Bio – Control of Insect pests | Agristudent.com

Bio control of insect pests

Bio control of Insect pests throws light on various aspects of biocontrol in entomology and will answer various questions like

What is bio control of Insect pests?

What are successful examples of Bio control of Insect pests?

What are good qualities of parasites?

What are examples of egg parasitoids and larval parasitoids? 

How are different parasites classified?

Bio control of insect pests

What is Biological Control?

The successful management of a pest by means of another living organism
(parasitoids, predators and pathogens) that is encouraged and disseminated by man is called biological control.

 

You may also like to read – Entomology : Important terms

 

In such programme, the natural enemies are introduced, encouraged, multiplied by artificial means

They are disseminated by man with his own
efforts instead of leaving it to nature.

Techniques in biological control

Biological control practices involve three techniques viz., Introduction, Augmentation
and Conservation.

1. Introduction or classical biological control

Deliberate introduction and establishment of natural enemies to a new locality where they did not occur or originate naturally.

 

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2. Augmentation

It is the rearing and releasing of natural enemies to supplement the numbers of naturally occurring natural enemies.

There are two approaches to augmentation.

a. Inoculative releases

Large number natural enemy individuals are released only once during the season

Natural enemies are expected to reproduce and increase its population for that growing season

Biocontrol agents are not released periodically but only once

 

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b. Inundative releases

It involves mass multiplication and periodic release of natural enemies when pest populations approach damaging levels

Biocontrol agents are eeleased periodically as and when required

3. Conservation

Conservation is defined as the actions to preserve and release of natural enemies by environmental manipulations

In this effort is made to alter production practices to protect natural enemies that are already present in an area

It mainly consists of non use of those pest control measures that destroy natural enemies.

 

You may also like to read – Classification and general characteristics of Insects

 

Important conservation measures

Use selective insecticide which is safe to natural enemies.

Avoidance of cultural practices which are harmful to natural enemies and use
fauorable cultural practices

Cultivation of varieties that favour colonization of natural enemies

Providing alternate hosts for natural enemies.

Preservation of inactive stages of natural enemies

Provide pollen and nectar for adult natural enemies

Parasite, Parasitoid and Parasitism

Parasite

A parasite is an organism which is usually much smaller than its host and a single individual usually doesn’t kill the host.

Parasite may complete their entire life
cycle (eg. Lice) by attaching itself to the body of the other living organism either externally or internally and getting nourishment

Parasitism

Is the phenomena of obtaining nourishment at the expense of the host to which the parasite is attached.

Parasitoid

It is an insect parasite of an arthopod, parasitic only in immature stages, destroys its host in the process of development and free living as an adult. Eg: Braconid wasps

Qualities of a Successful Parasitoid

A parasitoid should have the following qualities for its successful performance.

1. Should be adaptable to environmental conditions in the new locally

2. Should be able to survive in all habitats of the host

3. Should be specific to a particulars sp. of host or at least a narrowly limited range of hosts.

4. Should be able to multiply faster than the host

5. Should be having more fecundity

6. Life cycle must be shorter than that of the host

7. Should have high sex ratio

8. Should have good searching capacity for host

9. Should be amendable for mass multiplication in the labs

10. Should bring down host population within 3 years

11. There should be quick dispersal of the parasitoid in the locality

12. It Should be free from hyperparasitoids

 

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Successful examples if Biocontrol in India

Biological Control of Cottony Cushion scale by Vadalia Beetle

Control of cottony cushion scale, Icerya purchasi on fruit trees by its predatory
vedalia beetle, Rodolia cardinalis in Nilgiris.

The predator was imported from California in 1929 and from Egypt in 1930 and multiplied in the laboratory and released.

Within one year the pest was effectively checked.

Biological control of Water fern by weevil named C. salviniae

For the biological suppression of Water Fern -Salvinia molesta, the weevil named Cyrtobagous salviniae, was imported from Australia in 1982.

This Exotic weevil was released for the control of water fern in a lily pond in Bangalore in 1983-84.

Within 11 months of the release of the weevil in the lily pond the salvinia plants collapsed and the lily growth, which was suppressed by competition from salvinia resurrected.

