Pesticide

A pesticide is any substance or mixture of substances intended for

preventing , destroying , repelling , or mitigating any pest.

Pest include insects, plant pathogens, weeds, birds, and microbes

etc.

History Since before 2000 BC, humans have utilized pesticides.

The first known pesticide was elemental sulfur.

In 15 century toxic chemicals such as arsenic, mercury and lea

were being applied.

In 17th century use of nicotine sulphate started.

In 19th century use of natural pesticides started.

Until 1950 Ar- based pesticides were common.

Paul Muller discovered DDT as effective pesticide.

In 1975 organochlorines were replaced by organophosphates and

Carbamates.

In 1960 herbicides became common.

Pesticide use has increased 50 folds since 1950.

2.3 million tons of industrial pesticides are used each year.

Classification on the basis of Targeted

Organism

Pesticides

Algicides

Virucides

Rodenticide

Fungicides

Herbicides

insecticide

Avicides Bactericide

miticidesnematicide

Types Of Pesticides

Chemical Pesticides

1. Organochlorides, which have a high persistence in the

environment of up to about 15 years (DDT, dieldrin and aldrin

2. Organophosphates, which have an intermediate persistence of

several months (parathion, carbaryl and malathion)

3. Carbamates, which have a low persistence of around two weeks

(Tenik, Zectran and Zineb)

4. Synthetic pyrethroids, which are nonpersistent, contact and

residual acting insecticides (cypermethrin, permethrin), suitable for

a wide range of crops and target insect

Prominent Families of Herbicides

Phenoxy and Benzoic Acid Herbicides e.g. 2,4-D

Triazines e.g. ( Atrazine) interfere with photosynthesis

Ureas e.g Diuron

Chloroacetanilides e.g alachor

Biopesticides

Biopesticides are certain type of pesticides derived from such

natural materials as plants, animal and microbes like bacteria,

fungi etc.

Microbial Pesticides

Microbial pesticides are composed of microscopic living organisms (viruses,

bacteria, fungi, protozoa, or nematodes) or toxin produced by these organisms

Applied as conventional insecticidal sprays, dusts, or granules.

Their greatest strength is their specificity as most are essentially nontoxic and

non pathogenic to animals and humans.

Microbial pesticides includes insecticides, fungicides, herbicides and growth

regulators of microbial origin.

Some of the important microbial pesticides

a. Bacillus thuringiensis

Discovered in Japan in early 20th century and first become a

commercial product in France in 1938.

Control lepidopterous pests like

American bollworm in cotton

and stem borers in rice.

Fig: Bacillus thuringiensis

When ingested by pest larvae, Bt releases toxins which damage the mid

gut of the pest, eventually killing it.

Main sources for the production of Bt preparations are the strains of the

subspecies kurstaki, galeriae and dendrolimus

b. Agrobacterium radiobacter (Agrocin)

Agrobacterium radiobacter is used to treat roots during transplanting,

that checks crown gall.

Crown gall is a disease in peaches, grapevine, roses and various plants

caused by soil borne pathogen Agrobacterium tumefaciensm.

The effective strains of A. radiobacter posses two important features:

They are able to colonize host roots to a higher population density.

They produce an antibiotic, agrocin, that is toxic to A. tumefaciens.

c. Pseudomonas fluorescens (Phenazine)

•This bacteria is used to control damping off caused by Pythium sp., Rhizoctonia

solani, Gaeumannomyces graminis.

•It has ability to grow quickly in the rhizosphere

d. Trichoderma Fig: Pseudomonas

•Trichoderma is a fungicide effective against soil born diseases such as root rot.

•This is also used against Necteia

galligena, that causes silver leaf

disease of fruit trees by entering

through pruning wounds.

Fig. spores of Trichoderma

e. Metarizium anisopliae

•It infects spittlegbugs, rhinoceros beetles.

f. Beauveria bassiana

• Controls Colorado potato beetle.

g. Verticillum lecanii:

•Controls aphids and whiteflies.

h. Nomuraea riley:

• Controls soybean caterpillars.

i.Baculoviruses (Bvs)

• Control lepidopterous and hymenopterous pests.

•Rod shaped, circular double stranded super coiled DNA.

