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An entomopathogenic fungus is a fungus that can kill or seriously disable insects. They do no need to enter an insect's body through oral ingestion or intake; rather, they directly penetrate though the exoskeleton.
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). [1] 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.
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.
Fungi may also attack and kill other invertebrates: for example, Purpureocillium (Ophiocordycipitaceae) is used to control nematode pests.
Since they are considered natural mortality agents and environmentally safe, entomopathogenic fungi for biological control of insects have been studied for more than 100 years. 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 biopesticides. [2] The development of entomopathogens as pesticides depends on research into their host specificity, stability, formulation, and methods of application.
Most entomopathogenic fungi can be grown on artificial media. Some require complex media, while others, like Beauveria bassiana and exploitable species in the genus Metarhizium , can be grown on starch-rich substrates such as rice or wheat grains.
Entomophthorales are often reported as causing epizootics (outbreaks with many deaths) in nature. These fungi are virulent. The anamorphic Ascomycota (Metarhizium, Beauveria etc.) are reported as causing epizootics less frequently in nature.
Entomopathogenic fungi such as Beauveria bassiana and Metarhizium spp. successfully infect susceptible host populations through conidia . [3] [4] 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. [5] Because they cannot detect these parasites, either the host or the host's offspring become infected and/or die. In contrast, termites detect and avoid some lethal conidia strains. [6] Other soil-dwelling insects have evolved the ability to detect and avoid certain entomopathogenic fungi.[ citation needed ]
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 defining feature of this fungal group is the "ascus", a microscopic sexual structure in which nonmotile spores, called ascospores, are formed. However, some species of Ascomycota are asexual and thus do not form asci or ascospores. Familiar examples of sac fungi include morels, truffles, brewers' and bakers' yeast, dead man's fingers, and cup fungi. The fungal symbionts in the majority of lichens such as Cladonia belong to the Ascomycota.
Beauveria bassiana is a fungus that grows naturally in soils throughout the world and acts as a parasite on various arthropod species, causing white muscardine disease; it thus belongs to the group of entomopathogenic fungi. It is used as a biological insecticide to control a number of pests, including termites, thrips, whiteflies, aphids and various beetles. Its use in the control of bed bugs and malaria-transmitting mosquitos is under investigation.
A biopesticide is a biological substance or organism that damages, kills, or repels organisms seen as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.
Metarhizium robertsii is a fungus that grows naturally in soils throughout the world and causes disease in various insects by acting as a parasitoid. It is a mitosporic fungus with asexual reproduction, which was formerly classified in the form class Hyphomycetes of the phylum Deuteromycota.
Paecilomyces is a genus of fungi. A number of species in this genus are plant pathogens.
Hyphomycetes are a form classification of fungi, part of what has often been referred to as fungi imperfecti, Deuteromycota, or anamorphic fungi. Hyphomycetes lack closed fruit bodies, and are often referred to as moulds. Most hyphomycetes are now assigned to the Ascomycota, on the basis of genetic connections made by life-cycle studies or by phylogenetic analysis of DNA sequences; many remain unassigned phylogenetically.
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 of Cordyceps.
Entomophthora muscae is a species of pathogenic fungus in the order Entomophthorales which causes a fatal disease in flies. It can cause epizootic outbreaks of disease in houseflies and has been investigated as a potential biological control agent.
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 Sauteriaux. During its 13-year life, the programme identified an isolate of an entomopathogenic fungus belonging to the genus Metarhizium and virulent to locusts, and went through all the necessary steps to develop the commercial biopesticide product Green Muscle based on its spores.
Metarhizium flavoviride is a Sordariomycete in the order Hypocreales and family Clavicipitaceae. The genus Metarhizium currently consists of over 70 described species and are a group of fungal isolates that are known to be virulent against Hemiptera and some Coleoptera. M. flavoviride is described as its own species, but there also exists a variety of M. flavoviride, which is M. flavoviride var. flavoviride. Previously described varieties of M. flavoviride have been documented, however recent random amplified polymorphic DNA (RAPD) markers have assigned these varieties as new species. The reassigned species are as follows: M. flavoviride Type E is now M. brasiliense; M. flavoviride var. minus is now M. minus; M. flavoviride var. novozealandicum is now M. novozealandicum; and M. flavoviride var. pemphigi is now M. pemphigi.
The fungi imperfecti or imperfect fungi are fungi which do not fit into the commonly established taxonomic classifications of fungi that are based on biological species concepts or morphological characteristics of sexual structures because their sexual form of reproduction has never been observed. They are known as imperfect fungi because only their asexual and vegetative phases are known. They have asexual form of reproduction, meaning that these fungi produce their spores asexually, in the process called sporogenesis.
Purpureocillium lilacinum is a species of filamentous fungus in the family Ophiocordycipitaceae. It has been isolated from a wide range of habitats, including cultivated and uncultivated soils, forests, grassland, deserts, estuarine sediments and sewage sludge, and insects. It has also been found in nematode eggs, and occasionally from females of root-knot and cyst nematodes. In addition, it has frequently been detected in the rhizosphere of many crops. The species can grow at a wide range of temperatures – from 8 to 38 °C for a few isolates, with optimal growth in the range 26 to 30 °C. It also has a wide pH tolerance and can grow on a variety of substrates. P. lilacinum has shown promising results for use as a biocontrol agent to control the growth of destructive root-knot nematodes.
Muscardine is a disease of insects. It is caused by many species of entomopathogenic fungus. Many muscardines are known for affecting silkworms. Muscardine may also be called calcino.
Curculio elephas is a species of beetle in the family Curculionidae, the true weevils. It is known commonly as the chestnut weevil. It is a serious pest of chestnut in Europe.
Entomophaga grylli is a fungal pathogen which infects and kills grasshoppers. It is the causal agent of one of the most widespread diseases affecting grasshoppers. This is sometimes known as summit disease because infected insects climb to the upper part of a plant and grip the tip of the stem as they die; this ensures widespread dispersal of the fungal spores. The fungus is a species complex with several different pathotypes, each one of which seems to be host-specific to different subfamilies of grasshoppers. The pathogen is being investigated for its possible use in biological pest control of grasshoppers.
Hoplocampa testudinea, the apple sawfly or European apple sawfly, is a species of sawfly in the family Tenthredinidae. It is native to Europe but has been accidentally introduced into North America where it became invasive. The larvae feed inside the developing fruits of the apple tree.
Isaria fumosorosea is an entomopathogenic fungus, formerly known as Paecilomyces fumosoroseus. It shows promise as a biological pesticide with an extensive host range.
Tariq Butt is a British entomologist. He is a Professor of Biosciences at Swansea University in Wales.
Donald W. Roberts was an American insect pathologist and one of the originators of that field. He was especially known for research into biological pest control of Lepidoptera by Metarhizium but also Beauveria bassiana. He was a Research Professor Emeritus in the Biology Department of Utah State University.
Metarhizium anisopliae is the type species in its genus of fungi, that grows naturally in soils throughout the world and causes disease in various insects by acting as a parasitoid. Ilya I. Mechnikov named it Entomophthora anisopliae (basionym) after the insect species from which it was originally isolated – the beetle Anisoplia austriaca and from these early days, fungi such as this have been seen as potentially important tools for pest management. It is a mitosporic fungus with asexual reproduction, which was formerly classified in the form class Hyphomycetes of the phylum Deuteromycota.
