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BIOLOGICAL CONTROL
Biological control (biocontrol for short) is the use of animals, fungi, or other microbes to
feed upon, parasitize or otherwise interfere with a targeted pest species. Successful biocontrol
programs usually significantly reduce the abundance of the pest, but in some cases, they simply
prevent the damage caused by the pest (e.g. by preventing it from feeding on valued crops)
without reducing pest abundance.
Biocontrol is often viewed as a progressive and environmentally friendly way to control pest
organisms because it leaves behind no chemical residues that might have harmful impacts on
humans or other organisms, and when successful, it can provide essentially permanent,
widespread control with a very favorable cost-benefit ratio. However, some biocontrol programs
have resulted in significant, irreversible harm to untargeted (nonpest) organisms and to
ecological processes. Of course, all pest control methods have the potential to harm non-target
native species, and the pests themselves can cause harm to non-target species if they are left
uncontrolled. Therefore, before releasing a biocontrol agent (or using other methods), it is
important to balance its potential to benefit conservation targets and management goals against
its potential to cause harm.
Types of biological pest control
There are three broad and somewhat overlapping types of biological control:
● Conservation,
● Classical biological control (introduction of natural enemies to a new locale), and
● Augmentation
1. Conservation
The conservation of existing natural enemies in an environment is the third method of
biological pest control. Natural enemies are already adapted to the habitat and to the target pest,
and their conservation can be simple and cost-effective, as when nectar-producing crop plants are
grown in the borders of rice fields. These provide nectar to support parasitoids and predators of
plant-hopper pests and have been demonstrated to be so effective (reducing pest densities by 10-
or even 100-fold) that farmers sprayed 70% less insecticides, enjoyed yields boosted by 5%, and
this led to an economic advantage of 7.5%
For example, earwigs are natural predators which can be encouraged in gardens by hanging
upside-down flowerpots filled with straw or wood wool. Green lacewings can be encouraged by

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using plastic bottles with an open bottom and a roll of cardboard inside. Birdhouses enable
insectivorous birds to nest; the most useful birds can be attracted by choosing an opening just
large enough for the desired species
2. Classical Biological Control (Importation)
Classical biological control is the importation of pest natural enemies from other
countries, to a new locale where they do not occur naturally. It is the international introduction
of an exotic, usually co-evolved, biological control agent for permanent establishment and
long term pest control. The goal of classical biological control is to find useful natural
enemies, introduce them into the area of the target pest, and permanently establish them
so that they will provide continuing pest control with little or no additional human
intervention. The search for natural enemies in other countries is often referred to as foreign
exploration. The process of importation involves;
 Determining the origin of the introduced pest
 Collecting appropriate natural enemies associated with the pest or closely related
species.
 Selected natural enemies are then passed through a rigorous assessment, testing and
quarantine process, to ensure that they will work and that no unwanted organisms
(such as hyper parasitoids) are introduced.
 Mass production and release of selected natural enemies.
 Follow-up studies are conducted to determine if the natural enemy becomes
successfully established at the site of release, and to assess the long-term benefit of
its presence.
Historically, the first attempt by man at classical biological control of an arthropod pest was
a spectacular success. The cottony cushion scale (Icerya purchasi Maskell) program in
California over the period 1877-1879 was the first scientifically and institutionally backed
biological control program.
For example:
Alligator weed was introduced to the United States from South America. It takes root in
shallow water, interfering with navigation, irrigation, and flood control. The alligator weed flea
beetle and two other biological controls were released in Florida, enabling the state to ban the
use of herbicides to control alligator weed three years later.

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Another aquatic weed, the giant salvinia (Salvinia molesta) is a serious pest, covering
waterways, reducing water flow and harming native species. Control with the salvinia weevil
(Cyrtobagous salviniae) is effective in warm climates,[16]
and in Zimbabwe, a 99% control of the
weed was obtained over a two-year period
3. Augmentation
Augmentation involves the supplemental release of natural enemies, boosting the
naturally occurring population. In inoculative release, small numbers of the control agents are
released at intervals to allow them to reproduce, in the hope of setting up longer-term control,
and thus keeping the pest down to a low level, constituting prevention rather than cure. An
example of inoculative release occurs in greenhouse production of several crops. Periodic
releases of the parasitoid, Encarsia formosa, are used to control greenhouse whitefly, while the
predatory mite Phytoseiulus persimilis is used for control of the two-spotted spider mite.
In inundative release, in contrast, large numbers are released in the hope of rapidly reducing a
damaging pest population, correcting a problem that has already arisen. Augmentation can be
effective, but is not guaranteed to work, and relies on understanding of the situation. For example
The egg parasite Trichogramma is frequently released inundatively to control harmful moths.
Biological control agents:
1. Predators-
Predators are mainly free-living species that directly consume a large number
of prey during their whole lifetime. For example: Ladybugs, and in particular their larvae which
are active between May and July in the northern hemisphere, are voracious predators of aphids,
and also consume mites, scale insects and small caterpillars. Several species
of entomopathogenic nematode are important predators of insect and other invertebrate pests.
2. Parasitoids-
Parasitoids are among the most widely used biological control agents. Parasitoids lay
their eggs on or in the body of an insect host, which is then used as a food for developing
larvae. The host is ultimately killed. For example: Most insect parasitoids are wasps or flies, and
may have a very narrow host range. The most important groups are the ichneumonid wasps,
which prey mainly on caterpillars of butterflies and moths; braconid wasps, which attack
caterpillars and a wide range of other insects including greenfly; chalcid wasps, which parasitize
eggs and larvae of greenfly, whitefly, cabbage caterpillars, and scale insects; and tachinid flies,

