Submitted to: Oat Newsletter
Publication Type: Other
Publication Acceptance Date: April 13, 1999
Publication Date: N/A
Technical Abstract: Oat stem rust was more widespread in the Southeast in 1998 than in the five previous years, because of increased acreage of highly susceptible cultivars. In spite of increased incidences of stem rust, losses in the Southeast were light in 1998 with 1% loss in Texas being the worst recorded damage. There was minimal damage to oat by stem rust in the northern oat-growing region in 1998. Crown rust infection of oat in the Southeast was lighter in 1998 than in the past five years, and losses were limited to 1% to 2%. Aecial infections of crown rust on buckthorn in the Midwest occurred 2-4 weeks earlier than normal, but development of crown rust on oat was delayed by cool weather in early June. Losses to crown rust ranged from 2% to 3% in the Dakotas and Minnesota. Most of the crown rust losses were in fields of late planted oat. As in previous years, race NA27 was the predominant race of oat stem rust in the United States. A new race with virulence to Pg-1, -2, -3, -4, -8, -13, and likely -9 was found in a breeding nursery in South Dakota. Frequencies of virulence to oat crown rust resistance genes in 1998 changed little from those in recent years. Virulence to Pc-58, which was used in the Midwest in the early 1990s, has declined since cultivars with Pc-58 dropped out of production. Virulence to Pc-58 in the Midwest dropped from 19% in 1994 to 11% in 1996 and 0% in 1997 and 1998.