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Fall Season Review and Ideal Timing for Cattle Removal from Wheat Pasture

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Amanda de Oliveira Silva, Small Grains Extension Specialist

Oklahoma’s wheat planting season was heavily impacted by severe drought. The season was essentially divided into two main rain events that impacted crop growth. Dual-purpose producers who planted before September 22 established good stands in early fall. Warm temperatures promoted rapid growth, but the crop began to decline as drought conditions intensified (Figure 1).

The next significant rain event occurred about a month later, almost past the optimal wheat planting window in some areas. With rain in the forecast for late October, many farmers chose to “dust in” their wheat ahead of the rain, while others opted to wait.

In early November, wheat-growing regions across Oklahoma received between 1 and nearly 8 inches of rain, while the Panhandle saw up to 20 inches of snow from November 5–9 (Figure 2). These events quickly shifted conditions from extreme drought to flooding. Although November temperatures were above average (~53°F), seeds remained in cool, wet soils for weeks, leading to slow or failed germination. Some areas experienced standing water and soil crusting, causing plant losses. As a result, wheat stands across the state vary widely, with some fields establishing well while others remain highly uneven, contributing to overall low fall forage production.

For grain-only wheat sown in late fall, stands are just now closing in some areas. Though still small, the crop appears to be growing well.

Figure 1. Consecutive days with less than 0.25” rainfall as of October 29, 2024.
Figure 2. Four-day rainfall accumulation from November 2 to 6th, 2024.

Yield loss for grazing past first hollow

For the producers with available pasture for spring grazing, preserving some leaf tissue after grazing will be important for future grain crop. Ideally, at least 60% canopy coverage (as measured by the Canopeo app) should remain to support crop recovery after grazing (PSS-2170). Extending grazing for an additional two week past first hollow stem (FHS)—particularly under conditions unfavorable for plant regrowth and canopy recovery—could reduce wheat yield by approximately 60% of its potential (Figure 3).

Figure 3. Grazing past first hollow stem has been shown to reduce grain yield by as much as five percent per day or as little as one percent per day. This figure shows the anticipated yield loss for grazing past first hollow stem given favorable (solid line), unfavorable (dashed line) and average (dotted line) conditions for wheat regrowth following grazing termination (PSS-2147).

The first hollow stem stage as an indicator for cattle removal from wheat pasture

The first hollow stem stage indicates the beginning of stem elongation or just before the jointing stage. It is a good indicator of when producers should 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 (Figure 4). This is the optimal period because it gives enough time for the crop to recover from grazing and rebuild the canopy. Also, the added cattle weight gains associated with grazing past the FHS are not enough to offset the value of the potential reduced grain yield (1-5% every day past FHS) (Figure 3). The wheat variety, severity of grazing, time when cattle are removed, and weather conditions after cattle removal determine how much grain yield potential might be reduced.

Figure 4. The first hollow stem growth stage is reached when there is 1.5 cm of hollow stem (about the diameter of a dime) below the grain head. 

Methods for scouting for FHS

  • Check for FHS in a non-grazed area of the same variety and planting date. Variety can affect FHS date by as much as three weeks, and planting date can affect it even more.
  • Dig or pull up a few plants, split the largest tiller longitudinally (lengthways), and measure the amount of hollow stem present below the developing grain head. Plant tissue must be removed below the soil surface, because the developing grain head may still be below the soil surface.
  • If there is 1.5 cm (~5/8″) of hollow stem present, it is time to remove cattle. 1.5 cm is about the same as the diameter of a dime (see picture below).
  • Find detailed information on FHS and grazing by clicking here.

OSU Small Grains Program monitors FHS occurrence on a twice-per-week basis

As in previous years, we will continue monitoring FHS occurrence in our wheat plots at Stillwater and Chickasha and share updates on this blog. In past years, our forage trials—where FHS samples are collected—were seeded early to simulate a grazed system, though forage was not removed. This method created an accelerated growth environment, allowing us to identify the earliest onset of FHS. Varieties that reach FHS earliest in these trials should be closely monitored in commercial fields.

