This is a difficult question and there really is no easy answer. However, there are a few things you should consider:
- The ideal timing is early flower. Generally, wheat begins to flower about 3 days after head emergence and flowering usually lasts between 3 and 5 days. Target to hit as many heads as possible at the early flower stage.
- The majority of yield is determined by the main heads, so make sure you’re targeting early flowering on the main heads (ie. not the tillers)
- Consider the forecast. If your crop is really stagey and there is really no one time to hit the majority of the heads, think about the ideal conditions for infection – in the last week, has there been free moisture (precipitation or high humidity) for a 12 hour period and have temperatures ranged from 16 to 30°C? If not, consider holding off on an application until conditions are more favourable for disease. Use FHB risk models, such as the one produced by MAFRD (http://www.gov.mb.ca/agriculture/crops/seasonal-reports/) as a guide.
- It’s better to be early than too late. Fungicides are designed to be used preventatively, not curatively.
Submitted by: Holly Derksen, Field Crops Pathologist, MAFRD