Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu
Wheat harvest is underway. As typical, there is no magic bullet that will guarantee a perfect crop. Each field and situation differs as a result of variety, environment, production practices, and presence or absence of pathogens. Although this is the case, we can always learn something from each season. What can we take home this year?
1. Know your variety.
We all know varieties differ in yield potential, but they also differ in resistance to important diseases. This season we had elevated levels of stripe rust occur early in some parts of MD and DE. In cases where susceptible varieties were planted and the disease was present nearby or detected in fields chemical intervention was likely called for and may have protected significant losses of yield. However, note that I state susceptible varieties. Field days in DE and MD this year provided those in attendance with excellent examples of the differences between susceptible and resistant varieties, with good resistant varieties showing no or few stripe rust symptoms, even under extreme pressure (Figure 1). If you had a good resistant variety or the disease was not detected in your region or field you may have been able to save on the additional costs. Knowing your varieties and the strengths or weaknesses in terms of disease resistance can help you and your bottom line in the long run. A good disease resistance package can save you input costs and headaches.
Figure 1. Photos from a DE variety trial site showing difference in stripe rust susceptible (left) vs resistant (right) varieties. Photos taken on same day.
2. Watch your fields.
Scouting fields is essential in wheat production and allows not only for timely application of fungicides if needed, but avoidance of fungicides if not needed. In addition, scouting helps ensure proper product timing. Again, this all helps your bottom line in the long run.
3. Powdery mildew resistance ratings need to be modified.
With the defeat of the pm6 resistance gene we have seen some varieties that were listed as having good to excellent resistance to powdery mildew performing poorly in the presence of our wheat powdery mildew population. Check regional university variety trials for pm performance data that more accurately reflects our situation. Not all varieties have issues, but a few commonly planted varieties significantly underperformed.
4. Leaf blotch complex continues to be our most common disease and it’s no joke.
Stagonospora leaf and glume blotch, tan spot, and speckled leaf blotch continue to be detected to some degree in most fields. These are residue-borne diseases that spread from old small grain or grassy weed residue up the plant. Stagonospora glume blotch was especially prevalent this year and if it infected your glumes before soft dough, you may have taken a yield and quality hit (Figure 2). Resistance to leaf blotch complex or glume blotch should be the ranked just below fusarium head scab resistance when selecting a variety.
Figure 2. Difference in size of heads with glume blotch (left) and without disease (right).
5. Did it pay to (insert product, practice here)?
This continues to be the most commonly asked question. Unfortunately, the only way to truly answer this question is to leave some untreated areas for comparison. This doesn’t need to be a large area, but enough to assess yield and disease. This practice can be particularly helpful if you are trying out a new practice or product or looking at ways to improve your bottom line. Without a check, all you have is yield data, which will be influenced by all the inputs and issues that particular field dealt with over the course of the season. For example, let’s say we had 2 varieties (A and B) which differed in stripe rust resistance. While we are pretending, let’s say everything else about these fields is exactly the same. Finally, we will assume that it was cool and wet and stripe rust moved into these fields early, around flag leaf emergence. If we applied a fungicide to field A and B only at flag leaf and compared yields we see no difference. Did the application work? In the susceptible variety it may have, whereas in the resistant variety it may have been unneeded. You wouldn’t know this without a small check. One piece of hard data is more valuable than a slew of speculation.
6. Fusarium head scab variety data will be available.
We have the Fusarium head scab nursery up and running in Maryland (Figure 3.). Keep an eye out for preliminary data soon. Remember that the only reliable source of Fusarium head scab resistance and performance in wheat comes from misted nurseries. Keep an eye out for the result from this misted nursery, as well as regional variety trial results.
Figure 3. Photos from the MD misted nursery showing a FHB susceptible variety (top) and a moderately resistant variety (bottom). Both pictures were taken on the same day.
Bottom line: Pay attention to your wheat from the time you purchase your seed until harvest.