MCQ OBJECTIVE ON AGRICULTURAL PESTICIDEFlame Institute

General Introduction

Pesticide is

(a) Food grain preservative (b) Fungus killer

Mostly pesticides are

(a) Useful (b) Harmful

Pesticides cause

(a) Noise pollution (b) Air pollution

Pesticides disturb the ecosystem by eliminating the

(a) Micro-organism of crop

(b) Organisms which form the food chain

(d) None of the above

Stomach poisons are those

(a) When injected are harmful

(b) When inhaled and injected are harmful

(d) (a) and (c) both

The toxicants which kill the pests on coming in direct contact are known as

(a) Surface poisons (b) Contact poisons

Transgenic plants are mainly resistant to

(a) Pests (b) Genes

Full form of IPM is

(a) Integrated pest management

(b) Integrated programme for malnutrition

(d) None of the above

‘Central Plantation Research Institute‘ is located in

(a) Kerala (b) Delhi

First commercial pesticide was [RPMT 1998]

(a) DDT (b) 2,4-D

Pests resistant to insecticides have

(a) Less permeable utricles

(b) Capacity of faster storage of toxin in fat

(d) All the above features

Drinking of mineral water with very low level of pesticides (about 0.02 ppm) for long periods may [AIIMS 2002]

(a) Produce immunity agaisnt mosquito

(b) Cause leukemia (blood cancer) in most people

(d) Lead to accumulation of pesticide residues in body fat

As insecticides reach at higher trophic level in food chain their concentration [MP PMT 2003]

(a) Increases (b) Become irregular

The pesticide used in public health programmes

(a) BHC (b) Flit

Bordeaux mixture was discovered by

[MP PMT 1989, 92; BHU 1997]

(a) Millardet (b) Bordeaux

Which of the following is a herbicide

(a) Allethrin (b) Triazine

Which ingredient killed hundreds of people in Bhopal gas tragedy

[BHU 1988; CBSE PMT 1990, 99; DPMT 1990;

AMU 1991; Orissa JEE 1997]

(a) Carbon tetrachloride (b) Nitrous acid

DDT and 2, 4-D were Introduced

(a) Towards end of World War II

(b) Towards beginning of World War II

(d) Just after the World War I

Pyrethoids are of

(a) Synthetic origin (b) Plant origin

Most effective pesticides are [Bihar PMT 1988]

(a) Carbamates (b) Organochlorines

The pesticides are the chemicals that kill [KCET 1993]

(a) Weeds (b) Mites

Which one is pest [MH-CET 2004]

(a) Mouse (b) Pathogen

Chemical pesticide

Houseflies and mosquitoes have become resistant to the

(a) BHC (b) Aldrin

The pesticides used in killing the acquatic pests (including insects) is

(a) DDT (b) BHC

Carbaryl is a

(a) Carbamate (b) Organophosphate

The conc. of pesticide require to destroy 50% of pest is called [MP PMT 1993]

(a) LD 50 (b) LC 50

Ratio of and water in ‘Bordeaux mixture‘ is

(a) 4 : 4 : 40 (b) 4 : 4 : 50

Broad spectrum insecticide is

(a) DDT (b) Pyrethoids

Which of the following is a fungicide

(a) Thiram (b) Dichlone

Herbicticide derived from urea is

(a) Simazine (b) Atrazine

Which of the following when dissolved in water make(s) Bordeaux mixture [MP PMT 1994; AIIMS 1998; BHU 1998]

(a) Copper sulphate (b) Calcium hydroxide

Mosquito–repelling coils contain [MP PMT 1994]

(a) Aluminium phosphide (b) Arsenic

Mode of action of following pesticides is similar

(a) Organochlorines and organophosphates

(b) Organochlorines and carbamates

(d) DDT and parathion

The pesticides most toxic to vertebrates are

Which of the following pesticides does not inhibit cholinesterase

(a) Malathion (b) Parathion

Among pesticides zinc phosphide is used for [MP PMT 1995]

