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Greenbug infestations reported

By Tom Royer, OSU Extension Entomologist

I received several reports of treatable greenbug infestations in winter wheat in Major County. This means it is important to scout your fields for greenbugs. I encourage you to use the “Glance n’ Go system, as it is easy to use.

Greenbugs on wheat

Greenbugs on wheat

There are several things that make Glance ‘n Go sampling a desirable way to make such a decision. You only have to “Glance” at a tiller to see if it has greenbugs (no counting greenbug numbers). You can make a decision to treat “on the Go” because you stop sampling once a decision is reached (no set number of samples). Finally, you can account for the activity of the greenbug’s most important natural enemy, Lysiphlebus testaceipes. Aphid Mummies

The Glance ‘n Go system be accessed in two ways. One is to set up an account with the myFields platform: http://myFields.info and sign up for a personal account. This system will allow you to sample a field with a smart phone in the field. To use it, you must have cell phone connectivity. You can then select the Glance n’ Go tool, plug in your cost inputs, and start sampling. Once you sign up, you can scout multiple fields and myFields will keep track of all your sampling information.

Glance-N-Go using the myFields platform

The second way is to access the Cereal Aphids Decision Support Tool on your computer http://entoplp.okstate.edu/gbweb/index3.htm . You can customize the threshold and selecting the Greenbug Calculator. Put your inputs in and it will select a threshold for your field. You can then download a paper Glance n’ Go form; take it to the field and start scouting.

Cereal Aphids Decision Support Tool

Cereal Aphids Decision Support Tool

By answering a few simple questions, you can determine an economic threshold for controlling greenbugs. This threshold is based on the estimated cost of treating the field and the estimated price of wheat. Once a threshold is calculated, you can print a Glance ‘n Go scouting form, take it to a field and record your sampling results. The form will help you to decide if the field needs to be treatment for greenbugs.

When scouting with the Glance ‘n Go system, keep a running count of tillers that have one or more aphid mummies and a running count of tillers that are infested with one or more greenbugs. The Glance ‘n Go form directs you to look at your total number of infested tillers and tillers with mummies after 5 stops. You will be directed to treat, not treat, or continue sampling. If there is enough parasitoid (mummy) activity, you will be directed to stop sampling and DON’T TREAT, even if you have exceeded the treatment threshold for greenbugs! Why? Because research showed that at that level of parasitism, almost all of the healthy-looking greenbugs have been “sentenced to death” and will be ghosts within 3-5 days. If they have received their “sentence” you can save the cost of an unnecessary insecticide application.

aphid mummies

aphid mummies

I accessed the Glance n’ Go tool to determine a “general” threshold that you can use for a Spring infestation, based on a wheat price of $5.50 per bushel and an application cost of either $4, $6, and $8 per acre. You can go directly to the website and download a paper form (Greenbug Spring Infestation) directly. The threshold is 3 greenbugs per tiller if your application costs are $4 per acre or 2 greenbugs per tiller for application costs of $6 or $8 per acre.

Contact your local County Extension Agricultural Educator for more information. If a field needs to be treated, check with Current Report CR-7194, “Management of Insect and Mite Pests in Small Grains”.

Plant growth regulators for wheat

Wheat lodging is not generally a widespread problem in Oklahoma, but it does occur. Lodging occurs due to a variety of factors, and as shown in the figure below, the timing of lodging will determine the final impact on grain yield. Lodging at head emergence, for example, can cause as little as 30 or as much as 80% yield reduction. The numbers in the figure do not account for harvest losses, which can exceed losses associated with lower photosynthetic capacity shown in the figure.

Slide05

Freeze injury or disease can cause lodging due to stem failure, which is characterized by plant stems breaking near the base. I the absence of weakened stems due to freeze or disease, most lodging in wheat is caused by failure of the root anchorage system (root lodging). Root lodging occurs when the anchorage system of a top-heavy wheat plant is weakened due to moist soil and wind provides sufficient force to overcome the rotational stiffness of the root/soil complex. Research has shown that increasing the soil water content from 17 to 26% reduced the force required for anchorage failure by 33%, and as little as 0.25 inches of water plus 11 mph winds were enough to cause lodging. The thicker the wheat crop and/or the taller the wheat crop, the more force that winds exert on the root anchorage system and the greater the likelihood of lodging.

