Insecticides are substances used to kill, harm, repel, or mitigate one or more species of insects. They are used in agriculture, medicine, industry, and by consumers. Insecticides can be classified based on their chemical composition, mode of entry in the insects, and chemical nature. Some common types of insecticides include:

• Contact insecticides: These are toxic to insects upon direct contact. They can be inorganic insecticides, such as sulfur, arsenates, copper, and fluorine compounds, or organic insecticides, such as pyrethrum and neem oil.

• Systemic insecticides: These are absorbed by plants and transported to all parts of the plant, including the leaves, stems, and roots. When insects feed on the plant, they ingest the insecticide and are killed.

• Stomach poisons: These are ingested by insects and are toxic to them. They include organophosphates, carbamates, and synthetic pyrethroids.

• Fumigants: These are gases or vapors that are toxic to insects when inhaled. They are used to control pests in stored products, such as grains and fruits.

Insecticides can pose a different level of risk to non-target insects, people, pets, and the environment. Some disadvantages of insecticides include their potential to alter ecosystem components majorly, their toxicity to animals and humans, and their ability to become concentrated as they spread in the food chain.