There are many insects, plants, grass fungus which are harmful to farms and forests. So, they are considered unwanted insects, unwanted plants, etc. For preventing farms and forests from pests, pesticides are used. Pesticides are used to kill or destroy pests. Whereas, insecticides are used to destroy insects.

Pesticides

They are chemical substances, which are used directly or indirectly against pests in order to eliminate or control them. Pesticides are toxic or poisonous substances. Farmers generally use pesticides to control the pests or diseases of plants.

What is a pest?

A pest is a destructive plant or animal that directly or indirectly affects humans or the things that people are attached to, like crops, livestock, and forestry. They can be of following two types;

• Destructive plants: These are harmful plant-like weeds and fungi.
• Destructive animals: The animals that damage the farm or are harmful to the crop are considered destructive animals. For example, birds, rats, rabbits, grasshoppers, ants, silverfish, flies, moths, nematodes, etc.

According to ‘WHO’ one-third population of the world is suffering from malnutrition. As population size is increasing, so for meeting the requirements of this population, continuous efforts are going on in the field of agriculture. But the agriculture field is facing the problem due to the intervention of pests. These pests attack the crops in fields and the stored grains. So to eliminate this pest, pest control methods are used.

What is Pest Control?

Pest control is the regular process of management of pests and their species. Pest control can be achieved by agro-technical, mechanical, biological, and chemical control.

Properties or characteristics of pesticides:

• Pesticides are toxic chemicals, and they act as a pollutant. Therefore, they tend to pollute the atmosphere.
• Most pesticides have a simple structure and simple biological activities.
• Every pesticide is characterized by its LD 50 value.

What is LD 50 value/ lethal dose?

The pesticides which can seriously harm or kill 50% of the total population of a pest has LD50 value.

Side effects of pesticides on the environment:

• Pesticides may get accumulate in organisms which can cause bio-magnification.
• Some pesticides are non-biodegradable. They remain active for many years.
• Some pesticides produce harmful substances when decomposed.

Classification of pesticides

1) Based on the source

i) Natural pesticides: It refers to pesticides, which are obtained from a natural source like plant or animal or bacteria or fungi. E.g., nicotine, pyrethrins, neem oil, boric acid, diatomaceous earth powder, rotenone.

1. Nicotine: It is obtained from the leaves of the tobacco plant. It is used to kill leaf Hoppers.
2. Pyrethrins: It is obtained from the pyrethrum plant. Flowers are dried and powdered, this powder is extracted with an organic solvent to make the pyrethrins, which is used to kill flies.
3. Boric acids: It is used to kill microorganisms and cockroaches.
4. Rotenone: It is obtained from the roots of the derris plant. It is used as a fish poison.
5. Diatomaceous earth powder: It is used in the form of dry powder. It is obtained from the shells of marine organisms.

ii) Synthetic pesticides: These pesticides are produced in the lab with the help of chemicals. They are also called man-made pesticides. Because of their low cost and effectiveness, these synthetic pesticides are widely used. Arsenic is the first inorganic pesticide. But the most famous and commonly used pesticide is DDT that is Dichloro – Diphenyl trichloroethene. DDT is used to kill the mosquito, which spread malaria. Farmers are mostly dependent on the synthetic pesticides to protect their crop from the pest. Common examples are DDT, chloranil, malathion, parathion.

2. Based on the target

• Insecticide: Pesticides that are used specifically against insects.
• Herbicide: If pesticides attack unwanted plants, unwanted grass, then it is called herbicide.
• Fungicide: It is used to kill the fungi that grow on crops, fruits, or plants.
• Nematicide: It is used to kill nematodes means small organisms or organisms that grow on plant Roots.
• Rodenticide: It is used against rodents. For example, mice and rats.
• Ovicide: It is used to kill the eggs of insets.

3. Based on the mode of action

Mode of action means an area or part of the pest’s body on which pesticides show their effect.