Severe lodging in an Oklahoma wheat field in 2013

In 2013 and 2014 we evaluated the plant growth regulator trinexapac-ethyl, which is sold under the trade name Palisade®. Palisade is a giberellic acid inhibitor and works primarily by reducing plant height. In our study we evaluated 12 oz/ac of Palisade with and without 4 oz/ac of Tilt (propiconazole) applied at Feekes GS 7 (two nodes visible above the soil surface). We included an untreated check and ALL plots, including the check, received 10.5 oz/ac of Quilt Xcel at Feekes GS 10.5 (heading). We conducted the trial at Stillwater (Irr), Perkins (Irr), and Chickasha (Non-Irr).

 

I provided 2013 results in a blog post last year, and this post provides an update including our 2014 findings. While application of Palisade resulted in numeric reductions in plant height at Chickasha and Stillwater in 2013, differences among treatments were not statistically significant. In 2014 application of Palisade or Palisade plus Tilt significantly reduced plant height at Chickasha and Perkins.

Wheat plant height as affected by plant growth regulators in 2013

Wheat plant height as affected by plant growth regulators in 2013

 

Wheat plant height as affected by plant growth regulator in 2014

Wheat plant height as affected by plant growth regulator in 2014

We rated plots for lodging at harvest using a 1 – 10 scale with 0 equaling no lodging and 10 equaling complete lodging.  Application of Palisade plus Tilt reduced lodging over Palisade alone at Chickasha. Application of Palidsade or Palisade plus Tilt resulted in numeric reductions in lodging scores at Stillwater in 2013, but the result were too variable to result in statistical significance. Palisade did not affect lodging at Perkins in 2013. There was no lodging for any site or treatment in 2014.

 

Lodging as affected by plant growth regulator in 2013. No lodging occurred in 2014 regardless of treatment.

Lodging as affected by plant growth regulator in 2013. No lodging occurred in 2014 regardless of treatment.

 

Application of Palisade or Palisade plus Tilt increased grain yield at Chickasha and had no effect on grain yield at Stillwater or Perkins in 2013. It is interesting to note that the Palisade treatment increased grain yield at Perkins in 2013 even though the plots lodged at comparable levels as the non treated check. My best hypothesis is that the treated plots lodged later than the non treated plots, as all plots were standing at anthesis (see picture below). Application of Palisade or Palisade plus Tilt increased grain yield at Perkins in 2014 even though there was no lodging. There were no differences in grain yield at Stillwater or Chickasha in 2014. Lodging occurred at Chickasha, but occurred later in the season.

Wheat grain yield as affected by plant growth regulator in 2013

Wheat grain yield as affected by plant growth regulator in 2013

Wheat grain yield as affected by plant growth regulator in 2014

Wheat grain yield as affected by plant growth regulator in 2014

 

To summarize our work, we found a trend for one to two inch reductions in plant height when Palisade or Palisade plus Tilt were applied, but this did not consistently translate to increased grain yield. Our results are consistent with other wheat plant growth regulator research, which has reported similar variation in response among sites and years.  The literature also shows that reduction in lodging is relative to the straw strength of the variety. That is, a plant growth regulator will not make a lodging prone variety stand like one with excellent straw strength, rather they will make it less prone to lodging relative to the same variety non treated.

Based on current evidence, plant growth regulators in Oklahoma are best kept on acres with high (> 80 bu/ac) yield potential that may have greater propensity for lodging due to variety or fertility.  If these high yield potential acres are being sprayed with a growth regulator at GS 7, the addition of a foliar fungicide might be prudent if it can be included at a relatively low cost. This early-season fungicide application will not, however, substitute for a fungicide application at flag leaf.

Full disclosure: Syngenta donated the product for this trial, but the only funding for the research was provided by the Oklahoma Agricultural Experiment Station and the Oklahoma Cooperative Extension Service. We conducted a separate trial evaluating Palisade in drought stress environments that was partially funded by Syngenta. The analysis and recommendations made in this blog post are based on research findings from 2013 and 2014 production years. Recommendations may change as further research is conducted and new information is obtained.

