By Allie Noble, AAg, Crops Extension Specialist, Prince Albert
Fusarium Head Blight (FHB) is an economically damaging disease that affects cereals grown throughout Western Canada. Crops infected with FHB produce mycotoxins and can result in major downgrading. Unlike other diseases affecting cereal crops, FHB symptoms appear when it is too late to apply a fungicide. To find out more about FHB in cereal crops read this article.
It is important to assess the risk of FHB ahead of time to gauge whether or not spraying fungicide is warranted. To assess the FHB risk, you should also read the article 'Fusarium Head Blight Risk Maps' in this issue of CPN. Once a risk assessment has been completed and the decision is made to apply fungicide, you also need to consider the following:
- Selection of fungicide. There are several different fungicides on the market that can be used for FHB control. Fungicides used for FHB are only rated for suppression, so, application will reduce the severity of infection, if done properly, but will not completely eliminate FHB. Currently, most fungicides used for FHB suppression are from fungicide group 3. One new option introduced, is called Miravis Ace, which contains two active ingredients that are from fungicide groups 7 and 3. Several strategies should be used beyond fungicide itself to avoid creating resistance to our current fungicide sources and fungicides alone will not sufficiently control FHB.
- Timing for spray. Application time is critical as the infection window is long, from emergence to soft dough stage, but the crop is the most susceptible at flowering. Due to the highest susceptibility of the crop at flowering the spray window is very narrow. Spray timing is when 75 per cent of the main heads have emerged and 50 per cent of the heads are flowering as referenced in Figure 1. A plant is flowering when there are small yellow anthers hanging off the head, this will start in the middle of the head and work its way outwards. Barley is an exception as begins to flower while still in the boot but spraying should be timed for when the majority of heads have emerged from the boot.
- Method of Application. Fungicide application efficacy can be reduced due to the architecture of cereal heads as the upright heads are hard target to hit. Many cereals have awned varieties that create a barrier that can pick up small droplets that were intended to hit the targeted heads. Adequate coverage of the head with fungicide is required to have effective suppression. Dr. Tom Wolf has summarized the following key points when spraying for FHB:
- Angled sprays are essential, angle nozzles forward or use double nozzles
- Use coarse droplets
- Maintain low boom heights
- Slow travel speed is recommended to ensure fungicides reach the heads
- Optimum water volume is about 20 gpa (90 litres/acre), no less than 10 gpa (45 litres/acre)
To find details, please read sprayers101.
FHB prevention on the farm can come from many different strategies. An integrated approach to FHB control is the best approach as even the most effective of fungicide applications can only provide suppression of the disease. For more information on FHB:
- Contact your local Crops Extension Specialist; or
- Call the Agriculture Knowledge Centre at 1-866-457-2377.