Microbial insecticides

INTRODUCTIONInsect population is the largest with more

than 750000 speciesNegative effects of insectsSynthetic chemical insecticides provide

many benefits to food production and also pose some hazards.

Alternative methods of insect management offer adequate levels of pest control and pose fewer hazards.

MICROBIAL INSECTICIDESSingle cell organisms, such as bacteria,

fungi and protozoa, and viruses, have been mass produced and formulated for use in a manner similar to insecticides.

• Microbial insecticides can be1. Microbially produced toxic substance2. Organism

(Weinzieri, R. And T. Henn. 1989.)

TYPES

• BACTERIAL• ACTINOMYCETES• VIRAL• FUNGAL• PROTOZOAN• NEMATODES

BACTERIAL INSECTICIDES

• Spore forming• Rod-shaped• Genus bacillus.• Isolated from soil samples.• Stomach poisons.

TYPES

• OBLIGATE- B. papillae, B. lentimorbus• FACULTATIVE- B. cerens, BT• POTENTIAL- P. aeruginosa

HISTORY OF BT•Discovered in japan in 1901 by Ishiwata •Officially described by berliner in 1915, isolated from mediterranean flour moth in province of thuringia in 1911 •US production of a subspecies thuringiensis in late 1950’s •Discovery of highly active subspecies kurstaki HD-1 by dulmage, 1960’s, commercial production 1970s •Discovery of mosquito, black fly active subspecies israelensis by goldberg and margalit, 1980’s •Discovery of beetle-active subspecies morrisoni by krieg, 1980’s •Genetically engineered cotton, corn, potatoes ongoing

Bacillus thuringiensis berliner

• gram-positive, aerobic• parasporal body (known as the crystal)

that is proteinaceous and possesses insecticidal properties.

• The parasporal body comprises of crystals and tightly packed with proteins called protoxins or endotoxins.

• over 60,000 isolates of Bt are being maintained in culture collections worldwide.

. Three-dimensional structure of Cyt toxins from Bacillus thuringiensis displayed by Swiss PDB viewer. Cyt1Aa, pdb 3RON; Cyt2Aa, pdb 1CBY; and Cyt2Ba, pdb 2RCI.Mario Soberón, Jazmin A. López-Díaz, Alejandra BravoPeptides, Volume 41, 2013, 87–9

VARIOUS STRAINS OF B. thuringiensis Strain/subsp. Protein size Target Insects Cry

#shape

berliner 130-140 kDa

Lepidoptera Cry1 bipyramidal

kurstaki KTP, HD1 130-140 kDa

Lepidoptera Cry1 bipyramidal

entomocidus 6.01 130-140 kDa

Lepidoptera Cry1 bipyramidal

aizawai 7.29 130-140 kDa

Lepidoptera Cry1 Bipyramidal

aizawai IC 1 135 kDa Lepidoptera, Diptera

Cry2 Cuboidal

kurstaki HD-1 71 kDa Lepidoptera, Diptera

Cry2 cuboidal

tenebrionis (sd) 66-73 kDa Coleoptera Cry3 flat/irregular

morrisoni PG14 125-145 kDa

Diptera Cry4 bipyramidal

israelensis 68 kDa Diptera Cry4 bipyramidal

MODE OF ACTION• THREE STAGE PROCESSSTAGE1STAGE2STAGE3

B. thuringienis parasporal crystal composed of Cry1 protoxin protein. Conversion of the 130-kDa protoxin into an active 68-kDa toxin requires an alkaline environment (pH 7.5 to 8) and the action of a specific protease, both of which are found in the insect gut. The activated toxin binds to protein receptors on the insect gut epithelial cells.

The toxin is inserted in gut epithelial cell membranes of the insect and forms an ion channel between the cell cytoplasm and the external environment, leading to loss of cellular ATP and insect death.

