With stripe rust moving as far north as Salina as of April 5, and leaf rust found as far north as Riley County in eastern Kansas and Ness County in western Kansas, it’s a race to the finish line for the Kansas wheat crop, according to Erick DeWolf, plant pathologist for K-State Research and Extension.
Aerial application in north central Kansas
Recent rains have farmers and crop consultants on alert for the spread of these diseases, and DeWolf says farmers need to be checking fields for possible infestations.
For instance, the crop is heading out in southern Kansas. If farmers see active rust lesions in wheat fields now, be prepared to spray the crop with a fungicide.
If you don’t see rust lesions at heading, a fungicide application may not be warranted. "But you do need to continue scouting those fields," recommends DeWolf, who adds that growers need to remain vigilant and take steps to protect the crop until after the crop has flowered.
Diligent field scouting will help farmers overcome the uncertainty of this year’s race of stripe rust. "It appears that some varieties that looked vulnerable during our last stripe rust outbreak are not developing stripe rust this year," he says. "However, many varieties, including Tam 111, Everest, Armour and Cedar – all of which showed resistance in 2010 – are appearing susceptible to the variant of stripe rust that is showing up this year."
The Feekes Growth Scale (click on image to enlarge)
courtesy Oklahoma State University
Growers have until a given fungicide’s Pre-Harvest Interval, or the growth stage restriction on the label, to apply a fungicide. DeWolf advises farmers that for best results, apply fungicide between the growing stages of flag leaf fully extended (Feekes 9), and fully headed (Feekes 10.5). Some fungicides can be applied during the flowering stages of growth but generally have a 30-day pre-harvest interval. Once the flag leaf has emerged, farmers will have about two weeks to scout for disease and make a final decision about fungicide application.
Farmers have a choice of two basic categories of foliar fungicides: