In-vitro Evaluation of Botanicals/Biofumigants against Rhizoctonia solani Inciting Collar Rot and Web Blight of Yard Long Bean (Vigna unguiculata subsp sesquipedalis (L.) Verdcourt)

Abstract

Collar rot and web blight caused by Rhizoctonia solani is a major soil borne disease adversely affecting the growth and pod yield of yard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt). The disease is very difficult to control due to the prolonged survival capacity of pathogen in soil as sclerotia. The fungicides used for disease management are very expensive, and their non-judicious use poses severe threat to the environment and beneficial microorganisms. Soil biofumigation is an emerging method for the inhibition of soil borne plant pathogens and can be utilised for the management of collar rot and web blight of yard long bean incited by R. solani. In the present study, nine botanicals were evaluated for their biofumigation and antifungal potential against R. solani by paired plate and poisoned food technique respectively under laboratory conditions. Among the different botanicals tested, paired plate technique using 1g and 5g, each of Allium sativum (bulbs) and Mansoa alliacea (leaves) resulted in complete inhibition of the mycelial growth of R. solani under in vitro conditions. The bulb extract of A. sativum and leaf extract of M. alliacea at 10, 15 and 20 per cent, when tested by poisoned food technique resulted in cent per cent inhibition of the mycelial growth of the pathogen, revealing the antifungal potential of both botanicals.