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Occurrence and Distribution of Ergot and Estimates of Seed Loss in Kentucky Bluegrass Grown for Seed in Central Oregon

January 1998 , Volume 82 , Number  1
Pages  89 - 93

Stephen C. Alderman , Plant Pathologist, USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331 ; Dale D. Coats , Research Assistant , and Fred J. Crowe , Associate Professor, Department of Botany and Plant Pathology, Oregon State University ; and Marvin D. Butler , Extension Agronomist, Central Oregon Agricultural Research Center, Madras 97741

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Accepted for publication 3 October 1997.

In 1991 to 1993, ergot was detected in 36, 44, and 62%, respectively, of fields of Kentucky bluegrass grown for seed in central Oregon. Relatively few fields (2 to 13%) had a high (more than 20 sclerotia/gm seed) level of ergot. Ergot severity (percent sclerotia by weight) in 1991 to 1993 was estimated at 0.85, 0.07, and 0.34%, respectively. Percent seed replaced by ergot in 1991 to 1993 was estimated at 0.22, 0.02, and 0.08, respectively. Recleaning of seed to reduce ergot contamination and to meet purity standards resulted in a 7.8% reduction in marketable seed weight. Estimated value of seed replaced by ergot in 1991, 1992, and 1993, was $75,625, $4,758, and $17,076, respectively. Estimated value of seed lost during recleaning in 1991, 1992, and 1993, was $37,669, $8,171, and $21,964, respectively. Weed grasses supporting ergot at the time of harvest of Kentucky bluegrass were species of Bromus, Secale, Festuca, and Poa. However, very few seed heads of weed grasses were infected, and they appeared to contribute little to ergot development in central Oregon. Most infested fields (with more than one sclerotium/gm seed prior to recleaning) or weed grass sites with ergot were located in the southern range of the area of study.

Additional keywords: Claviceps purpurea, Poa pratensis, yield loss

The American Phytopathological Society, 1998