Published on July 20th, 2013 | by Henri


Fungus on siding comes from mulch

Q.    I hope you can help me. I have shotgun mold or fungus all over my white vinyl fence and house siding. I have been told it is from my mulch. We will be removing the mulch this spring. I tried everything I could think of to remove it. Nothing seems to work. It is so sticky and the little dots are everywhere! Do you have any ideas for me to try?

A.    You are referring to the spores of artillery fungus which develop in the decomposition of most organic mulches. These spores explode and are deposited on nearby surfaces; they prefer light-colored ones. They cannot be removed without risking some damage to the surfaces to which they adhere.

This is a spring and fall problem as these spores do not develop in cold or hot weather. The solution is to get rid of all organic mulch and replace it with new rubber mulch or other materials such as grass or ground cover or apply new mulch yearly over the old one to contain the spores.

Two readers have offered other solutions, which I can’t personally vouch for:

  • “Use cypress mulch to prevent this problem. To remove the spores, wait till freezing weather and they scrape off as they are now very hard.”
  • “Mix mushroom compost in with your hardwood mulch to prevent the fungus. This does prevent the growth.”

Worth a try anyway.

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