Insecticidal properties of the neem tree (Azadirachta indica): it’s for the birds!

New Scientist (6 June 1985, p. 10) reported that Azadirachta indica (Meliaceae), the Indian neem tree, would be a ’new’ wonder plant. Its medical properties have been known for ages to local people and western botanists (e.g. Garcia de Orta, 1567). In India about 14 million trees, typically planted along roadsides, produce fruit, wood and leaves, all of which have special uses to the villagers. Parts of the tree have strong insecticidal and anti-nematode properties and have been used traditionally in India and Indonesia. Infusions or tinctures prepared from the bark are believed to be beneficial against malaria, although experiments have not yet confirmed this. Although the leaves (as the other parts of the plant) are very bitter, they have been used in Madura as a fodder (Heyne, 1950). Dried leaves mixed among grain in storage, placed in books, among paper and clothes would keep insects away. Fruits on market stalls are wrapped in fresh leaves to ward off insects. The fruit is crushed in water to spray on crops. The cake left behind after the crushing can be ploughed into the land as mulch, where it acts both as a fertilizer and against the nematodes. Various authors have mentioned the oil, which may be used for a rather inferior soap, but Heyne warns that crushing of the seeds (after they have been heated) to extract it causes such a disgusting smell of garlic that no factory would be tolerated in the proximity of any inhabitated place.