Q: I’m a softball coach at Georgia State University. Our back stop netting at our softball facility has developed a “fungus” on it. This growth is starting to cover the entire netting area.
A: What you see is nothing more than lichens growing on the net. They typically grow on tree trunks, where they do no harm……but I can see why you want to get rid of them.
Lichens are a combination of an algae and a fungus. I think you could spray with a light solution of bleach and water and they will disappear pretty rapidly.
Also consider spraying with Wet and Forget (click for sources).