The fungus Ramularia pusilla causes Ramularia leaf spot (RLS), most commonly in spring and autumn, when it can seriously reduce yield and quality.
Ryegrass, prairie grass.
Rounded leaf spots, grey to brown in colour, sometimes with red edges, appear on the leaf surface. Part of a paddock can appear yellow as infected leaves become yellow and die.
Numerous small, egg-shaped spores are produced on older lesions. These spores are readily wind borne and can rapidly spread infection to new sites. The spread of RLS is favoured by wet, humid weather.
Prevention and management
Pasture should be grazed before becoming long and rank, to reduce the chance of RLS becoming established and lower the severity of the disease. Under serious infection, fungicides may be economical.
Ramularia leaf spot on ryegrass leaves.