The nematophagous or nematode feeding fungi that have been isolated are typically categorized as shown above. This categorization is somewhat arbitrary as it is based on feeding habits rather than phylogeny. However, it is sufficient for the purposes of this discussion. The taxonomic categorization of these fungi is unstable as is typical for organisms being actively studied and we will mention only a few of the hundreds of known parasites by name.

Each group utilizes a different type of structure to adhere to or to attack nematodes. For nematode trapping fungi, this is thought to be mainly a passive activity with the fungus waiting for the nematode to pass by and become stuck to knobs , networks, or conidia. The fungi which form rings have been shown to form more rings in the presence of nematodes than in their absence. It is not well understood why nematodes put their heads through the rings. However, when they do they either become wedged, or stuck on an adhesive substance, or the rings constrict. Fungal hyphae then penetrate the nematode and utilize it for food.

Some nematophagous fungi have been shown to be poor competitors in the natural environment. They utilize the nematode cuticle for protection from other organisms.

Many of the nematode parasitic fungi can be raised in the laboratory on various media.

Some have been encapsulated in pellets made from calcium arginate to aid in their dispersal in the field and to provide a food source until a nematode is encountered.

HIrsutella rhossiliensis is one example of a fungus with conidia which adhere to nematodes which may accidentally contact them. Fungal hyphae then penetrate the cuticle, utilize the internal contents for food, and the cuticle for protection. When the food source has been utilized, adhesive conidia grow out of the cuticle to await passage of another host.

Zoosporic fungi have swimming spores which can seek out nematodes, attach to the cuticle, and develop hyphae which feed on nematodes.

Some fungi parasitize vermiform adult or larval nematodes, while others parasitize eggs, or cysts. Egg parasites include fungi from a variety of taxonomic groups.