2017 Wheat Quality Tour report

The 2017 Wheat Quality Tour took place during May 1 – May 4. More than 70 people actively scouted hundreds of Kansas wheat fields in six routes (Fig. 1), leaving Manhattan and heading to Colby on day 1, from Colby to Wichita on day 2, and finally from Wichita to Manhattan on day 3. The overall 2017 production estimate for Kansas resulting from the tour was 282 million bushels of wheat.

Figure 1. Representation of the six routes (purple, green, pink, yellow, blue, and black) explored during the wheat quality tour. Image courtesy: Wheat Quality Council.

 

Despite the high production estimate resulting from the tour, the Kansas wheat crop is currently facing many challenges, as described below, and will have to be exposed to near perfect weather conditions to be able to produce the 282 million bushels estimated.

Freeze damage

Several wheat fields sampled in the north central region of Kansas (Clay, Cloud, Republic, Saline, eastern Mitchell and Jewell counties, and surrounding region) were showing early signs of freeze damage. These included outside symptoms such as purpling discoloration (Fig. 2) and, when more closely inspected, whitish and mushy anthers (Fig. 3). The cold stress slows down crop growth and, consequently, sugars being transported within the plant accumulate in particular regions of the canopy, causing the purple discoloration. In other words, there is a source/sink imbalance inside the plant, where the source (leaves) has produced sugars while the sink (developing grains or growing points) temporarily slowed down due to the cold, thus promoting sugar accumulation and purpling. Mushy and whitish anthers are a consequence of direct cold damage to the male part of the wheat flower, which is particularly sensitive to cold during anthesis.

Figure 2. Photosynthetic sugars accumulated on wheat heads due to cold stress. The imbalance between a great amount of sugars produced by the source (leaves) versus a decreased sink strength due to the cold (temporary decrease in grain development) causes sugars to build up in particular regions of the plant. Photos from Clay Co., KS, by Romulo Lollato, K-State Research and Extension.

 

This freeze damage is most likely a result of the freeze on the morning of April 27, when temperatures in north central Kansas were held below freezing for as much as 7.3 hours and reached a low of 24 degrees in Republic Co. (for an in-depth assessment of the April 27th freeze, please check the article “Effect of freeze on April 27, 2017, on wheat in boot and early heading stages”, available here). As this was a recent event, the full extent of the freeze damage is still uncertain, but we advise producers in the north central region to carefully scout for freeze damage before investing in the crop with any management practice, such as application of foliar fungicides. If the crop has been damaged by freeze, yield losses might be severe enough that fungicide applications might not be justified.

Figure 3. Comparison between wheat anthers possibly affected by freezing temperatures (left panel, anthers characterized by a whitish or light green color and a mushy aspect, photo from Cloud Co.) and healthy anthers (right panel, anthers with a darker green color and more turgid aspect, photo from Mitchell Co.). Photos by Romulo Lollato, K-State Research and Extension.

 

Snow Cover

As we moved into western portions of Kansas, into Graham Co. and surrounding region, it was hard to estimate wheat yields due to a heavy layer of snow covering the crop. This snow had fallen during the period April 29 – May 1, and was still covering the crop in the evening of May 2 and morning of May 3. For more details on the snowfall event, please read the eUpdate article “Effects of snowfall April 29 and May 1, 2017 on Kansas Wheat” here).

The snow was covering the majority of the fields, with a few isolated pockets of plants not covered by it (Fig. 4.). The thick layer of snow cover likely protected the wheat from the damaging effects of 40-60 mph winds observed during the period and from colder temperatures than the 30-32 F generally observed under the snow. Still, the wheat laying underneath the snow had anywhere from 20 to 50% broken stems (Fig. 4), depending on fields and portions within each field. Thus, yield losses from this event are still uncertain and represent the largest unknown within the production estimate from the 2017 Wheat Quality Tour. The area affected by snow represents roughly 40% of the wheat area grown in Kansas and depending on how the wheat recovers from snow, the final actual production numbers might have a great range. The two major consequences of the snow to the wheat crop were:

  1. Mechanical damage resulting from the snow weight breaking stems

 

  1. Possible cold damage from long exposure to temperatures at or below freezing

 

Figure 4. Wheat field lodging flat on the ground and covered in snow (upper left panel), broken and bent stems are a result of the heavy wet snow storm (lower left panel), and developing wheat head indicating the wheat stage of development (flag leaf emergence/pre-boot). Photos taken in Sheridan Co., by Romulo Lollato, K-State Research and Extension.

