Entomopathogenic fungus

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Entomopathogenic fungi are parasitic unicellular or multicellular microorganisms belonging to the kingdom of Fungi, that can infect and seriously disable or kill insects. Entomopathogenicity is not limited to a particular class of fungi and is found in six divisions in the fungal kingdom (Ascomycota, Oomycetes, Basidiomycota, Chytridiomycota, Zygomycota, and Microsporidia). [1] Some fungal entomopathogens are opportunistic whereas some have evolved into highly specific pathogens of insects. [1]

Contents

Unlike many other insect pathogens (entomopathogenic viruses, nematodes, or bacteria), most entomopathogenic fungi do not require entry through ingestion or oral intake and instead directly attack the insect cuticle and penetrate the insect body through the exoskeleton. [2] These fungi use a broad spectrum of virulence factors such as adhesins (to attach to insect cuticles), lytic enzymes (to hydrolyze insect cuticles), and secondary metabolites. [3] Some entomopathogenic fungi have evolved ability to manipulate insect behavior by hijacking insect nervous systems using various secondary metabolites [4]

Entomopathogenic fungi perform a vital ecological role in natural environments by controlling insect populations. 19 out of 30 insect orders have fungal pathogens. [1] [4] Because of this ability, they are used in agriculture as biocontrol agents/bioinsecticides and are considered to a sustainable alternative to chemical pesticides. [5]

Typical life cycle and general biology

Green peach aphid, Myzus persicae, killed by the fungus Pandora neoaphidis (Zygomycota: Entomophthorales) Scale bar = 0.3 mm Pandora neoaphidis.jpg
Green peach aphid, Myzus persicae, killed by the fungus Pandora neoaphidis (Zygomycota: Entomophthorales) Scale bar = 0.3 mm

Entomopathogenic fungi do not form a monophyletic group. Fungi from different lineages can have different life cycles and differences can be seen even within lineages, between species, or even between isolates within a species. [5] Because of this high diversity and contrasting differences between fungi from different lineages, it is difficult to define a detailed typical lifecycle that is common to all entomopathogenic fungi.

However, use of microscopic spores (usually asexual or Conidia) dispersed throughout the environment to initiate the infection process is common across all known entomopathogenic fungi. These spores commonly use Hydrophobins and Adhesins to attach to and recognize the host cuticle. [3] 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). Regardless of whether the infecting fungus is a host generalist or a specialist, the infection usually leads to the death of the insect, upon which the fungus emerges and sporulates on the dead insect. Sporulation usually takes place on the external surface of the cadaver. However, it can also occur on the internal surfaces of the cadaver depending on the environmental humidity. Some fungi keep the insect cadavers attached to foliage using rhizoids to ensure that they remain in the same environment where it is more likely to encounter suitable new hosts. [5]

Groups

Cordyceps fungi are parasitoids of various arthropod species. Here is a wasp parasitized by the fungus Cordyceps. Cordyceps.jpg
Cordyceps fungi are parasitoids of various arthropod species. Here is a wasp parasitized by the fungus Cordyceps.

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.

Pest management

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. [6] 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. 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.

Virulence

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.

Host relationship chemical cues

Entomopathogenic fungi such as Beauveria bassiana and Metarhizium spp. successfully infect susceptible host populations through conidia . [7] [8] 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. [9] 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. [10] Other soil-dwelling insects have evolved the ability to detect and avoid certain entomopathogenic fungi.[ citation needed ]

See also

Related Research Articles

<i>Beauveria bassiana</i> Species of fungus

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.

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.

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.

Clonostachys rosea f. rosea, also known as Gliocladium roseum, is a species of fungus in the family Bionectriaceae. It colonizes living plants as an endophyte, digests material in soil as a saprophyte and is also known as a parasite of other fungi and of nematodes. It produces a wide range of volatile organic compounds which are toxic to organisms including other fungi, bacteria, and insects, and is of interest as a biological pest control agent.

<i>Beauveria</i> Genus of fungi

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.

<span class="mw-page-title-main">Nematophagous fungus</span> Carnivorous fungi specialized in trapping and digesting nematodes

Nematophagous fungi are carnivorous fungi specialized in trapping and digesting nematodes. More than 700 species are known. Species exist that live inside the nematodes from the beginning and others that catch them, mostly with glue traps or in rings, some of which constrict on contact. Some species possess both types of traps. Another technique is to stun the nematodes using toxins, a method employed by Coprinus comatus, Stropharia rugosoannulata, and the family Pleurotaceae. The habit of feeding on nematodes has arisen many times among fungi, as is demonstrated by the fact that nematophagous species are found in all major fungal groups. Nematophagous fungi can be useful in controlling those nematodes that eat crops. Purpureocillium, for example, can be used as a bio-nematicide.

