There have been continued reports of wheat rust diseases in Texas and Oklahoma in early March. These reports indicate that both leaf rust and stripe rust are active in the region. Moreover, trace levels of leaf rust were detected in research plots near Manhattan this week. These early reports are significant because they indicate potential overwintering of the diseases within Kansas and throughout the region. Spores produced by disease outbreaks in the Southern Great Plains are often moved northward into Kansas by storm systems, where they initiate additional disease.
Figure 1. Overwintering leaf rust on wheat in Kansas, March 2015. Photo by Erick DeWolf, K-State Research and Extension.
Interestingly, there is also some information that suggests the risk of stripe rust is low in the Great Plains despite early reports of disease in the South. Analysis of the weather conditions associated with past outbreaks of stripe rust in Kansas suggest that dry conditions throughout the region in October-December and again in February will often reduce the risk of severe disease in Kansas. A look at these time periods for the current growing season suggests that conditions have not been favorable for severe stripe rust in 2015. It is not clear what effect these same conditions might have on leaf rust.
The bottom line is that it will be important to stay current on the disease situation in the southern states and scout the local fields for any early signs of rust. If the disease becomes established early, it may be beneficial to protect susceptible varieties with fungicide applications if the yield potential looks promising. There is no need for fungicides now because the most effective fungicide applications are those applied just prior to heading of the wheat crop. We still have time to gather more information and make a good decision.
Erick DeWolf, Extension Plant Pathologist