As wheat this week in Kansas ranges from Feekes 9 (flag leaf fully emerged) to Feekes 10.5 (full head emergence and flowering), stripe rust continues to be reported. New observations were made in north central Kansas in Jewell, McPherson, Mitchell, Ottawa, and Harper counties (Figure 1). Although incidence (the number of infected plants) and severity (how bad the infection was on each infected plant) were low in fields that were scouted in this region, lesions were found on the upper leaves (Figure 2). Infected upper leaves are most likely to result in yield loss. It is important to remember that there is a lag between when new leaves are infected and when they start to show symptoms. The severity of symptoms is dependent on weather conditions, and favors temperatures between 50-60° F with high humidity (for more information see: https://bookstore.ksre.ksu.edu/pubs/EP167.pdf). We are currently in the window to make a fungicide application to control stripe rust.
Figure 1. Distribution of stripe rust in Kansas as of May 15, 2020. Map is based on observations of K-State Research and Extension, crop consultants, and wheat producers in the state. Map created by Kelsey Andersen Onofre and Erick DeWolf, K-State Research and Extension.
Figure 2. Low levels of stripe rust found in a commercial field in Jewell County on May 14, 2020. Photo by K. Andersen Onofre, K-State Research and Extension.
Wheat streak mosaic virus
There have also been several reports of wheat streak mosaic virus (Figure 3), mostly in the central and western portions of the state. It is important to remember that fungicide will not provide any control for viral infections. Even for the highly trained eye, it can be difficult to differentiate symptoms of wheat viruses. Wheat streak mosaic virus symptoms can be easily confused with other viruses, such as barley yellow dwarf virus. Multiple viruses can also be present in the same plant, which can make yield loss worse.
Figure 3. Plants infected with characteristic symptoms of wheat streak mosaic virus in north central Kansas. Photos by K. Andersen Onofre, K-State Research and Extension.
Plant Disease Diagnostic Lab
If you would like confirmation of viral diseases in your wheat field, remember that K-State’s disease diagnostic lab is still accepting samples! We wanted to share some key reminders for wheat sample submission:
KSU Plant Disease Diagnostic Lab
1310A Westloop Pl #351
Manhattan, KS 66502
Complete information can be found on the Plant Disease Diagnostic Clinic’s website (https://www.plantpath.k-state.edu/extension/diagnostic-lab/) and the diagnostic lab can be contacted by email at email@example.com for additional information.
While scouting fields throughout the state, we continue to run into loose smut (Figure 4). As a reminder, infected heads will infect surrounding plants during flowering. This will lead to more infected plants next season if seed is saved. Loose smut can be reduced by purchasing certified seed or by applying a fungicide seed treatment.
Figure 4. Loose smut in a commercial field in north central Kansas. Photo by K. Andersen Onofre, K-State Research and Extension.
Kelsey Andersen Onofre, Extension Plant Pathologist
Erick DeWolf, Extension Plant Pathologist