By Jana Rumpel, Crop Lab and Field Technician and Alireza Akhavan, PhD, AAg, Provincial Plant Disease Specialist, Crops and Irrigation Branch, Regina
Fusarium Head Blight (FHB) is a fungal disease that affects cereals and some forage grasses. It is also known as scab. Saskatchewan's most affected crops are durum, spring wheat and barley. This disease is caused by different species of the fungus Fusarium. FHB can cause many crop production issues such as a lower yield, poorer grade and quality. Fusarium infection favours warm, moist conditions during anthesis (flowering). Symptoms of FHB can occur on just a few spikelets on a head, to sometimes even encompassing the entire head. Visible symptoms may be noted first around the end of July to the beginning of August. FHB can be recognized as early bleaching of the spikelets. If the disease occurs at early flowering, the kernel may ultimately die; if it is later in the flowering period, it may become a Fusarium Damaged Kernel (FDK).
FHB is a challenging disease to manage. To control it, you will need to use an integrated approach. This can include using seed treatment, crop rotations, growing cereals on the same piece of land once every three years and selecting a crop variety less susceptible to FHB. However, in cases where disease pressure is high, producers may need to decide whether to use a fungicide to further suppress the pathogen.
There is a relatively new FHB Risk Mapping Interactive Tool that can assist producers in determining the risk of their crop getting infected based on the weather patterns of your area, crop variety, type of cereal and seeding date. This tool provides information on the risk of FHB, FDK and Deoxynivalenol (DON) across the agricultural region.
When using this tool, we advise you make field observations to confirm the data presented on this tool, as models are not always 100 per cent accurate. Also, note that the risk model algorithms used for each crop and risk type were developed independently. Therefore, differences in the models' predictions for a given location and day are not directly comparable for each crop and risk type.
Your fungicide of choice for FHB is usually the most effective when you can protect the opening florets. In wheat, apply within the range of at least 75 per cent of heads on the main stem fully emerged to when 50 per cent of the heads on the main stem are flowering. For barley, apply within the range of at least 70 per cent of heads on the main stem fully emerged to three days after full head emergence. If the label of the product of your choice recommends otherwise, follow those instructions on the label. Due to the difficulties of trying to spray a vertical target, it is essential to always use the required amount of water to spray and consider using a higher amount as per the product label. For best results, you should angle the nozzles on the sprayer forward, maintain low boom heights and most importantly, maintain over 10 to 20 gallons per acre unless the label of the product recommends otherwise.
![An infographic explaining spray timing for fusarium head blight in wheat: aim for the crop stage when at least 75 per cent of the heads on the main stem have fully emerged to 50 per cent of the heads on the main stem are in flower.](https://www.saskatchewan.ca/-/media/images/agriculture/cpn/2024-05/figure-2.jpg?h=169&w=300&hash=F21C72BBBF4AB2EE45EB1F35D41E9C38)
The next consideration for FHB control will be at harvest. You can adjust the combine’s air speeds and openings to blow out the lighter fusarium damaged kernels. Using this method, you should not plant cereal on that land for the next two years as the pathogen can survive by overwintering on the seed within the soil. If you also clean your grain post-harvest to remove the shrunken and lighter kernels, you have a better chance at reducing your grade losses and DON; however, this is not a guarantee. The DON may still be present in the grain particularly if it is a severely infected crop.
Please visit our website for more information on Fusarium Head Blight.