Outlook for wheat leaf rust and stripe rust

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Leaf rust and stripe rust are some of the most damaging diseases of wheat in Kansas. Although making long-range predictions is challenging, we can often use reports of disease and weather information throughout the Southern Great Plains to project what may happen in Kansas. 

Regional reports of disease: The years with severe leaf rust and stripe rust epidemics in Kansas are often preceded by outbreaks of disease in Texas and Oklahoma. The first indications of problems often occur in Texas during February and March. So far, my colleagues in Texas and Oklahoma are reporting that leaf rust and stripe rust are absent or at low levels relative to recent years. However, there are a few spots in Texas that we will want to keep an eye on.

• Amir Ibrahim, wheat breeder for Texas A&M, reported both leaf rust and stripe rust in susceptible varieties in an irrigated field near San Antonio. This report indicates leaf rust has been slower to develop at this location than in previous years. A single focus of stripe rust was also reported at this location. Tom Isakeit, Extension Plant Pathologist for Texas A&M, shared an unconfirmed report of leaf rust and stripe rust near Warton, TX (about an hour south of Houston). Isakeit indicates that this area of Texas has little commercial wheat production. The isolation of this field may reduce risk of disease spread. Ibrahim and Isakeit both indicate that wheat was ranging from late jointing through flag leaf emergence stages of growth.
• Charlie Rush and Ron French, Texas A&M Amarillo, indicate that dry conditions still dominate in the Panhandle region of Texas and that there were no reports of rust to date.
• Bob Hunger, Oklahoma State University wheat pathologist, reports that are no reports of rust in Oklahoma so far this season, and that cold, dry weather conditions have not favored foliar diseases in Oklahoma. 

In Kansas, the wheat has been emerging from winter dormancy over the past two weeks.  There have been no reports of leaf rust or stripe rust so far in 2014. As you may recall, leaf rust was reported last fall near Manhattan, Kansas. I revisited these fields today and was unable to find the disease, suggesting that the leaf rust did not overwinter. In recent weeks I have also visited fields near Garden City, Great Bend, and Hutchinson. There was no evidence of disease in the fields I checked.

Assessment based on weather: Researchers here at K-State have been evaluating the weather conditions associated with historic epidemics of stripe rust in Kansas. This research indicates that stripe rust epidemics are most likely to occur when regional moisture conditions favor disease development in the fall (Oct-Dec) and winter months (Feb). Based on regional moisture in the fall and winter months in 2014, it appears that the risk severe stripe rust is low for Kansas. 

The bottom line...

My current evaluation of the regional disease reports and weather patterns indicate that the risk of severe leaf rust and stripe rust in Kansas is low. I will provide regular updates about the status of disease as the season progress. So stay tuned, because the disease situation can change rapidly.

Erick De Wolf, Extension Plant Pathology  
dewolf1@ksu.edu

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