The Disease and pest management function represents the capacity of soils to prevent the establishment and development of soil-borne plant pathogens and pests despite their presence in the field, the availability of a susceptible plant host, and a suitable environment. This function heavily relies on interactions between organisms that varies depending on the type of pests, pathogens, and crops present in the system. As such, this function is very sensitive to changes and influences from external factors that differently affect interactions and the organisms involved in these. This function is supported by two groups of underlying processes:
(1) Disease suppression and pest control – refers to the direct interaction of soil organisms with plant pathogens/pests, that ultimately decrease the damage that may be induced in the absence of these soil organisms. For example, soil fungi and bacteria can produce antibiotics, enzymes and other substances active against pests and pathogens, they can compete with pathogens and pests for space and nutrients and can parasitize them, sometime even causing their death. A variety of animals, microscopic and macroscopic, such as nematodes or spiders, are active in predating and graze upon pests and pathogens.
(2) Plant health promotion – refers to the interactions between soil organisms and plants that trigger the plants resistance and defence responses towards pests and pathogens, or enhance plant metabolism, for example through the production of growth hormones. Through these processes, soil organisms indirectly interact with pathogens and pests, ultimately helping plants to cope with diseases. Plants often release specific soil volatiles or exudates that attract beneficial organisms to help. For example, when plants experience pest or pathogen induced stresses, but also abiotic stressed, they can recruit beneficial organisms from the environment using the so-called ‘cry for help’ strategy.
The Disease and pest management function is important because it supports plant health and ultimately the quality and quantity of food, feed, fibre and fuel production. In addition to this effect on plant health, the Disease and pest management function can reduce the use of pesticides and fungicides ultimately decreasing the residues of these compounds in the environment, and their negative effect on non-target organisms. When these non-target organisms are involved in the abovementioned processes, these negative effects can, in turn, be detrimental for the Disease and pest management function.