Status Report on Global Neem Usage - Gtz

3. NEEM AS A NON-SYNTHETIC PESTICIDE• Repellent and inhibition of feeding:Plants that have been treated with neem are no longer attractive to insects and areavoided by them. Larvae or sedentary insects which cannot escape eat and suck onconsiderably fewer leaves.• Metamorphosis-inhibitor:Insect larvae that chew or suck on neem-treated plants suffer irreversible damagecaused by hormonal disturbances. They are unable to moult.• Impaired fitness and reproductive ability:Eating and sucking on neem-treated plants renders many insects unable to fly orcopulate, which results in reduced infestation by subsequent generations.• Egg-laying deterrent:Many insects make a point of avoiding plants that have been treated with neem.The seeds are primarily used as insecticides. They can be used in the form of simple aqueousextracts or as a basic raw material for formulated pesticides. Leaves are also used insimple aqueous extracts to repel insects.• Use as a nematicideUsing neem to control soil-borne pests such as nematodes is a subject that has undergonemuch research and practical testing in India in particular. The most common formof application is the press cake which is worked into the soil a few weeks before sowing.In this way it is possible to reduce, to a considerable extent, the reproduction andpopulation density of numerous phytopathogenic nematode species. There are manyindications that neem’s efficacy against nematodes is heavily dependent upon theprevailing soil conditions.• Use as a fungicideUsing neem against phytopathegenic fungi has not been so intensively investigated asyet as its effects on insect pests. However, neem has been proven to be effective in thecase of certain economically important fungal diseases. The most effective preparationsare emulsions based on neem oil. It was found that fungicidal activity was due to themixture of several compounds (both additive and synergistic effects); single isolatedsubstances were not found to be effective against fungi. The addition of certain saltssuch as sodium hydrogen carbonate can enhance fungicidal action against certain speciesof fungi (e.g. powdery mildew).Press cake and leaf extracts are also used against soil-borne fungal diseases.• Use as a molluscicideNeem is only being used to control these types of pests on a small scale. Deterrent effectson land snails have been observed and in tropical countries neem has proven to be23