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Wheat Disease Update – 19 May 2022
This article was written by Meriem Aoun, Small Grains Pathologist
During my visit to wheat fields in Morris (Okmulgee County) on May 16, I observed multiple fungal and bacterial diseases. Wheat crop in Morris looked good and tall compared to other locations in Oklahoma (Figure 1). Morris got substantial amount of precipitation, which favored some fungal and bacterial diseases.

Bacterial streak (on the leaf, Figure 2) and black chaff (on the head, Figure 3) were frequently observed on multiple winter wheat varieties including ‘Big country’ and ‘WB 4401’. Bacterial streak and black chaff are two phases of the same disease and are favored by humid and warm climate, which was the case in Morris.

In Morris, I also observed Septoria leaf spot and tan spot in the lower and mid canopy, but nothing much on flag leaves. Septoria leaf spot was more common and found on varieties like ‘Skydance’ and ‘Crescent AX’ (Figure 4). Both diseases were also observed in the Stillwater Agronomy Research Station on OSU winter wheat breeding lines. In addition, spot blotch and powdery mildew were found in multiple experimental plots in Stillwater on susceptible winter wheat varieties and OSU breeding lines (Figure 5).


Powdery mildew and leaf rust were observed in both Stillwater and Morris (Figure 6 and 7). As I previously reported powdery mildew was observed in multiple locations in Oklahoma since April whereas leaf rust was first observed this year in Oklahoma during the second week of May.


In addition to these foliar diseases, I observed some head diseases including sooty mold (black head mold) (Figure 8) in wheat fields in Morris, El Reno, and Stillwater. Humid conditions promote this disease on wheat heads. Often wheat that has been subjected to a stress such as freeze, root rot, or drought shows a greater severity of sooty mold than healthy wheat. I also observed loose smut (Figure 9) in Chickasha, Stillwater, and Morris.
Wheat Disease Update – 28 April 2022
This article was written by Meriem Aoun, Small Grains Pathologist
During April, the Plant Disease and Insect Diagnostic Laboratory at OSU received multiple wheat samples showing symptoms of streaking on the leaves. Leaf streaks were greenish yellow and parallel as shown in Figure 1. Enzyme linked immunosorbent assay (ELISA) on these samples from different wheat varieties were positive for wheat streak mosaic virus (WSM). WSM infected samples were from fields in multiple counties in Oklahoma including Payne, Blaine, Cimarron, Harper, Grady, and Garfield. A couple of samples that tested positive for WSM were also positive for high plains virus (HPV) and were from Harper and Blaine counties. Both WSM and HPV are transmitted by wheat curl mite. I also observed symptoms of barley yellow dwarf virus (Figure 2) in fields in Payne, Cleveland, and Grady counties.


I also observed leaf spotting on the wheat variety ‘OK Bullet’ in the Stillwater Agronomy Research Station. Culturing from the leaves resulted in the identification of the fungi Bipolaris sorokinana which causes spot blotch and Parastagonospora nodorum which causes septoria nodorum blotch. Parastagonospora nodorum was also recovered from leaf spots on leaves of the variety OK Corral in Cleveland County.
Around mid-April, the OSU Diagnostic Lab received a wheat sample from the variety ‘Doublestop CL Plus’ from Blaine County. I examined the sample and I found that the infected plants were stunted and brown and showed weak root systems (Figure 3). Culturing from infected tissues identified Bipolaris sorokiniana which causes common root rot and Fusarium sp. which cause root, crown and foot rots. These fungi are favored by drought conditions in Oklahoma during the fall and spring. Dr. Silva and Gary Strickland also reported seeing root rot at Cotton county.
Wheat Disease Update – 12 April 2022
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.
Wheat Disease Update – 25 March 2022
This article was written by Meriem Aoun, Small Grains Pathologist
Based on my observations in Stillwater wheat fields and communications with multiple county educators in Oklahoma, it is relatively quiet in terms of diseases. In southwestern Texas and during the first week of March, Dr. Amir Ibrahim (Regents Professor & Small Grains Breeder/Geneticist; Texas A&M AgriLife Research) and Dr. Bryan Simoneaux (Research Associate, Texas A&M AgriLife Research) reported infections of stripe rust and leaf rust in naturally infected rust nurseries.
In Castroville, TX (29.3558° N, 98.8786° W) nursery, Drs. Ibrahim and Simoneaux observed a little bit of leaf rust in the lower canopy of the hard red winter wheat variety ‘Jagalene’. In the Uvalde, TX (29.2097° N, 99.7862° W) nursery, they observed some leaf rust on the lower canopy of the hard red winter wheat varieties Jagalene and ‘TAM 110’, however leaf rust infection did not spread uniformly throughout the nursery. They also found good stripe rust infection on Jagalene in Uvalde, TX (Figure 1 & 2).


