Essential Oil of Mustard to Control Rhizoctonia solani Causing Seedling Damping off and Seedling Blight in Nursery

The essential oil extracted from mustard (Brassica rapa) seeds was evaluated for its effect on suppression of Rhizoctonia solani growth in vitro, and in field soils, for reducing saprophytic substrate colonization and seedling damping off and blight using snap beans as indicator plant, the in vitro growth was completely inhibited at a concentration of 50 μl/l. The saprophytic substrate colonization in soils 24 h after treatment was drastically reduced to 45% at 150 μl/kg soil concentration, in contrast to 100% colonization at concentrations of 0, 50, or 75 μl/kg. This recovery rate gradually declined to 6% and 60%, respectively, in nine days. A control of pre and post-emergence seedling damping off and blight in common beans (Phaseolus vulgaris), without any apparent phytotoxic effect was achieved by irrigating R. solani infested soils with water containing the emulsified essential oil to provide 150 μl/l soil volume ten days prior to planting, gave over 95%. The effect of the mustard essential oil was not influenced by the physical soil texture, and it appears to be a good substitute for methyl bromide fumigation in nurseries for seedling production. Additional keywords: allyl isothiocyanate, flavoring agent, soil treatment, nursery.