Submitted to: Wheat Newsletter
Publication Type: Other
Publication Acceptance Date: 6/5/1998
Publication Date: N/A
Technical Abstract: Wheat stem rust was light in the U.S. in 1997 with minimal yield losses. The only overwintering stem rust sites were found in central Louisiana. No stem rust overwintering sites were found in southern Texas where it is found almost every year. Traces of stem rust were reported in the northern soft red winter wheat area and the northern plains during the growing season. Several factors delayed stem rust development in the northern areas; first, little stem rust overwintered in the southern U.S.; second, dry weather in June limited infection; and third, stem rust resistance in the spring wheat remains highly effective in the northern Great Plains. As in recent years, Pgt-TPMK (69%) was the most common race in the U.S. In contrast to stem rust, more leaf rust overwintered in the southern Great Plains in 1997 than in 1996. Leaf rust was unusually heavy in Oklahoma where 10% of the crop was lost to leaf rust. Leaf rust losses in winter wheat ranged from 1 to 10% in the Pacific Northwest, the Southeast, and th Midwest. Although most of the spring wheat cultivars are resistant to leaf rust, some cases of higher than usual leaf rust severities were reported which resulted in heavier than usual losses. For example, a 1.5% loss was reported in Minnesota. MDRL was the predominant race while MBRL, which was the most common race identified from 1994-1996, was the second most common race. Two new races, which have Lr17 virulence, were identified from leaf rust collections made from Jagger, a cultivar with Lr17 resistance, which is being grown on a large portion of the hard winter wheat acreage this year. Stripe rust was severe in plots in the Pacific Northwest but losses in commercial fields were minimal because of effective adult plant resistance in the commonly grown cultivars.