This year, we are introducing a new approach by simulating grazing with a mower in the forage trial in Stillwater. This will allow us to compare whether varieties reach FHS at different times when grazed versus non-grazed. We hypothesize that the simulated grazing treatment will likely delay FHS relative to the non-grazed treatment, with FHS differences among varieties becoming less pronounced. We also hypothesize that the amount of delay will vary among varieties, such that an early-FHS variety in the non-grazed environment may appear more intermediate in its FHS arrival with canopy removal. This comparison will provide insight into how canopy removal from grazing impacts the timing of reproductive development.

The latest FHS results for each variety planted in our forage trials at Stillwater and Chickasha are summarized below (Tables 1 and 2). Most varieties are still well below the 1.5 cm FHS threshold. However, if moisture and warmer conditions develop in the coming weeks, values could increase quickly.

Table 1. First Hollow Stem (FHS) results for each wheat variety collected at Stillwater. Plots were planted on 10/11/24, with one section left unclipped and the other clipped to simulate grazing. The FHS threshold is 1.5 cm (5/8″ or approximately the diameter of a dime). Reported values represent the average of ten measurements per variety. Varieties that exceed the threshold are highlighted in red. For the simulated grazing, plots were mowed on January 3rd, 15th, and 28th at a 2.5-3” cutting height, with the frequency representing a light grazing treatment.

Table 2. First Hollow Stem (FHS) results for each wheat variety collected at Chickasha. Plots were planted on 10/02/24, with all sections left unclipped (i.e., not grazed). The FHS threshold is 1.5 cm (5/8″ or approximately the diameter of a dime). Reported values represent the average of ten measurements per variety. Varieties that exceed the threshold are highlighted in red.

Contact your local Extension office and us if you have questions. 

Acknowledgements: 

Tyler Lynch, Senior Agriculturalist

Israel Molina Cyrineu, PhD student

Gilmar Machado, Visiting Scholar

Rafael Moreira, Undergraduate Visiting Scholar

Harvest Makes Progress in Southern Oklahoma, Wheat Ready in Parts of Central Oklahoma, but Delayed by Rain

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By: The Oklahoma Wheat Commission

Oklahoma wheat harvest made good strides the last few days in parts of Southwest, Oklahoma. Producers as far North in the Okarche and Reeding area were also able to start earlier in the week before rains delayed progress on Wednesday morning. Samples and small cuttings were taken in at Greenfield. Cooler temperatures made for a late start in a lot of areas yesterday. High humidity, cloudy weather, with fog and mist today have hindered anything being cut this morning. Predicted rains late this afternoon/evening and over the weekend will likely stall progress over the Memorial Day weekend. Wheat being taken in at all locations show favorable yields and quality.

Devol/Grandfield/Chattanooga- This area has taken in a lot of wheat over the past 5 to 7 days, with approximately 15 percent of the crop harvested.   Yields are ranging from the low 20’s to high 40’s for the most part. Heavily grazed wheat having the lower yields.  It has been noted some intensively managed fields have been yielding 50, with a few yields in the lower 70’s being reported.  Test weights ranging from 60lbs. to 65lbs. per bushel.  Protein averages being reported from 10.5% to 12%, with the overall average being around 11.0% to 11.2%. 

Frederick- Great strides have been made in this area until cooler temperatures and higher humidities yesterday.  Yields being reported from as low as 25 to as high as 50 bushels per acre depending on management and whether or not it was grazed.  Test weights reported from 60lbs. to 63lbs. per bushel.  Protein average at 10.5%

Altus/Lone Wolf- Yields in this region mainly ranging from 35 to 40 bushels per acre. A couple of intensively managed fields making above 60 bushels per acre being reported. Test weights ranging from 60 lbs. to 64 lbs. per bushel. Harvest just getting a good start at these locations so no protein reports being made at this time. (Test cuttings and samples have been taken in at Hobart, Gotebo, Roosevelt, Sentinel, Rocky, Dill City and Cordell, but no actual reports being made until harvest starts in these regions.)

