The Neem tree is a tropical tree and is growing in semi-arid climates in Asian countries and in the tropical regions of the western hemisphere. Neem is known since centuries for its natural and comprehensive pest control properties. Indian farmers have been using neem as insecticide for a long time based on traditional knowledge. For example, it was a common practice in rural India to improve the storage of grains by mixing the grain with dried neem leaves.
Neem cake is applied to rice and sugarcane fields against stem borers and white ants since 1930. The mixing of neem leave (2-5%) with rice, wheat and other grains is still practised in some parts of India and Pakistan and farmers in India still put green twigs and leaves in rice nursery beds to produce robust seedling and simultaneously ward-off attack by early pests-leafhoppers, planthoppers, and whorl maggots.
In the 1960s Indian scientists reported the feeding deterrent property of neem seed kernel suspension against desert locust. Subsequently, several bioactive ingredients (particularly meliantriol and azadirachtin) were isolated from various parts of the tree. These findings aroused worldwide interest in the bioactivity of the neem tree.
Insects become increasingly resistant against traditional pesticides. The costs for developing a new pesticide are high. Moreover, many people all over the world are becoming aware of the fact that food, which is treated with pesticides, is not healthy. New, more environmentally sound pesticides are needed. A promising option are extracts of the neem tree, which is why the United Nations declared the neem tree as the "Tree of the 21st century".