Can you possibly repost this with photos illustrating what you are referring to? And what is "an organo-tin based fungicide"?

Also, your question has nothing to do with any appliances or flooring and is only very tangentially related to landscape design so posting in subject appropriate forums may actually generate some valid responses. Try Fruits and Orchards, Trees, or Garden Clinic.

Talk to your state university extension. They will have advice suited for your climate and region. It will be much better than what you crowdsource from strangers.

"It will be much better than what you crowdsource from strangers."

Not necessarily :-) There are a great many very talented and experienced horticulturists that visit these forums as well as a few plant pathologists. Diagnosing and recommending treatments for common plant problems - and most are very common and widespread problems - has been a long time benefit of these forums. And a heck of a lot easier to access than the extension service offices!!