Greenfield- Early test weights being reported on one field making 58.5 lbs. per bushel.  Protein was reported at 13%, no yields reported.

Okarche- Early cuttings reporting yields from 40 to 45 bushels per acre. Test weights reported at 61 lbs. to 62 lbs. per bushel.  Protein reports on early cuttings coming in at 13.5%

Reeding- Early cuttings on a couple fields in this region had reports of yields making 45 to 50 bushels per acre. Test weights ranging from 60lbs. to 62lbs. per bushel.  No proteins being reported on the early cuttings.

Early reports in all locations show test weights ranging from 60 to 65 lbs. per bushel. Proteins ranging from 10.5% to 13.5%, with an overall average of proteins being reported at 11.0% to 11.2%. The wheat being harvested in Southwest Oklahoma has not been stressed as much, so it is thought proteins will get higher as harvest progresses North where we have drought stress. Early yields being reported at 40 to 45 bushels per acre in most regions.  Higher yields being reported on intensively managed wheat with some yields on a few fields being reported in the mid 60’s to low 70’s.  The regions where this is being reported is considered the bright spot of the state for growing conditions this year. The state has received a large amount of hail damage in South Central, Southwest, and Northern, Oklahoma over the past two weeks.  Producers are hoping future predicted storms for tonight and over the weekend subside. The next harvest report to be published will be Tuesday, May 28th.  In honor of all the Veterans and Active Service members the Oklahoma Wheat Commission wants to wish everyone a Happy Memorial Day weekend!

Below, see the 6-10 day precipitation and storm potential outlook provided by the Oklahoma Mesonet.

Oklahoma Wheat Harvest for 2024 Season Begins in Southwest Oklahoma

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By: The Oklahoma Wheat Commission

Oklahoma wheat harvest has started in multiple locations in Southwest, Oklahoma over the weekend, with the wheat being 10 days ahead of normal schedule.   It has been reported that over 100,000 bushels was received between locations at Grandfield and Devol.  Trucks have also been received at Frederick. Early cutting has also started around Temple, Walters and Chattanooga. Test cutting has taken place around Altus with some producers hoping to start this afternoon. 

Early reports in all locations show test weights ranging from 60 to 63 lbs. per bushel. (The wheat reported at 60 lbs. per bushel was at a higher moisture level, so producers are hopeful as moisture goes down test weights will still go up.)

Proteins ranging from 11.1% to 12.5% with more of the proteins on early cuttings being reported in the 11.9% to 12.5% range. Early yields being reported at 40 to 45 bushels per acre.  Higher yields are predicted on intensively managed wheat.  Keep in mind this region has been considered the bright spot of the state for growing conditions this year. The state has received a large amount of hail damage in South Central, Oklahoma last night with large amounts of hail damage in other regions of Southwest Oklahoma and Northern Oklahoma over the past two weeks.  A more comprehensive report will be published on Thursday, May 23, 2024.

Below, see the 7-day forecast provided by the Oklahoma Mesonet.

First Hollow Stem Update – 2/9/2024

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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 and wheat update on FHS, 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 09/18/23 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 09/21/23 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.

Contact your local Extension office and us if you have questions. 

Additional resources available:

Acknowledgments: 

Tyler Lynch, Senior Agriculturalist

Israel Molina Cyrineu, Graduate Research Assistant

Samson Abiola, Graduate Research Assistant

Lettie Crabtree, Undergraduate Student

Joao Ferro, Undergraduate Student

Oklahoma Wheat Harvest Progresses in Southern Oklahoma

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Oklahoma Harvest Report by the Oklahoma Wheat Commission

Oklahoma wheat harvest has moved steadily in most regions of Southern Oklahoma this past week. Rains have hindered progress in other parts of the South Central and Western regions.  The rains in Central and Northern Oklahoma this past week along with the high humidity continue to delay ripening in those places. Test weights for the most part remain favorable on what is being taken in, although some areas are reporting lower test weights where the crop has been more stressed. Several locations are reporting 60-64 lbs. per bushel. Some lower test weights are being reported in the mid to high 50’s but overall the state average is still coming in between 60-61 lbs. per bushel.

