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?

Powdery mildew is not as lethal as black spot. It usually starts appearing from the top down on the newer growth, where as black spot starts from the bottom up on the older growth of the bush. Cold nights and warm days coupled with dry, rainless weather encourages the growth of powdery mildew. Wet weather is hard on PM, and can be counted upon to help control it. I know a rosarian who sprayed his PM afflicted roses twice a day, AM and PM, with water alone, no fungicide, and effectively halted the PM in its tracks. Spring and fall in our climate, NJ and PA, have very similar growing conditions, hot days coupled wth cool nights, are the powdery mildew seasons. PM, as stated earlier, is not as harsh a disease as is black spot. You can go for years with no outbreaks and almost overnight it can hit, not to return for several more years. Powdery mildew is sneaky, it appears subtly, some slighty misshapen newer growth that is mild, then bingo almost before your eyes it turns into a full blown case. It severely disfigures the foliage and buds, suppressing their development. An outbreak this fall does not mean your roses are from this day forward PM prone. PM is in the environment and really needs very specific conditions to manifest itself, conditions that are not present every spring or fall every year. I believe some rose varieties are more susceptible to PM. Those with dull, matte leaves being prime targets, with shiny leaved roses being more PM resistant. There are probably other susceptibility factors, too, but the foliage finish is the major one of which I know. Hybrid rugosas, as tough as they are, are PM susceptible, probably due to their dull finish foliage and rugose, pebble grained, texture. The nooks and crannies being perfect breeding grounds for the PM fungi. What to do? You have several choices: 1. Spray with a fungicide, organic or otherwise. 2. Spray twice a day, AM or PM, with plain water, wetting the foliage down. However this method may promote black spot! 3. Do nothing. It is now very late in the season, roses are slowing down and very soon to be dormant. The PM on the roses will not be a factor in the spring of 2017. Remember, PM is ever present in the environment, waiting for the perfect conditions to infest our roses. Fortunately the specific conditions it needs to be an outbreak are not easily met in our climate, thank God. One last thing, PM in the spring needs to be dealt with by some means. In the fall, the upcomming winter stops it dead in it tracks. Therefore, a hands off, do nothing approach, may be your wisest action at this time.

Ok, I dug a little trench around it enough to make sure there aren't any maple roots intruding. Its definitely not wet. No spider mites. It seems very well rooted and I didn't dig if up completely; I felt like I would disturb it too much? The leaves on one side definitely seem like they have some sort of mildew or fuzz on them. I don't like to use sprays but the garden store suggested Advanced rose and flower 2 in one spray. I will give it a try. I did fertilize it with osmocote in early spring and used compost. I really don't want to lose it. Thanks for taking the time to help....

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.