Wheat

Yes, Another Article About Freeze Symptoms in Winter Wheat

Source: Dr. Laura Lindsey, OSU

After a (short) second round of winter last week, there has been some concern regarding winter wheat. As a reminder, the magnitude of freeze damage depends on: 1) temperature, 2) duration of temperature, and 3) wheat growth stage. During the cold snap last week, the majority of winter wheat in Ohio was at the Feekes 6 to 8 growth stage. In northern Ohio, temperatures were in the low 30s to upper 20s. In Southern Ohio, temperatures were mostly above 30°F with a dip to 26°F on April 23, recorded by the CFAES weather system in Pike County. Underneath the snow, temperatures were warmer (Figure 1 records the temperature under the snow on April 21).

A few years ago, we conducted a freeze chamber experiment to examine the effect of low temperature on winter wheat at several growth stages (Table 1). Keep in mind, actual yield reductions in the field can be quite variable depending on the weather for the remainder of the growing season. At Feekes 6 growth stage, temperatures >20°F caused no damage. However, by Feekes 8 growth stage, temperatures of 25°F to 28°F caused a 10 to 25% reduction in wheat yield. These temperatures were from the crown of the wheat plant, not air temperature.

What to look for: After a freeze event, wait one to two weeks after active growing conditions resume to check for visual signs of freeze injury. Make sure to examine several areas of the field as landscape features influence the micro-climates within fields. Small differences in temperatures can cause large differences in damage and grain yield.

At Feekes 6 growth stage, damage from freezing will cause discoloration of the leaf tissue, with leaf tips or edges exhibiting symptoms first (Figure 2). However, discoloration does not necessarily indicate a reduction in grain yield. At Feekes 6 growth stage, damage can also be assessed by carefully cutting the wheat stem lengthwise to expose the developing spike at the first node. Damaged spikes will appear discolored and shriveled. A healthy, developing spike should be rigid and whitish-green (Figure 3).

Figure 2. At Feekes 6 growth stage, freeze damage causes yellowing of browning (necrosis) of the leaf and stem tissue. Wheat plants pictured (left to right) were exposed to temperatures of 3, 14, 21, 28, and 39°F corresponding to death of 100%, 80%, 50%, 25%, and 0% death of the plant tissue.

Figure 2. At Feekes 6 growth stage, freeze damage causes yellowing of browning (necrosis) of the leaf and stem tissue. Wheat plants pictured (left to right) were exposed to temperatures of 3, 14, 21, 28, and 39°F corresponding to death of 100%, 80%, 50%, 25%, and 0% death of the plant tissue.

Figure 3. At Feekes 6 growth stage, freeze injury causes damage to forming wheat spike within the stem. Wheat spikes pictured (left to right) were exposed to 39, 28, 21, 14, and 3°F temperature treatments. At 3°F, the wheat spike appears discolored and deformed.

Figure 3. At Feekes 6 growth stage, freeze injury causes damage to forming wheat spike within the stem. Wheat spikes pictured (left to right) were exposed to 39, 28, 21, 14, and 3°F temperature treatments. At 3°F, the wheat spike appears discolored and deformed.

At Feekes 8 growth stage, damage from freeze may include yellowing or browning of the flag leaf. The flag leaf may appear twisted or in a spiral (Figure 4). As the plant continues to grow, the wheat spike may get stuck in the leaf sheath, causing a crooked appearance at heading (Figure 5). (Although, this phenology can also be associated with spikes that emerge quickly due to warm temperatures.)

Overall, I think freeze damage should be minimal from this most recent cold snap. At Feekes 6 growth stage, wheat is still fairly tolerant of cold temperatures. In the southern portion of the state, where wheat stage was more advanced, temperatures tended to be warmer. However, the best way to assess for potential damage is to scout your field after active growing conditions resume this week. For more information, see our new ‘Freeze Symptoms and Associated Yield Loss in Soft Red Winter Wheat’ FactSheet: https://ohioline.osu.edu/factsheet/anr-93

Figure 4. Twisting or spiral appearance of the flag leaf can be caused by low temperatures. Photo credit: Greg LaBarge.

