As an organic grower on the west coast of the Pacific coast of Mexico, powdery miildew is a constant problem regardless of the season due to the average temp 80 degrees and humidity from the jungles. Those of us planting out of the U.S. do not have access to your recommended products,  However, we use 1 part raw milk to 9 parts water, sprayed every 6-8 days not only gets rid of the white mildew, it also prevents further development.  We spray for a 4 week term, twice a year.

I spray an organic oil on my apple trees in the dormant season as well as summer to protect against powerdy mildew.
Although I purchase some from you, I was wondering if purchasing gallons of either vegetable, corn, canola, or soybean oil purchased locally would do the same as the Stylet or other OMRI listed oils I currently purchase?

Krystal, Thanks for sharing your tip!

Rich, Stylet contains parafinnic oil, Saf T Side has petroleum oil, and Organocide is a combination of fish and sesame oil. It’s important to use the horticultural oil products only for their labeled purposes.

I’m sure the best for you to your friends   for more detail