Artillery Fungus: Identification, Prevention, and Removal from Cars and Buildings

Those stubborn brown dots coating your car and vinyl siding? They're likely not from your shrubs at all. The culprit is almost certainly artillery fungus (Sphaerobolus spp.), a wood-decay fungus that thrives in landscape mulch and "shoots" its spore masses up to 20 feet.

Understanding the Enemy

Artillery fungus grows in damp, organic mulch—especially hardwood bark. When mature, its fruiting bodies forcibly eject sticky, tar-like spore packets (peridioles) toward light sources. These quarter-inch dots adhere tenaciously to light-colored surfaces: white cars, vinyl siding, windows. They're harmless to plants and people but maddeningly difficult to remove once dried.

Prevention: The Best Cure

• Mulch selection: Use large pine bark nuggets, cedar, or cypress mulch—less hospitable to artillery fungus than shredded hardwood.
• Mulch management: Rake mulch regularly to disrupt fungal colonization. Replace mulch entirely every 1-2 years in problem areas.
• Distance: Keep mulch beds at least 30 feet from structures and parking areas when possible.

Removal Methods: Vehicles

Act quickly—fresh spores (under 2 weeks) remove more easily.

• Corn oil: Apply with soft nylon pad, rub gently, wash immediately with car soap. Never leave on hot surfaces.
• White vinegar: Soak spots, then wipe with microfiber cloth.
• Car wax: Apply, let haze, buff off—works on newer spots.
• Bug/tar removers: Products like Turtle Wax Bug & Tar Remover dissolve the adhesive matrix.
• Clay bar: Professional detailers use detailing clay for stubborn residue.

Removal Methods: Buildings

• Mr. Clean Magic Eraser: Surprisingly effective on vinyl siding with minimal scrubbing.
• Bleach solution: 1 quart 5% bleach + 3 quarts water + ½ cup detergent + ⅔ cup TSP. Scrub with soft brush.
• Pressure washing: Low-pressure with appropriate cleaner—high pressure can damage siding.
• Ink eraser + Simple Green: Tedious but effective for small areas.
• Commercial products: Jomax + bleach, Pro-Tek Chemical, or specialized artillery fungus removers.

Key Takeaway

Removal is labor-intensive and never 100% perfect. The only lasting solution is changing your mulch to a less fungus-friendly type and maintaining it proactively. Your shrubs aren't the problem—your mulch is.