A lot of my plants have been soaking in the over abundance of rain we have then a dry spell. Noticed a lot of leaf damage to fungus so I have been using Ortho MAX Garden Disease Control Concentrate with good results. Big box stores has it or other stuff doing the same function. Leaf damage is done but new leaves and rest of plant looks fine. Chemical to look for is Chlorothalonil, which is a staple fungicide. The stuff for Rose Bushes is the same stuff.