(a) Spraying (b) Fumigation

Which one among the following is likely to have the highest levels of DDT depositions in its body [CBSE PMT 1994]

(a) Eel (b) Crab

Major drawback of DDT as a pesticide is that

[CBSE PMT 1994; AFMC 2002]

(a) Organisms at once develop resistance to it

(b) It is significantly less effective than other pesticides

(d) It is not easily and rapidly degraded in nature

The chemical formula of ’paris green‘ is

(a)

(b)

(c)

(d) None of the above

Which one of the following pesticide is banned now–a–days

[MP PMT 1996; BVP 2003]

(a) Aldrin (b) Endrin

The first fungicide discovered for plant disease control was

(a) Bordeaux mixture (b) DDT

BHC and DDT belong to which class of pesticides

[MP PMT 1997]

(a) Organophosphates (b) Organochlorines

’Boredeaux mixture’ is used as a

[BHU 1995; MP PMT 1997; BVP 2004]

(a) Fertilizer

(b) Fungicide

(d) A chemical used in soil testing

Organophosphate insecticides inhibit [MP PMT 1998]

(a) Cholinesterases (b) Carbohydrases

What type of poison is ethylene dichloride [MP PMT 1999]

(a) Stomach poison (b) Contact poison

Which of the following pesticides is an acetylcholinesterase inhibitor [CBSE PMT 1998; MP PMT 2003]

(a) Aldrin (b) Y-BHC

Nobel prize was awarded to Paul Muller on the discovery of which of the following pesticides [MP PMT 2001]

(a) Malathion (b) Parathion

Which are the two active ingredients in ‘Flit’

(a) Malathion and Pyrethrin

(b) Carbofuran and Propoxur

(d) Pyrethrin and Propoxur

Bordeaux mixture was first used in:

(a) Germany (b) Japan

Baygon contains [EAMCET 1989]

(a) Malathion (b) Propoxur

A carbamate pesticide is

(a) Simazine (b) Atrazine

Which of the following pesticides have been successfully used in the control of locusts and grasshoppers in India

(a) Sevin (b) Aldrin

The pesticide used in foundations of buildings for preventing termite attack is

(a) DDT (b) BHC

Which of the following is not an organo-chlorine

(a) Endosulphan (b) Malathion

Which of the following pesticides is employed widely in antimalarial programmes

(a) Aldrin (b) Malathion

Mode of pesticide action is similar in

(a) DDT and parathion

(b) Organochlorines and organophosphates

(d) None

The chemical present in Temik is

(a) Malathion (b) Propoxur

Herbicide carbamates are [DPMT 1986]

(a) Dithiocarbamates (b) Thiocarbamates

Bordeaux mixture is named after

(a) Scientist (b) Chemical composition

The chemical present in flit (finit) is

(a) Malathion (b) DDT

Carbamates used as fungicides are

(a) Thiocarbamates (b) Dithiocarbamates

Pesticides with very low biodegradation but strong affinity for fatty tissues are [AFMC 1988]

(a) Triazines (b) Pyrethroids

Which pesticides are lipophilic

(a) Organochlorines (b) Organophosphates

Triazines are derived from

(a) Ammonia (b) Urea

2, 4-D is an effective

[CBSE PMT 1996; BHU 1997; MH-CET 2000]

(a) Insecticide (b) Herbicide

Which of the following pesticides are non-biodegradable

(a) Triazines (b) Organophosphates

Methyl isocyanate gas is used for synthesizing

(a) Temik (b) Baygon

Fumigants are volatile toxicants

(a) HCN only (b) HCN and CS₂ only

Which one is not matched [Bihar PMT 1988]

(a) Organochlorine-DDT

(b) Pyrethroid-Atrazine

(d) Carbamate-Carbofuran

Biological magnification refers to [BVP 2002]

(a) Concentration of insecticide in animals

(b) Concentration of organophosphate in plants

(d) Increase in number of animals and plants in ecosystem

What is the main problem caused by the use of pesticides

[AIEEE 2004]

