North Florida Watermelon Producers Should Guard Against Powdery Mildew

Jim Rogers Florida

By Clint Thompson

Even in the driest weather conditions, one disease can still torment watermelon producers. Powdery mildew is on the mind of Bob Hochmuth, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) regional specialized Extension agent in Live Oak, Florida, and should be at the forefront of Northeast Florida growers’ management strategies.

Powdery mildew disease
Picture courtesy of UF/IFAS/Shows powdery mildew disease on a watermelon vine.

He cautions growers to apply preventative fungicide sprays, so the disease does not become a problem.

“The reason that I get anxious about powdery mildew is that it is one of the diseases that can infect watermelon plants under these dry conditions. It’s different than most of the other major watermelon diseases in that it can become active under relatively dry conditions. That’s one of the things that makes me nervous right now about powdery mildew,” Hochmuth said. “The second thing that always makes me nervous and I might want to pull the trigger a little bit earlier than the other diseases is because we do not have excellent curative fungicides for powdery mildew.

“We have good preventative fungicides, but it is one of those diseases that if it gets established and we’ve missed the opportunity to get the preventative sprays on, it is very difficult to catch up on powdery mildew. I tend to be a little bit more anxious on the front end and would prefer that growers use a preventative spray.”

Hochmuth encourages producers to add Quintec or Procure to a broad-spectrum fungicide like Manzate or Penncozeb to stay ahead of powdery mildew.

“In the Suwanee Valley area we have not had any confirmation yet, and it’s possibly because a lot of the growers have started a good preventative regimen for powdery mildew,” Hochmuth said.

According to UF/IFAS, powdery mildew usually produces white, powder-like signs on the upper and lower surface of watermelon leaves. It starts as small, faint yellowish spots on the leaves which continue to develop to neighboring leaf surfaces. Symptoms first appear in the lower canopy on older leaves and
can quickly spread throughout a field.