Causal fungus – Associated with the following fungi, Drechslera spp., Curvularia spp., and Bipolaris spp. Damage caused – Small defined spots appear on the turf grass leaves that enlarge as the infection worsens. The centre of this spot turns brown as the cells die, with the margins of these spots turning dark brown. Some plants may exhibit spots with a yellow border to the brown dead spotted area. There will be no distinct overall visual margin to be seen from the surface just patches of infected grass.
Grass species affected – All grass species are susceptible to leaf spot although this disease is seen frequently attacking perennial ryegrass (Lolium perenne), as above and Smooth meadow grass (Poa pratensis)
Factors promoting infection – Warm humid weather conditions favour the disease, over fertilisation of a grass surface can trigger attack. High thatch levels are also thought to encourage this disease.