This will be an ongoing problem with the curcubits (squash, cucumbers, melons, and gourds). If the plant is heavily infected, you may have to remove the entire plant. We start spraying with the least harmful control - in this case it is Neem oil. If the problem persists, we will move to more powerful agents. Just remember that mother nature will get her share of our gardens - they will never be totally free of pests or disease. There may be resistant varieties of curcubits available - check with your retailer.
For some technical information, we've included the links below.
Judy and Richard
Note from Unwebmaster, you can see a photo of powdery mildew here.