Other successful examples of biological control

Biological Control of Water hycinth by three exotic natural enemies hydrophilic weevils – Neochetina bruchi, N. eichhorniae ( Argentina) and galumnid mite Orthogalumna terebrantis (South America) were introduced in India in 1982

Biocontrol of Apple woolly aphids – Eriosoma lanigerum by Aphelinus mali (parasitoid)

Control of shoot borers of sugarcane, cotton bollworms, stem borers of paddy and sorghum with the egg parasitoid – Trichogramma australicum @ 50,000/ha/week for 4-5 weeks from one month after planting

Centrococcus isolitus on brinjal; Pulvinaria psidi on guava and sapota; Meconellicoccus hirsutus on grape and Pseudococcus carymbatus on citrus suppressed by Cryptolaemus montrouzieri.

Classification of Parasites

Depending upon the nature of host,

1. Zoophagous – that attack animals (cattle pests)

2. Phytophagous – that attack plants (crop pests)

3. Entomophagous – that attack insects (parasites)

4. Entomophagous insects – parasitoids

Based on the specialization of the site of parasitisation

1. Ectoparasites

They attack its host from the outside of the body of the host.

The mother parasite lays its eggs on the body of the host and after the eggs are hatched the
larvae feed on the host by remaining outside only.

Eg – Head louse; Epiricania melanolenca,
Epipyrops sp. Sugarcane fly

2. Endoparasites

They enter the body of the host and feeds from inside.

The mother parasite either lays its eggs inside the tissues of the host or on the food material of the host to gain entry inside.

Eg. Braconids & Icheneumonids, Apanteles flavipes on jowar stemborer larvae.

Specialization based on the stage of the host

1. Egg parasite : Trichogramma australicum

2. Early larval parasite – Apanteles taragama

3. Mid larval parasite – (Micro) Bracon hebtor

4. Prepupal parasite – Gonizus nephantidis

5. Prepupal parasite – Elasmus nephantidis

6. Pupal parasite –Stomatoceros sulcatiscutellum Trichospilus pupivora, Testrastichus israeli,

Depending upon the duration of attack

1. Transitory parasite

It is not permanent but transitory parasite which spends a few stages of its life in one host and other stages on some other species of hosts or as a free living organism.

Eg. Braconids and Ichneumonids

2. Permanent parasite

Which spends all the stages of its life on the same host.

Eg. Head louse

Depending upon degree of parasitization

1. Obligatory parasites

Parasite, which can live only as a parasite and cannot live away from the host even for shorter period.

Eg. Bird lice, Head louse.

2. Facultative parasite

Parasite, which can live away from the host at least for a shorter period Eg. Fleas.

Depending upon the food habits

1. Polyphagous

Develops on number of widely different host species

Eg. Bracon sp. Apanteles sp on lepidopteran caterpillars

2. Oligophagous

It has very few hosts (more than one host) but all the hosts are closely related.

Eg. Isotema javensis on sugarcane and sorghum borers.

3. Monophagous

It has only one host sp. and can’t survive in another sp. i.e. host specific.

Eg. Gonizus nephantidis on Opisina aresosella

Kinds of Parasitism

1. Simple parasitism

Irrespective of number of eggs laid the parasitoid attacks the host only once.

Eg. Apanteles taragamae on the larvae of Opisina arenosella, Goniozus nephantids

2. Super parasitism

phenomenon of parasitization of an individual host by more larvae of single species that can mature in the host.

Eg. Apanteles glomeratus on Pieris brassica, and Trichospilus pupivora on Opisina arenosella.

3. Multiple parasitism

Phenomenon of simultaneous parasitization of host individual by two or more different species of primary parasites at the same time.

Eg:Trichogramma, Telenomous and Tetrastichus attack eggs of paddy stem
borer Scirpophaga incertulas.

4. Hyper parasitism

When a parasite itself is parasitized by another parasite.

Eg. Goniozus nephantidis is parasitized by Tetrastichus israeli, Most of the Bethylids and Braconids are hyper parasites.

Primary, secondary, tertiary and Quaternery parasites

Primary parasite

A parasite attacking an insect which itself is not a parasite (Beneficial to man.)

Secondary parasite

A hyperparasite attacking a primary parasite (Harmful to man )

Tertiary parasite

A hyperparasite attacking a secondary parasite ( Beneficial to man )

Quaternary parasite

A hyperparasite attacking tertiary parasite ( Harmful to man)

Further readings and references in Bio Control of Insect Pests

Handbook of Agriculture

Degree notes of B.Sc. Agri

http://www.wikipedia.com

 

 

 

Author: agristudent

Team Agristudent is a young and dynamic team of Agriculture specialists who have acquired specialised knowledge in their respective subjects. Their mission is to create a unique online encyclopedia of agriculture, which can be useful to millions around the world as an online reference library

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