Pesticides: Definition, Types, Process & Advantages - Chemistry - Aakash

Pesticides - Definition, Types, Process and Steps Involved in Manufacturing, Properties, Advantages and Disadvantages, Practice problems, FAQ

During Covid, you could have seen, your house, or street being sprayed with chemicals by the Municipality. Such a thing is quite common in the agricultural field. India being an agricultural-based country, such spraying is a regular and most practised practice in the name of eradicating pests. But what is a pest? Ant that moves around, mosquito that flies around and the rat that consume almost one-third of agricultural produce in the world are all examples of pest.

Pest is anything (chemical, an animal microorganism that is s troublesome or destructive to human/animal or plant. Definitely, you don’t like having them with you, right. How to eliminate them? Apply pesticide. Oh. Is it so simple? Wait. Why? Let us see.

But pesticide causes pollution to the environment and becomes a curse instead of a boon. Do you know a pest that survived long not only of pesticides but even of nuclear blast?. Natural pesticides are more beneficial for the surroundings than human manufactured. Natural insecticides degrade quickly, leaving less residue in the soil, and are less likely to damage humans or animals.

Table of content:

What are pesticides?
Types of pesticides.
Process and steps involved in manufacturing.
Advantages and Disadvantages
Toxicity of Pesticides
Practice problem
Frequently asked questions-FAQ

What are pesticides?
Any substance or mixture of substances that is effective in preventing, destroying, repelling or mitigating any pest (insect, rodent, nematode, fungus, weed, or microbes)..

Types of pesticides: Organic pesticides and inorganic pesticides are the two major types of pesticides based on their chemical nature.

Organic pesticides - These pesticides are obtained either from natural sources or by synthetic methods. Examples: Bacillus Thuringiensis, Neem oil, Pyrethrum, Plant oils etc.
Inorganic pesticides - These pesticides are obtained by using inorganic elements such as sulphur, copper, and iron etc.
Examples: Copper sulphate, Ferrous sulphate etc.,

Pesticides are classified-

Based on chemical structure:

Carbonate- These compounds are esters of carboxylic acid
Example: Sevin. The chemical formula of Sevin is C₁₂H₁₁NO₂

Pyrethroids-These compounds are called natural pesticides because they are produced from chrysanthemum flowers.
Example: Decis is one of the example of pyrethroids. The chemical formula of Decis is C₁₂H₁₉Br₂NO₃

Based on the target:

Insecticides - Used to kill insects. Example: malathion.
Fungicides - Used to kill different types of fungi. Example: pentachlorophenol.

Based on mode of action:

Direct application - Some pesticides kill the insects directly without any chemical change within the plants.
Acts as plant food - Some pesticides are absorbed by the plants, and on the consumption of these plants, insects are killed indirectly.

Based on formulation: There are different types of pesticides based on their different forms and shapes. They are dust, granular, wettable powders, wood preservatives, pheromones, etc.,

Process and steps involved in manufacturing.

While manufacturing pesticides few things we must keep in mind, These are,

Raw materials used during manufacturing: Active ingredients and inert ingredients.

Active ingredients - These are natural substances and are also synthesized in the laboratory. The role of active ingredients is to kill the insects. Chlorine, oxygen, and nitrogen are examples of such types.

Inert ingredients - These ingredients vary according to the type of pesticide used. The role of inert ingredients is to prevent the coating of the plants from the harmful effects of pesticides. Kerosene, water, and emulsifiers are examples of such types.

Steps involved: There are three steps involved in manufacturing the pesticides.
Step 1 – Synthesizing the active ingredient: Firstly, the organic molecule which is considered for preparing the pesticide is altered in the laboratory. Reagents and catalysts are used for this purpose, and the reactions occur under specific climatic conditions, pressure, temperature, etc. The active ingredient is obtained after this process.

Step 2 –Formulating the active ingredient: The active ingredient prepared in the previous step is mixed with inert powders to make dust pesticides. Inert powders are those which are chemically inactive. Liquid pesticides are also prepared by mixing the active ingredient with carriers. Carriers are either liquid or solid chemicals which are used to help the active ingredients. In this way, the pesticides are manufactured.

