Uncomposted wood chip mulches can spread pathogenic fungi and bacteria tohealthy roots.
There is little published literature that supports this possibility. Fungal species indecomposing wood chips are generally decomposers, not plant pathogens. Healthy soilcommunities include mycorrhizal species needed for optimum root health; under healthy("aerobic" or oxygen-rich) soil conditions, beneficial and harmless fungi probablyoutcompete pathogenic fungi. As for the flora, most healthy plants are not susceptible toopportunistic fungal pathogens such as those that may occur in wood chip mulches. Don't amend the soil itself with wood chips (in other words, don't mix them in); doing so will rob your soil of nitrogen as they decompose. Use wood chips only as a topdressing.