Biological control of pasture bare-patch disease with Trichoderma bio-inoculants

Abstract

Pasture ‘bare-patch’, characterized by death of perennial ryegrass (Lolium perenne L) plants within six months of pasture renewal, was diagnosed as being caused by the soil-borne pathogens Gaeumannomyces graminis (severe root rotting) and Fusarium culmorum (crown rotting). Pasture swards were cut from the affected areas and used in a glass-house experiment to assess the ability of seven Trichoderma strains to control the pathogens. Using the inverted sward technique, the Trichoderma strains were applied to the soil in prill formulation (at a rate equivalent to 30kg/ha) and seeds of perennial ryegrass cv. Bealey were sown (100 seeds/pot). Seedling emergence, recorded 21 days after sowing (DAS), did not differ from the untreated control (range 86-92%) and there were no differences in shoot dry matter (SDM) when assessed at 44 and 84 DAS. However, by 158 DAS all seven Trichoderma treatments had a significantly increased SDM and at 218 DAS, SDM for three of the treatments was still over 40% greater than that of the control. Root dry matter (RDM) was also between 80-100% greater at 124 and 218 DAS for three of the Trichoderma treatments. The two strains of T. atroviride which significantly increased (P<0.05) both SDM and RDM also had the lowest root disease score for G. graminis. Whether this response can be obtained in the field is yet to be determined.