Cause Fungi in the genera, Tilletia and Sphacelotheca. Species of bluegrass, bentgrass, fescue, ryegrass, and velvetgrass are susceptible. Spores from infected seeds are distributed to adjacent seeds and into soil. Spores on infested seed germinate when seed sprouts; infection occurs through immature seedling tissue. The fungus continues to grow within the plant and eventually infects the flowers. Rotation may be ineffective because spores of some species remain viable in soil 10 to 25 years, depending on species.
Symptoms Infected plants are stunted. As they grow, their ovaries are replaced by spore masses held together by the pericarp (part of the seed coat); these often are concealed by the glumes. When spore masses ripen at the end of summer, the kernel breaks and releases light to dark brown spore masses with a "rotten fish" smell.
Chemical control Treat infested seed used for seed production.
- 42-S Thiram at 8 fl oz/100 lb seed plus a dye. See label for reentry restrictions.