Entamopathogenic

Fungi as a

Biocontrol Agent

By V. Vigneshwaran

BASIC madonscience.blogspot.com

WITH A SPECIAL FOCUS ON

Beauveria bassiana and Hirsutella

Beauveria bassiana

Entomopathogenic Fungus An entomopathogenic fungus is a fungus that can act as a parasite of insects and

kills or seriously disables them.

Since they are considered natural mortality agents and environmentally safe, there is worldwide interest in the use and manipulation of entomopathogenic fungi for biological control of insects and other arthropod pests.

In particular, the asexual phases of Ascomycota (Beauveria spp., Lecanicillium lecanii, Metarhizium spp., Paecilomyces spp. and others) are under intense scrutiny due to the traits favouring their use as biological insecticides.

Beauveria bassiana, IntroductionIs a fungus

Grows naturally in soils throughout the world and acts as a parasite on various arthropod species,

Causes white muscardine disease

Belongs to the entomopathogenic fungi.

It is being used as a biological insecticide to control a number of pests such as termites, thrips, whiteflies, aphids and different beetles.

Chronicles, BEHIND

The fungus, Beauveria bassiana, was named after the Italian entomologist research scientist Agostino Bassi de Lodi.

He discovered it in 1835 while he was studying the white muscadine disease in silkworms. At that time the focus of his research was on preventing the disease.

He determined that the disease was caused by B. bassiana, a fungus that was present in the soil.

It was formerly also known as Tritirachium shiotae.

Agostino Bassi de Lodi

Stiff Silkworm is the dried body of 4th~5th stage larva of Bombyx mori L. (Fam. bombycidae) died of infection (or artificial infection) of Beauveria bassiana (Bals. ) Vuill.

Scientific Classification Kingdom: Fungi

Phylum: Ascomycota

Class: Sordariomycetes

Order: Hypocreales

Family: Cordycipitaceae

Genus: Beauveria

Species: B. bassiana

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Mode of action 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 permissive conditions of temperature and (usually high) moisture, these spores germinate, grow as hyphae and colonize the insect's cuticle; eventually they bore through it and reach 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).

After some time the insect is usually killed (sometimes by fungal toxins) and new propagules (spores) are formed in/on the insect if environmental conditions are again permissive; usually high humidity is required for sporulation.

Beauvericin

When the conidia land on an insect they secrete enzymes that eat through the cuticle and release beauvericin, a toxin.

The fungus replicates and feeds on the host, killing it in about three to seven days depending on conditions. After the host dies, the fungus continues to feed off of its dead host covering it in a white powdery mold. B. bassiana then releases its conidia spores and the cycle is complete.

Biology of Beauveria Beauveria bassiana is an aggressive parasite of many different insect host species.  Not

only does it have a wide host range but insects are attacked at larval or adult stages.  

The spores are tiny, measuring only a few microns. 

The hyphae and spores are non pigmented (hyaline) and so colonies appear white in cultures or tufts of white mycelium bearing masses of  powdery spores burst out through the body parts of infected insects as in the cicada, hawkmoth and chinch bugs illustrated below.  

Sympodial Spore Production in Beauveria The spore producing apparatus in Beauveria is small and delicate.  In B. bassiana the spores are produced sympodially.   A spore is produced at the tip of the mother cell  and the growth of

the mother cell ceases.    A new growing point initiates just below this terminal spore, grows past it,  and a second spore is produced at a higher level.  This uses up the new growing point and a third growing point is then initiated just below the second spore.    Every time a spore is produced the hyphal tip is used up and a new growing point is produced.   In this way a succession of spores is produced with the youngest spore at the tip (= i.e acropetal succession) and the spore head gets longer and longer.   When all the spores secede (= are dislodged) the spore-bearing  tip of the conidiogenous cell has a zig zag appearance and is referred to as a rachis ( this term is also used for the seed head in wheat when all the seeds are gone).

Formulation:Talc carrier based product. The product has minimum shelf life

of one year from the date of manufacture. 

Composition: Beauveria bassiana 1% (w/w)

Sticking agent – CMC – 1%. Inactive Ingredients 98.0% (Moisture 35%, talc 63%)

Panther - BB, a microbial insecticide, is of fungal origin causing a lethal disease (white muscadine disease) in insects.

Wide variety of insects like white flies, aphids, mealy bugs, thrips, leaf hoppers etc. succumb to the application of Panther - BB. Panther BB does not leave any residual toxicity on the crops

Beauvaria, Commercially…

Wide range of targets Aphids Whiteflies Mealybugs Psyllids Grasshoppers Thrips Termites Fire ants Flies Stem Borers Mites Fungal gnats Shoreflies

Lygus bugs Chinch bug

Beetles Black vine weevil Strawberry root weevil Coffee borer beetle Colorado potato beetle Mexican bean beetle Japanese beetle Boll weevil Cereal leaf beetle Bark beetles

Caterpillars European corn borer Codling moth Douglas fir tussock moth Silkworm

Current Research and Uses

Beauveria bassiana kills some insect pests that eat crops.

