Microbes as
Biopesticides
Vivek Kumar
Department of Biosciences
Swami Rama Himalayan University
Jolly Grant, Dehradun

Introduction
• Biopesticides are certain types of pesticides derived from
natural materials such as animals, plants, bacteria, and
certain minerals.
• For example, canola oil and baking soda have pesticidal
applications and are considered biopesticides.
• As of April 2016, there are 299 registered biopesticide active
ingredients and 1401 active biopesticide product
registrations.
• Even a chilli powder solution is a biopesticide.
• Crushed leaves, bark in solution act as excellent biopesticide.

Types of Biopesticides
• Biochemical pesticides
• These 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.

Microbes as biopesticides
• They come from naturally occurring or genetically altered
bacteria, fungi,algae, viruses or protozoans.
• 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.
• This is followed by multiplication of the pathogen resulting in
the death of the host, e.g., insects.
• Studies have demonstrated that the pathogens produce
insecticidal toxin important in pathogenesis.
• 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.

• Microbial pesticides 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].
• For example, there are fungi that control certain weeds and
other fungi that kill specific insects.
• 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.

Insect Control
• Bacteria - Bacillus thuringiensis, B. sphaericus, Paenibacillus popilliae,
Serratia entomophila
• Viruses - nuclear polyhedrosis viruses, granulosis viruses, non-
occluded baculoviruses
• Fungi - Beauveria spp, Metarhizium, Entomophaga, Zoopthora,
Paecilomyces fumosoroseus, Normuraea, Lecanicillium lecanii
• Protozoa - Nosema, Thelohania, Vairimorpha
• Entomopathogenic nematodes - Steinernema spp, Heterorhabditis
spp
• Others - Pheromones, parasitoids, predators, microbial by-products

Weed Control
• Fungi - Colletotrichum gloeosporioides,
Chondrostereum purpureum, Cylindrobasidium laeve
• Bacteria - Xanthomonas campestris pv. Poannua
• Plant Disease Control
• Fungi - Ampelomyces quisqualis, Candida spp.,
Clonostachys rosea f. catenulate, Coniothyrium
minitans, Pseudozyma flocculosa, Trichoderma spp

• Competitive and Soil Inoculants - Bacillus pumilus, B. subtilis,
Pseudomonas spp, Streptomyces griseoviridis, Burkholderia
cepacia
• Nematicides etc.
• Nematode Trapping Fungi - Myrothecium verrucaria,
Paecilomyces lilacinus
• Bacteria - Bacillus firmus, Pasteuria penetrans
• Mollusc parasitic nematode - Phasmarhabditis
hermaphrodita

Plant-Incorporated-Protectants
• Plant-Incorporated-Protectants (PIPs) 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.

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.
• Which results in lower exposures and largely avoiding the pollution
problems caused by conventional pesticides.

• 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.

• The organisms used in microbial insecticides are essentially
nontoxic and nonpathogenic to wildlife, humans, and other
organisms not closely related to the target pest.
• The safety offered by microbial insecticides is their greatest
strength.
• The toxic action of microbial insecticides is often specific to a
single group or species of insects.
• And this specificity means that most microbial insecticides
do not directly affect beneficial insects (including predators
or parasites of pests) in treated areas.

• Because their residues present no hazards to humans or
other animals, microbial insecticides can be applied even
when a crop is almost ready for harvest.
• In some cases, the pathogenic microorganisms can become
established in a pest population or its habitat and provide
control during subsequent pest generations or seasons.
• They also enhance the root and plant growth by way of
encouraging the beneficial soil microflora.
• By this way they take a part in the increase of the crop yield.

Disadvantages of microbial insecticides
• Because a single microbial insecticide is toxic to only a specific species
or group of insects, each application may control only a portion of the
pests present in a field and garden.
• If other types of pests are present in the treated area, they will
survive and may continue to cause damage.
• Conventional insecticides are subject to similar limitations because
they too are not equally effective against all pests.
• This is because of selectivity indeed and this negative aspect is often
more noticeable for both general predators, chemicals and
microbials.
• On the other hand predators and chemicals may be danger for other
beneficial insects in threatened area.

• Heat, desiccation (drying out), or exposure to ultraviolet
radiation reduces the effectiveness of several types of microbial
insecticides.
• Consequently, proper timing and application procedures are
especially important for some products.
• Special formulation and storage procedures are necessary for
some microbial pesticides.
• Although these procedures may complicate the production and
distribution of certain products, storage requirements do not
seriously limit the handling of microbial insecticides that are
widely available.

• Because several microbial insecticides are pest-
specific, the potential market for these products may
be limited.
• Their development, registration, and production costs
cannot be spread over a wide range of pest control
sales.
• Consequently, some products are not widely available
or are relatively expensive (several insect viruses, for
example).

Present Status of biopesticides
• Presently, biopesticides cover only 2% of the plant
protectants used globally.
• However, its growth rate shows an increasing trend in
past two decades.
• Global production of biopesticides has been estimated
to be over 3,000 tons per year, which is increasing
rapidly.

• Increasing demand of residue-free agricultural produce,
growing organic food market and easier registration than
chemical pesticides are some of the key drivers of the
biopesticide market.
• Globally, the use of biopesticides is increasing steadily by
10% every year.
• About 90% of the microbial biopesticides are derived from
just one entomopathogenic bacterium, Bacillus thuringiensis.

• More than 200 products are being sold in the US market, compared
to only 60 comparable products in the EU.
• More than 225 microbial biopesticides are manufactured in 30
OECD (Organisation for Economic Co-operation and Development)
countries.
• The NAFTA (North American Free Trade Agreement) countries (USA,
Canada, and Mexico) use about 45% of the biopesticides sold, while
Asia lacks behind with the use of only 5% of biopesticides sold
world over.

Recent Advances
• The science of biopesticide is still considered to be
young and evolving.
• In-depth research is needed in many areas such as
production, formulation, delivery and
commercialization of the products.
• Some of the biopesticides, currently under
development, may prove to be excellent alternatives
to the chemical pesticides.

• Many of them are based on the locally available plants like
beshram (Ipomoea carnea - the pink morning glory), neem,
garlic, triphala, Pinus kesiya etc.
• These can be easily processed and made available to the
farmers to improve biopesticide consumption.
• In addition to the continuous search for new biomolecules
and improving efficiency of the known biopesticides,
recombinant DNA technology is also being deployed for
enhancing efficacy of biopesticides.

• The technology allows a toxin (not toxic to higher
animals) to be combined with a carrier protein which
makes it toxic to insect pests when consumed orally,
while it was toxic only when injected into a target prey
by a predator.
• The fusion protein may be produced as a recombinant
protein in microbial system, which can be scaled up
for industrial production and commercial
formulations.