Insecticides
An insecticide is a pesticide used against insects in all developmental forms.
They include ovicides and larvicides used against the eggs and larvae of insects respectively.
The use of insecticides is believed to be one of the major factors behind the increase in agricultural productivity in the 20th century.
Herbicides
A herbicide is used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed.
Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant hormones.
Herbicides used to clear waste ground, industrial sites, railways and railway embankments are non-selective and kill all plant material with which they come into contact.
Smaller quantities are used in forestry, pasture systems, and management of areas set aside as wildlife habitat.
Fungicides
Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit.
Fungicides can either be contact or systemic. A contact fungicide kills fungi by direct contact; a systemic fungicide has to be absorbed by the plant.
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