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which parasitize a wide range of insects including caterpillars, adult and larval beetles, and true
bugs.
3. Pathogens-
Pathogenic micro-organisms include bacteria, fungi, and viruses. They kill or debilitate
their host and are relatively host-specific. Various microbial insect diseases occur naturally, but
may also be used as biological pesticides. When naturally occurring, these outbreaks are density-
dependent in that they generally only occur as insect populations become denser.
4. Bacteria-
Bacteria used for biological control infect insects via their digestive tracts, so they offer
only limited options for controlling insects with sucking mouth parts such as aphids and scale
insects. Bacillus thuringiensis is the most widely applied species of bacteria used for biological
control, with at least four sub-species used against Lepidopteran (moth, butterfly),
Coleopteran (beetle) and Dipteran (true fly) insect pests. The bacterium is available in sachets of
dried spores which are mixed with water and sprayed onto vulnerable plants such
as brassicas and fruit trees. B. thuringiensis has also been incorporated into crops, making them
resistant to these pests and thus reducing the use of pesticides. The bacterium Paenibacillus
popilliae causes milky spore disease has been found useful in the control of Japanese beetle,
killing the larvae. It is very specific to its host species and is harmless to vertebrates and other
invertebrates.
5. Fungi-
Most fungi used for the control of insect pests belong to the group hyphomycetes. Some
species have been developed as commercial products because of their ability to be mass
produced. Most fungi in this group are usually found in the soil and can cause natural outbreaks
on their own when environmental conditions are favorable. They can infect a wide range of
insect hosts. Specific fungal strains in commercial products target thrips, whiteflies, aphids,
caterpillars, weevils, grasshoppers, ants, Colorado potato beetle, and mealybugs. There is another
commonly encountered group of fungi called the entomophthorales. Fungi in this group can
cause natural outbreaks in the populations of their insect hosts. They tend to be much more host
specific; one well known species only infects aphids.

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Risks of biological control:
Despite the overwhelmingly positive aspects of biological control, some risks do exist.
These risks are associated with the introduction of an exotic organism and can result in direct or
indirect impacts to non-target species. Direct impacts occur with feeding on non-target plant
species. Indirect non-target impacts consist of changes in abundance of endemic predators (such
as field mice) that may alter foraging behavior and exploit a new resource. This can lead to
changes in the community food web.
BIOPESTICIDES
Biopesticides are certain types of pesticides derived from such natural materials as animals,
plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal
applications and are considered biopesticides
Classes of Biopesticides
Biopesticides fall into three major classes:
1. Microbial pesticides
It consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active
ingredient. Microbial pesticides can control many different kinds of pests, although each separate
active ingredient is relatively specific for its target pest[s].
Explanation:-
Microbial control agents can be effective and used as alternatives to chemical
insecticides. A microbial toxin can be defined as a biological toxin material derived from a
microorganism, such as a bacterium or fungus. Pathogenic effect of those microorganisms on the
target pests are so species specific. The effect by microbial entomopathogens occurs by invasion
through the integument or gut of the insect, followed by multiplication of the pathogen resulting
in the death of the host, e.g., insects. Most of the toxins produced by microbial pathogens which
have been identified are peptides, but they vary greatly in terms of structure, toxicity and
specificity. Microorganism e.g., a bacterium, fungus, virus or protozoan as the active ingredient
can control many different kinds of pests, although each separate active ingredient is relatively
specific for its target pest.
For example:
❖ There are fungi that control certain weeds and other fungi that kill specific insects.

