Larry - with the bog area, that may be part of the problem. Do you get a lot of shade there, too?
I find rust is more of a problem if I use the micro sprinklers too close to dark, so that tells me that the wet and damp leaves promote rust growth and spread. High humidity is a no-no for me.
I've got some rust resistant cultivars (1.5 -all the way to susceptible 5.0) that start showing rust during high humidity. I've been gravitating to 1.0 -1.5 resistant cultivars more and more.
But make sure that all the damage that you are seeing on the leaves is rust and not other issues. Thrips and leaf streak are a far worse problem for me this spring than rust. It's very frustrating to say the least ......