Figure 4. Twisting or spiral appearance of the flag leaf can be caused by low temperatures. Photo credit: Greg LaBarge.

Figure 5. At Feekes 8 growth stage, damage may include yellowing or browning of the flag leaf. The wheat head may get stuck in the leaf sheath causing a crooked appearance at heading.

Figure 5. At Feekes 8 growth stage, damage may include yellowing or browning of the flag leaf. The wheat head may get stuck in the leaf sheath causing a crooked appearance at heading.

Should you expect any freeze damage to winter wheat? Most likely, no.

Source: Laura Lindsey, Alexander Lindsey, OSU Extension

The incoming cold temperatures are not likely to impact winter wheat. The magnitude of freeze damage depends on: 1) temperature, 2) duration of temperature, and 3) wheat growth stage.

 

Prior to the Feekes 6 growth stage, the growing point of wheat is below the soil surface, protected from freezing temperatures. Most of the wheat in Ohio is at the Feekes 4 (beginning of erect growth) or Feekes 5 (leaf sheaths strongly erect) growth stage and should be unaffected by the incoming cold temperatures, predicted to be mid- to low 20s on Wednesday and Thursday.

At Feekes 6 growth stage, our research has shown only a 5% reduction in wheat yield at a temperature of 20°F for 15-minute duration and 50% reduction in wheat yield at a temperature of 12°F for 15-minute duration. (Although, it should be noted, there is a great deal of variability in response due to environmental conditions for the remainder of the growing season. Additionally, greater soil moisture levels can help buffer against short-term temperature fluctuations.)

For more information on Freeze Symptoms and Associated Yield Loss in Soft Red Winter Wheat, please see our new FactSheet: https://ohioline.osu.edu/factsheet/anr-93

Wheat Growth Stages and Associated Management- Feekes 6.0 through 9.0

Source: Laura Lindsey, Pierce Paul, Ed Lentz, OSU Extension

It is important to correctly identify winter wheat growth stages to enhance management decisions, avoiding damage to the crop and unwarranted or ineffective applications. Remember, exact growth stage cannot be determined by just looking at the height of the crop or based on calendar dates. Remember to stage several plants from several areas within your field.

Here, we will focus on staging wheat Feekes 6.0 through 9.0.

Feekes 6.0: At Feekes 6.0 growth stage, nodes are all formed, but sandwiched together so that they are not readily distinguishable. The first node is swollen and appears above the soil surface. This stage is commonly referred to as “jointing”. Above the node is the head or spike, which is being pushed upwards eventually from the boot. The spike at this stage is fully differentiated, containing future spikelets and florets.

Growers should remove and carefully examine plants for the first node. It can usually be seen and felt by removing the lower leaves and leaf sheaths from the large wheat stems. A sharp knife or razor blade is useful to split stems to determine the location of the developing head. A video showing how to identify the Feekes 6.0 growth stage can be found in the video below.

Feekes 7.0: At Feekes 7.0 growth stage, the second node becomes visible. This stage is characterized by the rapid expansion of the head and a second detectable node. Look for the presence of two nodes- one should be between 1.5 and 3 inches from the base of them stem and the other should be about 4 to 6 inches above the base of the stem. These nodes are usually seen as clearly swollen areas of a distinctively different (darker) shade of green than the rest of the stem. The upper node may be hidden by the leaf sheath; you may have to run your fingers up the stem to feel for it. If only one node is present, the wheat is still at Feekes 6.0 growth stage. Wheat will still respond to nitrogen applied at Feekes 7.0 if weather prevented an earlier application; however, mechanical damage may occur from applicator equipment. A video showing how to identify the Feekes 7.0 and 8.0 growth stages can be found here: https://www.youtube.com/watch?v=PZ7Lvsux1y8