Moisture has been ranging from 12-13%, with most wheat being taken in at around 12.5%.  Early yields reported in Southern Oklahoma are ranging from the low 20’s to the mid 50’s depending on location and management practices. Some intensive management producers in rare instances have reported yields in the mid 70’s to low 80’s. (Keep in mind this is in an area that received timely moisture in the Grandfield-Devol region. This area is predicted to have the best overall crop conditions for Oklahoma this year.) Protein averages are being reported in a wide range from 10.5% to 12.5% depending on location.  Some have reported protein to be as high as 15.5% on a few select fields.

The Oklahoma Wheat Commission is calling Oklahoma wheat harvest 15% complete.

Grandfield/Chattanooga- Producers in parts of this region were rained out this weekend, but are hopeful to get back into the fields late this afternoon. Test weights ranging from 61-64 lbs. per bushel. Moisture reported at 12.5%. Yields ranging mostly from 30 bushels to 50 bushels per acre. Grandfield region is 50% completed, Chattanooga region is 20% complete with harvest.

Devol- This area has made great progress over the past week and combines continue to move.  Yields reported from the low 30’s to mid 50’s.  Test weights ranging from 61-64 lbs. per bushel.  Moisture is 12.5%.  This region is 50% complete with harvest.

Frederick- Test weights in this region averaging 61 lbs. per bushel. Yields being reported from low 20’s to mid 40’s depending on location. Protein ranging from 10.5% to 12%.  This region is 60% complete with harvest.

Tipton- This area suffered more from drought than other areas in South Central, Oklahoma. Yields are being reported from the low 20’s to low 40’s, depending on location. Test weight has been lower on some fields,  but the average for the region is 59.5 lbs. per bushel.  Moisture was reported at 12 to 12.5%.  Protein is reported at 12% to 12.5%.  This area is 65% to 70% harvested.

Altus- Harvest continued to move in this region over the weekend, some producers were delayed with light rain showers. Test weights ranging 57 lbs. to 62 lbs. per bushel. Early yields reported from the high 20’s to low 40’s, depending on location.  This region is 40% harvested.

Hobart/Gotebo-   Harvest was slowed this past week due to rains, producers are hopeful to get back into the fields late this afternoon or tomorrow.  Early loads received last week had test weights reported at 60 to 62 lbs. per bushel. Yields ranging from the mid 20’s to low 30’s. This region is 15% harvested.

Lawton-  This region has made great progress over the past week. Test weight was 60 lbs. to 62 lbs. per bushel on wheat being harvested. Yields ranging from mid 30’s to mid 50’s.  This region is 50% complete with harvest.

Rocky/Sentinel- Early test cuttings took place last week and the wheat is ready to be harvested at Sentinel but heavy rains have delayed harvest in both the Sentinel and Rocky areas this week. Test weights on early cuttings ranged from 58 lbs. to 62 lbs. per bushel.  No yields have been reported.  This area is 5% complete with harvest.

Apache- No wheat has been taken in at the location as of today. Test cuttings took place late last week, with a sample close to 13.5%.  Heavy rains over the weekend hindered producers from getting started in this region.  West of town received 2 inches and other areas East of town received ¼ inch of rain.

