The effect of catmint, tobacco and thyme extracts on Sclerotinia sclerotiorum causal agent of tobacco collar rot

Sclerotinia sclerotiorum is an important phytopathogen causing tobacco collar rot which distributed worldwide and can impose high yield losses in tobacco growing countries. The disease management is possible by use of fungicides, resistant cultivars, biological control and use of plant extracts and essential oils. Crude extracts of catmint (Nepeta cataria), tobacco (Nicotiana tabaccum) and thyme (Thymus pubescens) were prepared by water, acetone, hexane, ethanol and methanol with concentrations of 1000 and 2000 ppm. The effect of those extracts against the fungus was examined in vitro in a factorial experiment based on completely randomized design with three replications. Minimal inhibitory concentration of extracts was determined by agar diffusion method. Crude extracts of tobacco, catmint and thyme had remarkable antifungal activity. Hexane, ethanol and methanol were the best solvents to extract antifungal compounds. Minimal inhibitory concentration of hexane, ethanol and methanol extracts of catmint, tobacco and thyme were 1 mg/ml as tested on the fungus. The most important components of extracts of catmint were menthanol, menthol, sailen, thymol, pipertenone, nonenal, carvacrol, camphor and limonene; in extracts of tobacco, globulol, phytol, nicotine, sailen, imidazole, limonene and thunbergol; and in extracts of thyme, thymol, anethole trans, sailen, carvacrol, imidazole and nonenal. Therefore, extracts of catmint, tobacco and thyme can be considered as natural fungicides for control of causal agent of tobacco collar rot.