Feekes 8.0: At Feekes 8.0 growth stage, the flag leaf is visible, but still rolled up. This growth stage begins when the last leaf (flag leaf) begins to emerge from the whorl. This stage is particularly significant because the flag leaf makes up approximately 75% of the effective leaf area that contributes to grain fill. It is therefore important to protect and maintain the health of this leaf (free of disease and insect damage) before and during grain development. When the flag leaf emerges, three nodes are visible above the soil surface. To confirm that the leaf emerging is the flag leaf, split the leaf sheath above the highest node. If the head and no additional leaves are found inside, Feekes 8.0 is confirmed and the grower should decide whether or not to use foliar fungicides to manage early-season and overwintering fungal diseases. Nitrogen fertilizer applications at or after Feekes 8.0 growth stage may enhance grain protein levels, but are questionable with respect to added yield. Moreover, additional N may increase the severity of some foliar diseases, particularly the rusts.

Feekes 9.0: Feekes 9.0 growth stage begins when the flag leaf is fully emerged from the whorl with the ligule and collar visible. From this point on, leaves are referred to in relation to the flag leaf (e.g., the first leaf below the flag leaf is the F-1, the second leaf below is F-2, and so forth). A video showing how to identify Feekes 9.0 and 10.0 growth stages can be found here: https://www.youtube.com/watch?v=OHGhq0qSM1o&t=22s

Is It Too Early to Apply Nitrogen to Wheat?—-Yes

Source: Laura Lindsey, Ed Lentz, OSU Extension

With melted snow and warmer weather in the forecast, is it time to apply nitrogen to wheat?

The short answer. Wait until green-up to apply N to wheat.

The long answer. Wheat does not require large amounts of N until stem elongation/jointing (Feekes Growth Stage 6), which is generally the middle or the end of April depending on the location in the state and spring temperature. Ohio research has shown no yield benefit from N applications made prior to this time. Soil organic matter and/or N applied at planting generally provide sufficient N for early growth until stem elongation.

Nitrogen applied prior to rapid uptake by the plant has the potential to be lost and unavailable for the crop. Nitrogen source will also affect the potential for loss. Urea-ammonium nitrate (28%) has the greatest potential for loss, ammonium sulfate the least, and urea would be somewhere between the two other sources.

Ohio research has shown that yield losses may occur from N applied prior to green-up regardless of the N source. The level of loss depends on the year (losses are smaller if the ground is not frozen or snow/ice covered). This same research did not observe a yield increase from applications made prior to green-up compared to green-up or Feekes Growth Stage 6 applications. Keep in mind that green-up is a descriptive, relative term and not a definable growth stage. Our definition of green-up is when the new growth of spring has covered the dead tissue from winter giving the field a solid green color- thus, growing plants.

There is a legitimate concern that wet weather may prevent application of N at early stem elongation. Ohio research has shown a yield decrease may occur when N application is delayed until Feekes Growth Stage 9 (flag leaf fully emerged). Thus, a practical comprise is to topdress N at any time fields are suitable for application after initial green-up to early stem elongation. There is still a potential for loss even at green-up applications. To lessen this risk a producer may want to use a N source that has a lower potential for loss such as urea or ammonium sulfate. ESN (polymer-coated urea) is another option but it needs to be blended with urea or ammonium sulfate to ensure enough N will be available for the crop between Feekes Growth Stage 6-9. The source of N becomes less important as the application date approaches stem elongation. The percentage of urea and/or ammonium sulfate would need to be increased with ESN for application times closer to Feekes Growth Stage 6. A producer may want to consider the use of a urease inhibitor with urea if conditions are favorable for volatilization losses: warming temperatures, drying winds and no rain in the forecast for 48 hours.

A split application of N may also be used to spread the risk of N loss and to improve N efficiency; however, Ohio State University research has not shown a yield increase from this practice compared to a single application after green-up. In a split system, the first application should be applied no sooner than green-up. A small rate should be applied with the first application since little is needed by the crop at that time and the larger rate applied closer to Feekes Growth Stage 6.

In summary, a producer may get away with applying N prior to green-up on wheat. However, university data has not shown a yield advantage for these early applications, but results have shown in certain years a major N loss and yield reduction from applications prior to green-up. Why take the risk? Just wait until green-up; the wheat does not need most of the N until April and May anyway.

