Artillery fungus

Artillery fungus (Latin: Sphaerobolus stellatus) is a wood-decaying fungus that is often mistaken for a plant disease. While it does not kill plants by parasitizing their tissues, it is notorious for attaching stubborn, tar-like black spots to plant stems, leaves, and various household exterior surfaces.

The organism acts as a saprophyte, decomposing organic matter such as wood chips, mulch, and decaying vegetable debris. The name "artillery" comes from its biological mechanism: the fungus can forcefully eject a sticky spore mass toward light sources, effectively covering nearby plants and structures with dark projectiles.

Symptoms are easily identifiable: numerous tiny, black, circular spots that are extremely difficult to remove. When these spots land on the lower foliage of sensitive plants, they create small black "specks" that resemble scale insects or dirt particles, often leading to unnecessary chemical treatments by gardeners.

Development and spread are facilitated by moist, temperate conditions and the presence of organic mulch. The fungus thrives when humidity levels are high, typically during spring and early autumn. Once the spores are launched, they can remain dormant and visible on leaf surfaces for extended periods, even after drying out.

Prevention is the most effective approach since there are no targeted fungicides that efficiently kill this saprophyte without harming the garden ecosystem. The primary strategies include:

• Switching from organic wood-based mulch to non-organic alternatives like gravel or landscape fabric.
• Maintaining well-aerated, dry soil conditions around plants.
• Removing old, decaying organic matter where the fungus may establish its colonies.
• Avoiding over-mulching around the base of sensitive ornamental plants.