Fig: Metarhizium anisopliae

Fig: Beauveria

Pesticides derived from plants

Generally act in one of two ways

Contact poison

Stomach poison

About 250000 plant species evaluated

2121 useful in pest management

1005 exhibited insecticidal activity

384antifeedants

297 repellents

27 attractants

31 growth inhibiting properties

Plant-incorporated-protectants (PIPs)

Pesticidal substances that plant produce from the genetic material that

has been added to the plant.

As the pest feed on such plants they will eventually die.Botanical pesticides:

These are naturally occurring plant material that may be crude

preparation of the plant parts ground to produce a dust or powder that

can be used in full strength or dilute form in a carrier such as clay, talc

or diatomaceous earth.

“Azadirachtin” effects the reproductive and digestive procees of pest.

Several plant based insecticides as nicotinoids, natural pyrethroids,

rotenoids, neem products etc are used.

Important botanical pesticides

Fig: Neem oil

Fig: Rotenone

Fig: Tobacco suspension

Common name Scientific name Plant parts used Active principle

Castor Ricinus communis Leaves and oil Ricin , ricinnie

Onion Allium cepa bulbOleic acid ,

cepocoded , α

asarone , β asarone

Custard apple Annona squamosa Leaves and bark Annonin ,

squamocin

Tobacco plant

• Nicotina tobaccum

• Family: Solonaceae

• Part used: dried leaves

• Annual herb

• Habitat: America and cultivated in many countries

• Active constituents

– Nicotine

– Nor nicotine

Nicotine

Colorless, Bitter, Pyridine like flavor, Very toxic

Turns brown when exposed to sunlight

Soluble in non-polar solvents like chloroform, alcohol, ether and

CCl4

Miscible with water

It is present in plat as: 18% stem, 64% leaves, 13% root and 5%

flower

Seeds don’t contain nicotine

It cause death by convulsions

Effective against soft pests

Pyrethrum

• Family: Compositae

• Parts used: Dry flower

• Active constituents

– Pyrithrine

– Linoleic acid

– Volatile oil

– Palmitic acid

• Perennial herb

• Drying is done by sunlight

• Habitat: Cultivated in Yugoslavia, Brazil, Africa etc.

Cont....

• Flowers are collected from 4-5 years plant. Closed flowers

contain more toxic principles

• These are mainly stomach poisons. But when flying insect’s skin

come in contact with them. They penetrate through skin and

cause death due to convulsions and respiratory failure

• Used along with DDT, ethylene glycol mixture to form aerosol

which is sprayed on fly and mosquito

• Used to preserve cotton during storage

Derris elliptica

• Family: Leguminosae

• Parts used: dried root

• Active constituents

– Rotenone

• Cultivation

• Philippines, Malaysia, Indonesia and Burma

• Rotenone

– Soluble in non-polar solvents

– Insoluble in water

– Used for both biting and sucking insects

– It leaves no harmful residues

4.Biochemical pesticides

They are naturally occurring substance to control pest by non-toxic

mechanisms.

Biochemical pesticides include substances as insect sex pheromones, that

interfere with

mating that attract insect pest

to traps.

The synthetic attractants-

are used in one of four ways:

i. As a lure in traps used to monitor pest populations;

ii. As a lure in traps designed to “trap out” a pest population;

iii. As a broadcast signal intended to disrupt insect mating

iv. As an attractant in a bait containing an insecticide

Fig: weevil pheromone trap

Biopesticides are usually inherently less toxic than conventional

pesticides.

Biopesticides generally affect only the target pest and closely

related organisms,

Biopesticides often decompose quickly, avoiding the pollution

problems caused by conventional pesticides.

Biopesticides can greatly decrease the use of conventional

pesticides, while crop yields remain high.

Cheap, renewable can be handled safely.

Difficult for insects to develop resistance to these pesticides.

Slow effect

Lack persistence and wide spectrum activity

Rapidly degraded by UV lights so residual action is slow.

Seasonal availability of plants products indicates the needs for storage.

They are not available easily

Poor water solubility and generally not systemic in nature

All products applied followed by growers have not been scientifically

verified.

Fate of Pesticides

Once a pesticide is applied, several things may happen.

It may be taken up by plants and/or ingested by animals, insects,

worms, or microorganisms in the soil

It may move downward in the soil and adhere to soil particles, or it

may dissolve

It may volatilize

It may be broken down into less toxic compounds

It may be leached or moved out of the plants root zone by rain or

irrigation water or

It may be carried away by runoff water or erosion

Factors Affecting Fate Of Pesticides

There are four major factors which affect the fate of pesticides.