Checking for first hollow stem

First hollow stem occurs just prior to jointing and is the optimal time to remove cattle from wheat pasture. First hollow stem usually occurs in mid to late February in southern Oklahoma and early March in northern Oklahoma. Grazing past first hollow stem can reduce wheat grain yield by as much as 5% per day and the added cattle gains are not enough to offset the value of the reduced wheat yield.

Similar to previous years, we will monitor occurrence of first hollow stem in our wheat plots at Stillwater and report the findings on this blog. There is also a new first hollow stem advisor available on the Oklahoma Mesonet that can assist in determining when to start scouting.

Checking for first hollow stem is fairly easy.

  • You must check first hollow stem in a nongrazed area of the same variety and planting date. Variety can affect date of first hollow stem 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 at this stage the developing grain head may still be below the soil surface.
  • If there is 1.5 cm of hollow stem present (see picture below), it is time to remove cattle. 1.5 cm is about the same as the diameter of a dime.
  • Detailed information on first hollow stem can be found at www.wheat.okstate.edu under ‘wheat management’ then ‘grazing’
  • Image
The plant on the left is past first hollow stem and is jointing. The plant on the right is at first hollow stem

The plant on the left is past first hollow stem and is jointing. The plant on the right is at first hollow stem

Time to start topdressing wheat

There are few crop inputs that deliver as much return on investment as nitrogen fertilizer. It takes approximately two pounds of nitrogen, costing approximately $1.00, to produce one bushel of grain worth about $5.00. Of course, nitrogen is not the only yield determining factor in a wheat crop. Also, the law of diminishing marginal returns eventually kicks in, but nitrogen fertilizer is still one of the safest bets in the house.

Top dress nitrogen fertilizer is especially important because it is applied and utilized at a time when the plant is transitioning from vegetative to reproductive growth. Several things, including the number of potential grain sites, are determined just prior to jointing and it is imperative that the plant has the fuel it needs to complete these tasks. Jointing also marks the beginning of rapid nitrogen uptake by the plant which is used to build new leaves, stem, and the developing grain head. The nitrogen stored in these plant parts will be used to fill the grain later in the season, and the plant is dependent on this stored nitrogen to complete grain fill.

In the bullet points below, I will hit the major points regarding top dress nitrogen for wheat.  I have also posted three slide presentations with audio regarding topdressing wheat at my YouTube channel available by clicking here or by searching YouTube for OSU Small Grains. 

When to apply

  • In order to have full benefit, nitrogen must be in the rooting zone by the time wheat is jointing. Jointing occurs around the end of February in southern OK and around the second week of March in northern OK.
  • Moisture is required to move nitrogen into the rooting zone. Since precipitation is usually very limited in January and February in Oklahoma we need the nitrogen out on the field when the precipitation arrives. This, along with the fact that we have 5.5 million acres to cover, means that we need to get started in January to get everything taken care of in a timely fashion.
  • If you are using the Sensor Based Nitrogen Recommendation system your yield predictions and nitrogen recommendations generally become more accurate as the season progresses; however, growers wishing to hedge their nitrogen bet could apply a partial top dress in January or early February and supplement with a second top dress just prior to jointing if SBNR recommendations call for additional nitrogen.
  • Do not apply nitrogen to frozen ground. Nitrogen will move with water. If melting snow or frozen rain is moving to the ditch, so will nitrogen applied to the soil surface.
  • Consider splitting or delaying top dress nitrogen applications to sandy soils until closer to jointing, as leaching can occur.

