Long distance diagnosis is nearly impossible. I suggest you take a sample to your local extension office (or a good full service garden center) so they can check the plant for various diseases and insects. That way you know exactly what problem you have and they will tell you what you need to do. Please don't spray chemicals without knowing the problem. If it turns out to be an insect or bacterial, you will have wasted your time and money.

Sandy

Thanks for your input. Unfortunately, for reasons we don't need to go into,taking a sample to the county extension agent or to the state lab is not an option for me at this time. While I awaited a reply to my post I removed the most severely infected leaves from the plants and discarded them I then sprayed the plants with ferti-loam Triple Action. There has been no further outbreak. Keeping my fingers crosed/ Thanks again.