Q: I have heard that used "mushroom compost" will suppress the artillery fungus. Will it?
A: Used mushroom compost, also known as "mushroom soil," "spent mushroom substrate (SMS)," and even "black gold" is a great product, if you live in an area where you can get it! Mushroom compost has many beneficial aspects for gardeners, one which is that it supports micro-organisms that inhibit many unwanted pest fungi. Mushroom compost is pasteurized before it is used to grow mushrooms, and then the used compost is pasteurized again when it leaves the mushroom house, so it should not contain weed seeds. Our research at Penn State has shown that blending used mushroom compost with a landscape mulch at about 40 % will greatly suppress artillery fungus sporulation. Mushroom compost is very "green" and environmentally friendly.
An article from the Journal of Environmental Horticulture entitled “Use of Mushroom Compost to Suppress Artillery Fungus” give insight.