Stewartias are remarkably trouble-free trees in the right climate and growing conditions. A lot of leaf spotting can be physiological in origin, arising many times from weather conditions. Any heavy rains or hail recently? Excessive cold? Especially when leafing out? These very much do resemble a fungal problem but are entirely nonpathogenic. At any rate, nothing to worry about and no need to treat.

Could it be fungal leaf spot? I've noticed this on my 5' Stewartia I just purchased from the nursery.

[edit]Bacterial leaf spot, rather[/edit]

Here is a link that might be useful: Host Pathogen Index

This post was edited by adam211 on Sun, Jul 14, 13 at 12:04