This document discusses biochemical pesticides, which are naturally occurring pesticides that control pests through nontoxic mechanisms. It provides examples of biochemical pesticides such as insect sex pheromones and plant extracts that attract insect pests to traps. The document also discusses biological control of pests using predation, parasitism, or ammensalism and gives examples such as Bacillus thuringiensis bacteria that infect insect digestive tracts and fungi like Beauveria bassiana that work against pests like whiteflies. Finally, it covers the advantages of biochemical pesticides like not leaving residues and reduced impact on non-target species, and disadvantages like high specificity and variable efficacy.

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