<span class="mw-page-title-main">LUBILOSA</span> Locust pesticide research program

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.

<i>Metarhizium flavoviride</i> Species of fungus

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.

<span class="mw-page-title-main">Fungi imperfecti</span> Fungal classification based on asexual characters when sexual reproduction is unidentified

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.

<i>Purpureocillium lilacinum</i> Species of fungus

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.

<span class="mw-page-title-main">Muscardine</span> Fungal disease of insects

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.

<span class="mw-page-title-main">Jean Beauverie</span> French botanist and mycologist

Jean Beauverie was a French botanist and mycologist.

Zoophthora is a genus of fungi in the family Entomophthoraceae. Like other taxa in this family, Zoophthora species cause disease in insects and as such are considered entomopathogenic fungi.

<i>Curculio elephas</i> Species of beetle

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.

<i>Isaria fumosorosea</i> Species of fungus

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.

<i>Metarhizium anisopliae</i> Species of fungus

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.

Batkoa major is a naturally occurring fungus that infects insects.

References

  1. 1 2 3 Araújo, J. P. M.; Hughes, D. P. (2016-01-01), Lovett, Brian; St. Leger, Raymond J. (eds.), "Chapter One - Diversity of Entomopathogenic Fungi: Which Groups Conquered the Insect Body?", Advances in Genetics, Genetics and Molecular Biology of Entomopathogenic Fungi, 94, Academic Press: 1–39, doi:10.1016/bs.adgen.2016.01.001, PMID   27131321 , retrieved 2024-09-11
  2. ↑ Ortiz-Urquiza, Almudena; Keyhani, Nemat O. (2013). "Action on the Surface: Entomopathogenic Fungi versus the Insect Cuticle". Insects. 4 (3): 357–374. doi: 10.3390/insects4030357 . ISSN   2075-4450. PMC   4553469 . PMID   26462424.
  3. 1 2 Litwin, Anna; Nowak, Monika; Różalska, Sylwia (2020-03-01). "Entomopathogenic fungi: unconventional applications". Reviews in Environmental Science and Bio/Technology. 19 (1): 23–42. doi:10.1007/s11157-020-09525-1. ISSN   1572-9826.
  4. 1 2 Xiao, Guohua; Ying, Sheng-Hua; Zheng, Peng; Wang, Zheng-Liang; Zhang, Siwei; Xie, Xue-Qin; Shang, Yanfang; St. Leger, Raymond J.; Zhao, Guo-Ping; Wang, Chengshu; Feng, Ming-Guang (2012-07-02). "Genomic perspectives on the evolution of fungal entomopathogenicity in Beauveria bassiana". Scientific Reports. 2 (1): 483. doi:10.1038/srep00483. ISSN   2045-2322. PMC   3387728 . PMID   22761991.
  5. 1 2 3 Shah, P. A.; Pell, J. K. (2003-06-01). "Entomopathogenic fungi as biological control agents". Applied Microbiology and Biotechnology. 61 (5): 413–423. doi:10.1007/s00253-003-1240-8. ISSN   1432-0614.
  6. ↑ Strasser H, Vey A, Butt TM (28 June 2010). "Are There any Risks in Using Entomopathogenic Fungi for Pest Control, with Particular Reference to the Bioactive Metabolites of Metarhizium, Tolypocladium and Beauveria species?". Biocontrol Science and Technology. 10 (6): 717–735. doi:10.1080/09583150020011690. S2CID   83558063.
  7. ↑ Vandenburg, J.D., Ramos, M. & Altre, J.A. (1998) Dose –response and age- and temperature-related susceptibility of the diamondback moth (Lepidoptera: Plutellidae) to two isolates of Beauveria bassiana (Hyphomycetes: Moniliaceae). Environmental Entomology, 27, 1017–1021.
  8. ↑ Hughes, W.O.H., Petersen, K.S., Ugelvig, L.V., Pedersen, D., Thomsen, L., Poulsen, M. et al. (2004) Density-dependence and within-host competition in a semelparous parasite of leafcutting ants. BMC Evolutionary Biology, 4, 45.
  9. ↑ Lord, J.C. (2001) Response of the wasp Cephalonomia tarsalis (Hymenoptera: Bethylidae) to Beauveria bassiana (Hyphomycetes: Moniliales) as free conidia or infection in its host, the sawtoothed grain beetle, Oryzaephilus surinamensis (Coleoptera: Silvanidae). Biological Control, 21, 300–304.
  10. ↑ 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.
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