Submitted to: Oat Newsletter
Publication Type: Other
Publication Acceptance Date: August 10, 1998
Publication Date: N/A
Technical Abstract: Oat stem rust infection was light in 1995, 1996, and 1997, particularly in the northern plains where there was much less stem rust than in previous years. For the U.S., yield losses to oat stem rust were less than 0.1%. Greatest losses were in LA, where losses of 3% and 1% were estimated for 1995 and 1997. The predominant race of oat crown rust in the U.S. is NA-27, ,which is virulent on Pg-1,-2,-3,-4, and -8. Race NA-16 was also found in 1995-97, mainly in TX and LA but also occasionally in the northern plains. NA-16 is virulent on Pg-1,-3, and -8. Races NA-5 (virulent on Pg-3, and -15) and NA-10 (virulent on Pg-2,-3, and -15) were found on wild oat in ID and CA. Oat crown rust was severe throughout the Southeast in 1995 and 1997. Yield losses as great as 10% in 1995 and 20% in 1997 were recorded in LA. During 1995, crown rust was seen for the first time in many years in oat nurseries in OH and PA. Losses to oat crown rust in the northern plains states were substantial but less than during the epidemic years of 1991-94. Losses ranged from 2% to 6% in MN, ND, and SD during 1995-97. Relatively late development of crown rust from infections on the alternate host, buckthorn, accounted for the reduced losses in the northern plains. In 1995, crown rust infections were found on buckthorn for the first time as far north as Saskatoon. Virulence to Pc-53,-62, and -68 remained low throughout North America in 1995-97, although virulence to Pc-68 was found in CA, Mexico, and the northeastern U.S. Virulence to Pc-50,-51, and -62 was more frequent in the southern than the northern plains in all 3 years. Similarities between crown rust virulence in TX and Mexico in 1996 indicate spread from Mexico during that year when crown rust was relatively light in the Southeast.