Submitted to: Wheat Newsletter
Publication Type: Other
Publication Acceptance Date: 2/24/1999
Publication Date: N/A
Technical Abstract: Wheat stem rust was light in 1998 with minimal yield losses reported except for 0.5-1.0% loss in Oregon and Washington. For the first time in wheat stem rust race surveys, Pgt-RCRS was the most commonly identified race. TPMK, which has been the predominant stem rust race on wheat in recent years was only the third most common race found in 1998 following QCFS. Virulences of RCRS, QCFS, or TPMK do not present a threat to current wheat cultivars grown in the Northern Plains. Wheat leaf rust was widely distributed in the South early in 1998, but weather conditions did not favor rapid buildup of leaf rust. Yield losses to leaf rust were less than normal in 1998. Greatest losses were 3.0% in Oklahoma, 2.5% in Kansas, 2.0% in Oregon and 2.0% in Washington. As in recent years, races MDRL, MCDL, and MBRL were the most commonly identified wheat leaf rust races. Cool spring weather in 1998 sustained the most extensive development of stripe rust on wheat in the Great Plains in the last 20 years, but the onset of hot summer weather in the Great Plains stopped the epidemic before significant yield losses could occur. Spring and summer weather was favorable for stripe rust in the Pacific Northwest, and certain susceptible wheat cultivars were seriously damaged. Overall, stripe rust losses in California, Oregon, Washington, and Idaho were limited to 2% largely because of effective adult plant resistance in most of the cultivars.