Also a similar question for my summer squash leaves.

How much and how often are you watering?

3 times a week. I use a 90 deg micro sprayer and cover prob like a 10ft x 10ft area. It runs for like 40 min
Also it should be noted that that I see this more so on the cucumber leaves around the root area and not out further on the vines

This post was edited by danstah on Sun, Apr 28, 13 at 20:06

Are you watering over head?
Plants like these do not like their leaves wet. This includes water melon, catalope, cuc's, butternut squash even strawberries. (vine type plants) etc. Over head watering can also cause fungus. Normally they are planted on a slight hill and you soak the hill. Hope this helps