I suspect that is not a disease but wooly aphids.

That's what it looks like to me too, but, if it is, that's one SERIOUS infestation. Try picking one off. If it is wooly aphids, you should be able to remove one of the raised white "specs" by hand.

This post was edited by brandon7 on Sun, Sep 29, 13 at 6:53

you dont mention where you are ..

but wont the leaves be falling off in a few weeks?

if so ... i would just do a fall clean up ... inspect the trunk .. and keep an eye on it next year ...

the odds of the same plague hitting next year..; are low to nil ...

trees like a deep drink.. and then near drying before the next ...

the are not really sprinkler plants... and i suspect.. your sprinkler has simply created a perfect .... . late fall ... culture for them ...

so what.. they are not going to live thru the first freeze ... depending on where you are ....

ken

Thank you for your responses. I checked, these are not wooly aphids. I have been looking through photos on the internet and I think it may be powdery mildew? I live in Central Texas, the trees are only irrigated 2x/week, about 15 gal at a time. I posted some close-ups.

It would be very easy to distinguish it 'in person', but not so much by photograph. Powdery mildew is much more two dimensional than something like wooly aphid. It's pretty host specific too, and something you might want to take more seriously than wooly aphid because by the time you see it presented on upper leaves, it's well into the tissue of your foliage. It usually begins on the leaf underside. I could write a book on it, having dealt with it on greenhouse poinsettias when a major breeder sold and shipped cuttings innnoculated with it all over the country to professional growers. In fact I diagnosed it before the extension agent did. It's 'everywhere' but needs certain environmental conditions to express itself. Most folks here get it routinely on things like lilac, and consider it not a big deal. But I can't say with any amount of confidence you can say that for a young, valuable tree specimen and you might want to confirm this with your local extension agent because if it is you might need to get a handle on it.

i agree in pix its hard ...

but PM is greyer ....

its not ivory snow white....

its more of a film ...

but again.. the leaves will fall off soon .. no need for chems.. but the quest for knowledge is always on the approved list ....

ken