How much to apply

  • On average it takes about 2 lbs/ac of N for every bushel of wheat yield. In addition, dual-purpose wheat requires 30 lbs/ac of N for every 100 lbs/ac of beef removed. You can subtract your soil test NO3-N from these total requirements.
  • It is okay to adjust topdress N plans based on your current yield potential. When you submitted your soil test, you might have stated a 50 bu/ac yield goal which would require 100 lbs/ac of nitrogen; however, it is important to take a hard look and determine if this yield goal is still realistic based on your current crop status. I am not suggesting to adjust based on what you think the weather might do, but it is okay to take inventory and adjust your topdress N up or down based on current field conditions.
  • Don’t have an N-rich strip? It would be a lot cooler if you did. An N-rich strip would take the guess work out of adjusting your topdress N up or down based on your current crop conditions. Your county extension educator can provide more information on N-rich strips and you can find more information on the web at www.npk.okstate.edu

What source to use

  • The plant does not care about nitrogen source. A pound of nitrogen is a pound of nitrogen. Focus on getting the correct amount applied at the correct time, and choose your product based on price and application uniformity.
  • Use a source that can be applied uniformly. In my experience, spinner trucks or buggies are generally the least uniform. Air trucks or streamers are the most uniform.
  • Streamer nozzles almost eliminate leaf burn from UAN; however, leaf burn is generally not an issue until temperatures warm and/or you are applying fairly large amounts of UAN. Stream nozzles are also not affected much by wind and deliver a uniform pattern in a variety of conditions. There are also some studies that indicate banding of UAN through the use of stream nozzles will reduce nitrogen immobilization on crop residue. All in all, I am a big fan of streamer nozzles. You cannot, however, tank mix herbicides when using streamer nozzles.
    Streamer nozzles provide uniform application of UAN in a wide variety of environmental conditions.

    Streamer nozzles provide uniform application of UAN in a wide variety of environmental conditions.

    Poor nitrogen application can result in a streaked field. Some of the areas in this field were over fertilized while some were under fertilized resulting in wasted nitrogen and less than optimal crop yield.

    Poor nitrogen application can result in a streaked field. Some of the areas in this field were over fertilized while some were under fertilized resulting in wasted nitrogen and less than optimal crop yield.

Winter grain mites in northcentral OK

Jeff Bedwell forwarded reports of winter grain mites in Major and Alfalfa counties over the past week. This does not appear to be a widespread problem, but growers should check wheat fields to see if winter grain mites are present. We had a lot of issues with winter grain mites and brown wheat mites in Oklahoma last year. Unfortunately, many of these fields were not diagnosed until the damage was severe and visible from a distance. In this case, a rescue treatment was still effective at controlling the pest, but some yield loss had already occurred thus reducing the return on pesticide investment.

Winter grain mites are small (about 1 mm long) with black bodies and orange-red legs. Winter grain mites complete two generations per year and the adults can live for up to 40 days. The generation we are dealing with now resulted from oversummering eggs laid last spring. The second generation peaks in March/April and results from eggs laid in January/February.

Image

Winter grain mites on wheat near Blair, Oklahoma.

 

Scouting
Winter grain mites are not a problem you will notice in a timely fashion while standing up. You will need to get close to the soil surface and move residue to find these pests. Winter grain mites are light sensitive and prefer calm air to windy conditions; therefore, scouting early in the morning, late in the evening, or on cloudy days generally works best. Be sure to look under residue in no-till fields and under clumps of soil in conventional-till fields.

Scouting for winter grain mites requires getting close to the soil surface and moving residue to disturb mites.

Scouting for winter grain mites requires getting close to the soil surface and moving residue to disturb mites.

Injury

Winter grain mites feed by piercing plant cells in the leaf, which results in “stippling”.  As injury continues, the leaves take on a characteristic grayish or silverish cast.  Winter grain mites are more likely to cause injury in wheat if it is already stressed due to lack of moisture or nutrients. Also be advised that freeze injury can easily be confused for winter grain mite injury.

Wheat damaged by winter grain mite often has a silver or grayish appearance from a distance

Wheat damaged by winter grain mite often has a silver or bronzed appearance from a distance

When to spray
There are no established thresholds for winter grain mite. Healthy, well-fertilized wheat plants can generally outgrow injury, so it takes large numbers to justify control. If there is injury present AND large numbers of mites (~10 per plant) present in grain only wheat this time of year, you might consider control. If the wheat is to be grazed, I would simply monitor the situation in most cases and only spray if injury became severe.

