Update on stripe rust and leaf rust in wheat
This week’s finding of stripe rust in southeast Kansas has stimulated a lot of questions and scouting activity in wheat. Here are some of the most common questions and thoughts to consider while evaluating the stripe rust situation.
What is the distribution and severity of the disease in Kansas?
K-State specialists have found stripe rust at low levels in many fields in southeastern and central Kansas. There have also been also a few reports north I-70 in a few counties. Leaf rust in trace amounts was also present in many of the same locations.
Figure 1. Comparison of stripe rust (yellow stripe on leaf in foreground) and leaf rust. Photo by Stu Duncan, K-State Research and Extension.
What is the disease level at these locations?
Stripe rust was present at only low levels in most fields we checked this week, with less than one percent of the plants infected. The disease was most common in the lower- to mid-canopy; however, a few fields in the southeast and south central region had infections in upper canopy.
Are fungicides needed to manage of stripe rust at this point?
No, at this point, the low levels of disease present in most fields do not warrant a fungicide application. It is important to scout these fields frequently because stripe rust can increase rapidly. If the disease moves to upper leaves (flag leaves) by the heading stages of growth, fungicide may be needed to prevent disease-related yield loss. Some fields may already be at the threshold for application.
At what growth stage would a fungicide be most beneficial?
The most effective fungicide applications are made between flag leaf emergence and the flowering stages of growth. The boot and heading stages of growth are optimal. Be sure and follow the label directions on the fungicide product. Some fungicides are off label for application when wheat reaches the flowering stages of growth. Other products labeling allow applications during flowering but have a pre-harvest interval of 30 days. For more information about fungicide options on wheat consider reviewing K-State Research and Extension publication EP-130, Foliar Fungicide Efficacy for Wheat Disease Management, at: http://www.ksre.ksu.edu/bookstore/pubs/EP130.pdf/
Erick DeWolf, Extension Plant Pathology