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''Metarhizium acridum'' is the new name given to a group of fungal isolates that are known to be virulent and specific to the Acrididea (grasshoppers). Previously, this species has had variety status in '' Metarhizium anisopliae'' (var. ''acridum'' ); before that, reference had been made to '' M. flavoviride'' or ''Metarhizium sp.'' describing an "apparently homologous and distinctive group" of isolates that were most virulent against '' Schistocerca gregaria'' (desert locust) in early screening bioassays.


Biology

''M. acridum'' almost exclusively infects
grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshopp ...
s in the order
Orthoptera Orthoptera () is an order of insects that comprises the grasshoppers, locusts, and crickets, including closely related insects, such as the bush crickets or katydids and wētā. The order is subdivided into two suborders: Caelifera – grassho ...
. ''M. acridum'' infects only grasshoppers and locusts. Researchers believe that this has to do with the ''Mest1'' gene which is not present in ''M. acridum''. By taking a strain of '' M. robertsii'' that has a nonfunctioning ''Mest1 gene'', researchers found that the mutant was only able to infect '' Melanoplus femurrubrum'', which is consistent with ''M. acridum'' activity. This allows the initiation of the infection process on the specific targets. The expression of '' Mest1'' in the entomopathogen ''M. acridum'' is triggered by substances that are only found on the waxy coat of the grasshoppers, which explains why this pathogen specifically only targets grasshoppers and locusts.


Applications


Pesticide

It has been used to control
locusts Locusts (derived from the Vulgar Latin ''locusta'', meaning grasshopper) are various species of short-horned grasshoppers in the family Acrididae that have a swarming phase. These insects are usually solitary, but under certain circumst ...
. The international LUBILOSA programme (which developed the product Green Muscle) identified and addressed key technical challenges for exploitation of microbial control agents, including isolate selection, mass production, and delivery systems (
formulation Formulation is a term used in various senses in various applications, both the material and the abstract or formal. Its fundamental meaning is the putting together of components in appropriate relationships or structures, according to a formul ...
and
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 ...
). Insect control (mortality) depends on factors such as the number of spores applied against the insect host, the formulation and weather conditions. Oil-based formulations allow the application of fungal spores under dry conditions, and are compatible with existing ultra-low volume (ULV) application techniques for locust control. As of 2012 ''M. acridum'' was under consideration by the USDA for release in the Western U.S. for control of native grasshoppers and crickets.


Important isolates

* IMI 330189 (= ARSEF 7486) is the ex-type of the species, originally collected from Niger: the active ingredient of 'Green Muscle'. * CSIRO FI 985 (= ARSEF 324) is an Australian isolate: the active ingredient of 'Green Guard'. * EVCH077 (= IMI 382977) has been isolated from an unidentified grasshopper in Benin: the active ingredient of 'NOVACRID'.


Gallery

Metarhizium acridum infecting locust (PLoS).jpg CSIRO ScienceImage 1367 Locusts attacked by the fungus Metarhizium.jpg, CSIRO isolate


References

{{Taxonbar, from=Q760265 Biopesticides Clavicipitaceae Parasitic fungi Fungi described in 2009