What to spray
Malathion is the only product labeled for wheat in Oklahoma that has winter grain mite on the label. There are many additional products, such as some of the pyrethroids and chlorpyrifos, that are effective at controlling winter grain mite, but they don’t have a specific label for them. These products can be applied under 2ee regulations; however since this pest is not specifically labeled, the user assumes all responsibility for the application of the product.  It is also important to read and follow label directions regarding grazing restrictions for these and all pesticides.  Consult OSU Current Report 7194 Management of insect and mite pests in small grains for a more complete listing of available pesticides.

Greenbugs reported in northwestern Oklahoma

By Tom Royer, OSU Extension Entomologist

Crop consultants have reported greenbugs in a few northwestern Oklahoma wheat fields. The hit or miss nature of greenbugs and other aphid pests in wheat fields can make scouting challenging. Fortunately, there is an online tool called the Cereal Aphid Decision Support Tool that simplifies scouting for greenbugs and also considers the effects of natural predators.

Greenbugs on wheat

Greenbugs on wheat

Start by going to the Cereal Aphids Decision Support Tool on your computer http://entoplp.okstate.edu/gbweb/index3.htm and selecting the Greenbug Calculator.

By answering a few simple questions, you can determine an economic threshold for controlling greenbugs.  This threshold is based on the estimated cost of treating the field and the estimated price of wheat.  Once a threshold is calculated, you can print a Glance ‘n Go scouting form, take it to a field and record your sampling results.  The form will help you to decide if the field needs to be treatment for greenbugs.  There are several things that make Glance ‘n Go a good way to make such a decision. You only have to “Glance” at a tiller to see if it has greenbugs (no counting greenbug numbers).  You can make a decision to treat “on the Go” because you stop sampling once a decision is reached (no set number of samples).  Finally, you can account for the activity of the greenbug’s most important natural enemy, Lysiphlebus testaceipes.

When scouting with the Glance ‘n Go system, keep a running count of tillers that have aphid mummies and a running count of tillers that are infested with one or more greenbugs.  After each set of 5 stops, the Glance ‘n Go form directs you to look at your total number of infested tillers and tillers with mummies.  If there is enough parasitoid (mummy) activity, you will be directed to stop sampling and DON’T TREAT, even if you have exceeded the treatment threshold for greenbugs!  Why? Because research showed that at that level of parasitism, almost all of the healthy-looking greenbugs have been “sentenced to death” and will be ghosts within 3-5 days.  If they have received their “sentence” you can save the cost of an unnecessary insecticide application.

Natural predators can keep greenbug infestations below economic thresholds

Natural predators can keep greenbug infestations below economic thresholds

Treatment thresholds will probably fall around 2-4 greenbugs per tiller, but make sure you are using the Fall (Sept.-December) form, not the spring form.  If a field needs to be treated, check with Current Report CR-7194, “Management of Insect and Mite Pests in Small Grains”.  If you treat for greenbugs and have a failure, please contact our Department and we will investigate further to determine if insecticide resistance might be an issue. Dr. Ed Bynum, Extension Entomologist from Amarillo, reported finding some greenbug populations in 2013 that were shown to be resistant to chlorpyrifos, the active ingredient in Lorsban 4E, and other generic products (Govern 4E, Hatchet, Nufos, Vulcan, Warhawk, Whirlwind).   The bottom line:  he tested some suspect greenbug populations using a diagnostic test that he developed for testing greenbugs in sorghum in the 1990’s, and found that they were resistant to chlorpyrifos at labeled rates.

Wheat protein report – 2014

This blog post contains information from OSU Current Report 2135 Protein Content of Winter Wheat Varieties in Oklahoma. A complete pdf version of the report with a brief explanation of sampling procedures can be found at www.wheat.okstate.edu.

The grass always seems to be greener on the other side when it comes to wheat protein. In a low protein year, everyone is scrambling to find higher protein wheat to blend. In a high protein year, such as this one, the same low protein wheat that was considered marginally acceptable the year before might command a slight premium. While wheat protein is important to end users, wheat protein is just one of many attributes which determine end-use quality and marketability of winter wheat. In fact, some millers and bakers would argue that functionality of wheat protein is more important than the quantity of protein. While varietal differences commonly exist, differences in wheat protein among environments are generally much larger than differences among varieties. Factors such as nitrogen fertility and drought stress, for example, can sharply impact final protein content of the grain, and most producers are better served focusing on good agronomic practices than slight genetic differences in wheat protein content.