They are as follows:

1. Properties of the pesticide

2. Properties of the soil

3. Conditions of the site

4. Management practices

Case Study: Use of DDT

An October 2007 study has linked breast cancer from exposure to

DDT before puberty.

Scientists estimated that DDT and other chemicals in

organophosphate class have saved 7 million human lives since 1945

by preventing the transmission of diseases such as Malaria, bubonic

plague, sleeping sickness and typhoid.

A study from WHO in 2000 from Vietnam established that non-

DDT malaria controls were significantly more effective than DDT

use.

The US National Academy of Sciences stated that the DDT

metabolite DDE causes eggshell thinning and that the bald eagle

population in the United States declined primarily because of

exposure to DDT and its metabolites

Case Study: Impacts on Human Health

An estimated 2.2 million people are at risk due to exposure from

agricultural pesticides, with the majority of this population being

locating in developing nations.

In 2004, carbofuran pesticide residues found on several batches of

noodles manufactured in Nigeria may have resulted in 23

reported cases of vomiting and one death.

Case Study : Environmental Impacts

Methyl bromide (CH3Br) is a broad spectrum agricultural

pesticide that has been used on more than 100 crops worldwide—

mainly in strawberry, bell pepper and tomato production.

Its primary use is as a soil fumigant

It has been found to cause stratospheric ozone layer depletion

and to be associated with serious health effects.

The U.S. Environmental Protection Agency (US EPA) placed it

under the U.S. Clean Air Act of 1990 for regulation. Under the

1998 amendment to this Act, the importation and production of

methyl bromide was to be reduced by 50% by the year 2001, 70%

by 2003, and total phase-out by 2005

Pesticide poisoning a case study

Potato farmers in the province of Carchi in northern

Ecuador suffer a number of health problems caused by high

exposure to chemical insecticides mostly carbofuran and

methamidophos.

The annual number of deaths resulting from pesticide

exposure is 4 per every 10,000 citizens

Questionnaire data, meanwhile, reveals that 4 out of every

100 rural people suffer pesticide poisonings that are not

reported to the medical authorities.

Case Study: Health effects

A study on workers (N=356) in four units manufacturing HCH in

India revealed neurological symptoms (21%) which were related to

the intensity of exposure

Observations confined to health surveillance in male formulators

engaged in production of dust and liquid formulations of various

pesticides (malathion, methyl parathion, DDT and lindane) in

industrial settings of the unorganised sector revealed a high

occurrence of generalised symptoms (headache, nausea, vomiting,

fatigue, irritation of skin and eyes) besides psychological,

neurological, cardiorespiratory and gastrointestinal symptoms

coupled with low plasma ChE activity (Gupta et al., 1984).

Case Study: Wheat poisoning

In India the first report of poisoning due to pesticides was from

Kerala in 1958, where over 100 people died after consuming wheat

flour contaminated with parathion (Karunakaran, 1958).

Special Committee on Harmful Effects of Pesticides collected

samples to assess the pesticide residues in selected food

commodities (Surveillance of Food Contaminants in India, 1993)

DDT residues were found in about 82% of the 2205 samples of

bovine milk collected from 12 states. About 37% of the samples

contained DDT residues above the tolerance limit of 0.05 mg/kg

(whole milk basis). The highest level of DDT residues found was

2.2 mg/kg.

Case Study: Barbasco Biopesticide

The Peruvian rainforests are home to promising plant barbasco.

Roots are used as natural poison

Active substance of barbasco rotenone is extremely poisonous to

insects and can be use to kill lice and flees on livestock

It’s a still poison but the positive thing is that it breaks naturally .

Rotenone loses its effectiveness in a week time and does not leave

harmful residues.

Conclusion

Biopesticides are typically microbial biological pest control that are

applied in a manner similar to chemical pesticides.

Available in different formulations

Also used to control soil borne and seed borne fungal pathogens

Disadvantages of them are, high specificity, slow speed of action and

their requirement of suitable condition for their survival.

Even though, biopesticides are best for controlling the pests of

agriculture then the chemicals

Therefore there should be more works on production on biopesticides

and encourage people to use biopesticides to control the pests.

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