(a) Their residues persists in water and other components of the environment

(b) Mosquitoes have become resistant to DDT

(d) They deform the gills of some fishes

To which class of pesticides do DDT, BHC, aldrin and endosulphan belong

(a) Biopesticides (b) Organochlorines

Which one among the following is likely to have the highest levels of DDT deposition in its body

[CBSE PMT 1994; BVP 2004]

(a) Seagull (b) Crab

Endosulphan is a [MP PMT 1996]

(a) Herbicide (b) Weedicide

In India, the most commonly used pesticide BHC is

(a) Carbamate (b) Triazine

Pyrethrin is extracted from [RPMT 1989; CPMT 1999]

(a) Chrysanthemum cinerarifolium

(b) Azadirachta indica

(d) Ryania speciosa

Drinking of mineral water with very low level of pesticides (about 0.02 ppm) for long periods may [AIIMS 2003]

(a) Produce immunity against mosquito

(b) Cause leukemia (blood cancer) in most people

(d) Lead to accumulation of pesticide residues in body fat

The most likely reason for the development of resistance against pesticides in insects damaging a crop is

[CBSE PMT 2004]

(a) Direct mutation

(b) Acquired heritable changes

(d) Genetic recombination

The chemical used in National Malaria Eradication Programme is [BHU 2004]

(a) 2, 4-D (b) BHC

Bordeaux mixture can be prepared by mixing the copper sulphate with [Manipal 2005]

(a) Sodium chloride (b) Milk of calcium

The pesticide useful in the control of aphids, caterpillars, plant bugs and borers is

(a) Aldrin (b) DDT

Biological pesticide

When a natural predator living being applied on the other pathogenic organisms to control them, this process is called

[CBSE PMT 1996]

(a) Biological control (b) Genetic engineering

Concentration of insecticide in the animals of a species is called [MP PMT 2002]

(a) Biomagnification (b) Bioconcentration

Which insect was used to check the spread of cacti

(a) Coleus eurythaeum (b) Cactoblastis cactorum

The carnivorous fish Gambusia, introduced in the lakes, ponds, etc., control a deadly disease in India, feeds on the larvae of [AIIMS 1997]

(a) Nephantis (b) Dragonfly

The prickly pear weed (Opuntia) bacame a menace and it has been successfully controlled by [DPMT 1993]

(a) DDT spray (b) Cattle

In India, the most popular bioinsecticide is the extract from

(a) Acacia (b) Delbergia

One of the major difficulties in the biological control of insect pests is that [CBSE PMT 1995]

(a) The predator develops a preference to other diets and may itself become a pest

(b) The predator does not always survive when transferred to a new environment

(d) The practical difficulty of introducing the predator to specific areas

What is agent orange [CBSE PMT 1997]

(a) A biodegradable insecticide

(b) A weedicide containing dioxin

(d) A hazardous chemical used in luminous plants

The two natural insecticides used before 1940

(a) Pyrethrum and rotenones

(b) Pyrethroids and nicotine

(d) Pyrethrum and squill

Insecticides kill

(a) Harmful insects

(b) Only plant pests

(d) Both harmful and useful insects

Bio-insecticides includes

(a) Pathogens (b) Parasites

The first natural insecticides discovered by chinese was

(a) Pyrethrum (b) Nicotine

Which one of the following is pest of tobacco

[JIPMER 1997]

(a) Tribolium sp. (b) Spodoptera sp.

