I've had a terrible time here in L.A.- zone 10- with powdery mildew - this time it got my squash, cucumbers, tomatoes and bush beans; now it's working on my pumpkins. I have tried a bunch of things - milk, baking soda and a little detergent, etc.- but they seem not to work. Realize I probably water too late in the day and put manure on at the wrong time...but still! Most sites states that "treating the soil" is not useful, but one site says to cover with clear plastic and let it sit for 4-6 weeks - longer if it's rainy. Seems like a long time to wait - but I'd do anything to fix this problem! Can anyone help? Another thing - I'm from the South and can't help but notice how much better plants like melons, okra, summer squashes do there. I'd attribute this to it nearly always dropping down to the 50's and 60's at night, instead of staying hot. Am I the only one that thinks this?

I was hoping to get some feedback from other people who have "David" to see how it performs for them. Rhizo, 10% infection would be pretty darned good if this were July or August, but here in PA May is not even powdery mildew season. Phlox normally does not get hit til near the end of summer, even the non-resistant varieties. My plant has severe enough infection to have total dieback on the bottom of the plant, and in the midsection of the plant the leaves are spotted. Only the very top is free, but we have 4 full months left to go. When I go online and read studies of powdery mildew, generally you don't see the studies make claims about resistance of plants or effectiveness of control products until late in the year; they are usually ALL fairly resistant/effective this early on in this climate. I spoke to the woman at the nursery and she was visibly surprised that I had that problem with that plant. She suggested trying to move it, but it doesn't have any place else it could go where it would be happy. When I pulled off the infected leaves at the bottom, it made the plant top-heavy which caused it to open up a bit as the stems all lean outward. That should help, but I am disappointed. My mother does not treat her phlox. She has some old unnamed garden phlox that is not meant to be resistant, her plants are huge and full and the earliest in the year they ever get a speck of mildew is mid-to-late summer. In a very bad year she might have dieback, but in many years they hardly get any and never once has she had it in the spring.

When powdery mildew is rubbed, much of it rubs off. If it doesn't rub off, it's not powdery mildew. Powdery mildew spreads. Variegated patterns don't. Variegated patterns mostly follow the veins. Much as what I see here. Powdery mildew is in splotches.

Cucurbits - squashes, zukes, cukes, melons, etc. - are extremely prone to PM unless selecting a variety specifically bred to be resistant. Much of it's due to their growth habit. They lay close to the ground and produce an abundance of pretty big leaves, both of which reduce air circulation, one of the key elements of PM development, as well as tending to keep the soil area rather dry (also a factor). Trellising these types of crops can go a long way in discouraging PM but not all cucurbits respond well or are adaptable to that sort of growth. Almost NO fungicides are curative - they are only preventative and need to be started very early in the growing season to be very effective although they will help to reduce the spread to unaffected foliage. Unfortunately, PM spores rapidly become resistant to single fungicides so best to rotate through 2 or 3 different ones to maximize effectiveness. And they all work more or less with a similar degree of efficacy - potassium bicarb, milk, neem oil, hydrogen peroxide, chlorothalonil or sulfur sprays PM tends to infect the oldest foliage first so removal of heavily damaged basal leaves should help. As will deep watering at the root zone to prevent the soil from drying excessively.