Use of organic composts to suppress bentgrass diseases in Agrostis stolonifera

Turfgrasses are affected by fungal diseases and their chemical control is currently limited by the legislation and the impact on the environment of fungicides and the possible development of fungicide resistance. This study was carried out during three years to evaluate the antagonistic effect of the microbiota associated with organic composts. Two composts were produced from agro-industrial residues, P1 and P2. Fungi from both composts were isolated and identified and their antagonistic capacity was evaluated, in vivo and in vitro tests, against Sclerotium rolfsii Sacc, Clarireedia gen. nov. (formerly Sclerotinia homoeocarpa (Benn, 1937)) and Rhizoctonia solani (Kühn 1858). In vivo tests were run for Agrostis stolonifera L., seeded in P1, P2 and a commercial peat (T) based substrate (Hansa Torf Floragard, Germany), in 100 mL pots. A part of each substrate was submitted to a thermic treatment, obtained Pt, P1t and P2t substrates. Antagonistic properties of the P, P1 and P2 were compared with substrates with thermic treatment. In the in vitro tests Trichoderma atroviride and Trichoderma asperellum showed higher growth than the tested pathogenic agents. T. atroviride showed the best antagonistic capacity, with inhibition percentages of 67.5%, 63.8% and 62.5% against Clarireedia spp., S. rolfsii and R. solani, respectively. In the in vivo tests, the efficacy and biological control index (BCI) were higher in P1 and P2 than in P. BCI ranged from 1.66 (Pt) to 39.03 (P2) on S. rolfsii control, from 1.38 (Pt) to 14.66 (P1) on Clarireedia spp. control, and from 1.87 (Pt) to 21.45 (P1) for R. solani control. Compost P2 showed the highest suppressive effect on the studied soil diseases in turfgrass, which did not occur when its microbiota was eliminated by thermic treatment.