We have had a very cooler and wet spring and the powdery mildew is back with a vengeance.
A day before our last good rain, I sprayed all of my crops with a mixture of Garrett Juice (2 tbsp per gallon), neem oil (almost 2 tbsp per gallon), and a tablespoon per gallon of ocean minerals. After wards, the leaves had a nice rich green shine to them and the powdery mildew could not be seen. I suspect that it was just hidden under the glossy finish. After a few more days of very light sprinkles, enough to wash the spray off, I can again see spots of powdery mildew all over.
I had a small pump bottle of copper fungicide, so I sprayed the most affected leaves. Tomorrow when I go to town I will look for a concentrated bottle of copper and I plan to add that to my spray mixture of Garrett Juice, neem and ocean minerals.
Neem oil can treat fungus, mites and insects, with varying efficacy.
It starts with just a few small spots here and there.
Then it spreads.
Another squash leaf. Different varieties of summer squash and zucchini have differing tolerances and immunity to the powdery mildew. Winter squash and gourds seem to have the strongest resistance, except for spagetti squash.
I cut out the leaves that are totally wiped out by the mildew. They are light yellow, covered with the white mess and dry and stiff. The powdery mildew if a parasite fungus that taps into the leaves and feeds off of the squash leaves.