DR, "I thought it was caused by cooler and wetter conditions..." It's favored by cooler more humid conditions. But liquid water actually prevents PM from growing. We had a very rainy period for several weeks and the rain itself prevented powdery mildew. "In other parts of the country, you could have PM on Zinnias during the summer? And you need to control it by some method all during growing season? Bummer." I think you have gotten a somewhat exaggerated impression of the seriousness of the problems with zinnias. PM is also mainly a problem here in the fall. Fall comes earlier here in Maine than in California. There are areas of California that are very favorable for zinnia seed production. I have zinnias that are still blooming that are seven months old. I have already harvested seed heads from them, so they are senescent and have much reduced resistance to foliage diseases. Part of the problem with zinnias in the fall is that the plants are older and declining with fading natural immunity. Next year I am going to experiment with Messenger on my zinnias. My fall crop of younger zinnias haven't been sprayed yet, and only in the last few days have I seen any traces of powdery mildew. It's highly likely they will be felled by a killing frost before the PM becomes serious, so I probably won't even spray them. Zinnias, like roses, can be affected by a number of diseases. If you are motivated to protect your plants, as many rose growers are, you may very well spray them fairly frequently with a number of products. For most people, zinnias are a "plant and forget" ornamental. But for hobbyists like me, the zinnias are "my babies" and I am willing to spend some time caring for them. And that includes spraying perfectly healthy plants as a preventative measure. My zinnias are my "roses". I even get some of my gardening products from RoseMania. MM

Copper won't help much in managing PM. If you want to go 'organic' you should start early in the season with sulfur applications. Powder sulfur tends to have a better preventive efficacy than wettable (sprayable) sulfur and vice versa with regards to their limited curative efficacy. Will not work when temps are cold. Another preventive (and somewhat curative) solution is light horticultural oils which will work at colder temps but should not be used when temps are high. Care must be taken not to apply sulfur within two-three weeks of applying oils, For both oil and sulfur applications test must be conducted first to determine if dosage is toxic to leaf tissue of the particular cultivar. With regards to synthetic fungicides I would tend to shy away from anything not labelled for the specific use when applying to edibles and then closely adhere to the time of last application and other label instructions. Nik

I got this Zinnia from a local nursery. I got it at a diffrent nursery than the one from last year. Does it look like a fungus to you? The soil looks black because I just watered it. No one else at the community garden has a problem. Should I use the Physon 20? This is the point at which I want to use the fungicide but i'm not sure which one. I think i'm just going to go ahead with the Bonide copper as it is the most readily available.

Why are you getting rid of them? Mildew is everywhere but it can be controlled fairly easily. Keep rexes and other mildew prone begonias in a well lit, warm area. DO NOT saturate the soil starting in fall through winter. This will take care of 90% of the mildew problem in my estimation. If you see mildew occurring, do not wait to treat it. The quicker you treat it the easier and more beautiful your rexes and other begonias will stay. There are lots of effective sprays out there including home remedies. I have found Orchard Spray as very effective controlling mildew. It is sulfur based and pyrethrin for insects. I used it 2 or 3 times this winter and came out looking very good.