Updated: May 8, 2019
There's a fungal canker I'm seeing in Japanese maples located in highly alkaline clay soils which makes sense. They prefer natural, loamy soils. Give me a bad diet and watch my immune system decline; I can't say it often enough. At least, I can't for as long as we East TN tolerate poor soils being dumped in our beautiful new homes!
So, what you'll see in the pics below is a fungal endophyte (fungus that lives the majority if not all, of its life inside the plant host tissues). This fungus has 100s of species and readily hybridizes so I can't tell you the species name but if your geeky enough to want the genus - email me!
The fungus is Opportunistic as is true of many endophytes (this is what I studied throughout and after my PhD) - meaning, it becomes a pathogen when the hosts' defense system breaks down. Bad vitamins, bad nutrients = compromised immune system.