Both Captan and Copper Fungicides work with downy mildew so what don't you understand? LOL Captan has certain problems with it but has been used for a lot of time. Copper products when repeatedly used over time tend to pollute the soil with heavy metals. That is where using different products helps somewhat. I use mancozeb products early as that helps with black rot also and controls downy, so you are protecting against multiple problems. You need to switch to Captan or something else as you can't spray that closer than 66 days to harvest.
Then powdery mildew requires something else to control it. Learn your diseases, what can be used to control them along with their precautions. Then scout for problems and act when a certain threshhold is reached. Most diseases you wan't to act proactively with a protective plan as it is harder to kill some of them than protect against them.
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