From Dr. Bhabesh Dutta:
Downy mildew has been detected on cucumber in Brooks County by Mr. Will Brown. These observations indicate that inoculum of downy mildew is currently in southern GA counties and under favorable conditions potential disease outbreak in cucurbit crops can occur. I would suggest our cucurbit growers to look for the downy mildew symptoms in their fields and start applying protective spray of below stated fungicides.
Watermelon: Rotation (foliar application) with Orondis ultra or Orondis opti;
Please do not use Orondis Opti or Bravo after fruit set.
Other cucurbits: Orondis opti;
If Orondis was used as a soil application, please do not use it as foliar (use restriction according to the product label).
Below are images of what Downy Mildew will typically look like in watermelon