In 1988 it was discovered for the first time a fungus (Arthrobotrys oligospora) was able to infect nematodes. Most of its hosts, nematodes, are parasites of plants or animals afecting cultives and cattle. Therefore, it is very interesting the possibility to use fungi eating nematodes and entomopathogenic as biological control agents versus the classic agrochemicals.
Nematophagus fungi are microorganisms with the capacity to attack, kill and digest nematodes (eggs, juvenile and adults). Apart from the nematophagic activity, most of these fungi may also live saprophytically on dead organic matter, attack other fungi (microparasytes) and colonise plant roots as endophytes. There are more than 300 species of nematophagus fungi described. Most of the phytopathogens nematodes live in the soil and attack plant roots.
The nematophagus fungi are divided in four groups, depending on their way to infect nematodes. The result of the infection is always the same: a fully-digested nematode. The nutrients coming from nematodes are used to form new fungic structures (hyphae, spores, etc.)
The four groups are:
- Nematode-catching fungi: They form several types of catching organs in their hyphae.
- Endoparasite fungi: they use their spores to infect nematodes.
- Egg-parasite fungi: they infect non-mobile (eggs) stages of nematodes.
- Toxin-producing fungi: las Hyphae from this fungi contain one drop of this toxin. When nematodes get in touch with the toxin, they are immediately immobilized and, therefore, hyphae in the fungi grow chemotropically through the mouth of the nematode, digesting it.
Entomopathogenic fungi may either eliminate or maintain pests at levels that don’t cause economic damage in crops. These fungi are found in stubbles of crops, manure, soil, plants and others, achieving a good development in fresh, wet places and with not much sunshine. They constitute, besides, the most important group in the biological control of insect pests. All insects are, practically, susceptible to some of the diseases caused by fungi. Approximately 100 genders and 700 species of entomopathogenic fungi are known. To be able to use these fungi as insecticides, in the first place we must produce massive amounts and, secondly, they assure their infecting capacity for a considerable long period of time. The exploitation of fungi for pest control implies a wide multidisciplinar investigation: genetics, physiology, ecology, pathology, massive production, etc.