Artillery fungi, genus Sphaerobolus, grow on decomposing wood mulch. These fungi prefer sunny, open areas, and shoot small, round solid masses of spores called glebal masses up to 20 feet away. The glebal masses tend to be directed towards light colored, reflective materials (Photo 1) and nearby plants (Photo 2). The glebal masses can be mistaken for insect excrement and scale insects. The glebal masses can be difficult to remove, and a couple of ways to reduce artillery fungi in a growing area are to remove heavily decomposed mulch and to add fresh mulch. Please contact the plant pest lab at plantlab@tennessee.edu with your plant questions, and you can visit your local county Extension office for assistance on submitting samples to the lab.
Photo 1. Glebal masses of artillery fungi on white, reflective mesh and on the undersides of the leaves of a boxwood plant. 
Photo 2. Closer look at glebal masses of artillery fungi on the undersides of boxwood leaves.
Post by Dr. Eleanor Lopez, plant pathogen and insect diagnostician.