Some winter squash, cucs, and cantaloupe have signs of powdery mildew. Acorn and honey boat squash are the worst, the others are just now showing some signs.
I don’t have any chlorothalonil. I have Sulfur plant fungicide and mancozeb. Neither lists winter squash on their label, Although cucs and melons are listed on the mancozeb label. Sulfur only lists beans and peas for vegetables. Reading several articles I found that sulfur Is used to prevent powdery mildew on curbit crops. I couldn’t find anything about control once plants are infected. It’s a little confusing. Advice?
I use Mancozeb on grapes but you are supposed to quit 60 days prior to harvest. Check the spraying recommendations for food crops.
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Most fungicides are preventative. Next time you grow these crops spray them before any trouble appears. I have used copper myself. Only as a preventative. Once you have it it is near impossible to control.
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I have to make some notes For next year to remind myself to do this. With so much harvesting and processing going on this time of year, I am bound to forget. I would say late July I probably needed to spray. Thanks @Drew51!
The eradicant for powdery is potassium bicarbonate, sold under the trade names Kaligreen or Armicarb. You can use Sodium Bicarbonate too but I wouldn’t make it a habit…
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For a organic spray use the Cornell formula. It my not totally stop it but it keeps it sufficiently under control.
Cornell formula once a week. Leaves need to be completely covered with the spray.
Add to 1 gal of water:
1 tbls baking soda (potassium bicarbonate is better)
2 tbs cotton seed oil (some other horticultural oil can be used)
2 drops of pure soap like Castile
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