1. PESTICIDES
Dr. Samia Ghani
M.Phil Pharmaceutics

2. Pests
• Animals or plants which destroy the crops or ornamental
plants and are dangerous to the health of domestic
animals or humans are called Pests
• For example
• Rodents (small mammals) damage stored food products
• Weeds effect the normal growth of growth and garden
plants
• Fungi destroy vegetables and fruit plants
• Insects damage the crop as well as food products.

3. Pesticide
• Any toxic substance used to ki;; pests i.e to kill harmful
animals and plants is called pesticide.
• They interfere with normal metabolic processes in the
pest organism and thus cause their destruction
• Hey are classifeid based upon the organism they control
for example
Fungicide
Herbicide
Insecticide
Rodenticide
Nematocide
Fumigants

4. Types of pets
• Pests may be:
1. Rodents (Rats, mouse, rabbit etc)
2. Arthropods
• Insects (ants, bees, dragonflies)
• Arachnids (Spiders and scorpion)
• Myriapods (many footed such as centipedes and
millipedes)
• Crustaceans (crabs, lobsters and shrimps)
3. Weeds (Ragweed etc)
4. Parasitic fungi (Claviceps purpurea)

5. 1. Rodents
• These are small mammals which have sharp teeth that
gnaw crops and food substances
• They cause damage of food substances and crude drugs.
The stored crude drugs are contaminated due to hairs
and excretory products of rats and mice. Removal of that
specified part is impossible and a lot of drug has to be
wasted and rejected.
• In addition to drug contamination, rodents also transfer
diseases from which they are suffering e.g.
• A biting rat can cause rat-bite fever.
• Lice on rodents can cause typhus fever (bacterial
infection spread by parasite), Plague (Yersinia pestis
bacterium) and rat leprosy.

7. 2. Arthropods
These ticks, mites, lice, spider and insexts etc
On the basis of mouth parts these are classified in to two
categories
Biting and chewing insects
Piercing and sucking insects

8. Biting and chewing insects
Such insects have chewing jaws with the help of which thy
bite and chew substances.
These are dependant on leave and stem of plants thus
destroying the whole crop.
E.g.
• Grasshopper
• Cockroach
• Cloth moth
• Bed bugs etc

9. Piercing and sucking insects
These have modified mouth parts which they penetrate into
epidermal tissues of plants or epithelial tissues of animals
thus sucking the plant juices or animal blood.
E.g.
• Flies
• Bed bugs
• Mosquitos
• Lice
• Mites

11. • Arthropods can cause various diseases such as malaria,
yellow fever, sleeping sickness and other infections.
• Hairy spider bites can kill birds and small mammals.
• Destruction of these insects can stop spreading of these
diseases.

12. 3. Weeds
Any undesirable plant growing among useful plants is
known weeds
For example
• Mustard in clove fields
• Dandelion (kakronda) in a lawn
• Thistle plant (oont ktara) in a vegetable garden.
Weeds cause damage to the cultivated plants because
weeds consume most of the available water and nutrients
which affects growth of cultivated plants.
It also affects quality and quantity of crops such as gains
will be reduced.

13. Dandelion plant

14. Mustard plant

15. • Number of weeds are toxic in nature e.g.
• Corn cockle seeds can cause death when they are
present in large amounts in wheat flour.
• Certain weeds can cause allergic reactions in
hypersensitive individuals e.g. asthma and contact
dermatitis.
• Some poisonous fungi (Claviceps purpurea) may produce
hallucination, when taken orally.

16. 4. Parasitic fungi
• Parasitic fungi e.g. fungi growing on plants may produces
many diseases such as ergot, apple scab ( due to
Venturia inaequalis, a parasitic ascomycetes fungi),
powdery mildew, rust and smuts etc.
• Some fungi may cause skin diseases such as ring worms
and athletes foot in humans.
• Similarly fungi spores can cause allergy in hyperensitive
individuals e.g. asthma and rhinitis.

17. • Some other microorganisms can also cause a number of
plant diseases e.g.
• Viruses can cause Tobacco mosaic and Bean mosaic
diseases.
• Bacteria can cause carrot rot, fire blight of pear and apple
etc.

