Like death and taxes, it's guaranteed and certain that the zucchini plant will be the first to come down with powdery mildew. And it always happens just as the zuke is starting to hit peak production.
(I refer to zuke in the singular as I only grow one plant per year.)
For the record, I don't plant the zuke in the same area in consecutive years. The spot is usually sunny and ventilated. The plant isn't over fertilized.
I've tried baking soda solutions and neem in the past but always after the plant has the symptoms. These only delay the eventual demise.
I tried Serenade this year, but the plant still came down with powdery mildew.
Suggestions on the 'Net seem to point to regular spraying with any of the above solution BEFORE the plant exhibits symptoms. If so, I am remiss.
So, what does one do after the plant is affected? For the moment, I am thinking of removing the affected leaves and continuing with treatment on non affected portions of the plant.
Any ideas or suggestions?
I've had good luck using a product called Organocide 3 in 1, found at most Home Depots or big box stores.
Every year I get the bad powdery mildew on my cucumbers and zucchini plants. I tried all the baking soda and milk solutions, but nothing worked the way I thought it would.
The organocide this year has worked incredibly well. I had plants that showed the signs of white spotting on the bottom and upper parts of the leaves. Mixed some organocide with water and sprayed the plants from both up top and below. I did them once a week, for 2 weeks in a row. I'd say about a week after the second application, all signs of powdery mildew were gone, the leaves became very green and filled out.
Other than that, I don't know what else to recommend.