About 11 years ago I planted Indian Hawthorne in my flower beds. After a few years it began to get black or brown spots on it so I asked Calloway's and they told me it was a fungus and to treat it with a copper fungicide. I did but every year after that the fungus came back and eventually the plants, even after treating it every year. About four years ago I planted tomatoes in the beds in the back of my house. Two years running they all died after the first harvest because the leaves begin turning brown from the bottom of the plant upwards. I didn't plant tomatoes the next year but did this year. The same thing is happening. My rose bush in the front bed begin developing brown spots two years ago. I treat it each year now with a copper fungicide. This year my peach tree begun having mold or fungus on the peaches and I got a fungus spray from Calloway's. What the heck is going on??? Why have so many different plants and trees been infected by fungus and what do I do about it?

I have not had that particular problem. Try what Howard Garret recommends.
https://www.dirtdoctor.com/garden/Cornmeal-Uses-and-Reports_vq306.htm