different methods of Chemical control of insect pest in agriculture and forestry with examples.

1. CHEMICAL CONTROL OF PESTS
Submitted To :-
College of Forestry
Odisha University of Agriculture & Technology

2. Use of chemicals for pest
control
Pesticides: chemicals that kill pests or inhibit their development
◦ Insecticides: insects
◦ Herbicides: plants
◦ Rodenticides: rodents
◦ Avicides: birds
Insect attractants, repellents and antifeedants affect the orientation of
pests towards the host
Chemosterilants, growth regulators etc. interfere with normal
reproduction or development of pests

3. How it began
In 18th and 19th centuries, farmers used soup of plants toxic to insects,
e.g. - chrysanthemum, tobacco etc.
Later, toxic compounds were extracted and applied as liquid sprays, e.g.
- nicotine, petroleum, turpentine, pyrethrum etc.
Eventually organic compounds were replaced with inorganic
compounds, e.g. - arsenic, lime, sulphur, strychnine, cyanide etc.

4. Use of pesticides over time

5. The DDT story
Insecticidal properties of DDT (dichlorodiphenyltrichloroethane) were
discovered during World War II
Extremely toxic to insects, seemed nontoxic to mammals
Cheap, broad spectrum, persistent
Effective disease prevention, e.g. - typhus fever, malaria
DDT is thought to biomagnify and hence was deemed harmful to the
environment by the EPA and other organizations
DDT is stored in the fat of animals and takes many years to break down
By the 1960s, the value of DDT as an insecticide had decreased
In the 1970s severe restrictions were imposed on use of DDT

6. Biomagnification of DDT across the food chain

7. Classification of pesticides
Based on the origin and source of supply
◦ Inorganic pesticides: comprise compounds of mineral origin
◦ Organic pesticides: comprise compounds of organic material
Based on the mode of entry
◦ Contact poisons: kill pests by coming in contact with the body
◦ Stomach poisons: act on the digestive system of the pest when ingested
◦ Fumigants: fumes gain entry to the body via respiration
◦ Systemic pesticides: capable of moving through vascular system of the plant
irrespective of site of application

8. Classification contd.
Based on the mode of action
◦ Physical poisons: kill by exerting a physical effect
◦ Protoplasmic poisons: responsible for precipitation of protein destroying cellular
protoplasm
◦ Respiratory poisons: block cellular respiration
◦ Nerve poisons: block Acetyl cholinesterase (AChE) and affect the nervous system
◦ Chitin inhibitors: interfere with process of synthesis of chitin
◦ General poisons: include neurotoxic symptoms after some period
Based on toxicity
◦ Extremely toxic: Oral LD 50 – 1-50, Dermal LD 50 – 1-200
◦ Highly toxic: Oral LD 50 – 51-500, Dermal LD 50 – 201-2000
◦ Moderately toxic: Oral LD 50 – 501-5000, Dermal LD 50 – 2001-20,000
◦ Less toxic: Oral LD 50 – >5000, Dermal LD 50 – >20,000

9. Classification contd.
Based on stage specificity
◦ Ovicides
◦ Larvicides
◦ Pupicides
◦ Adulticides
Generation wise
◦ First generation: inorganics and botanicals
◦ Second generation: synthetic organics
◦ Third generation: recent chemicals for reproductive control, IGRs
◦ Fourth generation: synthetic pyrethroids
◦ Fifth generation: synthetic pyrethroids

10. Formulations of pesticides
Dusts (D) - ready to use insecticides in powder form
Granules or Pelleted insecticides(G) - ready to use granular or pelleted form
Wettable Powders (WP) - powder formulation which is to be diluted with water
Emulsifiable Concentrates(EC) - clear solution which yields an emulsion of oil-in
water type when diluted with water
Soluble Powder or Water Soluble Powder (SP or WSP) – powder formulation
readily soluble in water
Suspension Concentrate (SC) - active ingredient is absorbed on to a filler which
is then suspended in a liquid matrix
Flowables (F) - active ingredient is insoluble in either water or organic solvents

11. Formulations contd.
Water Dispersible Granules (WDG) - appears as small pellets or granules
Solutions - soluble in organic solvents which themselves possesses some
insecticidal properties of their own
Concentrated liquids - toxicant at highly concentrated level dissolved in
non-volatile solvents
Aerosels - toxicant suspended as minute particles of 0.1-30 microns in air as
fog or mist
Fumigants - volatile at ordinary temperature
Microencapsulation - dry and liquid pesticide particles enclosed in tiny
plastic capsules
Mixtures - combinations of two or more insecticides in the right
concentration
Baits - active ingredient is mixed with edible substance

