Q: So what mulch(es) appear to be best?
A: We tested 27 mulches in the field, and found that some supported more artillery fungus than others. In one study, the most resistant mulch was large pine bark nuggets. The large bark nuggets stay hard and dry, conditions that the artillery fungus does not like. Cypress mulch also performed well, as it probably contains some anti-fungal, anti-decay chemical(s). However, there may be some environmental, non-sustainable reasons for not using cypress.
An article from the Journal of Environmental Horticulture entitled “Artillery Fungus Sporulation on 27 Different Mulches- A Field Study” has some results.