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Will poorly composted wood chips used as mulch around my trees spread disease to the trees' roots?

Last Updated: August 26, 2009

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There is little published literature that supports this possibility. Fungal species in decomposing wood chips are generally beneficial, not plant pathogens. Healthy soil communities include mycorrhizal species needed for optimum root health. Under aerobic (oxygen-rich) soil conditions, beneficial and harmless fungi probably outcompete pathogenic fungi as the wood chips decompose. As for the flora, most healthy plants are not susceptible to opportunistic fungal pathogens such as those that may occur in wood chip mulches.

Some advice: don’t amend the soil itself with fresh wood chips (don’t mix them in); doing so will rob your soil of nitrogen as the soil microbes decompose the chips. Also, use fresh wood chips only around well established woody plants as mulch or to fill in walkways and paths.

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