Step 3 –Dilution of dust pesticides: Finally, the farmer dilutes the dust pesticides to get the desired proportion which can then be applied to the plants and crops.

Properties: Most of the pesticides are water-soluble and volatile.

The chemical properties of a pesticide are greatly influenced by environmental conditions like temperature, pH, and moisture.
When pesticides are released into the atmosphere, they undergo chemical reactions.
If the pesticide has a high vapour pressure, then it easily gets converted into gas.
Depending on the half-life of the pesticides, it remains suspended in the environment.

Advantages and disadvantages of pesticides.

Advantages:

The diseases arising from water and insects are prevented.
It helps in the production of great quality foods at low prices.
It is inexpensive.
It is easy to store and is available in many countries.
It helps for higher crop yield.

Disadvantages:

The insects which are useful for the growth of crops also get killed in the process.
It may poison the food and cause harm to human health.
It damages the balance of the environment.
It also damages the soil, which leads to infertility.
Some of the birds and animals die when exposed to pesticides.
It also damages human health,creates hazards, colony collapse disorder, and also resist development.

Toxicity of pesticides:

A pesticide's toxicity refers to its ability to harm a living system, such as a human body
or sections of it (such as the lungs or respiratory system); a pond, a forest, and the organisms
that dwell there.
A pesticide's toxicity is determined by a variety of factors.
1. Dose: The amount of pesticide that is applied to a surface, plant, or animal.
2. Frequency: How frequently the exposure happens.
As a result, how much of the substance is involved and how frequently the substance is
exposed gives rise to this toxicity. Based on this two types of toxicity is present.
1. Acute toxicity, 2. Chronic toxicity

Acute toxicity: The toxicity of a pesticide to a human, animal, or plant after a single short-term exposure is
referred to as acute toxicity. Even if only a small amount is absorbed, a pesticide with high acute toxicity
is lethal. Acute oral toxicity, acute cutaneous toxicity, and acute inhalation toxicity are all examples
of acute toxicity.

Chronic toxicity: Chronic toxicity is the poisonous effect of pesticide exposure that occurs over time.
Pesticide chronic toxicity impacts the general people as well as individuals who work directly with
pesticides because pesticides can be found on/in food, water, and the air.

Benzene Hexachloride, DDT and Calcium Cyanide are examples of some pesticides which are
banned in our country India.

Practice problems:

Q1. What are herbicides?
Solution: Herbicides are chemicals that are used to destroy or hinder the growth or development of plants. Alachlor, butachlor, and metolachlor are some examples of herbicides.

Q2. Name one Organochlorine Pesticide.
Solution: One of the important organochlorine pesticide is polychlorinated derivatives of cyclohexane known as Lindane.

Q3. How toxicity of pesticides are measured?
Solution: Rats, rabbits, mice, guinea pigs, and other animals are used to investigate pesticide toxicity. Toxicology studies are only recommendations for evaluating and comparing pesticide harmful effects due to variances in human and animal bodies work.

Q4. What are algicides?
Solution: Algicides are chemicals that are used to kill or prevent algae growth. Copper sulphate, diuron, isoproturon, oxyfluorfen, and simazine are just a few examples.

Frequently asked questions-FAQ

Question 1. Do pesticides create air pollution?
Solution: The amount of pollutants in our atmosphere, which includes both indoor and outdoor air, is measured by air quality. Pesticides used in agriculture and urban areas have the potential to pollute our air, impacting the health of humans, animals, and plants.

Question 2. What happens if a child breathes in pesticides?
Solution: Pesticide particles can be quickly taken into the circulation by the lungs, making respiratory exposure extremely dangerous. If enough pesticides are inhaled, they can cause catastrophic harm to the nose, throat, and lungs. The most dangerous substances are vapours and very microscopic particles.

Question 3. What is the odour of pesticides?
Solution: Pesticides often contain a number of chemicals, any of which can emit a foul odour.

Question 4. Can boiling water remove pesticides?
Solution: Boiling water does not remove other impurities such as heavy metals, medicines, herbicides, insecticides, other organics, or inorganics.