 

Corn, Soybean and Wheat Enterprise Budgets – Projected Returns for 2021 Increasing Fertilizer Prices May Force Tough Decisions

Source: Barry Ward, John Barker, OSU Extension

The profit margin outlook for corn, soybeans and wheat is relatively positive as planting season approaches. Prices of all three of our main commodity crops have moved higher since last summer and forward prices for this fall are currently at levels high enough to project positive returns for 2021 crop production. Recent increases in fertilizer prices have negatively affected projected returns. Higher crop insurance costs as well as moderately higher energy costs relative to last year will also add to overall costs for 2021.

Production costs for Ohio field crops are forecast to be modestly higher compared to last year with higher fertilizer, fuel and crop insurance expenses. Variable costs for corn in Ohio for 2021 are projected to range from $386 to $470 per acre depending on land productivity. Variable costs for 2021 Ohio soybeans are projected to range from $216 to $242 per acre. Wheat variable expenses for 2021 are projected to range from $166 to $198 per acre.

Returns (excluding government payments) will likely be higher for many producers depending on price movement throughout the rest of the growing year. Grain prices currently used as assumptions in the 2021 crop enterprise budgets are $4.30/bushel for corn, $11.55/bushel for soybeans and $6.25/bushel for wheat. Projected returns above variable costs (contribution margin) range from $216 to $434 per acre for corn and $284 to $509 per acre for soybeans. Projected returns above variable costs for wheat range from $193 to $342 per acre. As a reminder, fixed costs (overhead) must be paid from these returns above variable costs. Fixed costs include machinery ownership costs, land costs including rent and payment for owner operator labor and management including other unpaid family labor.

Fertilizer prices continue to increase.  If you have not checked fertilizer prices lately, be prepared for some sticker shock. Producers with some fertilizer purchased and stored or pre-priced prior to recent price increases will likely see a healthier bottom line this upcoming crop year.

Those with little or no fertilizer pre-purchased and stored or pre-priced may want to consider using P and K buildup to furnish crop needs this year in anticipation of possibly lower prices in the future.  Now may be a good time review your fertilizer plans as you are considering how to best utilize your financial resources in 2021.

  • Use realistic yield goals.  Yield goals vary by field.  Each field has unique characteristics that can impact yield.
  • Utilize crop removal rates to determine crop nutrient needs.  Crop removal rates can be found in the new Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa (Tables 15 and 16), available at your local Extension Office.
  • Start with a recent soil test.  If your soil test levels are in the maintenance range or higher, 2021 may be a good year to “borrow” from your soil nutrient bank.

As an example, a 150-bushel corn crop will remove about 55 pounds of P2O5 per acre in the harvested grain.  This would result in a reduction in the soil test level of approximately 3 ppm.

Current budget analyses indicates favorable returns for soybeans compared to corn but crop price change and harvest yields may change this outcome. These projections are based on OSU Extension Ohio Crop Enterprise Budgets. Newly updated Enterprise Budgets for 2021 have been completed and posted to the Farm Office website: https://farmoffice.osu.edu/farm-mgt-tools/farm-budgets

 

Corn and Soybean School: Q and A on Corn Disease Management with Fungicides

On Feb 11, 2021, I gave a talk entitled “Management of Gibberella ear rot and Vomitoxin in Corn with Fungicides: Lessons Learned from Head Scab” as part of the 2021 Virtual Corn and Soybean School. I summarized years of fungicide efficacy research on head scab, a disease of wheat caused by the same fungus (Fusarium graminearum [Gibberella zeae]) that causes Gibberella ear rot (GER) in corn. Head scab and vomitoxin in wheat have been more widely studied than GER and vomitoxin in corn, as a result, a lot more is known about fungicide efficacy against scab/vomitoxin than against GER/vomitoxin. I therefore used lessons learned from head scab research, coupled with data from a limited number of GER fungicide efficacy studies to provide guideline on GER and vomitoxin management in corn. More than 220 people attended the 40-min-long program, asking questions covering various aspects of corn pathology. Below are more complete responses to several of these questions:

Q: How do you explain high vomitoxin levels in grain with no apparent ear rot observed?  Can drought stress alone be a culprit?

