treating rust on leaves
I planted several Pink Muhlys in a new bed that I made about a month ago. I amended the original clay soil with some cheap planting soil from Home Depot and raised the soil level in the bed about 4-6" above the surrounding area to improve drainage. Then I mulched the bed with composted bark.
I expected the Muhlys to thrive but noticed last week that their leaves are covered with orange rust. Not sure how that happened, unless I watered them too much the first few weeks. It had been very dry here and I wanted to make sure they didn't dry out. I don't want to apply any heavy duty fungicides because some of them are extremely toxic, but I did dust the grasses with sulfur powder. They don't seem to be getting any worse, but not better either. Since then, we've also had a lot of rain during the past week -- almost all in the form of late afternoon thunderstorms.
Are there any other remedies that anyone could suggest? I was tempted to return the grasses to the nursery where I bought them since the rust showed up within 2 weeks after I bought them, but thought it would be treatable. Was I wrong to mulch the bed heavily? (I did rake away the mulch from the immediate area around the plants.) The spot where they are planted gets full sun from about 10 a.m. to 4-5 p.m.