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David Marburger

David Marburger

Since April 2016, I have served as the Small Grains Extension Specialist at Oklahoma State University. My research and extension efforts focus on delivering science-based recommendations in order to increase small grains production and profitability for stakeholders throughout Oklahoma and the southern Great Plains.

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Final First Hollow Stem Update – 3/22

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 dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

 

The latest FHS results from Chickasha (Table 1) and Stillwater (Table 2) are listed below. All wheat varieties at Chickasha and Stillwater have now reached the 1.5 cm threshold, and some of the remaining varieties flew past the threshold since the last sampling date.

 

Keep in mind that several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, we cannot stress enough the importance of checking for FHS on a field-by-field basis

 

Table 1. First hollow stem (FHS) results by wheat, triticale, rye, barley, and oat variety collected on 2/20/18, 2/26/18, 3/2/18, 3/6/18, 3/8/18, 3/12/18, 3/15/18, and 3/20/18 at Chickasha. Plots were sown on 9/25/17. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

chick3.22

 

Table 2. First hollow stem (FHS) results by wheat variety collected on 2/27/18, 3/5/18, 3/8/18, 3/13/18, 3/16/18, and 3/21/18 at Stillwater. Plots were dusted in on 9/15/18 and did not receive significant rainfall until 9/25/17. The triticale, rye, barley, and oat plots were abandoned due to emergence issues. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

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First Hollow Stem Update – 3/16

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 dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

 

The latest FHS results from Chickasha (Table 1) and Stillwater (Table 2) are listed below. All but two of the wheat varieties at Chickasha are at FHS, but the two holdouts are very close. At Stillwater, 10 of the 18 remaining wheat varieties reached FHS today. A majority of the 8 varieties left will likely reach FHS soon.

 

Keep in mind that several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, we cannot stress enough the importance of checking for FHS on a field-by-field basis

 

Table 1. First hollow stem (FHS) results by wheat, triticale, rye, barley, and oat variety collected on 2/20/18, 2/26/18, 3/2/18, 3/6/18, 3/8/18, 3/12/18, and 3/15/18 at Chickasha. Plots were sown on 9/25/17. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

chick3.16

 

Table 2. First hollow stem (FHS) results by wheat variety collected on 2/27/18, 3/5/18, 3/8/18, 3/13/18, and 3/16/18 at Stillwater. Plots were dusted in on 9/15/18 and did not receive significant rainfall until 9/25/17. The triticale, rye, barley, and oat plots were abandoned due to emergence issues. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

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Wheat Disease Update – 14 March 2018

This article was written by Dr. Bob Hunger, Extension Wheat Pathologist

Department of Entomology & Plant Pathology

Oklahoma State University – 127 Noble Research Center

405-744-9958

 

I spent Monday (March 12) looking at wheat around Stillwater and found no foliar diseases. Gary Strickland (Extension Educator; Jackson County) indicated the same for southwestern OK. He indicated wheat is short and drought stressed with flag leaves emerging in some wheat even though it is only about 4 inches tall. Josh Bushong (Area Extn Agronomy Specialist) indicated a similar scenario for wheat west of Lahoma, (10 miles west of Enid). He also indicated he had heard of some spraying being done for aphids – both for bird cherry–oat and greenbug.

 

At this point, it appears there is not much rust inoculum building up to the south of us in Texas. On March 9th, Dr. Clark Neely (Small Grains/Oilseed Extension Specialist; Texas A&M AgriLife Extension) scouted sentinel plots for foliar diseases. Here is his report. “I checked sentinel plots at College Station, TX on Friday, March 9, for disease. I found moderate levels of stripe rust in ‘Sisson’ only. I did not observe stripe rust in any other sentinel plots. I was unable to go through the entire variety trial at the time, but there were no obvious signs of a stripe rust epidemic. There were trace amounts of stripe rust found in a nearby fungicide trial on ‘WB 4303’. There have been no reports from growers anywhere in the state yet of stripe rust in producer fields. Leaf rust was found on these varieties as well, but in trace amounts. Overall, leaf rust is much lower this time of year compared to the past two years due to cold temperatures we experienced this winter. Powdery mildew is very common due to cloudy, damp weather the past month and dense canopies. Many winter varieties are around Feekes 7-8. Hard red spring wheat ‘LCS Trigger’ in an adjacent trial was the most advanced of anything I observed and was at Feekes 9 (fully emerged flag leaf).” I have included one photo from Dr. Neely because it is an excellent photo that shows the difference between the pustules of an early infection of stripe rust and leaf rust (Figure 1).

stripe and leaf rust

Figure 1. Early stripe rust on wheat near College Station, TX observed on March 9 by Dr. Clark Neely (Small Grains/Oilseed Extn Specialist; Texas A&M AgriLife Extension). Compare the stripe rust pustules located on the left to the three leaf rust pustules on the right side of the leaf.

