>) of White Yam (<i>Dioscorea rotundata</i> Poir)

Abstract

Anthracnose is the most serious leaf and vine epiphytotic disease of yam that causes yield loss. Chemical fungicides could potentially form the basis of sustainable management strategies for anthracnose, however, the inorganic fungicides used in managing plant diseases are not degradable and may persist in the soils. Studies were conducted in vitro and in vivo to evaluate the efficacy of aqueous extracts of Azadirachta indica, Jatropha curcas and Nicotiana tabacum extracts for the control of anthracnose disease of white yam (Dioscorea rotundata Poir). The antifungal activities of 35, 45, 65 and 75% concentrations of each of the plant extracts wasassessed in vitro on potato dextrose agar using the food poison technique. The fungitoxicity of the plant extracts against yam anthracnose disease was assessed under in vivo conditions through foliar application of 75% concentrations of each plant extract. The in vitro results showed that each plant extract inhibited significantly (P ≤ 0.05) the mycelia growth of C. gloeosporioides The 75% concentration of the plant extracts exhibited the best inhibitory effect considering the percentage mycelial growth it recorded. The results of the field trial revealed that each plant extract at 75% concentration significantly (P ≤ .05) reduced the incidence and severity of the anthracnose disease. The plant extracts particularly, Azadirachta indica seed extracts produced higher yield. Farmers may use aqueous extracts of Azadirachta indica seed as an alternative to synthetic fungicides for the control of anthracnose disease of yam.

Keywords: Colletotrichum gloeosporioides, disease incidence, severity, plant extracts, Dioscorea rotundata