Fusarium Head Blight and Management in Wheat
- Premature whitening or bleaching of the wheat head is a primary symptom of Fusarium head blight (FHB).
- FHB is favoured by humid growing conditions during flowering and the early stages of kernel development.
- FHB management requires an integrated approach, including seed selection, crop rotation, and fungicides.
Disease and Significance
Fusarium head blight (FHB), also called head scab, is primarily caused by the fungal pathogen Fusarium graminearum. FHB can be a devastating disease resulting in premature bleaching of the wheat head, yield loss, low test-weights, poor seed quality, and contamination of the grain with the mycotoxin deoxynivalenol (known as vomitoxin, or DON), which may cause significant health problems to domestic animals and humans.1
FHB symptoms first occur shortly after flowering, and are confined to the wheat head, grain, and may occasionally be
observed on the peduncle (stem near the wheat head). Bleaching or premature whitening is a diagnostic symptom of FHB.
Bleaching generally appears near the middle of the head, on the first florets to flower, but can occur anywhere on the
head (Figure 1).1 Symptoms may begin with one or more spikelets, and over time the bleaching may progress throughout the entire head. Infected heads are easily visible in a green field (Figure 2). If the peduncle is infected early, the entire head will become sterile. Infected kernels that are bleached and shriveled are commonly referred to as
Fusarium-damaged kernels, scabby kernels, or “tomb-stones” (Figure 3).2 In wet and humid environments, pink to orange coloured spore masses (sporodochia) may be visible on infected spikelets. Later in the growing season, bluish-black spherical bodies may appear on the surface of affected spikelets, these are the sexual structures of the fungus known as perithecia (Figure 4).3
Figure 1. Wheat heads showing various degrees of FHB bleaching. G. J. Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org.
Figure 2. Bleached fusarium infected heads are easily visible in a green field. Donald Groth, Louisiana State University AgCenter, Bugwood.org.
Figure 3. Wheat “tombstone” kernels on the left versus healthy seed on the right. Bob Johnston, Montana State University, Bugwood.org.
Figure 4. Late-season symptoms of FHB may include bluish-black spherical bodies on affected spikelets. Howard F. Schwartz, Colorado State University, Bugwood.org.
F. graminearum overwinters on the infected residue of a host plant. Humid weather the following spring promotes the production and dispersal of spores. Wheat is susceptible to FHB infection at flowering (Feekes 10.5) through early dough stage (Feekes 11.2).1 Infection risk factors include:
- Excessive moisture before and during flowering
- Warm, wet spring
- Planting wheat following a host crop
- No-till or reduced tillage
- Susceptible cultivars
Disease management for FHB requires an integrated approach. This includes selecting tolerant wheat varieties, planting
high-quality seed, crop rotation, irrigation management, and timely application of fungicide.1
Using high-quality seed and selecting cultivars with tolerance to FHB is an important step in mitigating disease
development. Planting cultivars with differing flowering dates will also help to lessen the risk of FHB.
Crop rotation to a non-host crop, such as alfalfa or soybeans, can reduce the disease inoculum over time.1 Corn,
sorghum, and wheat are all host crops of the fungus. Corn is the primary host crop of FHB, therefore planting wheat
after corn should be avoided. In corn, the fungus is commonly known by its sexual phase, Gibberella zeae, which causes Gibberella stalk and ear rot. While wheat following corn is the primary concern, wheat following scabby wheat should also be avoided.
In irrigation systems, the crop canopy should be allowed to completely dry between irrigations to help manage disease
The optimal timing of fungicide application is at approximately 15% flowering (Feekes 10.5.1 or Zadoks 60) though
applications made shortly after could still provide a benefit if environmental conditions are favourable for disease
development. Thorough coverage is essential for maximum suppression of the fungus. Triazole fungicides are recommended
to manage FHB.1 Fungicides containing a strobilurin should not be used to manage FHB as these fungicides can increase the level of DON in the grain.4 As always, remember to check the product label for specific application instructions, including the pre-harvest interval, when applying any fungicide to your wheat crop. In Canada, Bayer fungicides that are labelled for suppression of FHB include Prosaro® XTR and Prosaro® PRO.
Figure 5. Wheat beginning to flower. Optimum time to apply fungicide for FHB management. Flowering Wheat_Todd Drummond
1 Wise, K., Woloschuk, C. and Freije, A. 2015. Fusarium head blight (head scab). Purdue Extension.
2 Wegulo, S.N, Bockus, W.W., Nopsa, J.F.H., Peiris, K.H.S., Dowell, F.E. 2013. Integration of fungicide
application and cultivar resistance to manage fusarium head blight in wheat.https://www.intechopen.com/books/fungicides-showcases-of-integrated-plant-disease-management-from-around-the-world/integration-of-fungicide-application-and-cultivar-resistance-to-manage-fusarium-head-blight-in-wheat
3 Schmale, D. and Bergstrom, G. 2003. Fusarium head blight (FHB) or scab. 2010. http://www.apsnet.org.
4 Telenko, D. 2020. Foliar diseases of wheat and fusarium head blight (scab) management. Purdue
5 Wegulo, S., Jackson, T., Baenziger, S., Carlson and M., Nopsa, J. 2008. Fusarium head blight of
wheat. EC 1896. University of Nebraska Extension. http://extension.unl.edu/
Web sources verified June 2021.
For additional agronomic information, please contact your local Bayer representative.
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
Tank mixtures: The applicable labeling for each product must be in the possession of the user at the time of
application. Follow applicable use instructions, including application rates, precautions and restrictions of each
product used in the tank mixture. Bayer has not tested all tank mix product formulations for compatibility or
performance other than specifically listed by brand name. Always predetermine the compatibility of tank mixtures by
mixing small proportional quantities in advance. Bayer, Bayer Cross and Prosaro® are registered trademarks of Bayer Group. Used under license. All other trademarks are the property of their respective owners. Bayer CropScience Inc. is a member of CropLife Canada. ©2021 Bayer Group. All rights reserved. 5023_S1