 

Finally, the OSU Diagnostic Lab has tested 11 samples from southwestern OK (Washita County) for the wheat viruses that cause wheat streak mosaic, high plains, Triticum mosaic (all transmitted by the wheat curl mite) and barley yellow dwarf (aphid transmitted). We are doing this to see if testing for the presence of these viruses early in the season with the ELISA procedure may have value in giving producers a “heads-up” related to the decision of removing cattle or to graze out a given field. We will follow these fields as the season progresses to see how the incidence of these viruses in these fields relates to the virus testing.

First Hollow Stem Update – 3/14

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 dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

 

The latest FHS results from Chickasha (Table 1) and Stillwater (Table 2) are listed below. Most of the wheat varieties at Chickasha have reached FHS, and the three remaining varieties will likely meet the threshold very soon. The warm temperatures at Stillwater over the weekend helped move a number of varieties along quickly. During yesterday’s measurements, 20 more varieties (36%) reached the 1.5 cm threshold. There are still 18 varieties which have not reached FHS at this location.

 

Keep in mind that several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, we cannot stress enough the importance of checking for FHS on a field-by-field basis

 

Table 1. First hollow stem (FHS) results by wheat, triticale, rye, barley, and oat variety collected on 2/20/18, 2/26/18, 3/2/18, 3/6/18, 3/8/18, and 3/12/18 at Chickasha. Plots were sown on 9/25/17. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

chick3.14

 

Table 2. First hollow stem (FHS) results by wheat variety collected on 2/27/18, 3/5/18, 3/8/18, and 3/13/18 at Stillwater. Plots were dusted in on 9/15/18 and did not receive significant rainfall until 9/25/17. The triticale, rye, barley, and oat plots were abandoned due to emergence issues. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

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First Hollow Stem Update – Week of 3/5-3/9

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 dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

 

The latest FHS results from Chickasha (Table 1) and Stillwater (Table 2) are listed below. Wheat stem elongation overall at Chickasha is starting to progress quickly now. As of March 6, 21 of the 31 wheat varieties (68%) have reached the 1.5 cm threshold, with 14 of those 21 varieties reaching the threshold on March 6. Stem elongation at Stillwater is moving, but not at the same pace as Chickasha. As of yesterday, March 8, only 18 of 56 wheat varieties (32%) have reached the 1.5 cm threshold.

 

Keep in mind that several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, we cannot stress enough the importance of checking for FHS on a field-by-field basis.

 

Table 1. First hollow stem (FHS) results by wheat, triticale, rye, barley, and oat variety collected on 2/20/18, 2/26/18, 3/2/18, and 3/6/18 at Chickasha. Plots were sown on 9/25/17. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

chick3.9

 

Table 2. First hollow stem (FHS) results by wheat variety collected on 2/27/18, 3/5/18, and 3/8/18 at Stillwater. Plots were dusted in on 9/15/18 and did not receive significant rainfall until 9/25/17. The triticale, rye, barley, and oat plots were abandoned due to emergence issues. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Stw3.9

What can I expect from wheat just now emerging?

Dusted-in wheat and spotty stands this past fall was a more common occurrence than we want to see in Oklahoma. Going into winter though, I thought we would get precipitation at some point to get the remaining seed to germinate, similar to the situation in northwestern Oklahoma last growing season. Unfortunately that did not happen, and the first water some of this seed has seen came with the late February rain. Now the remaining seed is germinating and emerging, begging the question what is a realistic expectation for this late-emerging wheat crop?

 

Will these plants produce a head?

In order to produce a head, winter wheat must be vernalized, which means it requires exposure to cool temperatures to trigger reproductive development. Winter wheat plants that do not go through vernalization will continue to grow vegetatively (i.e., produce leaves and tillers) but will not joint and produce a seed head (Figure 1).

