Abstract

During the last decade, the ‘artillery fungus’ has emerged from an interesting mycological curiosity that grows in landscape mulch to a problem of major financial concern to homeowners, insurance companies, mulch producers, and landscape contractors. This common inhabitant of landscape mulch produces sticky spore masses (gleba) that it shoots towards the light or towards reflective objects such as light-colored automobiles or house siding. We evaluated 27 different mulches in the field to determine their ability to support growth and sporulation of the artillery fungus. Each mulch type was inoculated in 1998 with the artillery fungus and the amount of sporulation (number of spore masses on targets) determined annually until 2002, approximately 4 years after inoculation. We grouped the 27 mulches into nine general categories that had common characteristics: mulches that originated from large piles of bark and wood mixtures, mulches blended with 5% compost, cedar mulch, mulches commercially designated as ‘bark’ but containing considerable wood, dyed wood chips, non-dyed wood chips, cypress mulch, large bark nuggets, and 100% spent mushroom substrate. The mulches obtained from large piles shredded blends of bark and wood supported significantly greater levels of artillery fungus sporulation than did other mulches. Such highly susceptible mulches should be avoided if the artillery fungus is to be minimized. In contrast, large bark nuggets, cypress mulch, and 100% spent mushroom substrate supported less artillery fungus. Other mulches supported intermediate levels of sporulation. All wood/bark landscape mulches will eventually support the artillery fungus over extended time periods (i.e., 34 years), and even more tolerant mulches should be replaced or covered with a fresh layer of mulch on a regular basis.