Vermicompost suppresses Rhizoctonia solani Kühn in cucumber seedlings

Disease suppressiveness of vermicompost produced from agricultural wastes consisting of cattle manure, tree bark ( Salix spp.), potato culls, and apples was assayed on damping-off of two days-old cucumber ( Cucumis sativus cv. Cevher) seedlings infected by Rhizoctonia solani Kühn (AG-4). Suppression effect was assessed at the rates of 0, 10, 20 and 30% (v/v) vermicompost, either blended with Trichoderma harzianum Rifai (KRL-AG2), amended with potting mixtures consisting of sand and garden soil (1:1, v/v). Effect of water extracts of vermicompost on growth of R. solani mycelium in Petri dishes was also analyzed. Disease suppression effect increased in proportion to the pot amendment rate of vermicompost. Vermicomposts not blended with T. h arz ian u m effectively controlled damping-off of cucumber by R. solani (AG-4) at the rate of 20% and 30%. Vermicompost not blended with T. harzianum improved plant growth as well as that blended with T. harzianum . Analysis of the effect of water extracts of vermicompost on growth of R. solani mycelium in Petri dishes revealed antagonistic activity of a putative bacterium. Heat sterilization eliminated the suppressive and antagonistic effect by vermicompost and its water extracts, respectively. Activity of an antagonistic bacterium, which expressed a strong inhibition of growth of the pathogen mycelium, indicated that the type of suppressiveness against Rhizoctonia disease by the vermicompost is specific.