Below, see the next 7-day forecast and 3-Day Rainfall Accumulations recorded by the Oklahoma Mesonet.  The next Oklahoma Harvest Report will be published on Wednesday, June 7, 2023, and a regional report will be published by Plains Grain Inc. on Friday, June 9, 2023

Planting wheat in hot and dry soils

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Amanda de Oliveira Silva, Small Grains Extension Specialist

With severe dry conditions and high temperatures in our state, it is good to consider the possible effects of high temperature and drought on wheat germination and early growth. As of September 19, soil temperature was in the 80’s F across the state and reached 97 F in some areas (Figure 1). Wheat can germinate in soil temperatures from 40 F to 99 F, but temperatures from 54 F to 77 F are optimal.

Figure 1. Soil temperature across Oklahoma. Figure courtesy Oklahoma Mesonet.

Wheat germination and emergence in HOT soils

Is the variety I am planting high-temperature germination sensitive?

High-temperature germination sensitivity is a more elaborate way of saying that some wheat varieties do not germinate well in hot soil conditions. This is not to say that the seed will not germinate, but it may not germinate until the soil temperature has lowered. Keep in mind too that this sensitivity can vary from year to year. For example, a sensitive variety like Ruby Lee may germinate fine in 90°F soils one year and only produce a 10% stand in the same soil conditions the next. When sowing early, it is best to plant varieties first that do not have high-temperature sensitivity (e.g., Duster, Gallagher). Soil temperatures typically begin to cool by about September 20 due to lower air temperatures and/or rainfall events. However, our summer temperatures seem to be sticking around for longer this year. Waiting until at least mid-September to plant sensitive varieties can help reduce the risk of this issue. A high temperature germination sensitivity rating for wheat varieties can be found in the OSU Fact Sheet (available by clicking here). An updated version of this factsheet will be published soon.

Coleoptile Length

Hot soil conditions at sowing also reduce coleoptile length. The coleoptile is the rigid, sheath-like structure that protects the first true leaf and aids it in navigating and reaching the soil surface. Once the coleoptile breaks the soil surface, the coleoptile will stop growing, and the first true leaf will emerge. If the coleoptile fails to reach the soil surface, the first true leaf will emerge below ground and take on an accordion-like appearance (Figure 2A-B). If this happens, the plant will die.

Figure 2A and 2B. Example of two different wheat seedlings in which the coleoptile failed to break the soil surface. The first true leaf emerged below the soil surface and resulted in this accordion-like appearance.

The coleoptile length for most wheat varieties today can allow for the seed to be safely planted up to 1.5 inches deep. Under hot soil conditions though, the coleoptile length tends to be decreased. Therefore, “dusting in” early-sown wheat at ¾ to 1 inch depth and waiting on a rain event may result in more uniform emergence than trying to plant into soil moisture at a deeper depth, if soil moisture is not available in the top 1 to 1.5 inches of the soil profile. A rating for coleoptile length for wheat varieties can be found in the OSU Fact Sheet PSS-2142 Wheat Variety Comparison. We are also working on updating this.

Wheat germination and emergence in DRY soils

The most important physiological requirement for wheat to germinate and sustain the developing seedling is soil water. Therefore, planting decisions should be based on a combination of available soil moisture and expected rainfall. In addition, other factors such as adequate seeding depth, sowing date, soil fertility, seed treatment, seed quality, etc., should be considered to guarantee good crop establishment. For more information, check the materials on our website.

Wheat seed needs a minimum water content of 35 to 45% of its dry weight to initiate germination, and germination will be more complete as moisture levels increase. Dry soils can still maintain a relative humidity of 99%, which can provide enough moisture for seeds to germinate. It might just take longer than with free-moisture availability. My concern with the current situation in Oklahoma is the severe drought we are in and the lack of rain in the forecast. In some cases, we could have enough moisture to start the germination process in some regions of the state, but seedling emergence and growth could be compromised if we do not see any rain soon.

What happens if the soil completely dries out before wheat emergence?

There are three phases during the germination process: water absorption, activation when the seed coat is ruptured, and visible germination when the radicle emerges, followed by the seminal roots and coleoptile. These processes will start and stop depending on soil moisture availability. Thus, if the soil dries out before the roots and shoots are visible, the seed remains viable, and germination will be paused and continue once water is available. However, if the soil dries out after those structures are emerged (approximately 4-5 days after germination has begun), the seedling may not tolerate the lack of water, resulting in incomplete or loss of stand.

