As our wheat crop progresses through spring, the risk of yield limiting disease occurrence increases. Often, we consider wheat good to go after a fungicide application at flag leaf. However, this is not the case. This article will focus on symptoms, disease mitigation, and fungicide treatment options for the control of Fusarium Head Blight.
What is Fusarium Head Blight (FHB)?
At flowering, Fusarium head blight (FHB), also called Head Scab, needs to be on our radar. FHB is caused by the fungus anamorph Fusarium graminearum which affects many other cereal grains as well. This genus is also responsible for seedling blight and crown rots in wheat. Including stalk and ear rots in corn.
When does FHB Appear?
Fusarium head blight appears later in the growing season, making symptoms easy to overlook or mistake for other issues with symptoms occurring as flowering initiates. Infected spikelets appear bleached and turn tan in color, which may be misidentified as frost damage. If an initial infection occurs lower on the stem or peduncle, the entire head may become affected and show signs of infection.
What does FHB look like?
Salmon colored spores and mycelium may be seen on the margins of infected spikelets 7 days after infection. As the disease progresses, infected spikelets will produce kernels that are off in color, shrunken, and scabby in appearance.
Diseased kernels are less desirable for their light test weight and lower milling and baking qualities. Mycotoxins produced by FHB include vomitoxin and deoxynivalenol (DON) that limit affected grain for animal consumption.
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What happens if FHB is left untreated?
Untreated infections can progress into dark purple to black fruiting bodies visible on matured wheat. It is important to test all grain from fields that may have been infected by FHB, since not all infected kernels will produce high levels of mycotoxins. The inverse can also occur, where some normal kernels may show greater levels of mycotoxins.
How do environmental conditions affect FHB infections?
Environmental conditions greatly impact the severity of the infection. Fusarium head blight favors wet and humid conditions immediately prior to flowering or during the flowering process.
Optimal temperatures within the range of 75-85℉ accelerate disease progression. No-till corn rotations should be scouted judiciously as FHB inoculum hosts on long-lasting corn residue.
How do I reduce the risk of FHB infection?
Tillage to deep bury residue is a key step in reducing the risk of infection. Drilling wheat behind a soybean crop, when possible, as well as several years between wheat crops are good tactics in mitigating FHB. Wheat varieties have different levels of susceptibility to FHB.
Understanding placement of resistant and susceptible varieties in your operation is critical for management. Ensure the selected variety has no Fusarium fungus present to lessen the occurrence of crown or root rot.
Fungicides to use for FHB infection
If the potential for Fusarium head blight is great in your wheat fields due to environmental conditions, there are a few fungicide options available. Triazole fungicides (FRAC Group 3), are provide the greatest efficacy when it comes to controlling FHB. Actives in the triazole group include prothioconazole, tebuconazole, or metconazole.
What fungicides to avoid with FHB infection
When selecting fungicides, it is recommended to avoid the strobilurin class (FRAC Group 11). Remember, coverage is key. Ensure applications are made with 10-20 GPA (ground) or 4-5 GPA (aerial). Use an appropriate nozzle to produce fine to medium-sized droplets. Include an appropriate adjuvant to increase coverage and uptake.
Factors to control FHB
Like many diseases, it is not a solo approach to managing Fusarium head blight. Below are several factors to keep in mind when it comes to controlling FHB.
- Plant Quality Seed
- Manage Residue
- Avoid Drilling Behind Corn
- Scout Vigilantly
- Plant Resistant Varieties
- Use Labeled Fungicides
The Takeaway
Whether FHB is an annual occurrence or new to your area, there are several practices that can be used to effectively manage the disease. If you have any questions or are looking for guidance, please consult any of your local Agronomic Sales Enablement Team members or your local Simplot Grower Solutions Crop Advisor.
Authors
Brice Bunck, Midwest
Kevin Caffrey, Eastern Cornbelt
Chris Carpenter, Great Plains
Darrin Roberts, Northern Plains
Click to read more about the authors
