Pesticides and Mode of Action - 1 | Agriculture Optional Notes for UPSC PDF Download

Introduction

A pesticide refers to a chemical substance or a combination of substances employed to eliminate, manage, or deter pests. Pests, which can cause significant damage to crops, encompass various organisms like insects, rodents, fungi, slugs, snails, bird mites, and weeds, leading to substantial financial losses in agriculture.

Brief History

Throughout the course of human civilization, agriculture has always played a crucial role. However, the challenge of protecting crops from various organisms has been a persistent issue. The Sumerians are credited as early adopters, utilizing sulfur as a pesticide over 4000 years ago. The 1940s marked a significant shift with the increased production of synthetic pesticides. Chemicals like DDT, BHC, aldrin, dieldrin, captan, and 2,4-D gained prominence due to their studied efficacy. DDT, in particular, became widely used for its cost-effectiveness and broad pesticidal impact, leading to the large-scale manufacturing of numerous pesticides.

Definition of Pesticides

Pesticides are those substances that help to repel, or control certain organisms that are harmful to plants.

Examples of Pesticides 

Numerous examples have been cited as examples of pesticides. They are insecticides, fungicides, larvicides, rodenticides, molluscicides etc.

Types of Pesticides

Pesticides are classified on the basis of their chemical structure, mode of action, formulation, persistence and the pests that they target. Some examples are given along with the products used.

Classification Based on Target Group

• Insecticides: Examples include Allethrin, Boric acid, Cypermethrin, and Malathion, designed to eliminate insects.
• Fungicides: Pentachlorophenol, effective against various fungi, mold, and mildew.
• Herbicides: 2,4-D, targeting plants acting as pests, such as weeds.
• Larvicides: Teknar, specifically formulated to attack larvae.
• Rodenticides: Rozol, Rodent cake, Warfarin, used against rodents like gophers, mice, and rats.
• Algaecides: Developed to kill or inhibit the growth of algae.
• Molluscicides: Metaldehyde, controlling snails, slugs, and other mollusks harmful to plants.
• Other Types: Desiccants, foggers, mothballs, repellents, serving specific purposes.

Classification Based on Chemical Structure

• Chlorinated Hydrocarbon: Illustrated by Kelthane.
• Carbamate: Represented by Sevin.
• Organophosphates: Basudin is an example.
• Pyrethroids: Decis falls into this category.

Classification Based on Mode of Action

• Direct Application: Insecticides applied as dust or spray, eliminating insects on contact.
• Control as Plant Food: Insecticides consumed by plants, eliminating insects when pests feed on the affected plants.
• Fumigants: Toxic fumes that destroy insects when inhaled.
• Selective Herbicides: Gesagard, which targets small seeds and weeds without harming the plant.

Classification Based on Formulation

• Dust Form: Dry, small particles.
• Granular Form: Large, dry particles.
• Wettable Powders: Finely distributed particles mixed with other substances, forming a stable solution or suspension when mixed with water.
• Dry Bait Pesticides: Mixed with pest food to create dry pellets consumed by pests.
• Emulsifiable Concentrate: Pesticide dissolved in an organic solvent to create an emulsifier.
• Pheromones: Active chemicals disrupting the mating behavior of certain insects.
• Wood Preservatives: Used to enhance wood resistance to fungus and insects.

Benefits of Pesticides

• Pesticides play a crucial role in maintaining low agricultural costs, enabling farmers to produce more food on the same plot. In contrast, cultivating organic vegetables requires greater investment, primarily due to the need for manual weeding as opposed to using herbicides.
• The application of pesticides contributes to the reduction of waterborne diseases and those transmitted by insects, effectively curbing the spread of diseases carried by insects and rodents.
• Furthermore, pesticides serve as a means to preserve and safeguard the environment, playing a role in minimizing deforestation, preventing soil erosion, and contributing to the conservation of natural resources.
• By enhancing crop yield, pesticides become instrumental in elevating farmers' income, thereby improving their living standards and overall quality of life.
• Pesticides also offer the practical benefit of saving farmers valuable time, as they protect crops from weeds without the need for extensive manual weeding. This eliminates the necessity for repeated tilling of the land to cultivate crops in a pest-free environment.
• In developing countries like India, the widespread use of pesticides has transformed them into significant food producers. Crop protection measures enable farmers to safeguard their crops, ensuring a plentiful harvest for the population.
• Additionally, pesticides contribute to extending the shelf life of food products stored in warehouses. They play a vital role in preventing substantial post-harvest losses attributed to plant diseases and pests, ensuring the safety and viability of the food supply.