Sporeine kills insects by inhibiting ion transport in the

(a) Midgut (b) Foregut

Most herbicides attack

(a) Photosystem I (b) Photosystem II

Nerve gas causes

(a) Inhibition or respiration

(b) Inhibition of PSII

(d) All of these

Much work on biological control of insects has been done in

(a) North America (b) Japan

Sporeine was developed in [CBSE PMT 1988]

(a) France (b) Germany

Cochineal insects have proved very useful for the control of

[CBSE PMT 1996]

(a) Eicchornia (b) Cactus

Most common pesticides used in the crops are

(a) BHC, aldrin, malathion, pyrethrin

(b) Aldrin, malathion, lead arsinate, sodium fluoride

(d) Cryolite, aldrin, pyrethrin

DDT is a [AMU 1986]

(a) Organochlorine (b) Organophosphate

Full name of BHC is [MP PMT 1987]

(a) Benzene hexachloride (b) Hexachlorohaxane

First pesticide used by man is

(a) Rotenone (b) Pyrethrin

The most famous pesticide of the world is [BVP 2003]

(a) Methyl isocyanate (b) DDT

‘Rotenone’ is [CBSE PMT 1995; BHU 1999; Pb. PMT 2000]

(a) A bioherbicide (b) An insect hormone

Natural insecticide obtained from neem is [AFMC 2004]

(a) Nicotine (b) Azadirectane

‘Sporeine’ is a

(a) Herbicide (b) Pesticide

First bioinsecticide to be developed on commercial scale was

[KCET 1998]

(a) Morphine (b) Quinine

Fish which eradicates the mosquito larva, is

[CBSE PMT 1999]

(a) Anabus (b) Rohu

DDT was first synthesized by

(a) Othnar Zeidler (b) Paul Muller

Pick out the correct statement

(a) DDT is more toxic than BHC

(b) Aldrin is an organophosphate

(d) To mammals DDT is highly toxic

The most common pesticide used in India is [BHU 1985]

(a) Baygon (b) BHC

The term ‘bio-magnification’ refers to the

[CET Chd. 1990; KCET 1997]

(a) Increase in population size

(b) Increase in the concentration of non-degradable pollutants as they pass through the food chains

(d) Growth of organisation due to food consumption

Eutrophication is due to [Wardha 2001]

(a) Air pollution (b) Radiation pollution

Thurioside is a proteinaceous toxin which is obtained from

[Manipal PMT 1990; CBSE PMT 1991]

(a) Biofertilizer (b) Farmyard manure

Which of the following is the first fungicide [BHU 1995]

(a) 2, 4-D (b) D.D.T.

Which of the following insecticide is obtained from the roots of Derris elleptica [BHU 2004]

(a) Cinerin (b) Nicotine

Biological control of agricultural pests, unlike the chemical control, is [CBSE PMT 1995]

(a) Toxic (b) Polluting

Herbicides prevent [MP PMT 1987]

(a) Water reabsorption (b) Photolysis of water

Read the assertion and reason carefully to mark the correct option out of the options given below :

(a) If both the assertion and the reason are true and the reason is a correct explanation of the assertion

(b) If both the assertion and reason are true but the reason is not a correct explanation of the assertion

(c) If the assertion is true but the reason is false

(d) If both the assertion and reason are false

(e) If the assertion is false but reason is true

Assertion : All pesticides are insecticides.

Reason : Some pesticides are called biocides.

Assertion : Use of organochlorines pose serious problem to the ecosystems.

Reason : Organochlorines accumulate in all organisms.

Assertion : 2, 4 – D and 2, 4, 5 – T are weedicides.

Reason : Their uses affect the ecology.

Assertion : Pesticides are used only when the crop is in cultivation.

Reason : They are used to destroy disease vectors.

Assertion : Fungicides act against fungal pathogens.

Reason : They are not harmful for human beings.

Assertion : Biocides are effective against animals.

Reason : Algicides are effective against weeds.

Assertion : In flit, Malathion is used.

Reason : Malathion is a natural insecticide.

Assertion : Use of pesticides disturb the predator prey population.

Reason : Use of pesticides may give rise to resistant varieties of pests.

Assertion : Weedicides are used only in agricultural field against unwanted plants.

Reason : Auxin – like weedicides are usually metabolic inhibitors.

Assertion : Organochlorine pesticides are organic compounds that have been chlorinated.

Reason : Fenitrothion is one of the organochlorine pesticides. [AIIMS 2003]

Assertion : Agricultural output increased several times after introduction of DDT.