A: Infection of the ear, development of visual symptoms (ear rot), and contamination of grain with vomitoxin all depend on weather conditions during the weeks after silk emergence. Once the fungus enters the ear via the silks (infection) and begins to colonize the developing grain, it produces vomitoxin, even if subsequent weather conditions are not favorable for mold and ear rot to develop on the outside of the ear. This is particularly true if infections occur late and conditions become relatively dry and unfavorable for visual symptoms to develop.

Q: It looks like the triazoles are doing the work on VOM, more than strobies, is this correct?

A: Pulling from my years of experience with head scab and a limited number of fungicide efficacy studies on Gibberella ear rot and vomitoxin in corn, I would be more inclined to recommend a triazole than a strobilurin fungicide for Gibberella ear rot and vomitoxin control in corn. Miravis Neo (a combination fungicide of a triazole, an SDHI, and a strobilurin) also looks promising.

Q: Is there any relationship between using a strobilurin for vomitoxins in corn compared to what is found in wheat?

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Burndown Herbicides for No-till Wheat

Source:  Mark Loux, OSU

Herbicide options for burndown of existing weeds prior to planting of no-till wheat include glyphosate, Gramoxone, Sharpen, and dicamba.  Among these, the combination of glyphosate and Sharpen probably provides the best combination of efficacy on marestail, flexibility in application timing and residual control.  Dicamba labels have the following restriction on preplant applications – “allow 10 days between application and planting for each 0.25 lb ai/A used”.  A rate of 0.5 lb ai/A would therefore need to be applied at least 20 days before planting.  We do not know of any 2,4-D product labels that support the use of 2,4-D prior to or at the time wheat planting.  There is some risk of stand reduction and injury to wheat from applications of 2,4-D too close to the time of planting.  Liberty and other glufosinate products are also not labeled for use as a burndown treatment for wheat.  Sharpen should provide limited residual control of winter annuals that emerge after herbicide application, and the rate can be increased from 1 to 2 oz/A to improve the length of residual.  Gramoxone should also effectively control small seedlings of marestail and other winter annuals.  Be sure to use the appropriate adjuvants with any of these, and increase spray volume to 15 to 20 gpa to ensure adequate coverage with Sharpen or Gramoxone.

There are several effective postemergence herbicide treatments for wheat that can be applied in November to control these weeds, in fields where preplant burndown treatments are not used.  The most effective postemergence treatments include Huskie, Quelex, or mixtures of dicamba with either Peak, tribenuron (Express etc), or a tribenuron/thifensulfuron premix (Harmony Xtra etc).  We discourage application of 2,4-D to emerged wheat in the fall due to the risk of injury and yield reduction.

2020 Ohio Wheat Performance Test

Source:  Laura Lindsey, Matthew Hankinson, OSU

Yield results for the 2020 Ohio Wheat Performance Test are online at: https://www.oardc.ohio-state.edu/wheattrials/default.asp?year=2020

The purpose of the Ohio Wheat Performance Test is to evaluate wheat varieties, blends, brands, and breeding lines for yield, grain quality, and other important performance characteristics. This information gives wheat producers comparative information for selecting the varieties best suited for their production system and market. Varieties differ in yield potential, winter hardiness, maturity, standability, disease and insect resistance, and other agronomic characteristics. Selection should be based on performance from multiple test sites and years.

In fall 2019, wheat was planted at four out of the five locations within 10 days of the fly-free date. Due to poor soil conditions, wheat was planted in Wood County 21 days after the fly-free date; however, wheat grain yield averaged 99.5 bu/acre at that location. Wheat entered dormancy in good to excellent condition. Early season wheat growth and development were slower than previous years due to cool temperatures and above average precipitation. Harvest conditions were favorable and harvest dates average. Results from Union County were not included in this report due to extreme field variability caused by high rainfall. Overall, grain test weight averaged 58.8 lb/bu (compared to an average test weight of 55.0 lb/bu in 2019). Across the Wood, Wayne, Darke, and Pickaway locations, grain yield averaged 93.8 bu/acre.

