Powdery Mildew

Description:

Celery, cucumber, oregano, squash, watermelon all affected. Reading sources says powdery mildew is very selective with one type of spore generally affecting one type of plant. Doesn’t seem to be that way for me, else I have a few different spore types which I read is very possible.

Removed Tatsoi from this list because it doesn’t look to be the same thing. Not white and powdery. More like brownish yellow and might be from the heat and being on the West side of maters instead of East. I did have a case of flea beetles on them too earlier in the season.

https://www.growingagreenerworld.com/controlling-or-eliminating-powdery-mildew/

Potassium Bicarbonate seems to be the best organic control. Inorganic controls generally have copper as an ingredient and might be ok when the foliage isn’t the edible part.