 

How cold and for how long?

In the literature, you will often see that winter cereals require exposure to cooler temperatures (33° to 51° F) for six weeks. However, the exact temperature and time period differs by variety. A general rule of thumb is varieties that are more winterhardy and later maturing tend to require lower temperatures for a longer period of time (i.e., a stronger vernalization requirement) than less winterhardy and earlier maturing varieties. Vernalization requirements for winter wheat varieties adapted to the southern Great Plains may range from 120 to 1080 hours (5 to 43 days) below 45° F (Neely, 2016).

 

Since this is a rare problem in Oklahoma, we do not have much data on variety-specific vernalization requirements. I spoke with Dr. Carver, and he feels exposure to constant temperatures at or below 45° F for three weeks should be sufficient for most winter wheat varieties grown in Oklahoma. If that time decreases to two weeks, though, there is a possibility that we may run into vernalization issues for some varieties. It is important to keep in mind that the vernalization clock starts clicking once the seed imbibes water and sprouts. Some good news is we have been experiencing cooler temperatures since the rain, and cooler temperatures are still in the forecast.

 

Figure1

Figure 1. Example of a wheat variety which was able to vernalize (left foreground) versus a variety that was not able (right foreground). Notice these differences in varieties from the foreground to the background. This photo was taken by Bryan Simoneaux at a Texas winter wheat variety trial.

 

Is it all just temperature dependent?

In addition to vernalization, many varieties have a photoperiod signal that can tell the plant to switch to reproductive growth regardless of the temperature. Therefore, if we do not get enough time spent with cooler temperatures to satisfy vernalization, the plant will still initiate reproductive development once the daylength has become long enough. However, the plants in this scenario will likely be two weeks or more behind in development compared to normal.

 

Do we have information on varieties?

While we do not have variety-specific vernalization requirements at the moment, parts of south Texas will experience vernalization problems now and then. This happened at the Wharton variety trial location in 2016. Some varieties at this location were able to produce grain while others did not. Looking at these results may give us an indication which varieties grown in Oklahoma this year might have a higher probability of producing heads (Table 1).

Table 1

Table 1. The 2016 Wharton, TX wheat variety trial results in which mild winter conditions resulted in vernalization issues for some varieties. Varieties that were able to still produce grain are those ranked 1-16.

 

What forage or grain yield potential do I have?

To dive into this question, we do have some data from Kansas that can provide some guidance. Researchers at Kansas State University conducted a seven-year study (1985-1991) near Garden City, KS where they planted winter wheat every month from October 1 to April 1 (Witt, 1996). They used one variety (TAM 107) and a seeding rate of 80 lbs/acre for each planting date. Table 2 summarizes the data from this study.

 

Wheat planted on all dates through March 1 was able to produce grain each year. Wheat planted on April 1 did not joint and produce heads. Relative to the October 1 planting date, the wheat planted on March 1 was:

  • the lowest yielding;
  • was the shortest statured (5 in. less);
  • had the most delay in heading (26 days later);
  • had the shortest grain-filling period (9 days fewer).
  • was the last to ripen (17 days later);
  • produced the fewest heads per plant (58% fewer);
  • produced the fewest kernels per head (33% fewer) and the fewest kernels per plant (73% fewer);
  • and produced the smallest seed weight (43% less) and the lowest test weight (59% less).

Table2

Table 2. Wheat response to delayed planting dates near Garden City, KS from 1985-1991 (Witt, 1996).

 

While there was variability in grain yield among the years, the average relative grain yield for each planting date compared to the first planting date was: October 1 = 100%, November 1 = 77%, December 1 = 59%, January 1 = 57%, February 1 = 41%, March 1 = 16%, and April 1 = 0%.

 

Forage data was not collected in this KSU study, so it is hard to say that the percent decrease in forage yield would be similar to the grain results. We can make some educated guesses on what the forage potential might have been, though. The number of heads per plant in the March 1 planting date was 58% less than the October 1 planting date (i.e., 58% less tiller production), and plant height was 20% less for the same comparison. So, it may not be out of the question to say that there was probably a 50-75% reduction in forage yield. Unless your seeding rate was significantly increased to compensate for less tiller production, the bottom line is that there is a low probability that late-emerging wheat will generate much tonnage.

