Herbicides also commonly known as weed killers, are chemical substances used to control unwanted plants. Selective herbicides control specific weed species, while leaving the desired crop relatively unharmed. Non-selective herbicides, sometimes called "total weed killers", can be used to clear grounds and field whenever required, as they can kill all plant material and weeds which they come into contact with. 

Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A Fungi can cause serious damage to crops, resulting in critical losses of yield, quality, and profit. Fungicides are used both in agriculture and to fight fungal infections in animals. Fungicides can be categorize as contact, translaminar or systemic. Contact fungicides are not taken up into the plant tissue and protect only the part of the plant where the spray is deposited. Translaminar fungicides redistribute the fungicide from the upper, sprayed leaf surface to the lower, unsprayed surface. While Systemic fungicides are taken up and redistributed through the xylem vessels. Some fungicides move to all parts of a plant also.

Insecticides are substances used to kill insects. They include ovicides and larvicides, which are used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and also by consumers. Insecticides are claimed to be a major factor behind the increase in agricultural productivity. Many insecticides are toxic to humans and animals. Insecticides can be classified into two major groups, systemic insecticides, which have residual or long-term activity and other one as contact insecticides, which have no residual activity. Furthermore, one can distinguish three types of insecticide. 1) Natural insecticides, made from plant using nicotine, pyrethrum and neem extracts to protect against insects. 2) Inorganic insecticides use metals. 3) Organic insecticides are organic chemical compounds, mostly work by contact.