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❖ The most widely used microbial pesticides are subspecies and strains of Bacillus
thuringiensis, or Bt. Each strain of this bacterium produces a different mix of proteins and
specifically kills one or a few related species of insect larvae.
❖ While some Bt ingredients control moth larvae found on plants, other Bt ingredients are
specific for larvae of flies and mosquitoes. The target insect species are determined by
whether the particular Bt produces a protein that can bind to a larval gut receptor, thereby
causing the insect larvae to starve.
2. Plant-Incorporated-Protectants (PIPs)
They are pesticidal substances that plants produce from genetic material that has been
added to the plant. For example, scientists can take the gene for the Bt pesticidal protein and
introduce the gene into the plant's own genetic material. Then the plant, instead of the Bt
bacterium, manufactures the substance that destroys the pest. The protein and its genetic
material, but not the plant itself, are regulated by EPA.
Explanation:- One approach, to reduce destruction of crops by phytophagous arthropod pests,
is to genetically modify plants to express genes encoding insecticidal toxins. The adoption of
genetically modified (GM) crops has increased dramatically in the last 11 years. Genetically
modified (GM) plants possess a gene or genes that have been transferred from a different
species.
Bacillus thuringiensis applications in agriculture
Bt GM (genetically modified) crops
Since 1996 plants have been modified with short sequences of genes from Bt to express
the crystal protein Bt makes. With this method, plants themselves can produce the proteins and
protect themselves from insects without any external Bt and/or synthetic pesticide sprays. In
1999, 29 million acres of Bt corn, potato and cotton were grown globally. It has been estimated
that by using Bt protected cotton, the United States was able to save approximately $92 million.
Bt GM crops are protected specifically against European corn borer, southwestern corn borer,
tobacco budworm, cotton bollworm, pink bollworm and the Colorado potato beetle. Other
benefits attributed to using Bt include:
● Reduced environmental impacts from pesticides – When the plants are producing the
toxins in their tissues there is no need to spray synthetic pesticides or apply Bt mixtures
topically.

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● Increased opportunity for beneficial insects – Bt proteins will not kill beneficial insects.
● Reduced pesticide exposure to farm workers and non-target organisms.
Potential risks to using Bt:
● Invasiveness – Genetic modifications, through traditional breeding or by genetic
engineering can potentially change the organism to become invasive. Few introduced
organisms become invasive, yet it’s a concern for the users.
● Resistance to Bt - The biggest potential risk to using Bt-crops is resistance. Farmers have
taken many steps to help prevent resistance.
● Cross-contamination of genes - Although unproven, genes from GM crops can potentially
introduce the new genes to native species.
3. Biochemical pesticides
They are naturally occurring substances that control pests by non-toxic mechanisms.
Conventional pesticides, by contrast, are generally synthetic materials that directly kill or
inactivate the pest. Biochemical pesticides include substances that interfere with mating, such as
insect sex pheromones, as well as various scented plant extracts that attract insect pests to traps.
Because it is sometimes difficult to determine whether a substance meets the criteria for
classification as a biochemical pesticide, EPA has established a special committee to make such
decisions.
Examples. Biochemical pesticides include, but are not limited to:
❖ Semiochemicals (insect pheromones and kairomones),
❖ Natural plant and insect regulators,
❖ Naturally-occurring repellents and attractants, and
❖ Enzymes
What are the advantages of using biopesticides?
● Biopesticides are usually inherently less toxic than conventional pesticides.
● Biopesticides generally affect only the target pest and closely related organisms, in
contrast to broad spectrum, conventional pesticides that may affect organisms as different
as birds, insects and mammals.
● Biopesticides often are effective in very small quantities and often decompose quickly,
resulting in lower exposures and largely avoiding the pollution problems caused by
conventional pesticides.

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● When used as a component of Integrated Pest Management (IPM) programs,
biopesticides can greatly reduce the use of conventional pesticides, while crop yields
remain high.
To use biopesticides effectively (and safely), however, users need to know a great deal about
managing pests and must carefully follow all label directions.
How does EPA encourage the development and use of biopesticides?
In 1994, we established the Biopesticides and Pollution Prevention Division in the Office
of Pesticide Programs to facilitate the registration of biopesticides. This division promotes the
use of safer pesticides, including biopesticides, as components of IPM programs. The division
also coordinates the Pesticide Environmental Stewardship Program (PESP).
Since biopesticides tend to pose fewer risks than conventional pesticides, EPA generally requires
much less data to register a biopesticide than to register a conventional pesticide. In fact, new
biopesticides are often registered in less than a year, compared with an average of more than
three years for conventional pesticides.
While biopesticides require less data and are registered in less time than conventional pesticides,
EPA always conducts rigorous reviews to ensure that registered pesticides will not harm
people or the environment. For EPA to be sure that a pesticide is safe, the Agency requires that
registrants submit the results of a variety of studies and other information about the composition,
toxicity, degradation, and other characteristics of the pesticide.