Such grazing certainly occurs, but the extent to which it modifies pathogenic interactions is unclear. Here, we consider feeding on fungi in broad terms by arthropods, nematodes, annelids, and protozoa. Understanding the impact of feeding is important when extending laboratory data on plant-pathogen interactions into the field. A summary of relevant published studies from pathogenic systems will be made. These studies will then be evaluated in terms of what can be learned from saprotrophic and mycorrhizal systems, as outlined below.
Grazing can affect ecosystem function and fungal community structure.
Effects on saprotrophic and mycorrhizal systems can be direct, such as by the excretion of nitrogen from the bodies of the grazers, which contributes to mineralisation. Indirect effects are possible as by the action of comminution and mixing of substrate, inoculum dispersal, and changes in vigour of the grazed fungus, all of which can modify mineralisation or immobilisation by the microbes. These indirect effects on mineralisation are important for saprotrophic fungi, but they may also be relevant for certain mycorrhizal fungi with limited saprotrophic capabilities. Effects of grazing on the collection of nutrients from soil and the transfer of them to the plant in mycorrhizal systems are mostly negative. However, at low animal densities a stimulation of mycorrhizal function can occur, which is perhaps related to a stimulation of fungal activity.