18. Methods of pests control
• Pests can be controlled by two ways.
• Natural control (crop rotation)
• Artificial control
• Following methods are used for pests control.
1. Mechanical methods
2. Biological method
3. Environmental methods
4. Agricultural methods
5. Chemical methods

19. 1. Mechanical method
• Mechanically pests can be controlled by;
i. Hand picking: pests are removed through hands
Weeds are removed by hand picking
Larvae of tomato hornworm may be removed by hands.
ii. Burning: in this case the plants are burnt where pests are
located. In this method a piece of cloth is soaked in oil and
the fastened at the end of a pole and burnt. This burning
torch is used for the destruction of both animal and plant
pests.

20. iii. Trapping: pests are trapped and caught by special
techniques e.g.
Flying insects or crawling insects are trapped by Anise oil,
Rose oil or other attractants placed in funnel shaped glass
containers. Due to pleasant smell and attractive colour of
oils, the insects are attracted. As a result the insects fly or
crawl through the opening into the jar and cannot escape
out.
Special traps are used o catch rats, mice and large insects.
iv. Pruning: in this case the branches of trees and shrubs
are cut pests are found. In this way the pests are removed
mechanically.

21. 2. Biological methods
• In biological methods small animals or insects are used to
control pests. For example:
Rabbits are used to control weeds i.e. pests, because
rabbits use weeds as a source of food.
Cats, owls and hawks are the natural enemies of mice, rats
etc. they eat such pests and thus help in controlling the
pests.
Insects are eaten by birds.
Some insects have a short life cycle, which parasitize large
insects and finally destroy them e.g. winged insects with
venomous sting such as flies and wasps lay eggs on the
body of large destructive insects and finally destroy them.
These larvae are converted into adult fly, which begins the
cycle once again. In this way they destroy the pests and
help in controling.

22. 3. Environmental methods
• In this method the normal environmental conditions of the
pests are changed due to which the pests are destroyed.
• For example:
Pests can be controlled by cutting off their food supply or
by controlling their life cycle i.e. mosquito larvae in water
are killed by spraying kerosene oil on water.

23. 4. Agricultural methods
• In this case such crops are developed which are resistant
to pest attack i.e. fungus, bacterial and other insects
attack for example:
Through agricultural techniques, such plants are developed
which are either tasteless to the insects or absorb sufficient
organic phosphorus compounds, through the roots or
leaves. Insects eating their leaves can die due to
phosphorous compounds.
Crop rotation is another agricultural method in which the
chief source of food i.e. crop of a particular insect is not
cultivated for one or more seasons due to which insects are
disappeared and thus controlled automatically.

24. 5. Chemical methods
• In this method, chemicals are used to control pests.
• These chemicals are toxic to the pests and are used in
the form of spray solutions, suspensions for spraying,
aerosol fumigants and poison baits.
• These chemicals are selective e.g.
A. Rodenticides; used to destroy rodents such as rats,mice
and moles.
B. Insecticides; against insects and arthropods.
C. Herbicides; against weeds and undesirable plants.
D. Fungicides; used against all types of fungi

25. A. Rodenticides
• These are toxic chemicals used to kill roddnts
• These are used in the form of Poison-Baits. There small
amount must be so toxic to kill rodents. They must be
acceptable to rodent so that rodents eat them.
• They may be of two types:
i- Natural rodenticides
Ii- Synthetic rodenticide

26. i- Natural rodenticides
• Two plant producers which are used as rodenticide
• Red squill: flowers obtained from Urgenia meritima are
used as Raticide from ancient times and again came into
prominence during mid 20th centuary. The toxic substance
is a glycoside which is toxic to rats and not toxic for other
substances. Naturally its used as emetic so when it is
taken by higher mammals and humans, it activates
vomiting center thus vomiting occurs an in this way its
toxic effects will be reduced, whereas rodents don’t hae
vomiting centre so they will die.
• Strychnine: alkaloid used to kill rodents and effective for
small rodents.