Reason : DDT was the first insecticide used on a wide scale. [AIIMS 2004]

General Introduction

1	d	2	d	3	c	4	b	5	c
6	b	7	a	8	a	9	d	10	d
11	d	12	d	13	a	14	a	15	a
16	b	17	d	18	a	19	b	20	c
21	d	22	d

Chemical pesticide

1	c	2	c	3	a	4	a	5	b
6	a	7	d	8	d	9	c	10	c
11	c	12	b	13	c	14	c	15	d
16	c	17	c	18	c	19	a	20	b
21	b	22	a	23	c	24	d	25	d
26	a	27	c	28	b	29	c	30	b
31	c	32	b	33	b	34	a	35	d
36	d	37	c	38	a	39	b	40	c
41	a	42	b	43	b	44	c	45	d
46	b	47	b	48	a	49	a	50	b
51	a	52	d	53	c	54	a	55	d
56	c	57	c	58	b	59	c

Biological pesticide

1	a	2	c	3	b	4	c	5	d
6	d	7	a	8	d	9	b	10	d
11	d	12	c	13	b	14	a	15	b
16	c	17	a	18	b	19	b

Critical Thinking Questions

1	a	2	a	3	a	4	a	5	b
6	d	7	b	8	d	9	c	10	c
11	a	12	c	13	b	14	b	15	c
16	d	17	d	18	c	19	d	20	b

Assertion and Reason

1	e	2	b	3	b	4	e	5	c
6	d	7	c	8	b	9	e	10	c
11	a

General Introduction

(d)Pesticides are chemicals that repel or destroy weeds, fungus, pathogens and other pests.
(c) Since pesticides are mostly soluble in water, so when they come in water streams, they cause water pollution of different nature.
(b)Pesticides also enter the food chain, their concentration goes as they move up in the food chain. This is called bio magnification or bioconcentration.
(c)Stomach poisons are those which reaches the alimentary canal or stomach of the insect along with the food.
(a) Integrated pest management is the technique of pest control which involves natural methods to a greater extent and using pesticides to the minimum and when it is essential.
(d) First commercial pesticide was discovered by millordet (1882). It is called Bordeaux mixture.
(a)BHC is more toxic to insects than DDT and is used mainly in public health programmes.
(a)First inorganic fungicide was developed by R.M.A millardet (1882) agiant downly mildew of Grape-vine at the university of Bordeaux and commonly known as Bordeaux mixture.
(d) Methyl isocyanate gas which caused Bhopal gas tragedy on 3^rd Dec. 1984.
(a) During the second world war, two synthetic pesticides i.e., DDT (dichloro diphenyl trichloroethane) and 2, 4-D (2, 4 dichlorophenoxy acetic acid) were mainly used.
(b)They are synthetic derivatives of pyrethrum having broad spectrum effect, pyrethrum is naturally got from inflorescence of chrysanthemum species like C. marshalli, C. cinerarifolium and C. Coccineum.
(c)Organophosphates are the most effective pesticides which are esters of phospharic acid and its derivatives e.g., malathion, parathion, ethion, TEPP. etc.

