Light seed and large seed dressing losses of perennial ryegrass seed crops were found to be associated with the presence of the root-rot pathogen Gaeumannomyces graminis var tritici (Ggt) which causes take-all in grasses and cereals. Preliminary pot experiments with a pasture bio-inoculant (PBI) comprising four isolates of Trichoderma atroviride demonstrated the potential for suppression of Ggt resulting in increased of perennial ryegrass dry matter and improved seed yield in prairie grass. During the 2019-20 and 2020-21 seed production seasons, large scale on-farm experiments with perennial ryegrass seed coated with PBI (new crop) or a prill formulation (drilled in an existing 2nd year crop) revealed good colonisation of the rhizosphere by Trichoderma and reduced Ggt root infection. PBI treatments increased perennial ryegrass dry matter and reproductive tiller number, resulting in a seed-yield increase of 4% (seed coat treatment) and 18% (prill formulation)
