chemical control

1. Chemical control

2. Chemical Control:
• Management of insect pests using chemical
pesticides is termed as chemical control.
• Pesticides - Chemicals which are used to kill
pests

3. History of insecticide development
Year Chemical
• 900 - Arsenites in China (Inorganic compound)
• 1690 - Tobacco used in Europe (Plant/natural product)
• 1787 - Soaps used in Europe
• 1867 - Paris Green in US
• 1874 - DDT synthezized by Zeidler
• 1883 - Bordeaux mixture in France
• 1925 - Dinitro compounds (First synthetic organic
insecticide)

4. • 1932 - Thiocyanates
• 1939 - DDT insecticidal property discovered by Paul
Muller awarded Nobel Prize in 1948.
• 1941 - BHC in France and UK (in 1942)
(BHC is presently called as HCH)
• 1944 - Parathion (Organo phosphate) discovered by
Gerhard Schrader in Germany
• 1945 - Chlordane (Cyclodian compound) in Germany
• 1947 - Carbamate insecticides in Switzerland

5. • 1962 - Rachel Carson’s Silent Spring appears (US)
(The book ‘ Silent Spring’ created awareness about ill effects
pesticides)
• 1967 - First JH mimic (Juvenile Hormone mimic) used in US
(Insect growth regulator)
• 1970 - Development of synthetic pyrethroids (UK) (Fast
degradation ,Effective at very low doses)
• 1980 - Discovery of avermectins (derived from bacteria). Effective
at low dose, Fast degradation
• 1990 - Discovery of newer groups like
(1) Neonicotinoids (Imidacloprid), similar to natural nicotin,
(2) Spinosyns (e.g. Spinosad) derived from actinomycet

6. Toxicity evaluation of
insecticides
Parameters of toxicity

7. LD50 (Lethal Dose):
• It is the amount of toxicant required to kill 50% of the
test population.
• It is expressed in terms of milligrams of the substance
of toxicant per kilogram body weight (mg/kg) of the test
animal (usually rat, when treated orally).
• In case of insects the LD50 (Median Lethal Dose) value is
expressed in terms of micrograms of the toxicant per
one gram body weight of the insect. (ug/g)

8. Higher the LD50
value lesser is the toxic nature of
the chemical and vice - versa.

9. LC50
(Median Lethal concentration):
• The concentration of insecticide required to
kill 50% of the population of a test animal
• It is expressed in terms of percentage of
the toxicant required
• It is usually determined by potters tower and
probit analysis.

10. 𝐋𝐓𝟓𝟎 (Lethal time 50 ):
• The time required to kill 50% of population
at certain dose concentration .
• It is expressed in terms of hours or minutes.
• It is used in field studies and also for
testing insect viruses (NPV).

11. 𝐊𝐃 𝟓𝟎/ 𝐊𝐓𝟓𝟎 (Knockdown Dose /Time )
• Dose of insecticide / Time required for 50%
of population having knockdown effect.
• 𝑲𝑫 𝟓𝟎/ 𝑲𝑻 𝟓𝟎 are used for evaluating synthetic
pyrethroids against insect.

12. 𝐄𝐃 𝟓𝟎/ 𝐄𝐂 𝟓𝟎
(Effective Dose/Concentration 50):
• Chemicals that gives desirable effects in
50% of test animals.
• The term is used to express the
effectiveness of insect growth regulator .
(IGR)

13. Toxicity
A substance which produces harmful
effects when ingested or inhaled or
absorbed by insect is termed as poison or
toxicity .

14. Acute toxicity
Toxic effect produced by a
single dose of toxicant.

15. Chronic toxicity
Toxic effect produced by the
accumulation of small amounts of the
toxicant over a long period of time .

16. Oral toxicity
Toxic effect produced by
consumption of pesticide
orally.

17. Dermal toxicity
Toxic effect produced when
insecticide enters through skin.

18. Inhalation toxicity
Toxic effect produced when
poisonous fumes of insecticide
are inhaled.( fumigants )

19. Ideal Qualities of an Insecticide
• Kill the target insect effectively and quickly .
• Be less toxic to natural enemies .
• Be less toxic to honey bees, soil microorganisms.
• Be less toxic to fishes and mammals.
• Less hazardous and less toxic during handling or
accidental consumption by human beings.
• Quickly degradable in environment and should be less
persistent (Residues should be very less) .

20. • Should not cause resurgence of the target insect
(i.e. Increase in population of target insect) e.g.
Chlorpyriphos causes resurgence of BPH on rice.
• Should not cause outbreak of secondary pest on a
minor pest by killing the natural enemies.
• Should have a complex mode of action against
which resistance development will take more
time. e.g. Azadirachtin from neem tree has
complex action
• Should have a longer storage life or shelf life

21. • It is advantageous to select an insecticide
which can kill a relatively broad spectrum of
target pests
• It should be cost effective (High benefit/Cost
ratio) and safe to use (High benefit/Risk ratio)
• It should not be phytotoxic.
• It should be available in different formulation.
• It should be compatible with different
insecticides ,fungicides, herbicide, fertilizer.

22. Generation Of Insecticide
GENERATION OF
INSECTICIDE
YEAR COMPOUND
First 1939-1942 BHC and DDT
Second 1944- 1947 Organophosphate And
Carbamate
Third 1967 Hormonal insecticide ,JH mimic
,IGR.
Fourth 1970s. Synthetic pyrethroids.