APPLICATION

• Spray when caterpillars are still small. • Completely cover all leaf surfaces. The

insects must ingest the bacteria when they are feeding.

• Spray in the evening or during cloudy (but not rainy) days.

• There may be a need to reapply if it rains soon after application.

COMMERCIAL BT PRODUCTSorganism Product name1.Bacillus thuringiensis var. kurstaki

Dipel®, Javelin®, Thuricide®, Worm Attack®, haltCaterpillar Killer®, Bactospeine®, and SOK-Bt®

2. B.thuringiensis var. aizawai

Certan®

3. B. thuringiensis var.israelensis (Bti)

Vectobac®, Teknar®, Bactimos®, Skeetal®, and Mosquito Attack®.

4. Bacillus popillae and Bacillus lentimorbus.

Doom®, Japidemic®, GrubAttack®,

5. Bacillus thurigiensis var. san diego,

M-One®,

GLOBAL SHARE OF BT• USA• INDIA• CHINA• ARGENTINA• BRAZIL• S. AFRICA• CANADA• PHILIPHINES• AUSTRALIA• URUGUAY

Plant Biotechnology Journal ª 2011 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd, Plant Biotechnology Journal, 9, 283–300

ACTINOMYCETES

Large group of gram positive bacteria that grow as hyphae like fungi

Mortality is due to secretion of bioactive materials which stimulate GABA system or disruption of nicotinic acetylcholine recepters

HISTORY• In 1978, an actinomycete was isolated at the

kitasato institute from a soil sample collected at kawana, japan.

• The family of compounds were finally characterized by a team at merck in 1978.

• In 2002, kitasato university and at the kitasato institute, proposed that streptomyces avermitilis be renamed streptomyces avermectinius.

1. AVERMECTIN

• From Streptomyces avermectin

• Major homologues- A1a, A2a, B1a, B2a

• Minor homologues- A1b, A2b, B1b, B2b

• B1b and B2b are effective- abamectin

• GABA agonist•  Vermac –A, albentin, verbend

2. MILBEMECTIN

• S. hygroscopicum var aureolacromosus

• Have 2 group- A3, A4• GABA abonists• milbeknock

3. SPINOSAD• S. spinosa• 2 metabolites- spinosin A(C4H65O10),

spinosin D (C4H67O10)• Against caterpilllars and thrips• Acts as Ach agonist• Success 2.5 EC , tracer 45EC

VIRAL PESTICIDES

GENERAL OVERVIEW • Insect-specific viruses can be highly effective natural controls of several caterpillar pests.

• Stomach poison• No threat to humans or wildlife is posed by insect viruses.

BACULOVIRUSES

• Rod shaped DNA viruses• Include NPV and GV• Pathogenic for lepidoptera(83%),

hymenoptera(10%) and diptera(4%)• Infection is by ingestion of food

• The polyhedrin protein dissolves in the alkaline environment of the new host's gut and the occluded virus is released.

• This virus infects the gut epithelial cells and virus replication takes place.

• Nonoccluded virus is then produced and budded from the infected gut cells

Mode of action

GRANULOSIS VIRUS

• Develop either in the nucleus/cytoplasm/ tracheal matrix / epithelial cells of host• virions are occluded singly in small inclusion bodies called capsules• rod shaped virion, ds DNA• oval occlusion bodies about 200x400nm• they enter through ingestion• fat body is the major organ invaded• diseased larvae – less active, flaccid, fragile, wilted prone to rupture in later stages, death in 6-20 days

• The recommended dosage is 200 ml of NPV/acre or 500 ml/ha containing 100 and 250 larval equivalent (LE) of NPV respectively as active infective material (one LE = 6 x 10^9 pobs).

