I potted a Japanese maple this summer on my roof garden, Its potted, I water it every other day it was doing fine, now its leaves have white spots and seem to be shriveled up. please offer help asap!
A picture would help, but based on this seasons extreme heat and humidity and your description; powdery mildew is to blame. This is rarely the cause of death, your tree would need to have other problems along with it in order to die. If left untreated, it will cause all of the leaves to fall. It may also spread to other things too. The product I use is not for sale in ny. Other forum members have found rose disease control to be effective. Consider morning waterings, and avoid getting the leaves wet. Once this latest round of humidity moves out over the weekend and dryer air moves in you can try spraying off the leaves to wash away the powdery mildew, if you don't want to use chemical spray. Do it over the course of a few days. Do it in the morning and give the tree plenty of air movement if possible.
