How to stop powdery mildew spreading? (2024)

Don't use soapy water on the leaves of the plant! That will harm the plant severely. I know because I accidentally splashed a tiny amount of soapy water on leaves of a squash plant in my garden.

The only advice related to soapy water is that one use it for disposal of cucumber and squash bugs. (This is because the dish liquid breaks the surface tension of the water so that the bugs will drown.) Wash your hands and dry them well. Then pick the bugs off the plant with your hands and throw them in a bucket with soapy water. Don't dump the soapy water in your soil; dispose of it properly in a sink drain or equivalent.

When I cleared squash bugs from my plants last summer, I used a plastic spoon to flick the nymphs and adult beetles into a small disposable plastic dish (about 3" high) that was half filled with soapy water. Then I periodically dumped the tray into a larger pail of soapy water and replaced the soapy water in the smaller dish.

I removed squash bug eggs by rubbing them between my fingers while holding them over an empty disposable plastic dish.