well.. in the case of PM... prevention is the key to them LOOKING GOOD ....

once you have it for the season .. you are set to look at it until it puts out some new growth and leaves.. or until those leaves fall off ...

a simple prevention is baking soda ... if i recall correctly ...

i suspect that you have sprayed for future problems.. and that you should probably stop looking for more chemicals to spray on them ...

check out the link for sites to review for prevention ...

PM is usually associated with darkness and heat .... never allow you plants to go into the dark night wet ... no giving them a bath after dinner ... if you have irrigation.. it should not be set for late afternoon spraying ....

and to reduce night time heat.. insure that they are in an open enough location that there is sufficient air movement ... its dead hot damp air.. that is a breeding ground for any mildew ....

ken

Here is a link that might be useful: link

I assume this a Cornus florida variety you have planted. These are prone to a number of fungal issues, powdery mildew being just one. In your climate, or anywhere that has high summer humidity, I'd look for a cultivar that has established disease resistance. As ken notes, good air circulation and avoidance of overhead watering can help but this is more of an environmental problem - humid conditions just promote the growth of this pathogen despite whatever good gardening practices you may follow.

The issue with most fungicides is that to be the most effective, they need to be applied before any symptoms are noticeable. And all they will do is prevent unaffected plant tissue from being infected - already affected foliage will not suddenly become blemish-free. It will remain contaminated and potentially contagious throughout the growing season and until leaf drop and the fallen leaves should be thoroughly and carefully raked up and destroyed. PM spores can overwinter on the fallen leaves as well as on the soil or on twigs and branches.

Here is a link that might be useful: Dogwood diseases fact sheet.

Tampa... the land of nearly endless heat and humidity. Good luck with that.

HI all, thanks for the help. So what you are all basically saying is that even with an application of fungicide, the "mildewy" leaves are gonna still be mildewy and curling until they fall off? Are all of the (mildewy) leaves gonna drop in the fall? And then I guess I will spray before the new growth comes out next year.

The reason I chose this tree (yep, Cornus Florida) is first and foremost because it is a native tree to Florida. It is also an understory tree, which is exactly where my trees are planted (under a live oak). Of course, under a live oak in Florida tends to be a humid, dark environment. But that is exactly what it SUPPOSEDLY likes!!!!??? That is exactly what its "native, natural" enviornment is supposed to be!>????

Haven't been to Florida, but further north, Cornus florida prefers the edges of clearings from what I recall. Usually it seems to flower very poorly from what I've seen if its growing as a true understory tree.

ejperryman,

Tampa might be too far south for dogwoods. They're really more prevalent in North Florida. We tried some in Merritt Island, on the east coast of Florida and north of you. When we purchased non-specific C. florida from one of the local stores, they mildewed badly and eventually died. We did find a named C. Florida cultivar "Weaver" (from mailordernatives.com) that didn't seem to have the powdery mildew problems and was doing ok (we moved before it got very big, so no telling long-term how it would do.) It's supposed to be a little better for farther south than some of the other cultivars. Ours were growing as understory trees with slash pines and scrub oaks--that far south you probalby don't want to let them get a lot of sun.

There are a lot of native options you could consider if the dogwoods don't work out. The Florida Native Plant Society (FNPS.org) is a good source for information regarding native plants. One that should grow well in your area is Firebush (Hamelia patens). It gets red-orange flowers that hummingbirds and butterflies love, and the foliage turns red in the fall. If it doesn't freeze, it can grow into a small tree, and is a great native understory plant.

If you want to try a spray, a mixture often used on roses for mildew is about 4 tsp baking soda, 2 tablespoons of vegetable oil, and a tsp of dishwashing liquid soap in a gallon of water sprayed your plants. Shouldn't hurt anything, might help--and won't hurt you, either. Like most sprays, try to do it when the weather's not going to be too hot--try for less than 80-85 degrees if you can or it might burn your plants.