a plant disease caused by fungi of the genus Typhula. Typhula blight affects a number of plants, including clover, wheat, and hops; it is observed in regions having a relatively high amount of moisture.
The disease develops on several species of clover (causative agent T. trifolii). Infection occurs in the autumn after sowing and in subsequent growing seasons. Masses of sclerotia appear inside the stem, on the leaves, and on the surface of the soil in the spring. The sclerotia grow and form basidia and basidiospores, which infect the plant. Infection is promoted by an increase in the moisture level and by air temperatures of 10° to 16°C. In the second year the plants exhibit retarded growth, and their leaves wither. By the spring of the third year the plants die. The disease severely depletes the clover stand, sharply decreasing the yield of hay. Control measures include removal of the sclerotia from the clover seeds, presowing treatment of seeds, and liming of acid soils. The disease may also be controlled by drying swamped fields and clearing them of plant remains on which the fungus winters.
Typhula blight of winter wheat (causative agents T. graminum and T. itoana) imparts an unnatural dark-green coloration to the affected plants. The tillering node is destroyed, and the above-ground part of the plant separates readily from the roots. Infection occurs in the autumn or, less commonly, in the spring. The sources of infection include many wild grasses and debris on harvested wheat fields; another source is soil containing the sclerotia of the fungus. Control measures include deep autumn plowing, spring harrowing, and destruction of weeds.
Typhula blight of hops (causative agent T. humulina) affects the underground stems and rootstocks in the budding zone. The source of infection is in the soil, where dark red sclerotia form on the underground stems and rootstocks. Infection occurs in the autumn. Cuttings from diseased plants should not be used for propagation, since 50 percent or more of the new plants will die. When the weather is comparatively warm, the fungus may develop in late autumn or early spring—even under snow, breaking down the tissues of plants. Control measures include the use of healthy planting material, the planting of varieties resistant to Typhula, good maintenance of hops plantings, and the destruction of diseased plants.