HELP!! What should I do? I found mildew on a ton of leaves today!
Well, you have several choices. All of these choices can help to slow down the spread, but once you have it, it's pretty impossible to get rid of. You can buy neem oil and spray the leaves down...it leaves a coating on the good, unaffected leaves to help block the powdery mildew from sticking and spreading. This is probably the best choice. Second, you can go the cheaper route, like I usually do, and fill up a spray bottle with water, a pinch of baking soda and a couple teaspoons or so of milk...shake it up and spray the leaves with that. It doesn't work as well as neem oil, but it helps a little for some people. With the neem oil or milk water spray, do this about once a week in the morning. Last resort, and least helpful, is to grab your hose, put it on a good strong spray and, in the morning, not night, give all the leaves a good spray down every so often to help knock off any spores. I do the milk spray and the water hose spray every week...obviously dont spray the leaves RIGHT after you sprayed them with neem or milk, though, as that would wash it all off.
Also, I found, in the early stages, that removing the severely infected leaves and throwing them away in the garbage will help slow the spreading, too. (Don't throw infected leaves into compost or anywhere that it can still spread to other plants...put them in the garbage.)
At this point in the season, I usually just let it go and do it's thing because my pumpkins are mostly grown and near harvest ready...but if you stil have young pumpkins growing, I'd ty to fight the PM as much as you can until they are closer to harvest.