To reflect environmental impacts on wheat grain protein content, 2014 wheat variety test data are reported by variety and location in Table 1. The 18.5% average wheat grain protein for the Thomas location is a good example of how fertility and environment can impact protein content. Soil tests at the time of sowing revealed 141 lb/acre of residual nitrogen available, which should be enough to produce a 70 bu/acre wheat crop. Due to extreme drought, however, average grain yield at Thomas was 13 bu/acre. Under these circumstances, wheat plants were able to pull large amounts of nitrogen from the soil and move this nitrogen to the developing grain. Grain size was reduced and grains were shriveled due to drought, thus resulting in abnormally high wheat protein. A similar situation was reported for Altus in 2013.

In Table 2 we reported the wheat grain protein content as a deviation from location mean for each variety, as this provides easier comparison of wheat grain protein among varieties across locations. Billings, for example, is a variety with solidly positive deviation from location means, indicating it has a tendency for above-average grain protein content. Iba, on the other hand, has negative deviations from location means, indicating a tendency for lower than average grain protein content. Adequate nitrogen fertility as recommended by a recent soil test or sensor-based nitrogen management program can help ensure that varieties such as Iba produce grain protein within the acceptable range for end-use customers. Iba is also a prime example of how protein data can sometimes be misused, as the functionality of the protein in Iba is above average, which can offset lower absolute grain protein content.

How to make $100,000 in a day

No, this blog post is not about a get rich quick scheme, but there is a way for the average wheat farmer in the southern Great Plains to add $50,000 to $100,000 to the bottom line in a single day. Most soil tests I have pulled this summer have shown 50 to 90 lb/ac of NO3-N in the top 18 inches of soil. Ninety pounds of N equates to about $45 of N fertilizer, and this knowledge could save a 2,500 acre wheat farmer in excess of $100,000 in fertilizer cost. Soil testing is laborious, but the potential economic returns for spending a day or two soil sampling are outstanding.

There is still time to soil sample. Soil samples only take a few days to process once they are in the OSU lab. It is not unusual for transit time to the lab to the slowest part of the process, so if you need a fast turnaround a trip to drop samples in the Ag Hall basement in Stillwater will help (plus you have probably been wanting cheese fries). If you have already applied pre-plant fertilizer or sown wheat, there is still time to assess soil N availability and uptake via the N-Rich Strip. In its simplest form, the N-rich strip is an area where N is not limiting. Either by visual assessment or with the assistance of an optical sensor, you can use the N-rich strip to determine your top dress N requirement, but you must create the N-rich strip this fall.

Soil testing is not always easy, but it is time well spent. My high school shop teacher would have labeled me a "Primitive Pete" for this photo.

Soil testing is not always easy, but it is time well spent. My high school shop teacher would have labeled me a “Primitive Pete” for this photo.

The bottom line is that a day of soil testing or putting out N-rich strips is well worth your time investment. On another note, how would you like to make money and improve your health at the same time? I have a multi-level marketing opportunity that I can get you in on the ground floor, but don’t tell anyone else. I can only make this deal for you and only today. There will be a small “buy in” fee that you will need to pay cash up front, though.

Partial funding for the research included in this blog post was provided by USDA Project No.2012-02355 through the National Institute for Food and Agriculture’s Agriculture and Food Research Initiative, Regional Approaches for Adaptation to and Mitigation of Climate Variability and Change

Planting wheat in hot soils

Kickoff of the college football season and the start of wheat planting are Labor Day traditions in the southern Great Plains. Many producers are waiting to see if rain forecasted for this weekend materializes, but it is likely that forage-based wheat farmers will start sowing wheat next week whether it rains or not. This means sowing wheat into hot soil conditions which can cause wheat germination and emergence issues. Given the potential problems, there are a few questions producers should ask themselves prior to planting into soil temperatures >90F.

coleoptile length

If the wheat coleoptile does not break the soil surface, the germinating wheat plant will not survive.