True Armyworm Infestations

Source: Andy Michel, Curtis Young, CCA, Kelley Tilmon, OSU

 

As you scout your fields this week be on the lookout for this pest!

 

We received many reports of true armyworm infestations in wheat, barley, and corn. These are black or green caterpillars with stripes along the side and orange heads.  In the spring, true armyworm moths migrate from the south and lay eggs in grasses such as forage and weed grasses, winter wheat and barley, and rye cover crops.  When the eggs hatch, the larvae can significantly damage wheat and barley before then moving to young corn. Usually, moth flights occur in April, but we may have had a second peak the first or second week of May—it’s likely the caterpillars feeding now are from this later flight. Right now, wheat, barley, and corn should be inspected for true armyworm populations. Armyworms like to hide during the day and feed at night, so scouting should occur at dusk or dawn, and/or on cloudy days.

Corn: True armyworm in corn cause the most damage when planted in no-till grassy fields, such as a rye cover crop.  In this case, after feeding on the cover crop, the caterpillars shift onto the emerging corn.  The name armyworm comes from the caterpillars’ behavior of migrating en masse from one location to another. Thus, one should pay particular attention to cornfields adjacent to wheat fields that may have supported a high armyworm population, especially the first several rows into the cornfield. As the wheat matures and dries down, it could stimulate the caterpillars to move.

One may only need to treat the edge of the field closest to the wheat field from which the caterpillars are marching. If armyworms are found in a cornfield, check for the percentage of plants damaged in 5 sets of 20 plants.  If more than 10% of the stand has feeding damage, it may indicate a large infestation, and the field should be re-checked in a few days to see if defoliation is increasing. If defoliation has increased and plants have two or more caterpillars per corn seedling, an insecticide application may be necessary. However, if most larvae are longer than 1 inch, then much of the feeding is complete as the caterpillars will begin to pupate. Also, look for the presence of diseased (black and shriveled) or parasitized caterpillars (having a few or several small, white egg cases on their body)—if found, do not include them in your counting.

If defoliation exceeds 50%, even a rescue treatment may not recover the field without a significant impact on yield.  According to the Handy Bt Trait Table (https://agrilife.org/lubbock/files/2020/02/BtTraitTable_FEB_2020.pdf), only the Vip3A (e.g., Viptera) Bt trait is effective against true armyworm.  Insecticidal seed treatments may offer some control but can be overwhelmed with high populations. Plus, insecticidal seed treatments last only about 4-6 weeks after planting.

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Winter Wheat Stand Evaluation

Source: Laura Lindsey, OSU Extension

Between planting in the fall and Feekes 4 growth stage (beginning of erect growth) in the spring, winter wheat is vulnerable to environmental stress such as saturated soils and freeze-thaw cycles that cause soil heaving. All of which may lead to substantial stand reduction, and consequently, low grain yield. However, a stand that looks thin in the spring does not always correspond to lower grain yield. Rather than relying on a visual assessment, we suggest counting the number of wheat stems or using the mobile phone app (Canopeo) to estimate wheat grain yield.

Wheat stem count method. Wheat stems (main stem plus tillers) should be counted at Feekes 5 growth stage (leaf sheaths strongly erect) from one linear foot of row from several areas within a field.

 

 

 

Canopeo mobile phone app method. Canopy cover should be measured at Feekes 5 growth stage using the mobile phone application, Canopeo (http://canopeoapp.com). After accessing the app, hold your cell phone parallel to the ground to capture three rows of wheat in the image and take a picture. The app will convert the picture to black and white and quantify (as a percentage) the amount of green pixels in the image. For example, the screen shot here shows 44.86% canopy cover. (Keep in mind, this app will quantify anything green in the image. So, if you have a weedy field, the weeds will also be quantified in the canopy cover estimate.) Continue reading →