Shotgun Fungus Leaves Indelible Black Spots

Summary

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Q. Very small black dots have been showing up on the vinyl siding on two sides of our house. We have tried scrubbing with "house wash" and using bleach, but it didn't help. What's going on? M. Petri

This sounds like an attack of artillery fungus, or shotgun fungus, which usually originates in rotting wood mulch. The fungus develops in the mulch, then fires spores up to 20 feet onto any nearby surfaces such as siding, cars, decks and plants. Unfortunately, the tar-like spores are virtually impossible to remove by any practical means without damaging underlying surfaces. Even pressure washing won't usually work unless it is done shortly after the fungus attacks. Researchers at Pennsylvania State University had some success by scrubbing the fungus vigorously with heavy-duty cleaners such as automotive cleaners, but usually the most practical solution is to scrape the fungus off the siding (some discoloration usually remains on the surface), prime it with a stain- blocking primer and paint it.

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Extract

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Shotgun Fungus Leaves Indelible Black Spots

Your first step should be to rake up any old wood mulch near your house and dispose of it. Bark mulches, such as...

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