 

In Oklahoma, especially southern Oklahoma, we warm more quickly than the location for the KSU study. Their March 1 planting date is probably more like a February 15 planting date in Oklahoma. Again, this is all estimation, but when taking this and the Kansas data into consideration, the February emergence dates for some of our Oklahoma wheat puts us in vernalization limbo. Only time will tell us whether or not our wheat was exposed to enough cooler temperatures to trigger reproductive development. Again, the good news is we are still getting these cooler temperatures. If we do run into the scenario where we do not get enough cooler temperatures but still go through reproductive development because of the photoperiod component, our forage or grain yield will likely be even lower, as growth and development will be extremely delayed.

 

We’re working on it

To help us gather more variety specific information on whether heads and grain will be produced or not, we planted 36 different wheat varieties at Stillwater on March 6. I will post pictures and updates of this study to keep you informed as to what we are seeing and likely outcomes.

 

Final thoughts:

  1. If you have crop insurance, contact your agent to discuss your options.
  2. To get a ballpark estimate on what your forage or grain yield potential might be, you need to first assess your stand. Ideally, we need 60-70 heads per square foot to maximize grain yield potential. In areas that typically have lower yield potential, we can likely lower that number to 50-60 heads per square foot. To help you with your tiller counts and yield estimates, you can find more information in fact sheet PSS-2149: Estimating Wheat Grain Yield Potential.
  3. Wheat that was established prior to the February rain will have had enough time under cooler temperatures to vernalize and go through reproductive development. For most of these acres which did receive rain, we still have a chance at producing full or close full yield potential if the wheat tillered or if you increased your seeding rate to compensate for the late planting.
  4. For those who had spotty stands prior to the rain, we can still get an estimate on potential here too. You will need to estimate the percent of the field with an established stand, and then obtain a plant/tiller count as described above. Again, these established plants may still have full yield potential. For the plants now emerging, I doubt we will get much, if any, additional tillers produced. Also, the amount of grain produced by that single head will likely be less (refer to Table 2 for an estimate on how much less), unless the variety has a low vernalization requirement (Table1 may give indication to varieties with a lower vernalization requirement).
  5. With wheat that was planted very late and is just now emerging (after cotton in southwest Oklahoma for example), again, I doubt there will be additional tillers produced. The grain yield potential here may be similar to the results described in the Kansas study. If a producer increased their seeding rate to compensate for less tiller development, the amount of grain yield reduction may not be as much depending on the seeding rate, but it will still likely not reach close to full yield potential.

 

Sources:

First Hollow Stem Update – 3/5

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 dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

 

Results from measurements collected recently at Chickasha (Table 1) and Stillwater (Table 2) are listed below. Wheat stem elongation at both locations is progressing, and I believe it will progress a little more rapidly in these plots throughout this week. Keep in mind that several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, we cannot stress enough the importance of checking for FHS on a field-by-field basis.

 

Table 1. First hollow stem (FHS) results by wheat, triticale, rye, barley, and oat variety collected on 2/20/18, 2/26/18, and 3/1/18 at Chickasha. Plots were sown on 9/25/17. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Table1chick3.5

 

Table 2. First hollow stem (FHS) results by wheat variety collected on 2/27/18 and 3/5/18 at Stillwater. Plots were dusted in on 9/15/18 and did not receive significant rainfall until 9/25/17. The triticale, rye, barley, and oat plots were abandoned due to emergence issues. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Table2stw3.5

We are collecting measurements from Chickasha tomorrow and Stillwater on Thursday. The next update will be Thursday afternoon or Friday morning.

First Hollow Stem Update – Week of 2/26-3/2

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 dime) of stem below the developing grain head (full explanation). Each year, we collect FHS measurements from our forage variety trials. We have three forage variety trial locations this year: Chickasha, Haskell, and Stillwater. We are only collecting FHS measurements though at Chickasha and Stillwater. Both of these locations were sown in September. To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

 

Results from measurements collected recently at Chickasha (Table 1) and Stillwater (Table 2) are listed below. Keep in mind that several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, we cannot stress enough the importance of checking for FHS on a field-by-field basis.