What should I do then? Choose your battle!

The optimal time for planting wheat in central Oklahoma is around mid-September for a dual-purpose system or around mid-October for a grain-only system (Figure 3). With the current forecast, we are planning to wait another 7-10 days to decide on our dual-purpose and forage trials. There are different ways we can go about it, but we must remember that there is always risk involved when planting wheat in dry and hot soil conditions.

Figure 3. Forage and grain yield potential in relation to the day of the year. Every 1,000 kg/ha is equal to approximately 900 lb/acre or 15 bu/acre. Ideal planting dates for dual-purpose wheat in Oklahoma are mid-September (i.e., approximately day 260). Planting for grain-only should occur at least 2-3 weeks after dual-purpose planting (i.e., mid-October or approximately day 285).

If you decide to dust in your wheat and wait for a rainfall event to drive germination, watch your seeding depth. The optimum seeding depth to plant wheat is about 1-1.5” deep. We typically do not have as many issues with winterkill in Oklahoma as in more northern states, so I am comfortable with dusting in at about 0.75 – 1” deep. Planting at 0.5” or less is too shallow in most circumstances. Also, there is always a chance for a pounding rainfall event and subsequent soil crusting, which makes it difficult for the coleoptile to push through the soil surface and may result in poor emergence. Fields with stubble cover may be less affected and reduce the risk of soil crusting. If we receive light rain in the following weeks, that could cause wheat to emerge, but it may not be enough for wheat to continue growing. Most of the fields do not have good subsoil moisture, either.

If subsoil moisture is available and you decide to plant deeper to reach moisture, be careful with the coleoptile length of your variety, and make sure it has a long-enough coleoptile that will allow emergence if conditions are favorable. Consider increasing seeding rate to compensate for reduced emergence, which is prone to occur in this situation.

Should we wait for rain to plant then? This is a farm-by-farm call and it depends on which source of risk you find most comfortable. Personally, I would rather plant my wheat in the optimal planting window and adequate seeding depth than waiting for a rain that may take too long to happen or missing my optimal planting window. If the latter is the case, consider bumping seeding rate to try to compensate for the reduced time for tillering (especially in a grain-only system). Planting wheat at optimal time allows for more time for root growth in seedlings, helping the crop to establish more quickly under dry conditions and possibly help the plant to scavenge for water that is available deeper in the soil profile.

Are there any specific agronomic traits that could help wheat seedling growth under water stress?

Traits that will help with seedling growth in dry conditions are coleoptile length potential, which allows to plant a little deeper in moisture and good emergence (if deep planting is the practice of your choice). There are indications that sowing wheat varieties with larger seed may help to reduce the negative effects of drought during early growth (Mian and Nafziger, 1994). In general, the greater reserves of larger seed result in faster germination and crop establishment by increasing root growth and tiller production. Keep in mind, however, there are varieties with small seed size that germinate more rapidly than larger seeded varieties, owing to their differential response to available moisture.

Wheat Disease Update – 19 May 2022

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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.

Figure 1. Winter wheat crop in Morris, Oklahoma was in good condition as of May 16, 2022 (Courtesy Dr. Amanda Silva).

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.

Figure 2. Symptoms of bacterial streak on the winter wheat variety ‘WB 4401’ in Morris, Oklahoma (Courtesy Dr. Amanda Silva; May 16, 2022).
Figure 3. Symptoms of black chaff on glumes and neck (Morris, Oklahoma; May 16, 2022).

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).

Figure 4. Septoria leaf spot symptoms on the winter wheat variety ‘Crescent AX’ in Morris, Oklahoma (May 16, 2022).
Figure 5. The black spots show symptoms of spot blotch whereas the white patches correspond to powdery mildew infection on an OSU winter wheat breeding line (Stillwater, Oklahoma; May 11, 2022).