 

Wheat streak mosaic

The majority of the fields visited west of Mitchell / Osborne counties had some level of wheat streak mosaic. In some fields, disease levels were minor and chances are that the crop will succeed in producing a decent yield despite the infection. As the tour moved into southwest Kansas, however, the extent of the damage by wheat streak mosaic virus was worsened, especially in Greeley, Hamilton, Wichita, Kearney, and Lane counties. Yield losses by wheat streak mosaic can be severe; which might result in greater area abandonment than the historical average.

One example of a field likely damaged by the snow and with a severe wheat streak mosaic infection is shown in Figure 5. For more details on wheat streak mosaic spread across Kansas, please see accompanying article in this issue of the Agronomy eUpdate.

Figure 5. Wheat field with frozen layer of ice / snow near the corner, and severe wheat streak mosaic infection (inset panel). Photos taken in Greeley Co. by Romulo Lollato, K-State Research and Extension.

 

Nitrogen deficiency

Another common theme observed in the 2017 Wheat Quality Tour was nitrogen deficiency. Many wheat fields had a good yield potential, as function of large number of heads per area and head size; however, many fields were showing signs of N deficiency which will result in decreased grain yields. The yield potential of these fields was being expressed in some cow pocks of high N fertility present in the fields (Fig. 6), but the average field conditions was much poorer. Nitrogen deficiency was more commonly seen in the central portion of the state.

Figure 6. Nitrogen deficiency, a common theme of the 2017 Kansas wheat crop. Photo taken in Kiowa Co., by Romulo Lollato, K-State Research and Extension.

 

A few possible explanations for such a common incidence of N deficient fields are:

  1. A depleted soil profile at wheat sowing, as a consequence of the high yields from the 2016 wheat or summer crops. Greater yields result in greater nutrient removal from the soil, depleting the reserves for the current wheat crop.
  2. High growing season precipitation totals, which in parts of the state already surpasses 30 inches. The high precipitation totals could result in N leaching down the soil profile, ultimately out of the root zone.
  3.  Low N input by producers due to low wheat prices.

Stripe rust and leaf rust

While the 2017 tour encountered stripe and leaf rusts much less frequently than in previous years, it was present in many fields sampled in the central portion of the state. The greatest concern observed in the tour were cases in which the crop is already past the fungicide application window, and the disease is now at the flag leaf (Fig. 7). In these cases, producers don’t have the option to control the disease anymore. This situation occurred more frequently in the southern tier of counties, where the crop is further along in development. Northern counties are mostly within the application window for foliar fungicides. For more details on stripe rust and leaf rust distribution in Kansas, please refer to the accompanying article in this issue of the Agronomy eUpdate.

Figure 7. Wheat in between ¼ and ½ berry, past the fungicide application window and showing stripe rust on the flag leaf. Photo from Pratt Co., taken by Romulo Lollato, K-State Research and Extension.

 

Water logging

South central Kansas is also facing an additional problem, which is water logging. Many fields in Sumner and Sedgwick counties are now showing symptoms of water logging, which often consist of portions of the field where the entire wheat plant is dead due to anaerobic conditions. These portions of the field are often white and will not produce grain yield. The high incidence of water logged fields is the result of high total growing season precipitation coupled with poor drainage capacity of soils in the region.

The above factors are challenges that the 2017 Kansas wheat crop is currently facing. While all should contribute to restricted wheat yields to a certain extent, the largest uncertainty when estimating wheat production at the state level is whether the crop in western Kansas will be able to recover from the snowfall and still produce a decent yield.

 

Romulo Lollato, Wheat and Forages specialist
lollato@ksu.edu

Erick DeWolf, Extension Wheat Pathologist
dewolf1@ksu.edu