Cause Cercosporidium graminis (teleomorph: Mycosphaerella recutita), a fungus that overwinters as mycelial stromata in affected leaves and debris and infects all cool season turf and forage grasses including: orchardgrass, fescue, ryegrass, bluegrass, and bentgrass. Conidia develop from overwintering mycelium and are splashed, blown, or otherwise disseminated to healthy leaves. The brown stripe fungus sporulates during cool, moist weather in spring and autumn. Warm, dry summers restrict the ability of the fungus to cause disease.
Symptoms Leaf spots appear as brown to gray elongated lesions on leaves by mid-spring or in the fall. Small gray to black groups of conidiophores visibly erupt through leaf stomata. This is one of the common leaf spot fungi observed on orchardgrass, usually appearing later than scald or purple eyespot. It does not appear to attack the head or to cause severe leaf loss late in the season as the scald fungus does, but it can contribute to loss of leaf tissue.
Chemical control In most years, control is not necessary.
- Bravo Ultrex at 0.9 to 1.4 lb/A. Begin applications during stem elongation when conditions favor disease development. Do not allow livestock to graze in treated areas or feed treated plant parts to livestock. 12-hr reentry.