23. Pesticides Groups :
• 1. Based on organisms
• a) Insecticides : Chemicals used to kill or control
insects (eg.) malathion
• b) Rodenticides : Chemicals exclusively used to
control rats (eg.) Zinc phosphide

24. • c) Acaricides : Chemicals used to control mites on
crops /animals (eg.) Dicofol
• d) Avicides : Chemicals used to repel the birds
(eg.) Anthraquionone
• e) Molluscicides : Chemicals used to kill the snails and
slugs (eg.) Metaldehyde
• f) Nematicides : Chemicals used to control
nematodes (eg.) Ethylene dibromide

25. • g)Fungicides : Chemicals used to control plant
diseases caused by fungi (eg.)
Copperoxy cholirde
• h)Bactericide : Chemicals used to control the plant
diseases caused by bacteria (eg.)
Streptomycin sulphate
• i)Herbicide : Chemicals used to control weeds (eg.)
2,4, - D

26. 2.Based on mode of entry
• a) Stomach poison : The insecticide applied in the
leaves and other parts of the plant when ingested,
act in the digestive system of the insect and bring
about kill (eg.) Malathion.
• b) Contact Poison : The toxicant which brings about
death of the pest species by means of contact (eg.)
Fenvalerate

27. • c)Fumigant : Toxicant enter in vapour form into the
tracheal system (respiratory poison) through spiracles
(eg.) Aluminium phosphide
• d) Systemic poison : Chemicals when applied to plant
or soil are absorbed by foliage (or) roots and
translocate through vascular system and cause death
of insect feeding on plant. (eg.) Dimethoate.

28. 3.Based on mode of action
• a) Physical poison : Toxicant which brings about kill
of one insect by exerting a physical effect (eg.)
Activated clay.
• b) Protoplasmic poison : Toxicant responsible for
precipitation of protein (eg.) Arsenicals.

29. • c)Respiratory poison : Chemicals which inactivate
respiratory enzymes (eg.) hydrogen cyanide.
• d)Nerve poison : Chemicals inhibit impulse
conduction (eg.) Malathion.
• e) Chitin inhibition : Chemicals inhibit chitin
synthesis (eg.) Diflubenzuron.

30. Based on chemical nature
• I. Inorganic pesticides
• Inorganic chemicals used as insecticides
• Eg. Arsenic, Fluorine, Sulphur, lime sulphur
(Insecticides) zinc phosphide (Rodenticide)

31. II.Organic pesticides
• 1.Hydrocarbon oil (or) Petroleum oil – eg. Coal
tar oil, kerosine etc.,
• 2.Animal origin insecticides – eg. Nereistoxin
extracted from marine annelids –
commercially available as cartap.

32. 3.Plant origin insecticides
• Nicotine from tobacco plants .
• Pyrethrum from Chrysanthemum flowers .
• Rotenoids from roots of Derris plant .
• Azadirachtin from Neem .

33. 4.Synthetic organic compounds
• These organic chemicals are synthetically produced in
laboratory.
• i. Chlorinated hydrocarbon (or) organochlorines Eg.
DDT, HCH, Lindane, Dicofol (DDT, HCH banned)
• ii. Cyclodienes Eg. Chlordane, Heptachlor (Banned
chemicals)

34. • iii Organophosphates : (Esters of phosphoric acid)
Eg. Dichlorvos, Monocrotophos, Phospamidon,
Methyl parathion, Fenthion, Dimethoate, Malathion,
Acephate, Chlorpyriphos
• iv. Carbamates: (Derivatives of carbamic acid)
Eg. Carbaryl, Carbofuran, Carbosulfan
• v. Synthetic pyrethroids ; (Synthetic analogues of
pyrethrum)
Eg. Allethrin, Cypermethrin, Fenvalerate

35. vi. Miscellaneous compounds
• Neonicotinoids (Analogues of nicotine) eg. Imidacloprid
• Spinosyns (Isolated from actinomycetes) eg. Spinosad
• Avermectins (Isolated from bacteria) eg. Avermectin,
• Fumigants : Eg. Aluminium phosphide, Hydrogen cyanide,
EDCT

36. INSECT RESISTANCE TO
INSECTICIDES
• The development of an ability in a strain of insects to
tolerate a dose of an insecticide toxicant, which would prove
lethal to majority of individuals in a normal population of the
same species.
• The Division Entomology, IARI, New Delhi was the first to
report insecticide resistance (IR) in the Singhara beetle,
• At present there are many insects have developed
resistance to insecticides

37. INSECT RESURGENCE
• It refers to an abnormal increase in pest population
or damage following insecticide application often for
exceeding the EIL’s.
• Pest resurgence mostly noticed in Homoptera,
Lepidoptera and phytophagous mites

38. Insecticide
• Quinalphos , phorate , Carbaryl
Deltamethrin, methyl parathion
Monocrotophos,
• Synthetic pyrethroids
• Carbaryl
Resurgence of insect species
• BPH
• Aphids, whiteflies, mite in cotton
• Mites on mango and brinjal

39. INSECTICIDE RESIDUES
• The very small quantity of insecticide that can remain in a
crop after harvesting or storage and makes its way into
food chain is called insecticide residues.
• Some insecticides continue to remain toxic for long periods
after application this period of activity is called persistence
or residual action
• Pyrethrum and rotenone are less persistent (12 hrs) while
Organochlorines are most persistent.

40. Maximum Residue Limits (MRLs)
(Residue Tolerance Level)
• The amount of the residue of the toxicant that can be permitted to
be present in / on the produce used by man and his animals is called
tolerance limits.
• It is expressed in ppm.
• The residues should not exceed than the tolerance limits when
offered for consumption.
• It is measure of safety against the harmful effects of pesticide
• Endosulfan - cabbage, brinjal, tomato 2.00 ppm
• Malathion - cabbage, brinjal tomato 8.00 ppm