2002 Cereal Rust Bulletin #2 April 4, 2002 ------------------------------------------------------------------------ * Wheat leaf rust is more prevalent than last year in the southern U.S. * Wheat stripe rust is not as severe as last year in Texas. * Oat crown rust is light this year throughout the southern U.S. * Oat stem rust was found in a plot in southern Texas. ------------------------------------------------------------------------ In the southern U.S., the winter-sown small grain crop is in fair condition and near normal crop development in much of the area. In the central Great Plains, the crop is in fair shape and near normal maturity. Wheat stem rust. As of April 8, no wheat stem rust has been reported in the U.S. Wheat leaf rust. In early-April, leaf rust was light in wheat fields and severe on susceptible cultivars in nursery plots from central Texas to Georgia. During the first week in April, in southern and central Texas, 60% severities were observed on the lower leaves of cultivars in nurseries and 10% on the lower leaves in fields. In late March, only traces of leaf rust were found in wheat fields throughout the state of Oklahoma. The drier and cooler than normal weather in March contributed to the slower than normal rust development in the southern U.S. Leaf rust will increase rapidly with adequate moisture and warmer weather conditions in April. Currently, leaf rust is more prevalent and severe than on the same date last year throughout much of the southern U.S. From leaf rust collections made during January and February the following races were identified: Texas - MCDS, MBDS, TCDS and TLGJ; Arkansas - MCDS, MBDS, SBDG, FMMQ and TLGJ. As in 2001, the MCDS and MBDS races have been the two most common races identified so far this year, in the southern plains region. Wheat stripe rust. In early April, light wheat stripe rust was found in wheat fields in southern and central Texas and rust readings ranged from trace amounts to approximately 40% severity in southern Texas nurseries. Last year in early April, stripe rust caused complete losses in many of the cultivars in southern Texas nurseries. But this year in the same plots stripe rust was severe on the lower leaves but rust infections had not developed onto the upper leaves because of dry and cool weather in March. However, if temperatures stay less than 70 F with adequate moisture, stripe rust will continue to develop. Stripe rust severities on soft red winter wheat cultivars generally were higher than those on the hard red winter cultivars in the southern and central Texas nurseries. Jagger and Cutter are two cultivars that have the best stripe rust resistance in the Uvalde nursery in southern Texas. By late March, stripe rust was found in wheat fields and variety demonstration plots in east central Arkansas. Weather conditions currently favor stripe rust development in this area which will be monitored in the next few weeks. In early April, wheat stripe rust was prevalent and severe in northwestern Washington, where environmental conditions have been favorable for stripe rust infection, overwintering , and development. Stripe rust severities of 20 to 30% were observed in winter wheat nurseries and 5% severities were observed in fields. By early April, no wheat stripe rust has been found in California. Oat stem rust. In early April, in the southern Texas nursery at Uvalde, an overwintering site of oat stem rust was found on the cultivar Harrison. Stem rust infections at 5% severity were found on the sheath of the oldest tillers in this plot. There have not yet been any reports of oat stem rust in Louisiana which is very unusual. The drier and cooler than normal temperatures have slowed oat stem rust development throughout the southern U.S. Oat crown rust. In early April, oat crown rust was severe in plots in a central Texas nursery at Giddings, where there has been adequate moisture for rust development. Traces of crown rust were found in grazed oat fields in southern Texas. Buckthorn. Buds on buckthorn, the alternate host for oat crown rust, have not yet started to break dormancy in the buckthorn nursery at St. Paul. This is comparable to last year but later than normal for most years. Barley stem rust. As of April 8, no barley stem rust has been reported in the U.S. Barley leaf rust. In early April, 60% severities were observed in a plot of the P-721 line at Uvalde, Texas. Stripe rust on barley. As of April 8, no barley stripe rust has been reported in the U.S. Rye rusts. In early April, 60% rye leaf rust severities were observed in plots of winter rye in a central Texas nursery at Giddings. In this area moisture conditions were more suitable for rust development than other parts of the state. In early April, 20% leaf rust severities were observed on rye growing in plots in Plains, Georgia.