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.

Figure 6. Leaf rust symptoms on the hard red winter wheat variety ‘Baker’s Ann’ (Morris, Oklahoma; May 16, 2022).
Figure 7. Symptoms of leaf rust (circular orange pustules) and powdery mildew (white patches) on the hard red winter wheat variety ‘Baker’s Ann’ (Morris, Oklahoma; May 16, 2022).

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.

Figure 8. Symptoms of sooty mold on winter wheat in Morris, Oklahoma (May 16, 2022).
Figure 9. Symptoms of loose smut on the winter wheat variety ‘WB 2158’ (May 3, 2022).

Wheat Disease Update – 12 May 2022

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This article was written by Meriem Aoun, Small Grains Pathologist

Root/crown/foot rots were observed in multiple wheat fields in April and May in Woods, Cherokee, Blaine, Cotton, and Payne counties. Dr. Amanda Silva reported severely damaged wheat plants in drought stressed fields mainly in Cherokee and Woods counties (Figure 1). Infected plants were stunted and white and had poor root systems. Although the plants were drought stressed throughout the growing season, much of the damage was not noticeable until after wheat heading. Dr. Silva observed pinkish discoloration on infected plants in Cherokee after peeling the leaf sheath in the lower stem internodes, which indicates that the infection was caused by Fusarium (Figure 2).

Figure 1. White, stunted, and drought-stressed plants showing symptoms of root/crown/foot rots (Cherokee county, Oklahoma; photo credit: Dr. Amanda Silva; May 12, 2022).
Figure 2. Pink discoloration indicates that root/crown/foot rot was caused by Fusarium (Cherokee county, Oklahoma; photo credit: Dr. Amanda Silva; May 12, 2022).

The rain in early May in some locations in Oklahoma provided suitable environmental conditions for the appearance of some fungal diseases including rusts. This week, stripe rust was observed in the Stillwater Agronomy Research Station on susceptible wheat varieties like ‘Pete’ and some OSU breeding lines (Figure 3). Leaf rust was found on the susceptible wheat variety ‘OK Bullet” and on some OSU breeding lines (Figure 4). Rust diseases have not been found in other locations in Oklahoma. The current pressure is low and late compared to the previous year due to drought conditions through the growing season. However, rust disease incidence can increase in coming weeks if weather conditions are favorable.

Figure 3. Stripe rust on a susceptible OSU winter wheat breeding line in the Stillwater Agronomy Research Station, Oklahoma (the photo was taken on May 10, 2022).
Figure 4. Initial leaf rust pathogen infection on a winter wheat OSU breeding line in the Stillwater Agronomy Research Station, Oklahoma (the photo was taken on May 10, 2022).

Wheat Disease Update – 28 April 2022

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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.

Figure 1. Wheat streak mosaic virus symptoms on the wheat variety ‘OK Corral’ (Grady County, April 13, 2022).
Figure 2. Symptoms of barley yellow dwarf infection on the wheat variety ‘OK Corral’ in a farmer field in Cleveland County, OK (the photo was taken by Bradley Secraw, extension educator, at Cleveland County on April 26, 2022).

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.

Figure 3. Common root rot and Fusarium root, crown and foot rots in a wheat sample from the wheat variety ‘Doublestop CL Plus’ (Blaine County, April 13, 2022).

Wheat Disease Update – 25 March 2022

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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).

Figure 1. Leaf rust and stripe rust infections on the same leaf of the susceptible wheat variety Jagalene at Uvalde, TX (Photo by Dr. Bryan Simoneaux on 3 March 2022).
Figure 2. Stripe rust infections on the susceptible wheat variety Jagalene at Uvalde, TX (Photo by Dr. Bryan Simoneaux, on 3 March 2022).

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.

Figure 3. Symptoms of wheat soil-borne mosaic/wheat spindle streak mosaic virus complex on the susceptible wheat variety Vona in Stillwater, OK