Downy mildew disease has been confirmed in a North Florida watermelon field, according to Bob Hochmuth, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Regional Specialized Extension agent in Live Oak, Florida. Not only that, it was also confirmed in South Georgia as well.
But growers must consider all the facts before responding to the breaking news.
Hochmuth stressed in an email alert that the Georgia case was confirmed to come in on transplants from outside Georgia, but the plants were planted before confirmation. The field is being treated for downy mildew.
As for the North Florida incidence, the exact source has not been confirmed. Growers need to consider the following:
- Nearest case of downy mildew south of North Florida is at least a few hundred miles away.
- Both Georgia and Florida cases are very isolated and a few hundred miles from any other known cases.
- Recent weather patterns and weather forecasts suggest that conditions are not typical of downy mildew outbreaks.
- Very likely both cases did not come into the area with the normal air-borne method of pathogen movement.
Hochmuth stresses that growers do not panic, but be diligent in scouting fields.
“It could be an expensive mistake to automatically start spraying fungicides specifically for downy mildew unless there is reasonable evidence you can justify starting,” Hochmuth wrote in an email alert. “Materials like Ranman, Elumin, or Orondis Ultra should only be used when more justification emerges. If we start too early needlessly, we will use up the limited number of applications allowed and increase the likelihood of resistance in these materials to downy mildew.”
Chlorothalonil and mancozeb provide some management of downy mildew.