I sent off an email to ask if "Drop-Off" would work on Artillery Fungus. Here is the response I received.
We have not tested our product on fungi, and I am not sure if Drop-Off will work on this application. I do know our product is designed to attack "organic" compounds, and that it has been used very successfully for removal of spider droppings on vinyl siding, painted window sills, and stucco. I would say that it might work, but can not make any guarantees. In the event you want to give it a try, we currently have a 2 for 1 special on individual bottles that are ordered from our website
www.dropoffcleaner.com