Will you have to plant deep to reach moisture? That first structure protruding from a germinating wheat seed is actually not a leaf. It is the coleoptile. The wheat coleoptile is a rigid structure whose sole purpose is to “punch through” the soil surface so that the first true leaf emerges above the soil surface. If this does not happen, the first true leaf will try to extend below the soil surface, turn yellow, and take on an accordion-like appearance (picture above). Modern semi-dwarf wheat varieties have shorter coleoptiles than older, tall wheat varieties and coleoptile length is shortened even further by hot soil conditions. So it is important to plant a variety with a longer coleoptile length (e.g. Garrison or Doans) if planting deeply into hot soils. A rating of coleoptile lengths for wheat varieties can be found in OSU Fact Sheet 2141 OSU Wheat Variety Comparison Chart available at www.wheat.okstate.edu or at the direct link to the publication here.

Is the variety high temperature germination sensitive? High temperature germination sensitivity is a fancy way of saying that some wheat varieties simply don’t germinate well in hot soil conditions (e.g. 2174, Overley). The extent of the sensitivity varies by year, so Overley might germinate fine in 95F soils one year and produce a 10% stand in the same soil conditions the next. When sowing early, it is best to plant varieties that do not have high temperature germination sensitivity (e.g. Duster, Gallagher, or Armour). Soil conditions generally cool due to lower ambient temperatures or cooling rains by about September 20; however our summer temperatures seem to be arriving late this year, so it is best to know the level of germination sensitivity in the variety you are planting. A rating of high temperature germination sensitivity for wheat varieties can be found in the variety comparison chart linked above. A more detailed explanation of the phenomenon can be found in OSU Fact Sheet PSS 2256 Factors affecting wheat germination and stand establishment in hot soils (available by clicking here).

Partial funding for the research included in this blog post was provided by USDA Project No.2012-02355 through the National Institute for Food and Agriculture’s Agriculture and Food Research Initiative, Regional Approaches for Adaptation to and Mitigation of Climate Variability and Change

2014 Wheat Crop Overview

This blog post is an excerpt from the 2014 OSU Small Grains Variety Performance Tests report, which is available at http://www.wheat.okstate.edu or by clicking here.

At the time of writing this post, 2014 Oklahoma wheat production is estimated to be approximately 51 million bushels, which is roughly half of 2013 production (Table 1). Oklahoma has not seen wheat production this low since the 43 million bushel crop of 1957, and with any luck, production will not be this low again for at least another 60 years.

 

Table 1. Oklahoma wheat production for 2013 and 2014 as estimated by OK NASS, July 2014
2013 2014
Harvested Acres 3.4 million 3.0 million
Yield (bu/ac) 31 17
Total bushels 105 million 51 million

 

The 2013-2014 wheat production season had a good start in central Oklahoma. Topsoil moisture was short in September, but October rains resulted in favorable conditions for wheat emergence and establishment. In addition, many areas had a fair amount of stored soil moisture from the summer of 2013. This stored soil moisture allowed sites such as Chickasha and Lahoma to produce 43 and 47 bu/ac average wheat yield on less than eight inches of rainfall during the growing season. Stored soil moisture also contributed to adequate forage production at grazed sites such as Marshall Dual-Purpose, but production of a forage crop did not leave behind enough moisture to fuel much of a grain crop.

 

The multi-year drought never released its stranglehold on western Oklahoma during the 2013-2014 wheat production season. Small rains here or there allowed most producers to obtain an acceptable stand of wheat, but moisture was never sufficient to spur tillering or leaf area development. Early winter snowfall made for a few bright spots for forage production in southwestern Oklahoma, but this moisture was quickly utilized by growing wheat plants and dry conditions soon returned. As a result, many fields in southwestern and western Oklahoma were abandoned and not taken to harvest.

This photo of a wheat field near Altus, Oklahoma in April 2014 shows the level of devastation from the extreme, multi-year drought. Most wheat fields in this region were abandoned due to drought.

This photo of a wheat field near Altus, Oklahoma in April 2014 shows the level of devastation from the extreme, multi-year drought. Most wheat fields in this region were abandoned due to drought.

