ENTOMOGENOUS FUNGI

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            Entomogenous means ‘growing on or in the bodies of insects’ and strictly-speaking applies to all those organisms including bacteria and fungi. However, the word is most often used to describe filamentous fungi that invade their insect hosts by penetrating directly through the cuticle.
            Many common and important entomogenous fungi belong to the order Hypocreales of the Ascomycota – Beauveria, Isaria, Hirsutella, Metarhizium, Nomuraea, Cordyceps; and of the order Entomophthorales of the Zygomycota - Entomophthora, Zoophthora, Pandora, Entomophaga.
            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 favourable. High humidity is usually required for sporulation.
             IMPORTANCE
          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, Isaria, Hirsutella, Metarhizium, Nomuraea, etc,.) are under intense scrutiny due to the traits favouring their use as biological insecticides.
            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.

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