• Stomach poison: Such pesticides start their mode of action in the stomach of the pest. Such pesticides are initially swallowed by insects or pests in the form of food. As soon as digestion is started, it shows its toxic effects. For example, BHC, DDT, lead, etc.
• Contact poison:These pesticides destroy the insects simply by body contacts or they enter through the skin and reach the targeted site.
• Fumigate:It acts through the respiratory tract. Such pesticides ate inhaled in the form of gas or vapor. This type of pesticide is used on the farm. For example, HCN, CS2, Nicotine.
• Systematic pesticides: These pesticides are absorbed by the roots, stems, and leaves of plants. When insects sit on them, they are killed.

4. Based on the chemical

i) Inorganic Pesticides

• These pesticides are generally non-carbon compounds containing metal salt, compounds of sulphurs, halogen, etc. For example, lead arsenate, calcium arsenate, cyanides, etc.
• These pesticides are used before world war two.
• The major limitation of pesticides is their toxic nature to the whole ecosystem.

ii) Organic pesticides

In this type of pesticide, hydrocarbon is present. They are of two types that are natural and synthetic.

• Natural Pesticides: Natural pesticides that are extracted from roots, leaves, flowers, stems, or oil obtained from plants. For example, pyrethrins.
• Synthetic Pesticides: Synthetic pesticides are carbonates, quinones, organophosphates, organochlorine, and organophosphates.

Toxicity labels of pesticides

There are four toxicity labels that indicate the harmfulness of pesticides. These labels are present on the packet of pesticides for user reference and understanding.

• Label 1: It is shown with a red color label. This pesticide is very poisonous or extremely toxic. The example of toxic pesticides is monocrotophos, dichlorvos pesticide, Zinc phosphide, foret, Aluminium phosphide.
• Label 2: It is shown with a yellow color label. This pesticide is highly toxic. Examples are chlorpyrifos, Cypermethrin, quinalphos, fenvalerate, etc.
• Label 3: It comes with a blue color label and is moderately toxic. Examples are malathion, Thiram, glyphosate, metalaxyl, etc.
• Label 4: It comes with a green color label. It is slightly toxic. Examples are mancozeb, Acifluorfen, and other household pesticides.

Insecticide

The insecticide is used to destroy insects. It is a type of pesticide, which is used to kill insects that harm or are dangerous for farms and plants. The insecticides enter insect bodies in different ways such as through stomach, contact, and fumigate.

Insecticides enter the stomach of insects when the insects eat the plant on which the insecticide is sprayed. That’s why it is called stomach enter mode. After insects come in contact with the plant or crop on which the insecticide is sprayed, the insecticide enters into the body of the insect. This is called contact enter mode. Fumigate is another entering mode. In this mode, the insecticides enter the body of insects through vapor or air.

Types of Insecticides

1. Organochlorine insecticides:

These insecticides are made by mixing chlorine with some other molecule. For example, Hexachlorocyclohexane pesticides are made by adding hydrogen and carbon to the chlorine. So in this type of pesticide, chlorine is the fixed molecule in every insecticide. For example, DDT, Hexachlorocyclohexane, aldrin, etc.

2. Organophosphorus insecticide:

These insecticides are made by mixing phosphate with some other molecule. For example, Tetraethyl pyrophosphate, parathion, etc.

3. Carbomate insecticide: This pesticide is made by using carbonic acid. For example, aldicarb, carbofuran, etc.

4. Botanical insecticide: This insecticide is made from plants. For example, by using neem leaves, using neem branches, other herbal things, these insecticides are produced. It is also known as an herbal insecticide.

Difference Between Insecticide and Pesticide

Pesticides	Insecticides
It is used against insects, bacteria, unwanted plants.	It is used mainly against insects.
Pesticides are the main category that includes insecticides, fungicides, ovicides, etc.	It is a type of pesticide.
Pesticides are used on pests like mildews, rusts, weeds, mice, and rats, etc.	Insecticides are used on insects like ticks, flies, spiders, etc.
Examples: aldrin, Parathion, aldicarb, Hexachlorocyclohexane, Lindarel, dieldrin, Thiram, fenvalerate, etc.	Examples: DDT, BHC, HCN, CS2, Tetraethyl pyrophosphate, carbofuran, etc.