Cause A fungus, Gloeotinia temulenta, that lives in infected grass seed. Over 40 species of grass are susceptible. The disease is most common in annual ryegrass, perennial ryegrass, and tall fescue. In spring, the fungus emerges as stalked, cup-shaped apothecia (one to several per seed). Ascospores are ejected from the apothecia into the air; only those that land on flowers of a susceptible grass host will infect. Within two weeks of infection, secondary spores (conidia) may form on the surface of developing seed. Conidia are spread to healthy flowers by rain splashing. Rainy conditions are required for blind seed development and spread. The disease often develops in early maturing varieties, especially when prolonged rainy weather occurs during flowering.
Symptoms Poor seed germination. Infected seed may be shrunken, rusty in color, or may have a pink coloration. Infected seed are difficult to find. Tests for blind seed include soaking the seeds in water to dislodge conidia, concentration by centrifugation, and examination under the microscope for conidia typical of Gloeotinia sp.
Sampling The OSU Plant Clinic tests grass seed for the presence of the pathogen. See the section "OSU Plant Clinic Fees" in "Testing Services" Section 2 of this handbook for current fee information.
Cultural control
- Plant pathogen-free seed. Infected seed stored dry for 24 months is considered safe to plant.
- Plant later-maturing varieties.
- Apply optimum rates of nitrogen fertilizer, and maintain a healthy and vigorous stand.
- Remove as much seed as possible from the field during combining, especially lightweight seed.
- Harvest at the proper time to reduce seed shatter.
- Open field burning has proven effective in blind seed control.
- Plow the field after harvest or bury seed deeper than 2 inches. At this depth the fruiting bodies cannot reach the soil surface.