biochemical pesticides

1. BIOCHEMICAL PESTICIDES
Presented by-
MD.MASUD RANA
Jahangirnagar university

2. BIOCHEMICAL PESTICIDES
 Naturally occuring pesticides.
 Control pests by nontoxic mechanisms.
 Biochemical pesticides include substances, such as-
 Insect sex pheromones, that interfere with
mating
 various scented plant extracts that attract
insect pests to traps.
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3. BIOLOGICAL CONTROL THROUGH
INTERACTION
 Controlling pests relies on following interaction:
• Predation
• Parasitism or
• Ammensalism.
Parasitism:
 Bacteria used for biological control infect insect via their
digestive tract.
For example, Bacillus thuringiensis, with at least four sub-
species used to control:
Lepidopteran (moth,butterfly)
Dipteran (true flies). 3

4. Insecticidal toxin of Bacillus
thuringiensis
• B. thuringiensis is a gram positive soil
bacterium that produces a toxin or crystal
protein (Bt toxin or Cry) that kills certain
insects
• The Bt toxin or Cry is produced when the
bacteria sporulates and is present in the
parasporal crystal.

6. mode of action
• The Cry protein is made as an inactive protoxin
• Conversion of the protoxin into the active toxin
requires the combination of a slightly alkaline pH
(7.5-8) and the action of a specific protease found
in the insect gut.
• The active toxin binds to protein receptors on the
insect gut epithelial cell membrane.
• The toxin forms an ion channel between the cell
cytoplasm and the external environment, leading
to loss of cellular ATP and insect death.

7. Genetically Modified Organisms

8. FUNGUS
 Fungi that cause disease in insects are known as
entomo pathogenic fungi.
Examples of entomo pathogenic fungi:
– Beauveria bassiana works against white flies,
aphids.
– Metarhizium spp. Against beetles, spider mites or
other pests.
– Trichoderma spp. are used to manage some soil
borne plant pathogens.

9. MODE OF ACTION OF FUNGI
• Invade insects by penetrating their cuticle or
skin.
• Rapidly multiplies throughout the body.
• Death is caused by tissue destruction or by
toxin production.
• Emerges from insects body by producing
spores.
• Can spread infection by-Wind, Rain, and
Contact with other insects.

10. VIRUS
• Baculoviruses are pathogens that attack insects
and arthropods.
• Insects infected by consuming plant material with
viral particles.
• Viral infection begins in the insects digestive
system but spread throughout the body.
• Virus killed insects break open and spill virus
particles into the environment.

11. VIRAL ACTION

12. Predation:
 Protozoa : protozoa must be applied before outbreaks
of disease to effect proper control.
Example : Nosema, Vairimorpha used for controlling
insects (grasshoppers, mosquitoes etc).
 Nematodes: Romanomermis are used to control
insects.
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13. Ammensalism:
Streptomyces spp. that have ammensal effects
and are useful in agricultural pest control.
– Produce Antibiotics such as streptomycin that are
effective against bacterial pathogens and
– Other substances such as bilanafos that are active
against weeds.
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14. HOW TO APPLY ?
 Biopesticides are typically microbial biological pest control
agents that are applied in a manner similar to chemical
pesticides. Such as-
 Soil applied biopesticides: are appliede to the soil.
 Contact biopesticides: Generally control pests as a
result of direct contact.
 Preplant herbicides: are applied to the soil before
seeding.
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15.  Selective biopesticides: only control certain pests
 Non-selective biopesticides: control wide range of
pests.
 Foliar biopesticides: applied to plant leaves, stems
and branches.
 Postmergent herbicides: apllied after the crop or
weed has emerged.
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16. ADVANTAGES
• Do not leave harmful residues.
• Substantially reduced impact on non-target
species
• Can be cheaper than chemical pesticides when
locally produced.
• Can be more effective than chemical pesticides
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17. DISADVANTAGES
 High specificity, which will require an exact
identification of the pest/pathogen .
 May require multiple pesticides to be used.
 Often slow speed of action.
 Often variable efficacy due to the influences of various
biotic and abiotic factors.
 Living organisms increase their resistance to biological,
chemical, physical or any other form of control. 17