Garlic, odorous cure all, for long has been in use mainly in cooking. Apart from its popularity as a spice, it has been used from ancient times, especially in India and China, as a folk medicine. Garlic is perhaps, one of the few herbs that have been used for thousands of years without any toxic after effects.
In the ceaseless search for alternatives to chemical pesticides, one of the promising candidates is garlic. It is found to be nature's natural pesticide. Modern scientists have found that it contains a compound called Allicin having antiseptic properties. Many of the qualities ascribed to garlic by herbal and allopathic doctors have been confirmed by scientific methods, and it is now certain that garlic possesses anti bacterial properties, inhibits the growth of various tumours, activates the flow of urine and assists in digestion of foods. Its active principle, Allicin, shows a broad spectrum of activity against various human disease-producing bacteria.
When scientists used the crude garlic extract, they found that it could destroy mosquito larvae even at low concentration, within twenty-four hours. Field collected larvae of highly insecticide resistant strains of mosquitoes were also exposed to the garlic extract. All the species of larvae died within a short time. These experiments indicated that the active principle for killing the larvae was present in the oil of Allicin of garlic.
In studies made by scientists at the Bio organic Division of the Bhaba Atomic Research Centre, Mumbai, fresh garlic was used to extract a colourless volatile liquid. Two compounds were found in this oil and both showed high larvicidal properties. These two chemicals were observed to destroy several insect pests when these were exposed to the vapours of the chemicals.
Since garlic has been used in cooking without any adverse effects, it is likely to be non toxic to man at any of the levels. Also, these compounds are comparatively volatile and will not pollute the environment by any residual effects. These properties suggest that the compounds may have some potential value in the control of insects and pests. These are simple organic compounds and can be prepared very easily. The synthetic samples compared very well with the natural samples in destroying mosquito larvae.