Last Monday morning (January 30, 2012), stripe rust was detected in several wheat plants in a Bolivar County wheat field. Unlike the recent report of stripe rust from Arkansas (http://www.arkansas-crops.com/2012/01/27/stripe-rust-found-in-arkansas-2/), the infected plants were in a localized area along the field edge so the size of the affected area was quite small. The area in the field is highlighted by the flag and water bottle in the attached photo. Wheat throughout the state is currently in the tillering stage. Stripe rust development is typically favored by an environment with temperatures between 50F and 65F, heavy dews, and intermittent rain showers (e.g. high humidity). In addition, development of the disease can occur above 70F.
Generally speaking, the report of stripe rust is several months earlier than what could be considered a “typical” timing. However, with the mild winter temperatures we’ve encountered and the frequent rainfall finding stripe rust is not unexpected. The report of stripe rust from AR and MS are the first of the disease east of the Rockies this year.
Presently, management options in the form of a fungicide application are not necessary. Generally speaking, wheat is more susceptible to rust diseases at early growth stages and will become more tolerant of the fungus as the plant ages. However, with that said it is still important to determine A) the specific wheat variety planted in each field and B) determine the rating for stripe rust and other important yield-limiting diseases. If a particular variety is labeled as moderately resistant or resistant than monitoring for the disease will likely be more economical than simply making a labeled fungicide application.
When scouting for stripe rust keep in mind there are two common rust diseases in the MS production system. Leaf rust produces a sporulating pustule more orange in color and likely will be present on the leaf in a more random, scattered pattern. Stripe rust will produce pustules with a defined pattern in rows of pustules and the sporulating pustules will be more yellow in color when compared to leaf rust.