The Growing Point | June 2019
Fusarium head blight – Protect yourself with the risk forecast tool
If you farm in Alberta, Fusarium graminearum is a yearly concern that can lead to fusarium head blight (FHB) in cereals. Between Fusarium damaged kernels (FDK) and deoxynivalenol (DON), FHB can lead to significant impacts to your crop’s yield, quality and grade. In some cases, it can render your crop unmarketable. Once flag leaf emerges, it is important to be on the lookout for environmental conditions conducive to fusarium development. Attention to this can help you protect your crop and help you make a decision on fungicide application.
Fusarium overwinters in grain and crop residue in the field. Those fields with a shorter rotation will be at higher risk of infection due to a build-up of infected crop residues. Given temperatures of 10-30oC and moisture, the fusarium fungus becomes active eventually sporulating to produce fruiting structures known as perithecia on old crop residues. Within these perithecia, the wind-dispersed spore stage known as ascospores is produced. There can also be sporulation and subsequent development of the rain-splashed spore stage known as macroconidia. Spore germination requires at least 12 hours of high humidity or rainfall and temperatures within the range of 10-30°C. However, optimum temperatures are around 25°C. Although your greatest risk of infection and impact occurs during anthesis (flowering), infection can occur at any point the head is out of the boot. Infections that occur during anthesis are more likely to cause FDK, especially in wheat. Infections that occur outside of anthesis timing may not cause FDK, however they can still lead to high levels of DON within your grain.
Image of FHB on wheat head indicated by premature kernel ripening and salmon pink/orange material between infected florets
Image of FHB on barley head indicated by brownish discolouration. Barley FHB can often be mistaken with spot blotch/kernel smudge infection or even hail damage. A key indicator with barley is pinkish/orange or whitish growth on affected head portions. Images courtesy of Dr. Kelly Turkington Agriculture and Agri-Food Canada
Between the cost of application and mitigating risk of fungicide resistance through overuse, the need to apply fungicides only when truly necessary is vital in sustainable agriculture. Reviewing weather in relation to temperature, rainfall and humidity over an extended period of time to determine your regions risk of FHB can be a challenge. This is why the Fusarium Head Blight Risk Tool was developed for Alberta producers. By selecting the weather station closest to you, you can see Fusarium Disease Severity Value for that area. The system runs from June 1 – August 15. Feedback from this tool will assist with your decision on whether to spray for FHB or not. Keep in mind, this information is only part of the decision-making process. It is important to also ground truth the weather information you are seeing. Walk your fields and determine if moisture in the canopy is representative of the FHB risk tool – for example, if the soil surface and crop canopy are still wet well into mid-afternoon, then likely conditions are favourable for disease. You will also want to consider field history of FHB infection, variety susceptibility, crop stage and value of potential crop. Once all of the factors are taken into consideration, an informed decision on fungicide application can be made. A decision table considering these factors along with other information can be found here.