 

Thin wheat stands left some fields vulnerable to blowing sand and wind erosion

Thin wheat stands left some fields vulnerable to blowing sand and wind erosion

The winter of 2013-2014 wasn’t just dry; it was cold too. Young, drought-stressed wheat plants had difficulty dealing with the cold, windy conditions, and winterkill was common in late-sown wheat. Winterkill was also common in grazed wheat that was stressed by heavy grazing pressure and inadequate soil moisture. Considerable winterkill was also present in no-till wheat without adequate seed to soil contact in northwestern Oklahoma. The inadequate seed to soil contact was generally the result of heavy residue from the previous year’s wheat crop.

Winterkill was common in northwestern Oklahoma, with the greatest injury occurring in no-till and/or grazed wheat fields.

Winterkill was common in northwestern Oklahoma, with the greatest injury occurring in no-till and/or grazed wheat fields.

Closer inspection of some no-till fields with winterkill revealed shallow seed placement due to heavy and/or unevenly spread residue from the 2103 wheat crop.

Closer inspection of some no-till fields with winterkill revealed shallow seed placement due to heavy and/or unevenly spread residue from the 2103 wheat crop.

 

While the wheat crop did not appear to be on its way to bumper production, most producers hoped for a turnaround similar to 2013 and topdressed in late winter. Unlike the spring of 2013, however, the rains never came and much of this topdress N applied did not make it into the soil until the crop was at boot stage or later.

 

The cold winter delayed the onset of first hollow stem by about five days as compared to 2013 and 25 days as compared to 2012. Despite a slow start to the spring, wheat in southern Oklahoma was near heading when a hard freeze occurred the morning of April 15, 2014. As expected, drought stressed wheat in advanced stages in southwestern Oklahoma suffered severe freeze damage; however, injury from the 2014 spring freeze did not always follow the “rule of thumb” guidelines used by agronomists. Many areas that received small amounts of rain just prior to the freeze seemed to escape widespread injury, regardless of growth stage. In southcentral Oklahoma, injury seemed to be most severe on later maturing varieties that were approximately Feekes GS 7 to booting, while earlier-maturing varieties that were just starting to head escaped freeze injury. Wheat that was barely past two nodes in northern Oklahoma suffered severe injury, while more advanced wheat in central Oklahoma endured similar temperatures with minimal injury.

 

There were relatively few insect or disease issues to deal with during the 2013-2014 wheat production season. Winter grain mite and/or brown wheat mite infestations proved to be too much for some drought stressed wheat fields in northcentral and northwestern Oklahoma. Some fields already devastated by the drought were left unsprayed, while others still showing some sign of yield potential were treated.

 

Injury, such as the bronzed areas in the picture above, was the result of brown wheat mite and/or winter grain mite infestations in late winter.

Injury, such as the bronzed areas in the picture above, was the result of brown wheat mite and/or winter grain mite infestations in late winter.

 

Other than a rare siting of a single leaf rust pustule, there was no foliar disease in Oklahoma in 2014. The lack of foliar disease is evidenced by the lack of response to foliar fungicides at either Chickasha or Lahoma. These two sites provided a rare opportunity in 2014 to observe yield impacts of foliar fungicides in the absence of disease, as most years we report at least light or negligible foliar disease at these sites. While foliar disease was not an issue in 2014, wheat streak mosaic virus was an issue for many producers. This disease has historically been most prevalent in northwestern Oklahoma and the Panhandle. Wheat streak mosaic virus was confirmed in several fields downstate this year, however, and it is likely that some fields affected by wheat streak mosaic virus were not identified as such because it is sometimes difficult to distinguish wheat streak mosaic virus symptoms from those of severe drought stress. The wheat variety testing program was not immune from this disease, and we lost our Kildare location to wheat streak mosaic virus.

 

Warmer temperatures in May hastened crop maturity and the Oklahoma wheat harvest began near Frederick on May 22, 2014. By the first week of June, harvest was in full swing, only to be delayed by rain shortly thereafter. Harvest resumed across most of the state by June 13 and was mostly completed by June 30. The exceptions being some waterlogged areas in northern Oklahoma. The Cherokee Mesonet site, for example, reported 5.1 inches of rainfall from October 1, 2013 to May 31, 2014, but the same site received 10 inches of rain from June 1 to June 30, 2014.