An entomopathogenic fungus is a
fungus
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...
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
spores (usually asexual,
mitosporic spores also called
conidia). 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 and colonize the insect's
cuticle; which they bore through by way of
enzymatic hydrolysis
In biochemistry, enzymatic hydrolysis is a process in which enzymes facilitate the cleavage of bonds in molecules with the addition of the elements of water (i.e. hydrolysis). It plays an important role in the digestion of food.
It may be used t ...
, reaching the insects' body cavity (
hemocoel
The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
).
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
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
![Cordyceps](https://upload.wikimedia.org/wikipedia/commons/8/89/Cordyceps.jpg)
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 nam ...
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
''Beauveria'' is a genus of asexually-reproducing fungi allied with the ascomycete family Cordycipitaceae. Its several species are typically insect pathogens. The sexual states (teleomorphs) of ''Beauveria'' species, where known, are species o ...
'', ''
Isaria
''Isaria'' is a genus of fungi mostly in the order Hypocreales and family Clavicipitaceae, or by some authorities the Cordycipitaceae. It includes a large number of entomopathogenic species, some of them exploited as biopesticides (''e.g. I. ...
'' (was ''Paecilomyces''), ''
Hirsutella
''Hirsutella'' is a genus of asexually reproducing fungi in the Ophiocordycipitaceae family. Originally described by French mycologist Narcisse Théophile Patouillard in 1892, this genus includes species that are pathogens of insects, mites and ne ...
'', ''
Metarhizium
''Metarhizium'' is a genus of entomopathogenic fungi in the Clavicipitaceae family. With the advent of genetic profiling, placing these fungi in proper taxa has now become possible. Most turn out to be the asexual forms (anamorphs) of fungi in ...
'', ''
Nomuraea
''Nomuraea'' is a genus of fungi in the family Clavicipitaceae.
The genus name of ''Nomuraea'' is in honour of H. Nomura (b.1897), who was a Japanese scientist.
The genus was circumscribed by André Maublanc in Bull. Soc. Mycol. France vol.19 ...
'' and the sexual (
teleomorph
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota:
*Teleomorph: the sexual reproductive stage (morph), typically a fruiting body.
*Anamorph: an asex ...
) state ''
Cordyceps''; others (''Entomophthora'', ''Zoophthora'', ''Pandora'', ''Entomophaga'') belong in the order
Entomophthorales
The Entomophthorales are an order of fungi that were previously classified in the class Zygomycetes. A new subdivision, Entomophthoromycotina, has recently been circumscribed for them.
Most species of the Entomophthorales are pathogens of ins ...
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 chordat ...
(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 also i ...
of insects and other arthropod pests has emerged. In particular, the asexual phases of Ascomycota (''
Beauveria
''Beauveria'' is a genus of asexually-reproducing fungi allied with the ascomycete family Cordycipitaceae. Its several species are typically insect pathogens. The sexual states (teleomorphs) of ''Beauveria'' species, where known, are species o ...
'' spp., ''
Isaria
''Isaria'' is a genus of fungi mostly in the order Hypocreales and family Clavicipitaceae, or by some authorities the Cordycipitaceae. It includes a large number of entomopathogenic species, some of them exploited as biopesticides (''e.g. I. ...
'' spp., ''
Lecanicillium
''Lecanicillium'' is a genus of fungi in the order Hypocreales and is described as anamorphic Cordycipitaceae; 21 species are currently described. Some of these entomopathogenic fungus species were previously widely known as ''Verticillium leca ...
'' spp., ''
Metarhizium
''Metarhizium'' is a genus of entomopathogenic fungi in the Clavicipitaceae family. With the advent of genetic profiling, placing these fungi in proper taxa has now become possible. Most turn out to be the asexual forms (anamorphs) of fungi in ...
'' spp., ''
Purpureocillium
''Purpureocillium'' is a fungal genus in the Ophiocordycipitaceae family. The genus now contains at least 5 species with the type species ''Purpureocillium lilacinum'', a common saprobic, filamentous fungus. It has been isolated from a wide range ...
'' spp. and others) are under scrutiny due to traits favouring their use as
biological insecticides
A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.
They are obtained from organisms inclu ...
. 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 complex media; others, like ''
Beauveria bassiana'' and exploitable species in the genus ''
Metarhizium
''Metarhizium'' is a genus of entomopathogenic fungi in the Clavicipitaceae family. With the advent of genetic profiling, placing these fungi in proper taxa has now become possible. Most turn out to be the asexual forms (anamorphs) of fungi in ...
'', 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 "epi ...
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
''Beauveria'' is a genus of asexually-reproducing fungi allied with the ascomycete family Cordycipitaceae. Its several species are typically insect pathogens. The sexual states (teleomorphs) of ''Beauveria'' species, where known, are species o ...
'' etc.) are reported as causing epizootics less frequently in nature.
Host relationship chemical cues
Entomopathogenic fungi such as ''
Beauveria bassiana'' and ''
Metarhizium anisopliae
''Metarhizium robertsii'' formerly known as ''M. anisopliae'', and even earlier as ''Entomophthora anisopliae'' (basionym) is a fungus that grows naturally in soils throughout the world and causes disease in various insects by acting as a paras ...
'' successfully infect susceptible host populations through ''
conidia'' 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 ''
Cephalonomia tarsalis'' 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.
See also
*
Biological insecticides
A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.
They are obtained from organisms inclu ...
*
Entomopathogenic nematode
Entomopathogenic nematodes (EPN) are a group of nematodes (thread worms), that cause death to insects. The term ''entomopathogenic'' has a Greek origin, with ''entomon'', meaning ''insect'', and ''pathogenic'', which means ''causing disease''. Th ...
*
LUBILOSA
LUBILOSA was the name of a research programme that aimed at developing a biological alternative to the chemical control of locusts. This name is an acronym of the French title of the programme: Lutte Biologique contre les Locustes et les Sauteri ...
and the
desert locust
The desert locust (''Schistocerca gregaria'') is a species of locust, a periodically swarming, short-horned grasshopper in the family Acrididae. They are found primarily in the deserts and dry areas of northern and eastern Africa, Arabia, and sou ...
pages for more on use of ''Metarhizium'' as a biological insecticide.
References
{{reflist
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