Worms, particularly composting species like the red wiggler, are classified as detritus feeders, meaning they consume decomposing organic matter. The short answer to whether worms eat mold is yes. Fungi and molds are a preferred and valuable part of their diet, central to the process of breaking down waste in a vermicomposting system. This feeding behavior is a fundamental part of how organic materials are recycled in nature, transforming waste into nutrient-rich soil amendments.
The Worm’s Primary Diet
Earthworms and composting worms primarily feed on decaying plant material, but they are not consuming the raw substance itself. Instead, their sustenance comes from the dense layer of microorganisms—bacteria, protozoa, and fungi—that colonize the surface of the decomposing material. They act as grazers, stripping this microbial film from organic scraps as they pass through. This microbial consumption provides the necessary nutrition for the worm to thrive.
Fungi and Mold as a Preferred Food Source
Worms actively seek out and consume mold and fungi, a behavior that classifies them as fungivores. Fungi represent a highly desirable food source compared to raw, undecayed plant matter. This preference is due to the high nutritional content of the fungal biomass. Fungi are rich in protein and nitrogen, two elements that are often limiting in the carbon-heavy diets of detritivores.
Earthworm species often exhibit a strong preference for soils and environments where fungal propagules are abundant. This grazing behavior is so effective that the presence of earthworms can significantly reduce the overall fungal population in a given area. Fungi are viewed as a high-quality meal, fueling faster growth and reproduction in the worm population. Composting worms fed on substrates rich in fungal growth, like spent mushroom substrate, show enhanced biomass gains.
The Biology of Fungal Digestion
The ability of a worm to digest fungi and mold focuses on breaking down the fungal cell wall. Unlike plants, whose cell walls are made of cellulose, fungal cell walls are composed mainly of chitin, a tough polymer. To process this material, earthworms possess specialized enzymes. The primary enzyme responsible for breaking down the fungal structure is chitinase.
Chitinase activity is produced either directly by the worm’s own digestive system or by the symbiotic microbes living within its gut. This enzyme allows the worm to extract the valuable nutrients, particularly the protein, locked within the fungal biomass. The ingested material is physically ground in the worm’s gizzard, then chemically broken down in the intestine, allowing nutrient absorption before the processed material is excreted as castings.
Safe and Unsafe Molds in Compost Systems
In a well-managed vermicomposting bin, the majority of mold and fungi that appear are beneficial and safe for the worms. Common molds appearing in various colors, such as white, green, or gray, are harmless decomposers that speed up the composting process. Their growth is a natural sign of organic breakdown and a healthy microbial community. These molds help break down complex materials that bacteria alone cannot handle efficiently.
Certain types of mold and fungi should be avoided, especially those associated with food safety concerns. Molds that produce mycotoxins, such as aflatoxins, are problematic because these toxins can be harmful to the worms and potentially the resulting compost. Avoid adding molds that grow on meat, dairy, or fatty and oily foods, as these often promote anaerobic conditions and attract undesirable pests.