Colorado, USA
March 31, 2016
Rust diseases are among the most widespread and devastating economically diseases of cereal crops worldwide. The fungi that cause these diseases are notorious for their ability to increase rapidly and overcome the resistance of wheat or barley varieties. The potential yield loss caused by these diseases depends on host susceptibility and weather conditions, but the loss also is influenced by the timing and severity of disease outbreaks relative to crop growth stage.
Favorable conditions for the spread of stripe rust include temperatures in the 50s-70s. Wind also increases the spread of the disease as it carriers the spores and enables it to infect other areas. These conditions are forecasted for the upcoming weeks so it is very important to watch for the spread of the disease. Spore formation is stopped when daytime temperatures exceed 80 degrees.
Currently there has been confirmed reports of stripe rust in the Prospect Valley region northeast of Denver. CSU Extension specialist Wilma Trujillo was able to examine wheat in the southwest part of the state near Lamar, where stripe was present last fall. The leaves examined found no evidence that stripe rust was able to overwinter in this region of the state. Producers are encouraged to scout their fields often for any signs of rust.
If a producer believes they have found rust in their fields they are encouraged to fill out a survey at coloradowheat.org/6113 as well as alert Kirk Broders, Assistant Professor, Department of Bioagricultural Sciences and Pest Management at Colorado State University. He can be reached at kirk.broders@colostate.edu and requests that pictures are attached to the email. Broders also requests that samples be sent to his lab for positive identification of stripe rust or leaf rust. The samples can be sent to: Kirk Broders, Bioagricultural Sciences and Pest Management, C-030 Plant Science Bldg, 1177 Campus Delivery, Fort Collins, CO 80523.
A rust management recommendation from Broders for those who already have noticeable levels of rust in their field is to consider including a fungicide at tillering (GS 4) or when herbicide is applied. If rust is not present then he recommends waiting until closer to flag leaf and monitoring the spread of stripe rust in the state.
If you have any questions regarding rust please contact Broders. Updates on the spread of the rust will be provided often as we enter the prime temperatures and conditions for it to be spread.
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