In southwestern Oklahoma and during the first week of March, Gary Strickland (Jackson County Extn Educator) reported seeing only very little tan spot on bottom leaves but nothing major (in terms of percentage infestation). He also noted a few leaves infected with stripe rust. Gary Strickland mentioned that the major issue he observed was winter grain mites.
In the Stillwater Agronomy Research Station and on 24 March 2022, I am starting to observe symptoms of the wheat soil-borne mosaic (SB)/wheat spindle streak mosaic (SS) virus complex on the susceptible hard red winter wheat variety ‘Vona’ in the SB-SS nursery (Figure 3). However, due to the use of resistant varieties, these viral diseases are not a problem in Oklahoma and the central plains.
First Hollow Stem Update – 3/15/2022
Amanda de Oliveira Silva, Small Grains Extension Specialist
First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8”, or the diameter of a dime) of hollow stem below the developing grain head (see full explanation). The latest FHS results from OSU forage trials in Stillwater (Table 1) and Chickasha (Table 2) are listed below. For an additional resource, see the Mesonet First Hollow Stem Advisor.
We use an accelerated growth system to report the earliest onset of FHS stage. Trials are seeded early to simulate a grazed system, but the forage is not removed. Varieties reported here with the earliest FHS date should be the first to monitor in commercial fields. In practice, wheat that is grazed will likely reach FHS stage later than reported here, and differences between varieties will likely moderate.
Values can fluctuate from one sampling to another due to environmental variation associated with, among other factors, the winter storm on February 2-4. Additionally, varieties differed widely in their FHS response following this cold period.
Table 1. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/27/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red. The overall average represents the mean FHS for the varieties measured within a date.
Table 2. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/28/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red. The overall average represents the mean FHS for the varieties measured within a date.
Additional resources available:
- PSS-2147 First Hollow Stem: A Critical Wheat Growth Stage for Dual-Purpose Producers.
- CR-2141 Fall forage production and first hollow stem date in small grain varieties during the 2019-2020 crop year
- Mesonet First Hollow Stem Advisor
Acknowledgements:
Tyler Lynch, Senior Agriculturalist
Israel Molina Cyrineu, Graduate Research Assistant
Cassidy Stowers, Undergraduate student
Ephraim Muyombo, Undergraduate student
Lettie Crabtree, Undergraduate student
Teresa Swantek, Undergraduate student
First Hollow Stem Update – 3/02/2022
Amanda de Oliveira Silva, Small Grains Extension Specialist
First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8”, or the diameter of a dime) of hollow stem below the developing grain head (see full explanation). The latest FHS results from OSU forage trials in Stillwater (Table 1) and Chickasha (Table 2) are listed below. For an additional resource, see the Mesonet First Hollow Stem Advisor.
We use an accelerated growth system to report the earliest onset of FHS stage. Trials are seeded early to simulate a grazed system, but the forage is not removed. Varieties reported here with the earliest FHS date should be the first to monitor in commercial fields. In practice, wheat that is grazed will likely reach FHS stage later than reported here, and differences between varieties will likely moderate.
Values can fluctuate from one sampling to another due to environmental variation associated with, among other factors, the winter storm on February 2-4. Additionally, varieties differed widely in their FHS response following this cold period.
Table 1. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/27/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red. The overall average represents the mean FHS for the varieties measured within a date.
Table 2. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/28/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red. The overall average represents the mean FHS for the varieties measured within a date.
- Additional resources available:
First Hollow Stem Update – 2/22/2022
Amanda de Oliveira Silva, Small Grains Extension Specialist
First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8”, or the diameter of a dime) of hollow stem below the developing grain head (see full explanation). The latest FHS results from OSU forage trials in Stillwater (Table 1) and Chickasha (Table 2) are listed below. For an additional resource, see the Mesonet First Hollow Stem Advisor.
