Update From The Field: Stay Ahead of Wheat Diseases
Posted by Dave Dyson, Agronomist on May 28, 2019
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The wet weather of late is not only playing havoc on planting crops this year, but also fueling fungal spores that may damage existing crops. Due to the slow accumulation of growing degree days (GDD) the wheat is much farther behind in maturity than last year. As of May 20th, 2019, the wheat crop in central Indiana is at Feekes stage 10.1 (Figure 1). Historically at this date, the wheat would be within 10 days of full flower, Feekes stage 10.5 (Figure 2). In addition to the slow maturity, there are a few wheat diseases that you need to be aware of right now: Fusarium head blight (or head scab), strip and leaf rust, and Septoria leaf spot.
Figure 1: This picture taken near Walton, Indiana, on 5/20/19 shows the wheat head just emerging, Feekes stage 10.1, and leaf disease starting to develop on the flag leaf.
Figure 2: This picture near Walton, Indiana, taken on 5/22/18 shows the wheat crop was much farther along last year at this time. It shows wheat at Feekes stage 10.5 with the flowers open. This would be the correct time for a fungicide application for Fusarium head scab.
Early stages of many foliar diseases oftentimes present as leaf spotting on the wheat’s leaf (Figure 1), making identification difficult. Holding the flag leaf up to a light or the sky can be helpful in locating early foliar disease development. We want to catch diseases like rust or Septoria before they destroy the cells on the flag leaf. You can think of every cell on the flag leaf as a solar panel providing energy to a building. If someone starts destroying the individual solar panels with a hammer, the building will start losing power. A similar effect will occur in a disease-infected wheat plant; the more cells that are destroyed due to the presence of foliar disease, the less energy the plant will receive. The flag leaf constitutes about 75% of the effective leaf area that will feed the head and fill the grain.
One of the primary concerns right now is Fusarium head blight. This disease is caused by the fungus Fusarium graminearium. It infects wheat during the flowering stage and can only be prevented by an application of a fungicide during Feekes stage 10.5. Symptoms of Fusarium will appear as bleached spikelets on the head later in the season. Infection can lead to small or shriveled grain kernels. In addition to shriveled grain, this fungus produces mycotoxins such as deoxynivalenol (DON), which can accumulate in the infected grain. At harvest, if the DON level reaches 2ppm, elevators will start issuing a price penalty, and most will start rejecting wheat after the level reaches 5ppm. Controlling DON level both increases yield and helps in selling your crop overall.
There are only a few fungicides that control Fusarium head blight. We have used Caramba® by BASF or Prosaro® by Bayer with great results, and in my experience, any wheat treated with either of these two products has had DON levels within or below the acceptable range by the elevator. A new product, Miravis® Ace by Syngenta, has a wider window of application, and the trial data looks favorable thus far. Time will tell if it will perform as well as the other two. Once the wheat head is exposed, DO NOT apply any fungicide containing strobilurin. Studies have shown this may increase the DON levels in the wheat.
Applying OverPass® CF to the wheat at a rate of 1 gal/ac while applying your fungicide will boost seed set and increase test weight. The addition of OverPass CF contributes to a boost of nitrogen in the plant while also providing potassium, sulfur, and boron. OverPass CF provides a nice kick of energy for the wheat, especially after the slow and cool spring in which topdress applications of nitrogen may have washed away in heavy rains. This nitrogen may not have been fully utilized to result in rapid spring growth. The application of OverPass CF to wheat is equally as important as a fungicide application. The plant needs nutrients to support and increase grain fill as much as it needs the disease protection from a fungicide.
In conclusion, the environment is right for wheat diseases. It is important to scout your fields and protect yield potential by determining when and what type of fungicide to apply. To prevent Fusarium head blight in wheat, the fungicide has to be applied while the flower is open and being pollinated. The addition of OverPass CF to a fungicide application will boost seed set and increase test weight.
Contact your local Ag Advisor from The Andersons for timing and product recommendations.
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
© 2019 The Andersons, Inc. All rights reserved. Caramba is a registered trademark of BASF. Prosaro is a registered trademark of Bayer. Miravis is a registered trademark of Syngenta. OverPass is a registered trademark of The Andersons, Inc. All rights reserved.