 

Table 1. First hollow stem (FHS) results by wheat, triticale, rye, barley, and oat variety collected on 2/20/18 and 2/26/18 at Chickasha. Plots were sown on 9/25/17. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

chick2

 

Table 2. First hollow stem (FHS) results by wheat variety collected on 2/27/18 at Stillwater. Plots were dusted in on 9/15/18 and did not receive significant rainfall until 9/25/17. The triticale, rye, barley, and oat plots were abandoned due to emergence issues. The threshold target for FHS is 1.5 cm (5/8” or the diameter of a dime). The amount of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

stw

We are collecting measurements from Chickasha today and Stillwater on Monday. The next update will be early next week.

 

 

Wheat Disease Update – 21 February 2018

This article was written by Dr. Bob Hunger, Extension Wheat Pathologist

Department of Entomology & Plant Pathology

Oklahoma State University – 127 Noble Research Center

405-744-9958

 

Foliar diseases such as leaf rust and stripe rust were scarce across Oklahoma last fall and into 2018 because of the drought. I have seen a few leaf rust pustules on wheat plants in trials around Stillwater and have heard of leaf and stripe rust as well as powdery mildew from growers across the state. However, my observations and these reports all indicate extremely light levels. More importantly, reports of foliar diseases from Texas were lacking until recently. These reports are critical because areas in Texas provide the inoculum for Oklahoma. On February 9th, Dr. Clark Neely (Small Grains/Oilseed Extension Specialist; Texas A&M AgriLife Extension) reported seeing stripe rust on the susceptible variety ‘Patton’ in trials near Uvalde, TX (Fig 1). Here is Dr. Neely’s report: “I wanted to notify everyone that we have our first stripe rust siting in Uvalde, TX as of last Friday (02/9/18). At the time, it was mainly limited to the susceptible border rows (‘Patton’). A few leaf rust pustules were present as well, but very few. Growth stage is around Feekes’ 5 with some already initiating jointing at Feekes’ 6. Central and South Texas has been experiencing very damp, overcast conditions for the past week and are expecting more of the same for the foreseeable future, so I would expect to see further development. Variety trials at Castroville, College Station, Thrall, Hillsboro, McGregor, and Muenster, TX have all appeared clean so far over the past couple of weeks while topdressing nitrogen.”

 

Figure 1. Stripe rust on wheat near Uvalde, TX observed on 2/9/18 by Dr. Clark Neely (Small Grains/Oilseed Extension Specialist – Texas A&M AgriLife Extension).

figure1

 

Remember, stripe rust typically forms stripes in older plants (Fig 2A), but early infections have pustules not typically in stripes (Fig 2B). In contrast, pustules of leaf rust are not formed in stripes and are more of a brownish-rust color as compared to the yellowish-golden rust color of stripe rust (Fig 2C).

 

Figure 2. Wheat stripe rust on adult plant (2A), an initial stripe rust infection in February (2B), and a wheat leaf with both stripe and leaf rust pustules (2C).

figure2

 

Other foliar diseases to watch for include tan spot, Septoria leaf blotch, and powdery mildew (Figure 3A-C). These diseases (especially tan spot and Septoria leaf blotch) are more likely to occur in no-till, continuous wheat fields. If sufficiently severe in a no-till field, spraying for these in March may be beneficial but only if young wheat plants are severely spotted with one of these diseases. Regarding leaf and stripe rust, there was not much rust overwintering in Oklahoma, and inoculum to start this disease in the spring will mostly come from Texas.

 

Figure 3. Wheat diseases typically observed in no-till, continuous wheat fields include (A) Tan spot; (B) Septoria leaf blotch; (C) Early season powdery mildew.

figure3

 

Finally, the recent rain events in Oklahoma will revive the wheat in the state, but also will provide conditions favorable for foliar diseases (especially as temperatures become more moderate). Hence, I recommend scouting fields for the foliar diseases discussed above during the coming weeks and paying attention to what is happening to the south of us in Texas. For additional information regarding early season foliar wheat diseases and possible control with an early fungicide application, please see our fact sheet (PSS-2138) that discusses split application of fungicides at www.wheat.okstate.edu.