We use an accelerated growth system to report the earliest onset of FHS stage. Trials are seeded early to simulate a grazed system, but the forage is not removed. Varieties reported here with the earliest FHS date should be the first to monitor in commercial fields. In practice, wheat that is grazed will likely reach FHS stage later than reported here, and differences between varieties will likely moderate.
Values can fluctuate from one sampling to another due to environmental variation associated with, among other factors, the winter storm on February 2-4. Additionally, varieties differed widely in their FHS response following this cold period.
Table 1. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/27/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red.
Table 2. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/28/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red.
First Hollow Stem Update – 2/15/2022
Amanda de Oliveira Silva, Small Grains Extension Specialist
First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8”, or the diameter of a dime) of hollow stem below the developing grain head (see full explanation). The latest FHS results from OSU forage trials in Stillwater (Table 1) and Chickasha (Table 2) are listed below. For an additional resource, see the Mesonet First Hollow Stem Advisor.
We use an accelerated growth system to report the earliest onset of FHS stage. Trials are seeded early to simulate a grazed system, but the forage is not removed. Varieties reported here with the earliest FHS date should be the first to monitor in commercial fields. In practice, wheat that is grazed will likely reach FHS stage later than reported here, and differences between varieties will likely moderate.
Values can fluctuate from one sampling to another due to environmental variation associated with, among other factors, the winter storm on February 2-4. Additionally, varieties differed widely in their FHS response following this cold period.
Table 1. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/27/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red.
Table 2. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/28/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red.
- Additional resources available:
First Hollow Stem Update – 2/10/2022
Amanda de Oliveira Silva, Small Grains Extension Specialist
First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8”, or the diameter of a dime) of hollow stem below the developing grain head (see full explanation). The latest FHS results from OSU forage trials in Stillwater(Table 1) and Chickasha (Table 2) are listed below. For an additional resource, see the Mesonet First Hollow Stem Advisor.
We use an accelerated growth system to report the earliest onset of FHS stage. Trials are seeded early to simulate a grazed system, but the forage is not removed. Varieties reported here with the earliest FHS date should be the first to monitor in commercial fields. In practice, wheat that is grazed will likely reach FHS stage later than reported here, and differences between varieties will likely moderate.
Table 1. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/27/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red.
Table 2. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/28/21 but not grazed or clipped. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements. Varieties exceeding the threshold are highlighted in red.
- Additional resources available:
Join me in congratulating Dr. Bob Hunger for his retirement after 39 years of service!
Amanda de Oliveira Silva, Small Grains Extension Specialist
Today I would like to dedicate a post to Dr. Bob Hunger, who has served as the OSU Wheat Extension Pathologist for 39 years and is officially retiring today!
Bob, I am grateful to have had the chance to work with you during our time at OSU. Thanks for being a mentor, colleague, and a friend. I know you have many fun plans, but I hope you won’t forget us.
I had so much fun traveling with you to field days this year. I learned many things with you, including a few American sayings like “bright-eyed and bushy-tailed” on our early morning trips and how to use a printed road map to get to our sites instead of using a GPS. However, I am not sure I will follow you on this last one lol.
Bob, I hope you know the great contributions you have made to the OK wheat industry and how much we appreciate you. See a few pictures below 🙂


Thank you, Bob!
Feel free to leave a message to Bob here below. I am sure he will be glad to read it.