Charles, I stopped using anything for it. I tried the copper/bordeaux sprays, but it did not seem to help. Having said that...
My experience with the sprays was while growing in Houston (high humidity). In central Texas it is a much dryer environment. The leaves still get rust, but it is generally on the older leaves. Most trees outpace the rust, and I just pull the rusty leaves off. I do not know if the sprays would work better in this environment, but it seems like I would need to spray every couple of weeks over the growing season.
In high humidity, I wasn't able to stop it.
~james