Retired commercial agriculture Extension educator Robert Bellm observed stripe rust yesterday in several wheat fields in Madison County (Figure).
Rust pathogens are obligate parasites, meaning that they need a living host in order to survive. Wind and rain systems from further south bring spores to our area. This is why rust sightings in states to the South can help us in Illinois anticipate its arrival. Wet leaves and temperatures below 70 °F favor disease development.
Stripe rust is caused by the fungus Puccinia striiformis. Symptoms of stripe rust begin as chlorotic stripes on the leaf. As lesions develop, the fungus produces spores that can cause secondary infections. These spores, which are yellow to orange in color, develop under the leaf epidermis and swell the leaf tissue into a pustule (blister) which breaks open to reveal the spores (Figure).
Several fungicides are registered for stripe rust management, but the most effective time to apply fungicides is between last leaf emergence and complete head emergence. Applications that occur later are not likely to provide adequate protection. Additionally, caution must be exercised when selecting fungicide active ingredients as fungicides in the strobilurin class can only be applied up to complete heading (Feekes 10.5).
Fungicide Efficacy for Control of Wheat Diseases – A fact sheet authored by Purdue Extension Plant Pathologist Dr. Kiersten Wise.
Physiological Feekes Growth Stages in Winter Wheat – A diagram and listing of growth stages adapted by Oklahoma State University from an article written in 1954 by E.C. Large.
Management of Wheat Diseases in Illinois – An interactive online course containing content developed by former University of Illinois Extension Plant Pathologist Dr. Carl Bradley. The course content begins with head scab management, but beginning with section 1.28 (accessed through the menu on the left-hand side) covers other wheat diseases including stripe rust.