Chemical pesticide

(c) DDT has become ineffective for killing mosquitoes and houseflies because of the development of adaptive resistance.
(c) By the spraying of kerosine oil on the surface of water bodies, larva and pupa of insects can not live due to the lacking of breething.
(b) Bordeaux mixture is prepared by dissolving 40 gm of copper sulphate and 40 gm of calcium hydroxide in 5 liters of water.
(d) Triazines (Simazine, Atrazine etc.) are a group of herbicides derived from urea.
(c) Bordeaux mixture is prepared by dissolving copper sulphate, and calcium hydroxide in water.
(c) Mode of action of carbonate is quite similar to that of organophosphates.
(b) Organophosphates are the pesticides most toxic to vertebrates.
(c) DDT does not inhibit cholinesterase activity and is relatively non-toxic to mammals but in oil solution it is absorbed by skin.
(c) DDT has a long residual effect.
(c) DDT has been banned in most countries due to its effect on nervous system, cirrhosis of liver. Cancer, malfunctioning of sex hormones and thinning of bird egg shells.
(b) Organochlorines are chlorine containing hydrocarbones e.g., DDT, BHC, Aldrin, endrin, dieldrin, endosulphan.
(b) Inorganic fungicides include Bordeaux mixture.
(a) Organophophates inhibit cholinesterase an enzyme essential for transmission of nerve impulse across synapse.
(d) Malathion is an organophosphate pesticide which has strong effect on nervous system. It inhibits the action of acetylcholinesterase enzyme.
(d) DDT insecticidal value was discovered by paul muller in 1939. and got Nobel prize.
(a) Malathion is one of the two active ingredients in flit, the second being pyrethrin.
(c) Bordeaux mixture was discovered by millardet in France in 1882.
(b) Aldrin has been successfully used in control of Locusts and Grasshoppers in India.
(c) Aldrin is an insecticide applied to foundation of buildings to prevent termites.
(b)Malathion is also employed widely in anti-malarial programmes.
(d)Commonly used carbamates is aldicarb (Temik).
(b) Derivatives of carbamates are also used as fungicides (dithiocarbamates).
(c)Organo chlorines have very low bio-degreadation, get accumulated in environment posing serious problems.
(a) Organochlorines are lipophilic and show much affinity for fatty tissue of animals.
(b) 2,4-D is a derivatives of auxin herbicides.
(c) Organochlorines have very low biodegradation.
(d) Methyl isocyanate gas is used as a row material for synthesizing carbaryl (trade name selvin).
(b)Examples of pyrethroides are Allethrin, Cyclethrin and Barthrin.
(a) Biological mangification related to the concentration of insecticides in animals. It is defined as increase in the concentration of a persistent chemical by the organisms at successive trophic level in of food chain. The best example of biomagnification is minimata disease of Japan.
(a) Most of pesticides, especially organochlorines are non biodegradable and accumulate in the environment resulting in pollution.
(b)Important examples of organochlorines are DDT, BHC, Aldrin, and Endosulphan.
(a)Pyrethroides are synthetic derivatives of pyrethrin, a chemical produced by grinding of flowers of the plant Chrysanthemum cinerarifolium.
(d)In India, as a result of prolonged use of 13-31 ppm of DDT (Pesticides) can be detected in body fat of the people, highest in world.
(c) DDT (Dichloro diphenyl trichloroethane) was synthesised by a Germam student and rediscovered by Dr. Paul muller. It was used in national malaria Eradication programme to kill Anopheles mosquitoes.

Biological pesticide

(a) Biological control method include using natural predators of pests, using resistant varieties crop rotation etc.
(c) Biomagnification/Bioconcentration is increase in percentage of a chemical in the body of organisms with the rise in trohpic level most organochlorines are fat soluble and undergo biomagnification (13-31 ppm. of DDT in human body in India).
(b)In India and Australia the overgrowth of cacti was checked by the introduction of cochineal insect (Cactoblastis Cactorum).
(c) Gambusia is a carnivorous fish. It feeds on larva of Anopheles this is used in biological control of mosquito.
(d) Pesticides kill both harmful and useful insects.
(d) Bioinsecticides include pathogens, parasites and predators, steritization strategy insect hormones, natural insecticides.
(a) Sporeine kills insects by inhibiting ion transport in the midgut.
(b)Most herbicides attack the photosystem II (Photolysis of water and oxygen evolution) in photosynthesis.
(a) Much of the work using insects for biological control has been done in North America.
(b)Sporeine was the first bioinsecticides developed on commerical scale in Germany.