• Field efficacy 70-80%

FUNGAL INSECTICIDES>750 fungi on insect are reported• Beauveria• Metarrhizium• Paecilomyces lilacinus• Verticilium lecanii• Hirsutella thompsoni

MODE OF ACTION

• Formation of an infection structure • Penetration of the cuticle • Production of toxins beauvericin, beauverolides by B. bassiana

dextruxines by M. anisopliae

LIFE CYCLE

B. bassiana• Infect lepidoptera, coleopteran, hemipteran,

and few diptera and hymenoptera• Boverin, boverol, boverosil, mycotrop,

mycojaal, metaguard etc• H. armigera, S. litura, H. consaguinea, coffee

berry borer, rice hispaM. anisopliae

• Biogreen, metaguino, biopath, bioplast• Rhinocerous beetle , white grub

V. lecani

• Pathogen of homoptera• Mycolol, vertilec

H. Thompsoni• Citrus red mite, coconut eriophid mite

Entomopathogenic Fungi1. Metarhizium anisopliae2. Beauveria bassiana

Green muscardine diseased grub White muscardine diseased grub

• Pre-sowing soil application of Beauveria bassiana and Metarhizium anisopilae @ 10 g/m2 (containing 1012 spores /ha) against white grub and cut worm larvae, mole crickets, field crickets and Verticillium lacanii @ 48 X 106/ml is effective against epilachna beetles

(DUTTA & BHATTACHARYYA,2013)

• The entomogenous nematodes Steinernema feltiae S. Scapteriscae, S. Riobravis, S. Carpocapsae and Heterorhabditis heliothidis are the Species most commonly used in insecticidal Preparations.

• effective against over 400 pest species, Including numerous beetles, fly larvae, and Caterpillars.

Entomopathogenic nematode

G. C. SMART, JR. 1995

ADVANTAGES OF EPN• Biocontrol ability to search

( chemoreceptors ) the target insect• broad host range • easily cultured • compatibles with many pesticides • easy delivery system by spraying EPN

suspension or irrigation system• safe to vertebrates, plants and non-targets

and environmentally safe • long-term control

PROTOZOAN INSECTICIDES• Not suited for short time • Effective against grasshoppers,

mosquitoes, boll weevils• They reduce host reproduction or feeding

rather than killing the pest.

• Must be eaten to infect an insect, but there many also be some natural transmission within a pest population,

• The pathogen enters the insect body via the gut wall, spreads to various tissues and organs, and multiplies, sometimes causing tissue breakdown and septicemia.

• Infected insects may be sluggish and smaller than normal, sometimes with reduced feeding and reproduction.Weinzieri, R. and T. Henn. 1989. 

• Species in the genera Nosema and vairimorpha Seem to offer the greatest potential for use as Insecticides.

• Pathogens in these genera attack Lepidopteran larvae and insects in the order Orthoptera

• Nosema locustae , a pathogen of grasshoppers is sold as NOLO bait® and grasshopper attack®, germspore bait®

• Infect atleast 90 sp of grasshopper• Non toxic to mammals

Weinzieri, R. and T. Henn. 1989. 

Vairimorpha necatrix

• Infect 36 lepidopterans- 20 noctuids

• Mortality due to damage of gut followed by septicaemia or by microsporidia

• Swelling of fat body is seen

Global biopesticide market

Biopesticides/Bioagents Quantity/annum (approx)

Bt 50,000 kg

NPV (liquid) 500,000 Le

Beauveria Meager

 Annual availability of biopesticides in India

 

 Source:  Kalra & Khanuja 2007

 

ADVANTAGES • Non toxic and nonpathogenic to organisms

not closely related to the target pest.• often specific to a single group or species

of insects• Most microbial insecticides can be used in

conjunction with synthetic chemical insecticides

• Residues present no hazards to other animals,

• The pathogenic microorganisms can become established in a pest population

DISADVANTAGES

• Heat, desiccation (drying out), or exposure to ultraviolet radiation

• pest-specific, the potential market for these products may be limited

REFERENCES

• Integrated pest management- concepts and approaches by G.S Dhaliwal and Ramesh arora

• WIKIPEDIA

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