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Managing FHB in 2018

By Barb Ziesman PhD AAg, Provincial Specialist, Plant Disease, Regina

Fusarium head blight (FHB) is an important disease of cereal crops that causes yield losses and reduces grain quality through the presence of fusarium-damaged kernels and mycotoxins, such as deoxynivalenol (DON; also known as vomitoxin), which may make the harvested grain unsuitable for human or animal consumption. Durum and wheat are the most susceptible to FHB, but other cereals such as barley, oats, rye and canaryseed can also be affected.

FHB should be managed using an integrated approach that includes crop rotation, residue management to encourage decomposition and variety selection. These strategies influence the variety’s susceptibility to the disease and the amount of pathogen present in the field to cause disease.  These are preventative strategies and therefore must be completed prior to seeding the crop. During the growing season, the focus switches from FHB prevention to FHB management. Fungicides for FHB suppression can be applied when the crop is most susceptible to infection, during anthesis (flowering).

Fungicides need to be applied proactively prior to symptom development since FHB is a monocyclic disease (one infection cycle per season). FHB risk will not be consistent every year; as a result, fungicide decisions should be made annually and need to take into consideration the level of the pathogen present to cause diseases, the favourability of the environment (the biggest driving factor) and the economics of applying the fungicide.

Map showing fusarium head blight risk
FHB risk map for spring wheat crops flowering on
Friday, July 6, 2018
Fortunately, there are tools available to help. The Saskatchewan Wheat Development Commission works with Weather Innovations Network to deliver FHB risk maps for spring and winter wheat in June and July each year. These maps should be referenced daily as crops are at or approaching the susceptible stage (flowering). The risk maps should contribute to determining if a fungicide application is warranted.

Additionally, it is important to take into consideration the local weather conditions that can be missed on a large-scale map. Fusarium spores need 12 hours of high humidity to germinate and infect.

The history of FHB in the field or neighbouring fields will influence the risk of FHB development. The pathogen will overwinter in the field on infected crop residue. If the infected residue is present, the pathogen will be present to cause infection if the environment is favourable.

Understanding the risk is the first step, but it is also important to consider the economics. The cost of the fungicide and application should be balanced with the anticipated crop yield and value of the crop. These calculations should be conducted prior to the crop reaching flowering, so that you can quickly make a decision to make targeted and timely applications that fit the narrow application window.

The following risk assessment table can be used along with FHB risk maps to guide fungicide decisions.  

Assessing Fusarium Head Blight Risk in Saskatchewan 
Lower Risk 
Medium Risk  Higher Risk
Step 1

Predict Pathogen

Is Fusarium established here? 

Has wheat produced in this field been downgraded due to fusarium damaged kernels? 
No By a grade By >1 grade
Has >5% F. graminearum been isolated from wheat seed produced in this field? 
No > 4 years ago Within 4 years
Has >10% other Fusarium species been isolated from seed produced in this field? 
No > 2 years ago Within 2 years
Have any crops produced in this field experienced root rots due to Fusarium spp?
No > 2 years ago Within 2 years

Step 2

Stage Crop

When crop will be susceptible? 

Stage crop at least one week before expected flowering date. Use experience or estimate GDD from seeding date. Anticipate Day 0, when 75% of the heads on main stems to be fully emerged, to be one to two days before flowering. Also consider susceptibility of crop.

Seeding Date + 807 to 901 GGD C or 1484 to 1653 GGD F = Expected Flowering Date 
Even Crop, FHB Rating
G or VG 
Uneven Crop, More Tillers, FHB Rating F 
Uneven Crop, Many Tillers, FHB Rating
P or VP 
Step 3

Watch Weather

Check FHB Map 
Select the FHB forecast map for the estimated head emergence date (Day 0), and determine risk for the area. At least 12 hours of precipitation or high humidity (above 80%) is required for Fusarium spore germination and infection, as well as favouring temperatures ranging from 16 to 30 C (F. graminearum optimum is 25 to 28 C). 
Low Moderate High

Step 4

Crunch Numbers 
Estimated Yield (unit/acre) x Estimated Yield Savings (%) x Selling Price ($/unit)

MINUS the Fungicide Application Cost ($/acre)

= Expected Net Return ($/acre) 
Negative Net Return 
Net Return




Step 5

Make a Decision 

Note that foliar fungicides are registered for the suppression of FHB on wheat, rather than control. Flowering may be variable, but aim for when at least 75 % of the heads on main stems are fully emerged to 50 % of the heads on main stems are in flower. Ensure adequate water volumes and spray coverage to get the most benefit from application. 
Mostly Low Risk?
Do Not Spray 
Medium Risk? Pencil it in; reassess risk before spray day 
Mostly High Risk? Likely to see a benefit from a FHB fungicide 

Once the decision to apply a fungicide for FHB has been made, it is important to ensure that the fungicide is applied at the correct time and in a manner that will optimize protection. The application window is narrow and should correspond with the period of time when the crop is most susceptible to infection (flowering for wheat and durum).

Fungicide application timing for fusarium head blight suppression
Fungicide application timing for FHB suppression
Even when applied at the right time, fungicides will not offer complete protection since they are only registered for FHB suppression. As a result, it is important to use the correct rates, not to cut water volumes, and to drive slowly to optimize coverage and to get the best protection from the fungicide. From more information on FHB fungicide application, see Tom Wolf’s recommendations on Sprayers101.

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