Kentucky Wheat: Head Scab – To Spray or Not to Spray?

Fusarium head blight, or wheat scab.

Many wheat producers in the state have already sprayed a fungicide to help protect against Fusarium head blight (scab).  However, some fields in the state were just nearing the beginning flowering stage (Feekes growth stage 10.51) when the May 9 freeze hit.

Producers with these fields may have held off on spraying a fungicide to determine how much freeze damage had occurred in their wheat fields.  Now that freeze damage may be apparent in these fields, producers must now make a fungicide application decision.

Since freeze damage can vary from field to field, these decisions must be made on a field-by-field decision.  If freeze damage is severe, then applying a fungicide at this point, may not be worth the cost.

Below are some considerations from a disease control perspective:

  • Many parts of Kentucky have had a medium to high risk of Fusarium head blight (scab) up through the last few weeks (see the risk map here) for susceptible varieties. However, risk on moderately-susceptible and moderately-resistant varieties have been low to medium.
  • Wheat heads are susceptible to infection by the Fusarium head blight fungus from beginning flowering through soft dough
  • In multi-state research studies funded by the U.S. Wheat and Barley Scab Initiative, effective fungicides tested have shown efficacy against Fusarium head blight and deoxynivalenol (DON; vomitoxin) contamination when applied up to around 7 days after the Feekes 10.51 growth stage
  • When making a fungicide application after the Feekes 10.51 growth stage, be sure to check the label for the pre-harvest interval (PHI). The PHI for different fungicides that have efficacy against Fusarium head blight are listed below:
    • Caramba = do not apply within 30 days of harvest
    • Miravis Ace = do not apply after full head emergence (Feekes 10.54)
    • Prosaro = do not apply within 30 days of harvest
    • Proline = do not apply within 30 days of harvest
    • Tebuconazole products = do not apply within 30 days of harvest



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