The pathogenicity of Rhizoctonia solani AG-4 HGI on bean (Phaseolus vulgaris L.) plants was evaluated, in artificially infested soil under greenhouse conditions, when submitted to the following treatments: amendments with different C:N ratios (castor-oil cake and sugar-cane bagasse); different organic matter decomposition levels; different moisture contents of the amended soil. Until the moment of sowing the soil moisture was maintained at 20% of the moisture-holding capacity or above 80%. The sowings were made at 0, 7, 14, 21, 28 and 35 days after the inoculation and amendments incorporation. Evaluations were carried out 14 days after each sowing date. The amendment with low C:N ratio increased the incidence of R. solani on bean plants, in any decomposition level, whereas the amendment with high C:N ratio did not interfere on the incidence of the pathogen. The incidence of R. solani on bean plants, in a soil amended with both castor-oil cake or sugar-cane bagasse, was independent of the soil moisture condition.
