There are several types of mites associated with cultivated mushrooms. Three are detailed here; compost mites, bacterial feeding mites and predatory mites. Predatory mites are the most common in North America.
These mites all occur in compost raw materials and their presence on a farm indicates problems with Phase II composting. The compost mites feed on weed molds, yeasts or bacteria. Predatory mites will feed on nematodes, fly eggs and young larvae. If there is no prey present, they can develop and reproduce readily on weed mold spores.
Since the compost mites feed on weed molds or bacteria, they are also indicator species for composting problems. However, unlike what you would expect, the composting problems relate more to conditioning than to the kill phase.
Generally, factors that minimize the occurrence of weed molds will also minimize the occurrence of compost mites.