12. Aerial application of pesticides covering a large area

13. Attractants
Chemical substances which cause orientation of pests towards the
source of attractant
Pheromones or ectohormones are released by insects which cause
attraction towards individuals of same species
Used as bait to attract pests to a particular place where they can be
killed by application of pesticides
May fail in unsuitable environments or less vapour concentration
Suitable for evaluation of population density of pest in the particular
field
Geraniol & Eugenol acts as attractants for Japanese beetle

14. Attractants can be used in insect traps to attract the insects into the trap and kill them

15. Repellents
Prevent pests by making their food or living conditions unattractive
Physical repellents like waxes on leaf surface repel insects
Auditory repellents like amplified sound producing devices used to repel
mosquitoes
Pentachlorophenol repels termites

16. Antifeedants
Make the plant distasteful to the pests
Insect may die by feeding on plants having antifeedants
Azadirachtin present on Neem plant is antifeedant for desert locust and
other insects
Bordeaux mixture acts as antifeedant for flea beetles and leaf hoppers

17. Caterpillar (larva) feeding on a leaf

18. Chemosterilants
Cause reproductive sterility in insects
Prevent cell division or obstruct normal embryonic development by
◦ Inhibiting ovarian growth and development
◦ Inducing changes in fundamental structure of nucleic acids like DNA and RNA
Applied directly to the insect or incorporated into diet
May also cause cancer, birth defects and other mutation in mammals
Antimetabolites, triazines, antibiotics etc. are some examples of
chemosterilants

19. Insect Growth Regulators
Inhibit the life cycle of an insect
Target juvenile harmful insect populations while causing less
detrimental effects to beneficial insects
Do not affect an insect's nervous system unlike classic insecticides
More compatible with pest management systems that use biological
controls
Insects are less likely to become resistant to IGRs
IGRs prevent an insect from reaching maturity by interfering with the
moulting process

20. Process of moulting in insects involves shedding of exoskeleton

21. Types of IGRs
Hormonal IGRs
◦ Work by mimicking or inhibiting the juvenile hormone (JH)
◦ Can also inhibit the hormone ecdysone
◦ IGRs that mimic JH Can produce premature moulting of young immature stages or can
also act on eggs, causing sterilization
◦ IGRs that inhibit JH production can cause insects to prematurely moult into a non-
functional adult
◦ IGRs that inhibit ecdysone can cause pupal mortality by interrupting the
transformation of larval tissues into adult tissues during the pupal stage
Chitin synthesis inhibitors
◦ Work by preventing the formation of chitin, a carbohydrate needed to form the
insect's exoskeleton
◦ Also kill eggs by disrupting normal embryonic development
◦ Affect insects for longer periods of time than hormonal IGRs

22. Advantages & disadvantages of
chemical pest control methods
Advantages
◦ Less expensive and are readily available
◦ Very easy to use
◦ Deliver results instantly right after application
Disadvantages
◦ May also harm the beneficial organisms
◦ May have adverse effects on the environment and human health
◦ The effects are mostly short-term
◦ Resurgences and secondary pest outbreaks are more likely to happen

23. Population of resistant insects increasing over time

24. The cycle of chemical
pesticides
Pest
problems
Use of
chemical
pesticides
Resistance,
resurgence,
secondary
outbreaks

25. Negative effects of pesticides
Human health effects
◦ Cancer, dermatitis, neurological disorder, birth defects, sterility, endocrine
system disruption, immune system depression
◦ Agricultural workers suffer acute poisoning during pesticide application
◦ Aerial spraying and dumping bring pesticides in contact with families and
children
Environmental effects
◦ DDT led to the decline in populations of several bird species like Bald eagle
and Peregrine falcon
◦ Bioaccumulation in an individual over time
◦ Biomagnification of chemicals pesticides

26. Conclusion
Chemical control methods are easier, quicker and more effective, but
come with negative consequences
In the current scenario, it is difficult to completely abandon the use of
chemical control methods due to various factors like cost, ease of use
etc.
But we can try to lessen the use of chemical control methods by using
other methods of pest control like ecological control, cultural control,
biological control etc.

27. Thank you