Abstract

Since the early 1920's a disease problem commonly referred to as yellow tuft has been reported on bentgrass (Agrostis spp.) turf in the northeast U.S. and also in Europe. Symptoms appear as small yellowed clusters of shoots proliferating from creeping stems and forming a dense tuft 1 to 3 cm in diameter. Individual shoots making up the tuft form few adventitious roots and the tufts are easily detached from the turf.

Recently, similar symptoms occurred on Kentucky bluegrass (Poa pratensis L.) in several sod producing areas in the United States. The disease has also appeared on bluegrasses(Poa spp.), perennial ryegrass (Lolium perenne L.), and red fescue (Festuca rubra L.) comprising golf fairway turf.

Investigations at the University of Rhode Island indicate that the downy mildew fungus (Sclerophthora macrospora) is consistently associated with yellow tuft symptoms and the causal relationship has been established. Mycelium of this obligate parasite is present in the diseased plants and propagules of the fungus; i.e., zoosporeproducing sporangia and oospores occur respectively on and in the leaves given optimum conditions.

In addition to overwintering oospores, resting mycelium survives in the crowns of infected plants and the disease presents a recurring problem in permanent turf. Infected weed grasses on the headlands and volunteer bluegrass plants surviving from the previous crop provide a reservoir of infection on sod farms. Although the disease is unsightly on bentgrass turf, there is usually no permanent injury. However, symptoms on bluegrass sod may be intense enough to render this turf temporarily unsaleable. Cultivar evaluation for resistance and the screening of possible fungicides is underway.

Copyright © 1980. . Copyright © 1980 by the American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, and International Turfgrass Society, 5585 Guilford Rd., Madison, WI 53711 USA