Determining the optimal time to remove cattle from wheat pasture (if you still have pasture to graze…)

The wheat growing season up to this point has been extremely tough to say the least. The forage situation has been a kick-in-the-knees in addition to taking it on the chin with the grain prices. Trying to get wheat pasture established was hard enough between fighting off the fall armyworm and working around the rain. Then on top of all that after getting a stand established, it has not rained since. As a result, many producers have already grazed as much as they could and have removed their cattle, or they have not even had the chance to graze. For the few producers who still have pasture to graze, leaving some leaf material out there after grazing will be important for having any chance of a decent grain crop. Ideally, there should be a minimum of 60% canopy coverage left. It also does not look like we will have cool and wet conditions after cattle removal to allow the plants more time to recover from the grazing injury. This situation is shaping up to be similar to last year, and that puts even more emphasis on removing cattle from wheat pasture at the right time.

 

The optimal time to remove cattle from wheat pasture is at a growth stage called first hollow stem (FHS, between Feekes 5 and 6). This is the optimal time because the added cattle weight gains associated with grazing past first hollow stem are not enough to offset the value of the reduced grain yield (1-5% every day past FHS). The wheat variety, amount of grazing, time when cattle are removed, and weather conditions after cattle removal determine how much total grain yield potential might be reduced.

 

One of the moving targets each year is determining when to start scouting for FHS. To help combat this, the First Hollow Stem Advisor was developed by researchers at Oklahoma State University. This is an online tool available on the Mesonet website, https://www.mesonet.org/index.php/agriculture/category/crop/wheat/hollow_stem_advisor. This tool uses soil temperature data to show the current probability of FHS occurrence, as well as 1-week and 2-week projections. With this tool, producers can select their variety from a list of varieties that separates them into three FHS categories: early, middle, and late. Then, maps can be generated to provide the probability of FHS based on current conditions and the 1- and 2-week projections. Charts and tables can also be generated for individual Mesonet sites. Created maps have a color scheme to represent the probability of FHS occurrence. When using this tool, it is recommended to start scouting for FHS from a non-grazed part of the field once the 5% probability is reached (green color). Because stem elongation will begin moving quickly as the temperature warms up, starting your scouting at the 5% level will help give you the time it takes for making the preparations for cattle removal by the time FHS occurs. Methods on how to scout for FHS are listed at the end of this post. For producers who do not scout, it is recommended to remove cattle when the 50% probability level is reached. A 50% probability level indicates that over an evaluated period (e.g., 10 years), FHS would have occurred by that date in 50% of those years (e.g., 5 years). The same interpretation is used for other probability levels.

 

To give an example of what the tool provides and show some of the FHS conditions around Oklahoma, I have generated some statewide maps below. For producers along the southern Oklahoma border who planted an “early” wheat variety (e.g., Gallagher), now would be the time to go out and start scouting for FHS (Figure 1).

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Figure 1. Current FHS probabilities for “early” wheat varieties.

 

Looking at the 1-week projection for “early” varieties, you can see how the probabilities have increased, and areas further north should begin scouting (Figure 2).

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Figure 2. One-week FHS projection (i.e., through February 22) for “early” wheat varieties.

 

For producers who planted “middle” (e.g., Duster) or “late”  (e.g., Doublestop) FHS varieties, the 1-week projections indicate producers across much of the state still have a little bit of time yet before beginning to scout. However, producers along the southern border should begin scouting (Figure 3).

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Figure 3. One-week FHS projections (i.e., through February 22) for “middle” (top) and “late” (bottom) wheat varieties.

 

Remember that this tool should be used as a proxy to begin scouting for FHS. The best estimate of FHS is still to split stems from plants in each field to determine where they are developmentally. Another word of caution I want to mention when using the tool for this year especially is to consider when you were finally able to get stand establishment. If this did not occur until the end of September to the beginning of October, this tool may be a little ahead of where your plants are developmentally. In this case, the tool can still give you the cue to start scouting, but checking for FHS in each field will let you know if you do have some grazing time left.

 

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 and split the largest tiller longitudinally (lengthways), and measure the amount of hollow stem present below the developing grain head. You must dig plants because the developing grain head may still be below the soil surface at this stage.
  • 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).
  • More detailed information on FHS can be found at wheat.okstate.edu under ‘Wheat Management’ then ‘Grazing’ or by clicking here.

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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. 

 

Similar to previous years, we will monitor occurrence of FHS in our wheat plots at Stillwater and Chickasha and report the findings on this blog.