Common Mulch Fungus: Does Mulch Cause Fungus And Can It Be Treated?

Mulching is one of the most common ways to keep plants alive in gardens. However, it’s not without its risks. Some fungi are able to grow on mulches, and some even thrive there. These fungi are called “mold” or “fungi.” They’re often referred to as “white” because they look like white mold growing on wood. White fungus may cause mild symptoms such as small spots on leaves and stems, but it’s usually harmless. But other fungi, known as “artillery,” can be deadly if left unchecked.

White fungus on mulch can be treated with fungicides, but the best way to prevent it from happening again is to remove any mulched areas immediately after use. If you don’t do so, your garden will suffer a second round of white fungus later.

(See our article How To Prevent White Mold On Wood.)

Artillery mushrooms have been found growing in almost every type of soil and at all times of year. It is common in many areas of the world, so you may have some in your garden.

Even if you don’t see your plants withering up and dying, you should be careful around artillery fungus (even if it looks dead).

If you or anyone in your family begins to feel ill after mowing the lawn, pruning bushes or raking leaves, get immediate medical attention.

Can I Find Fungus On My Mulch?

Yes. Fungus lives almost everywhere, and it loves to eat dead trees and plants. (In fact, that’s what it does best!) So if you have some rotting wood lying around, there’s a good chance some of it will be infected with white fungus or artillery fungus. However, not all types of mulch contain these types of mold.

For example, if you buy a bag of shredded hardwood at the store, it should be completely free of any type of fungus. This is because fungus needs a specific combination of things to grow, including moisture and oxygen.

Shredded wood has very little surface area (and therefore oxygen), so it can’t support a fungal colony.

Sources & references used in this article:

White mold intensity on common bean in response to plant density, irrigation frequency, grass mulching, Trichoderma spp., and fungicide by TJ Paula Júnior, RF Vieira, PRR Rocha… – Summa …, 2009 – SciELO Brasil

Association of Cellulytic Enzyme Activities in Eucalyptus Mulches with Biological Control of Phytophthora cinnamomi by AJ Downer, JA Menge, E Pond – Phytopathology, 2001 – Am Phytopath Society

Impact of mulches on landscape plants and the environment—a review by L Chalker-Scott – Journal of Environmental Horticulture, 2007 –

Fulminant mulch pneumonitis: an emergency presentation of chronic granulomatous disease by S Siddiqui, VL Anderson, DM Hilligoss… – Clinical Infectious …, 2007 –

Influence of film mulches and soil pesticides on root diseases and populations of soil-borne fungi in vegetables by DR Sumner, AW Johnson, CA Jaworski, RB Chalfant – Plant and Soil, 1978 – Springer

Solar heating by polyethylene mulching for the control of diseases caused by soil-borne pathogens by J Katan, A Greenberger, H Alon, A Grinstein – Phytopathology, 1976 –

Tree pathogen survival in chipped wood mulch by R Koski, WR Jacobi – Arboriculture & Urban Forestry, 2004 –

Polyethylene and biodegradable mulches for agricultural applications: a review by S Kasirajan, M Ngouajio – Agronomy for Sustainable Development, 2012 – Springer



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