Critical Thinking Questions

(a)Full name of BHC is Benzene hexachloride
(a) Rotenone is a natural insecticide which are first used by man.
(b) DDT is most famous pesticide of the world
(b) Natural insecticides Azadirachtin are obtained from seed of Azadirachta indica (Neem or margosa) plants.
(a)DDT was first synthesized by a German chemist othnar Zeidler in 1874.
(c)DDT is the famous pesticidie, it is a nonbiodegradable pollutant.
(b) The most common pesticide used in India is BHC. It represent about 50% of total volume of pesticides used in India.
(c) Due to eutrophication decreases oxygen replenishment inside water. Blue green alage present in the bloom also release toxins. Both toxicity and decreased oxygen level kill aquatic animals so the water pollution occurs in water bodies.
(c) Natural insecticide Rotenone are obtained from root of Derris elliptica.

Assertion and Reason

(e) Pesticides are of several types depending upon the types of pests killed or controlled – algicides (algal pathogens and blooms in water reservoirs), fungicides (fungal pathogens), bacteriocides (bacterial pathogen), herbicides or weedicides (weeds), insecticides (insects and related organisms), nematicides (nematodes), rodenticides (rodents – rats, mice) etc. The most widely used among them are insecticides. Pesticides are sprayed in the form of fine mist, powder or solution. The pesticides are generally broad spectrum and affect useful plants, animals and human beings. They are therefore also called biocides.
(b) Rate of degradation of organochlorines is low. Only 5% degradation of DDT per year has been reported in the soil. Organochlorines are not soluble in water. They are lipophilic (lipid loving) and therefore tend to accumulate in the stored fats of all organisms including the fatty tissues of animals. In excess the organochlorines can directly kill higher animals.
(b) 2, 4 – D and 2, 4, 5 – T cause death of plant due to proliferation of phloem cells and block transport of organic foods. They are commonly biodegradable but have long term side effect like mutation in plant and animals and thus affect the ecology of a place.
(e) Pests are organisms which harm human interests through destruction of food articles in cultivation, storage, preparation and in homes as well as bring about physical harm to domesticated animals and human being through blood loss, spread of diseases etc. Pesticides are sprayed over crops, inside and outside human dwellings. Pesticides were initially employed to protect crop plants against pests but they are now equally important for destroying or controlling vectors for various animals and human pathogens.
(c) Fungicides are chemicals which are specifically effective against fungal pathogens. Fungicides are divided into two major types, inorganic and organic. Most inorganic fungicides are harmful to other living beings as well.
(d) The pesticides are generally broad spectrum and affect useful plants, animals and human beings. They are ‘therefore’ also called biocides. Algicides are effective against algal pathogens i.e., they affect on variety of organisms and blooms in water reservoirs. The chemicals used against are called weedicides g., 2, 4 – D.
(c) Malathion is an organophosphorus and it is a synthetic pesticide. It is an ingredient of finit (flit).
(b) Pesticides often disturb the predator prey population and bring about ecological imbalance. In nature the number of plant pests is always higher than their predators. Pesticides being broad spectrum harm both the predators and their preys. Since the population of predators is small, they are likely to suffer the major loss.

On the other hand the population of preys of plant pests is always large. Use of pesticide is likely to produce a small population resistant to the pesticides the population will multiply rapidly in the absence of their natural predators.

(e) Weedicides are employed in clearing areas for building new residential or industrial colonies, highways, railway tracks, weeds in agriculture (g., Tea, Tobacco, Cotton, Wheat), horticulture and forest management. Auxin like weedicides or herbicides are usually metabolic inhibitors which stop photosynthesis by attacking photosystem II connected with photolysis of water and evolution of oxygen.
(c) Pesticides are the substances used to kill or repel pests. On the basis of chemical structure, major pesticides are grouped under five categories. (i) organochlorines (ii) organophosphates (iii) carbamates (iv) pyrethroids (v) triazines. Organochlorines are basically organic compounds that have been chlorinated and have very low bio – degradation and get accumulated in environment and possess serious problems. DDT, BHC, Aldrin and Endosulphan are the examples of orgenochlorines. Fenitrothion is an example of organophosphate.
(a) DDT is pesticide which help in improving crop yield and in public health programmes. DDT is the most famous pesticide of world and it is a non biodegradable pollutant which used on a wide scale.

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