27. ii- Synthetic rodenticides
• Two synthetic products are used as rodenticides
• Norbormide: most effective specially for rats,
concentration of 0.5% is sufficient to kill both male and
females.
• Warfarin: most effective rodenticide. Its tasteless and
when rodents take 4 to 5 doses per day, they die. warfarin
is an anticoagulant which causes hemorrhage and
ultimately death of rodenticides.
Disadvantages of warfarin: warfarin can not kill all rodents
because most of them produce sufficient amount of
coagulant i.e. Vit K thus counteract the effect of warfarin.
Sulphaquinoxaline+Warfarin= reduced production of
warfarin

28. Precaution: pet animals and small children should not
swallow these poisons
Fumigants: besides these poisons, fumigants such as
calcium cyanide, methyl bromide and carbon mono oxide
are used to kill or drive the rodents from the place where
they live.

29. B- Herbicides
• The substances used to kill or inhibit the growth of plants
are known as herbicides.
• There are two main classes of herbicides:
i. Selective herbicides
ii. Non-selective herbicides

30. i- Selective herbicides
• The herbicides which destroy the unwanted plants but
have no effect on wanted plants.
• For example:
2-4 D (2-4 dichloro phenoxy acetic acid) is a selective
herbicide because it is toxic to dicotyledonous plants but
has little effect on monocotyledonous plants, because of
this effect it is used to destroy dicotyledonous plants i.e.
weeds from grass lawns and other plants.

31. ii- non-selective herbicides
• Those herbicides which can kill all types of plants life.
• For example:
Calcium cyanamide, potassium and sodium cyanides ,
ammonium thiocyanate, sodium chloride and sulphuric acid
are effective non-selective herbicides.
Non-selective herbicides are used to kill weeds and other
vegetables grown along railroad sides, highways, around
the buildings and playgrounds.

32. C-Fungicides
• Toxic chemicals used to kill or inhibit the growth of fungi,
molds and yeasts etc are called fungicides.
• Mostly these are applied in the form of sprays or dust
• They are of two types:
i- Protective fungicides
Ii- Eradicant fungicides

33. i- Protective fungicides
• They are applied before the fungus attacks.
• They are applied in the form of dust or sprays to protect
the leaves, fruits and other parts of plants from fungus
attacks.
• For example:
Bordeaux mixture: a combination of copper, lime and water
used as protective fungicide

34. Bordeaux mixture

35. ii- Eradicant fungicides
• They are applied after fungus attacks. They either kill the
fungi by direct contact or prevent the formation of spores.
In this they inhibit further spread of fungus.
• For example:
Sulfur or Lime-sulfur mixture is used as fungicide having
both protective and eradicant properties. It is applied in the
form of sprays or dust. Its activity is due to calcium
polysulphide, which is very toxic to fungus.

36. Other fungicides
• Other useful fungicides are thiocarbamates, mercury
compounds, quaternary ammonium compounds, nitro and
heterocyclic nitrogen compounds, antibiotics, phenols and
formaldehydes.

37. D- Insecticides
• Chemicals used for the destruction of insects are called
insecticides.
• They are classified depending upon the stage of life cycle
on which they act. For example:
• Ovicides: used against egg stage
• Larvicides: used against larvae, caterpillars and maggots
• Musicides: used against houseflies
• Pediculicides: used against body lice
• Miticides or scabicides: used against scabies mites.

39. Types of insecticides
• Insecticides may be of following types:
i. Stomach poison
ii. Contact poison
iii. Repellants

40. i- Stomach poisons
• Stomach poisons are the chemicals used against chewing
insects.
• They are of protective type
• Applied in the form of dust, sprays, solutions and
suspensions.
• Poison is taken to stomach of insects when they eat them.
• After ingestion, they affect respiratory system and depress
the nervous system, in this way causing death of insect.

41. Examples
• Calcium arsenate: used on cotton, tomatoes and potatoes etc.
• Phosphorous compounds: these are synthetic insecticides
such as schradan and demeton.
They are readily absorbed through both the roots and the
foliage of the plants. After absorption they remain with in the ants
tissues and protect the plants against insects for a long time.
These compounds are toxic to mammals and therefore used to
treat non-edible crops.
Cockroaches are killed by sodium flouride and sodium
flourosilicate. They are applied in powdered form. When
cockroaches come in contact with these powders, it stick to their
antennae, legs and other parts. Insects clean themselves due to
which powder gets ingested and than absorbed which causes
death.
Sodium arsenate in the form of dust is used to control ants in
houses.

