Powdery mildew in woody ornamentals tends very much to be a late season phenomenon when conditions are just right for its development. And in most cases, this is more of a cosmetic problem than a real threat to the plant's health. Since your new tree will be dropping leaves and going dormant soon, there is really no need to treat now. Just gather up all the leaves and dispose in your yard waste.

Most often proper cultural conditions will eliminate the occurrence of PM. Proper sunlight, good air circulation and adequate watering at the root zone will all help.

discuss with your seller ...

one would EXPECT ... to receive CLEAN... undiseased stock ...

a clear thinking seller... would have sent it dormant.. AFTER leaf loss ... thereby avoiding this situation ...

its simply baffling to me.. that they sent such... unless you demanded shipping at this point in time ...

it is possible.. that they did spray for such.. as most remedies.. will not remove such from the plant...

are you positive.. its not a spray remnant... as compared to PM???? .. can you offer a pic???

ken

Powdery Mildew is both pretty common and fairly easy to control, if one understands it. The article linked below may help with that.

Here is a link that might be useful: Powdery Mildew control