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?
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.
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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
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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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
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.
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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
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
Is the phenomena of obtaining nourishment at the expense of the host to which the parasite is attached.
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
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
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
Develops on number of widely different host species
Eg. Bracon sp. Apanteles sp on lepidopteran caterpillars
It has very few hosts (more than one host) but all the hosts are closely related.
Eg. Isotema javensis on sugarcane and sorghum borers.
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
A parasite attacking an insect which itself is not a parasite (Beneficial to man.)
A hyperparasite attacking a primary parasite (Harmful to man )
A hyperparasite attacking a secondary parasite ( Beneficial to man )
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