There are a number of ongoing studies being conducted by educational institutions and commercial pest control producers.

The long list of insect pests that can be controlled by Beauveria bassiana include: Colorado potato beetle, May beetle, Argentine stem weevil, whitefly, aphids, thrips, mealybugs, psyllids, weevils, caterpillars, fungus gnats, shoreflies, leafhoppers and malaria-spreading mosquitoes.

Its use in the control of malaria-transmitting mosquitosis under investigation

Although no specific harm has been shown to humans, precautions should be taken when using commercially manufactured Beauveria bassiana.

Hirsutella

Hirsutella – Introduction

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 nematodes;

There is interest in the use of these fungi as biological controls of insect and nematode pests.

Scientific classification Kingdom:Fungi

Division:Ascomycota

Subdivision:Pezizomycotina

Class:Sordariomycetes

Order:Hypocreales

Family:Ophiocordycipitaceae

Genus:Hirsutella

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Patouillard’s description about the Hirsutella

It consits of yellowish or hyaline mycelium covering the beetle larva or arthropods

The synnemata which arise from the all parts of the insects are simple, slender, narrowing upward (1-3 mm long, 0.1-0.2 mm thick)

The phialides are crowded and compactly bundled.

The lower portions of the phialides are elliptical, subulate and they abrubtly narrow at the apex.

Most are covered with persistant mucus forming a globose droplet (4-7µ)

Entomogenous Species of Hirsutella A. SPECIES ON ORTHOPTERA

[Grasshoppers and locusts; crickets]

Hirsutella fusiformis

B. SPECIES ON HOMOPTERA

[Plant lice (aphids); whiteflies; cicadas; leafhoppers; plant hoppers; scale insects and mealybugs; spittle insects]

Hirsutella citriformis

Hirsutella abeitina

C. SPECIES Of COLEOPTERA

[Beetles]

Hirsutella entomophila

…Continued

D. SPECIES ON LEPIDOPTERA

[Moths and butterflies]

Hirsutella barberi

Hirsutella subulata

Hirsutella gigantea

E. SPECIES ON DIPTERA [true flies and mosquitoes and gnats and crane flies]

Hirsutella radiata

Hirsutella dipterigena

F. SPECIES ON HYMENOPTERA

[bees; wasps; ants; ichneumons; sawflies; gall wasps; etc.]

Hirsutella saussurei

Hirsutella formicarum

Hirsutella radiata

Hirsutella entomophila

H. saussurei, on Polistes annuloris, Georgia, synnemata

H. sawsurei, on Polistes rubiginosus, Arkansas, Nest with infected wasps

Hirsutella citriformis

Hirsutella barberi Hirsutella subulata Hirsutella gigantea

Hirsutella subulata, Berryville, showingsection through bark with larva below and synnemata above

Hirsutella lecaniicola (Hyphomycetes) killing scale insects and producing synnematal conidiomata on them.

One of a couple of spores [Hirsutella thompsonii] that will infect the virrolla mites.

Study about the Hirsutella is based on

Farlow Herbarium (Harvard University)

The Herbarium of the New York Botanical Garden

The Herbarium of the University of Michigan

The Herbarium of the Florida Agricultural Experiment station

Conclusion

Since, because different strains are now being used as insect pest control, studies are ongoing as to the degree of mutation that occurs in the soil. Retaining the properties which make it an effective pest control, and preventing the qualities which cause it to be harmful to beneficial insects, is the topic of several ongoing studies.

Its use in the control of malaria-transmitting mosquitosis are under investigation.

Webliographyhttp://www.mycologia.org/content/96/4/929.full

http://www.piercesdisease.org/papers/1032

http://www.greenmaxagrotech.com/beauveria-bassiana.html

http://www.uoguelph.ca/~gbarron/MISCELLANEOUS/nov01.htm

http://www.ehow.com/about_6698075_life-cycle-beauveria.html

http://en.wikipedia.org/wiki/Beauveria_bassiana

http://www.king-stone.co/Products/show.asp?id=498

http://www.gardeningrhythms.com/OnLineShows/Soil/MicroBio/ControlingPests.html

http://www.fotocommunity.com/pc/pc/display/25339321

NOTE: ALL THE IMAGES THAT WERE USED IN THIS POWER POINT SLIDES WERE DOWNLOADED FROM THE GOOGLE IMAGES.

Thank you

AUTHOR INFORMATION

By Vigneshwaran V.PhD Scholar, Kuvempu University, INDIA

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