Entomopathogenic fungus

An entomopathogenic fungus is a fungus that can act as a parasite of insects and kills or seriously disables them.
Typical life cycle.
These fungi usually attach to the external body surface of insects in the form of microscopic spores (usually asexual, mitosporic spores also called conidia). Under the right conditions of temperature and (usually high) humidity, these spores germinate, grow as hyphae and colonize the insect's cuticle; which they bore through by way of enzymatic hydrolysis, reaching the insects' body cavity (hemocoel). Then, the fungal cells proliferate in the host body cavity, usually as walled hyphae or in the form of wall-less protoplasts (depending on the fungus involved). After some time the insect is usually killed (sometimes by fungal toxins), and new propagules (spores) are formed in or on the insect if environmental conditions are again right. High humidity is usually required for sporulation.
Groups.
The entomopathogenic fungi include taxa from several of the main fungal groups and do not form a monophyletic group. Many common and/or important entomopathogenic fungi are in the order Hypocreales of the Ascomycota: the asexual (anamorph) phases "Beauveria", "Isaria" (was "Paecilomyces"), "Hirsutella", "Metarhizium", "Nomuraea" and the sexual (teleomorph) state "Cordyceps"; others ("Entomophthora", "Zoophthora", "Pandora", "Entomophaga") belong in the order Entomophthorales of the Zygomycota.
Related fungi attack and kill other invertebrates (e.g. nematodes).
Pest control.
Since they are considered natural mortality agents and environmentally safe, there is worldwide interest in the use and manipulation of entomopathogenic fungi for biological control of insects and other arthropod pests. In particular, the asexual phases of Ascomycota ("Beauveria" spp., "Isaria" spp., "Lecanicillium" spp., "Metarhizium" spp., "Purpureocillium" spp. and others) are under intense scrutiny due to traits favouring their use as biological insecticides. The development of entomopathogens as pesticides depends on research into their host specificity, stability, formulation, and methods of application.
Production.
Most entomopathogenic fungi can be grown on artificial media. However, some require extremely complex media; others, like "Beauveria bassiana" and exploitable species in the genus "Metarhizium", can be grown on starch-rich substrates like cereal grains (rice, wheat).
Virulence.
The Entomophthorales are often reported as causing high levels of mortality (epizootics) in nature. These fungi are highly virulent. The anamorphic Ascomycota ("Metarhizium", "Beauveria" etc.) are reported as causing epizootics less frequently in nature.
Host Relationship Chemical Cues.
Entomopathogenic fungi like "Beauveria bassiana", "Vuillemin" , and "Metarhizium anisopliae" successfully infect susceptible host populations through "conidia" There is continued research to determine the signaling cues between this fungus and its host targets. After all, the ability to sense this parasite can increase fitness for the host targets. There is evidence that the signal recognition occurs within some hosts, but not others. 
For example, the ectoparasitoid "Cephalonomia tarsalis" is susceptible to "B. bassiana" but it cannot detect the presence of free conidia of this fungus or living hosts that were infected by the fungus. Because they cannot detect these parasites, either the host or the host's offsping become infected and/or dies. In contrast, termites are able to detect and avoid some lethal strains of conidia. Furthermore, other soil-dwelling insects have evolved the ability to detect and avoid certain entomopathogenic fungi.