This article was written by Meriem Aoun, Small Grains Pathologist
In my previous update on April 12, I reported barley yellow dwarf virus (BYD) infection on the susceptible wheat variety ‘Pete’ in the BYD nursery in the Stillwater Agronomy Research Station. Last week, Dr. Amanda De Oliveira Silva (OSU Extension small grains specialist) observed yellowing of the leaf tips in most of the hard red winter wheat variety demonstration plots in Stillwater (Figure 1). We performed Enzyme linked immunosorbent assay (ELISA) on symptomatic samples from different OSU wheat varieties including ‘OK Corral’, ‘Strad CL Plus’, ‘Guardian’, ‘Baker’s Ann’, ‘Showdown’, and ‘Breakthrough’. All samples were tested positive for BYD. In these demonstration plots, the variety ‘Uncharted’, which carries two BYD resistance genes, Bdv1 and Bdv2, was the most resistant OSU wheat variety to BYD (Figure 1). Dr. Silva indicated that the plots planted earlier in September were more infected than the plots planted later in October. This shows the importance of breaking the ‘green bridge’ to manage this virus which is transmitted by cereal aphids.
During the last couple of weeks, the Plant Disease and Insect Diagnostic Laboratory at OSU received wheat samples from Garfield, Blaine, Cleveland, and Harper counties in Oklahoma and from an unknown location in Kansas state. I examined these samples and I observed yellowing and streaking indicative of viral infection (Figure 2). I did not observe any symptoms of fungal diseases on the leaves of the received samples. For the samples received from Garfield county and Kansas state, many of the leaves were dry and brown suggesting freeze damage (Figure 3).
Some of these samples were tested using ELISA for several viruses that affect wheat in the Great Plains. The sample from Cleveland county which was collected on the wheat variety OK Corral was positive for BYD. The sample from Kansas state (from the variety ‘Zenda’) and the sample from Garfield county (from the variety ‘WB 4401’) were tested positive for wheat streak mosaic virus (WSM). ELISA for the remaining samples from Blaine and Harper counties is in progress but the symptoms suggest WSM infection.
This article was written by Dr. Meriem Aoun, Small Grains Pathologist
During the first and second week of April, some wheat diseases appeared in Oklahoma. For example, in the Stillwater Agronomy Research Station, I observed high powdery mildew infection on the susceptible wheat variety ‘OK Bullet’ (Figure 1). Similarly, Bradley Secraw (Extension educator at Cleveland county; March, 31, 2022) found little powdery mildew infection on the variety ‘OK Corral’ which is moderately resistant to this disease. In Stillwater and on April 11th, I observed initial stripe rust infection on OK Bullet (Figure 2). Also recall in my previous update of 25-March, I indicated seeing little stripe rust infection in Jackson county. Therefore, I encourage growers to start scouting their fields for these diseases, especially if they are growing susceptible varieties. We will continue to monitor these diseases as we approach flag leaf stage and provide recommendations.
In the Stillwater Agronomy Research Station, I also observed barley yellow dwarf virus (BYD) symptoms on the susceptible wheat variety ‘Pete’. The symptoms appeared as yellow, red/purple discoloration on the leaves as shown in Figure 2. This virus is transmitted from plant to plant by cereal aphids. Enzyme linked immunosorbent assay (ELISA) on a symptomatic sample from Pete was positive for two BYD strains; BYD strain 2 (BYDV-PAV) and cereal yellow dwarf (CYDV-RPV).
In Stillwater, I observed yellowing on the wheat variety ‘Lonerider’. Older leaves were completely chlorotic (Figure 3). Laboratory diagnosis of a sample using ELISA was positive for wheat streak mosaic virus (WSM) which is transmitted by wheat curl mite. This disease is an issue in our region as many wheat varieties growing in Oklahoma are susceptible to WSM.