Pesticides are substances that are meant to control pests.
The first known pesticide was elemental sulfur dusting used in ancient Sumer about 4,500 years
ago in ancient Mesopotamia.
By the 15th century, toxic chemicals such as arsenic, mercury, and lead were being applied to
crops to kill pests.
In the 17th century, nicotine sulfate was extracted from tobacco leaves for use as an insecticide.
Insecticides are substances used to kill insects.
They include ovicides and larvicides used against insect eggs and larvae, respectively.
Insecticides are used in agriculture, medicine, industry and by consumers.
Dichlorodiphenyltrichloroethane (DDT) is an insecticide used in agriculture. The United States
banned the use of DDT in 1972. Some countries outside the United States still use DDT to control
of mosquitoes that spread malaria.
2. Organic pesticides:
• Mostly synthesized chemicals, but some are natural toxins produced by certain plants that are
extracted and used as pesticides.
•Substances derived from plants, minerals, and microorganisms.
•Also called bio-pesticides.
•Contain carbon .
•Red squill ,extracted from the sea onion (Scilla maritime), is a rodenticide.
Nicotine and related alkaloids are extracted from tobacco (Nicotiana tabacum) and used as
Protozoan pesticides control caterpillar pest .(protozoan spore ingested by insect)
Bacillus thuringiensis, or Bt. Each strain of this bacterium produces a different mix of proteins
and specifically kills one or a few related species of insect larvae.
3. Inorganic pesticides
Inorganic pesticides do not contain carbon
usually derived from mineral ores extracted from the earth.
Examples of inorganic pesticides include copper sulphate, ferrous sulphate, copper and sulphur.
Recently, inorganic pesticides have been widely replaced by synthetic organics.
•They are highly persistent in terrestrial environments, being only slowly dispersed by leaching
and erosion by wind or water.
•Bordeaux mixture, a complex of copper-based compounds that is used as a fungicide
•Arsenicals such as arsenic trioxide are used as herbicides and soil sterilants.
•Paris green, lead arsenate, and calcium arsenate are used as insecticides.
•compounds that contain toxic elements such as arsenic, copper, lead, or mercury.
•The global use of pesticides was about 2.4-million tones in 2007, a total that includes
insecticides, herbicides, fungicides, preservatives, and disinfectants
•Global pesticide trade in 2007 had a value of about US$39 billion.
•About 39% (by weight) of pesticides used were herbicides; insecticides accounted for 18%,
fungicides for 10%, and “other chemicals” for 33% (mostly used as soil fumigants).
• The most important uses of pesticides are in agriculture and forestry, around the home, and in
human health and sanitation programs.
Pesticide Use for Human Health
•Various insects and ticks are vectors that transmit pathogens among individuals of the same
species, or from an alternate host to people, or to domestic and wild animals
•Typhoid caused by bacterium.
•Black death by rat flea.
During 1933-1935, India recorded about 100-million cases of malaria per year and 750-thousand
deaths. However, the incidence was reduced to 150-thousand cases and 1,500 deaths in 1966
because of spraying with DDT.
DDT was used during the Second World War, to prevent a deadly plague of typhus that could
have decimated Allied troops and the civilian population. The British prime minister at the time,
Winston Churchill, referred to the insecticide as “that miraculous DDT powder.”
Diarrhea and death
Disruption of the endocrine system.
Pesticides and Agriculture
The role of pesticides in agriculture is to help control the abundance of the following problems:
i. weeds that compete with crop plants
ii. invertebrates and rodents that feed on crops or stored produce
iii. microbial diseases that can kill the crop or diminish its yield
Even with the use of pesticides the damage caused by pests and diseases around the world are
equivalent to about 24% of the potential crop of wheat, 46% of rice, 35% of corn (maize), 55% of
sugar cane, 37% of grapes, and 28% of vegetables .
Pesticides in Forestry
•Pesticides are used in forestry mainly to control epidemics of defoliating insects and to manage
weeds in re-forested areas and plantations.
•The most common use of herbicide in forestry is to keep weeds from competing with young
conifers, allowing them to grow more rapidly so that harvests can be more frequent.
•Novascotia forest of conifers.
Pesticides in the Home and Horticulture
• Insecticide may be used to kill bedbugs and cockroaches, and rodenticide to poison rats and
• As well, large amounts of pesticide are used in horticulture.
• Herbicides are especially widely applied, mostly to achieve the grass-lawn aesthetic that many
•Low toxic inorganic pesticides :
•Boric acid for crawling pests
•Diatomaceous earth for indoor pests only
•All chemicals are potentially toxic.
•Not all exposures to potentially toxic chemicals result in poisoning (because organisms are to
some degree tolerant to pesticides and other chemicals)
•Some pesticides and some naturally occurring chemicals are extremely toxic to many organisms,
•Humans are subject to both involuntary and voluntary exposures to certain toxic chemicals.
•Rodenticide can be used judiciously to kill rats and mice around the home, while minimizing
toxic exposures to non-target cats, dogs, and children.
Broad-spectrum insecticides kill large numbers of arthropods, which reduces the amount of food
available for birds and other animals. These and other indirect effects of pesticide use can result
in ecological damage, in addition to the directly toxic effects.
Targeted and non targeted:
A crop-dusting aircraft or tractor-drawn sprayer is often used, which results in many non-target
species being exposed to the spray.
The non-target organisms may live on the sprayed site, or they may be off-site and suffer
exposure from aerial or aquatic drift of a pesticide.
Non-target exposures include both direct contact with a sprayed pesticide as well as indirect
exposure through the food web.
•Fenitrothion and aminocarb are highly toxic to all arthropods including many predators of
budworm. One study estimated that a typical Fenitrothion spray killed as many as 7.5-million
individuals of hundreds of species of arthropods per hectare.
•Kinglets forage high in the canopy, kinglets are particularly vulnerable to insecticide exposure
during an aerial spray. The presumed damage to birds was the key reason why
phosphamidon was banned.
Alternatives to Insecticide and pesticides
Use of crop varieties that are resistant to pest
Management of habitat to make it less suitable for pests
Learn to live with a few insects.
Practice natural lawn care.
Use pesticides as a last resort.
Pest problems don't necessarily require pesticides.
soap insecticides (potassium salts of fatty acids)
Microbial insecticides( spinosad fire ant killer)
Insecticidal oils (controls virus)
Food left over:
Cucumber peels -------repel ants , orange peels-------------raccoons ,foxes
Coffee grounds ----------repel fruit fly , salt spray-----------------snails and slugs
Garlic peel --------------mites
Banana peel -------------aphids
Pesticides are a wide range of substances that are used to gain an advantage over species that cause
diseases or are pests in agriculture, forestry, or horticulture.
Pesticides have become an integrated component of most of the intensive systems by which foods
and other crops are grown, and there are not yet good replacements for all of their uses.
It is important that pesticide use be reduced to the lowest amounts possible and that the most
damaging chemicals are withdrawn from legal use.