An entomopathogenic fungus is a

fungus A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...

that can kill or seriously disable insects.

Typical life cycle

These fungi usually attach to the external body surface of insects in the form of microscopic

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

s (usually asexual, mitosporic spores also called

conidia A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to th ...

). Under the right conditions of temperature and (usually high)

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

, these spores germinate, grow as

hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

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

protoplast Protoplast (), is a biological term coined by Hanstein in 1880 to refer to the entire cell, excluding the cell wall. Protoplasts can be generated by stripping the cell wall from plant, bacterial, or fungal cells by mechanical, chemical or en ...

s (depending on the fungus involved). After some time the insect is usually killed (sometimes by fungal

toxins A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...

), and new propagules (spores) are formed in or on the insect if environmental conditions are again right. High humidity is usually required for

sporulation In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae ...

Groups

The entomopathogenic fungi include

taxa In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

from several of the main fungal groups and do not form a

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic ...

group. Many common and/or important entomopathogenic fungi are in the order

Hypocreales The Hypocreales are an order of fungi within the class Sordariomycetes. In 2008, it was estimated that it contained some 237 genera, and 2647 species in seven families. Since then, a considerable number of further taxa have been identified, i ...

of the

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The de ...

: the asexual (

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the Biological life cycle, life cycles of fungi in the Phylum, phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a Asc ...

) phases '' Beauveria'', '' Isaria'' (was ''Paecilomyces''), '' Hirsutella'', '' Metarhizium'', '' Nomuraea'' and the sexual ( teleomorph) state ''

Cordyceps ''Cordyceps'' is a genus of ascomycete fungi (sac fungi) that includes about 600 species. Most ''Cordyceps'' species are endoparasitoids, parasitic mainly on insects and other arthropods (they are thus entomopathogenic fungi); a few are parasit ...

''; others (''Entomophthora'', ''Zoophthora'', ''Pandora'', ''Entomophaga'') belong in the order Entomophthorales of the

Zygomycota Zygomycota, or zygote fungi, is a former division or phylum of the kingdom Fungi. The members are now part of two phyla: the Mucoromycota and Zoopagomycota. Approximately 1060 species are known. They are mostly terrestrial in habitat, living ...

. Related fungi attack and kill other

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

(e.g.

nematodes The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a broa ...

Pest control

Since they are considered natural mortality agents and environmentally safe, interest in the use of entomopathogenic fungi for

biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically als ...

of insects and other arthropod pests has emerged. In particular, the asexual phases of Ascomycota ('' Beauveria'' spp., '' Isaria'' spp., '' Lecanicillium'' spp., '' Metarhizium'' spp., '' Purpureocillium'' spp. and others) are under 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 Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...

Production

Most entomopathogenic fungi can be grown on artificial media. However, some require complex media; others, like '' Beauveria bassiana'' and exploitable species in the genus '' Metarhizium'', can be grown on starch-rich substrates such as rice or wheat grains.

Virulence

Entomophthorales are often reported as causing high levels of mortality (

epizootic In epizoology, an epizootic (from Greek: ''epi-'' upon + ''zoon'' animal) is a disease event in a nonhuman animal population analogous to an epidemic in humans. An epizootic may be restricted to a specific locale (an "outbreak"), general (an "ep ...

s) in nature. These fungi are

virulent Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its ability to ...

. The anamorphic Ascomycota (''Metarhizium'', '' Beauveria'' etc.) are reported as causing epizootics less frequently in nature.

Host relationship chemical cues

Entomopathogenic fungi such as '' Beauveria bassiana'' and '' Metarhizium anisopliae'' successfully infect susceptible host populations through ''

'' The signaling cues between these fungi and their host targets are under investigation. The ability to sense these parasites can increase fitness for the host targets. Evidence suggests that signal recognition occurs within some hosts, but not others. For example, the

ectoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

Cephalonomia tarsalis ''Cephalonomia tarsalis'' is a idiobiont ectoparasitoid hymenopteran in the family Bethylidae. Known hosts include: ''Oryzaephilus surinamensis'', ''Sitophilus granarius'', ''Sitophilus oryzae'', ''Sitophilus zeamais'', and ''Tribolium castaneum ...

'' is susceptible to ''B. bassiana'' but it cannot detect the presence of free conidia of this fungus or infected hosts. Because they cannot detect these parasites, either the host or the host's offspring become infected and/or die. In contrast, termites are able to detect and avoid some lethal conidia strains.Myles, T.G. (2002) Alarm, aggregation, and defense by Reticulitermes flavipes in response to a naturally occurring isolate of Metarhizium anisopliae. Sociobiology, 40, 243–255. Other soil-dwelling insects have evolved the ability to detect and avoid certain entomopathogenic fungi.

References

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External links

Entomopathogens and microbial control
from the University of Warwick
Insect mycology
by Dr. Richard A. Humber

Entomopathogenic Fungi as Effective Insect Pest Management Tactic: A Review
by Hafiza Tahira Gul Animal fungal diseases Insect ecology Parasites of insects id:Cendawan entomopatogen