Fermentation period, moisture content, and substrate effects on inoculum effectiveness of Dilophospora alopecuri: a biocontrol agent of annual ryegrass toxicity

The efficacy of biological control agents is affected by numerous cultural conditions. This study was undertaken to determine how the efficacy of Dilophospora alopecuri inoculum was affected by various conditions, including length of fermentation, moisture content, and growth substrate. Dilophospora alopecuri (Fr.) Fr. provides biological control of the organisms (Rathayibacter toxicus and Anguina funesta) responsible for annual ryegrass toxicity. The effectiveness of D. alopecuri inoculum was evaluated under different conditions for establishment in ryegrass. Prolongation of incubation of the inoculum for 3–10 weeks had no significant effect on the inoculum as a biological control agent. The effect of inoculum moisture content was mixed. With wheat as the substrate, air-drying the inoculum had no apparent effect. However, with ryegrass as the substrate, air-drying the inoculum decreased the effectiveness of the inoculum in the field experiment but not in the pot experiment. The substrate itself also had a significant effect. In the pots, application of colonized ryegrass gave a mean of 56.9 infected inflorescences per pot compared to 30.4 for colonized wheat. In the field experiment, 87.5% of plots inoculated with colonized ryegrass had 25 or more infected inflorescences, twice that of plots treated with colonized wheat.