42. ii- Contact poison
• They destroy insects by direct contact.
• Applied in the form of dust, sprays or aerosols.
• May be of two types
a) Natural contact insecticides: obtained from natural
poisons.
e.g. leaf tobacco consists of cured and dried leaves of
Nicotiana tabacum and contain nicotine which is an alkaloid
and used as insecticide and fumigants.
Nicotine sulphate 40% soln is toxic to aphids.
Tobacco can be used as dust on vegetable crops against
certain insects.
As contact poison, its most effective in the form of soap.

43. Pyrethrum flowers: these have been proven effective
against flies, fleas, body lice and malarial mosquitos.
It contains four esters namely; pyrethrin I, pyrethrin II,
cinerins I, cinerins II and these are responsible for
insecticidal activity. In spray forms, these esters are
dissolved in kerosene or other organic solvents which are
effective against flies and mosquitos. In malarial infested
areas, pyrethrum bombs were standard equipments which
contained insecticide in a solvent under pressure of 90lbs
per square inches. A 3-second application permanently
paralyzed most insects. Pyrethrum coils are still in use in
mosquito-infested areas. They are burned like incense and
have a pleasant odour. Pyrethrum ointment is used in
treatment of scabies.

44. • Sabadilla or Cevadilla seeds: seeds contains veratrine
alkaloids. Veradine is composed of cevadine, veratridine
and sabadelline etc. Cevadine is very toxic to certain
insects. Powdered seeds and veratrine preparations are
used as dust or sprays against various insects that attack
vegetables.
• Disadvantages: oxidizes very rapidly to non-toxic form,
which is ineffective against insects. It causes a
sternutatory reflex i.e. causes sneezing.

45. • Ryania: roots and stems contain ryanodine alkaloids
which are resposible for insecticidal property. Its 40%
extract in the form of dust is used against certain insects
such as sugar cane borer and european corn borer. Its
less toxic and has no residual effects.
• Rotenone: roots of several species of Lonchocarpus are
good sources of a resin called rotenone. Ground roots
dust of Lonchocarpus is insecticidal but have no effect on
humans, specially when taken through mouth.

46. b) Synthetic contact insecticides: these are classified into
three groups.
• Organic sulfur: it includes carbamates, thiazines and
organic thiocyanate.
• Chlorinated hydrocarbons: these substances exert there
lethal action after they have passed through insect cuticle.
Examples include;
Dichlophane or DDT
(dichlorodiphenyltrichloroethanepediculicide i.e. used for
the eradication of head lice, applied as dusting powder)
Gamma Benzene Hexachloride (to destroy head lice and to
treat scabies, applied as 1% ointment or lotion and
available with trade name of KWELL®

47. Aldrin (used to control grasshoppers and certain cotton plant
pests, due to its long residual action it is not used commonly)
Chlordane (used to control lawn, garden and home insects)
All these chlorinated hydrocarbons are toxic to man and animals
therefore they should be kept away from foodstuffs and animal
feed.
• Non-halogenated organic compounds: these include Allethrin,
Cinerin I, these are effective against flying insects
• Organophosphorous insecticides: these include parathion,
malathion, TEPP (tetrathylpyrophosphate). They show a wide
range of toxicity. They become inactivated by hydrolysis or
decomposition.

48. iii- Repellents
• These substances drive back the insects and thus prevent
insect attack.
E.g. Citronella oil, compound dimethyl phthalate solution
(622 mixture) diethyltoluamide etc.
622 mixture is effective insect repellant on clothes and skin.
Diethyltoluamide used against certain insects specially
mosquitos.
Repellants are available as alcoholic solution, aerosols and
ointments for topical use.

49. Fumigants
• Fumigant is a volatile poisonous substance used to kill
insects, nematodes and certain other pests.
• E.g. methyl bromide is excellent fumigant used for
treatment of stored products and for fresh green
vegetables. When dissolved in suitable liquid than used
as soil sterilizant for the control of nematodes and other
insects.
• Other fumigants used for the destruction of insect pests
include carbon tetrachloride, ethylene dichloride and
ethylene dibromide etc.
• These are applied in gaseous form or as an aerosol in
enclosed space such as rooms, cupboards, boxes etc.