Lynn,

I am not really sure that any one 'control' is better than another and you're correct that control is all you can hope for once your plants have powdery mildew because a cure just doesn't happen.

If you're organic, Potassium bicarbonate seems to work better than plain old baking soda, which is Sodium bicarbonate. I don't know where you can buy potassium bicarbonate in Oklahoma. I buy it at nurseries in the D-FW area that carry a full line of organic products and it is not as hard to find as it used to be. Greencure ia a potassium bicarbonate developed by a Cornell plant pathologist (Dr. Horst) and although I've never used it, it has received generally great reviews since it was introduced. If I was fighting PM and couldn't find plain old potassium bicarbonate locally, I'd order Greencure online. (I've never seen Greencure in stores here....you might find it there.)

Some people have had good control with Serenade (Bacillus subtilis) but I have found its performance to be sporadic.

If you use chemicals, cholorothalonil (found in products like Daconil) is probably as effective as anything. It works best if applied regularly as a preventive before powdery mildew appears.

I'd try treating the current plants first to see what response, if any, there is to your chosen treatment. You can always start another round of plants in a week or two if the PM doesn't respond to treatment or worsens. With any PM treatment, it is often most helpful to alternate between 2 or 3 different products so the PM does not develop a resistance to one single product.

Good luck,

Dawn

Here is a link that might be useful: Greencure

It has also been reported (IÂve never used this myself) that urine when diluted at 1 part urine to 4 parts water is an effective powdery mildew control.

Cornmeal.

One time I overwintered some strawberry plants in my garage and they started getting this white mildew looking stuff on them, put cornmeal down and it was gone.

for what it is worth....