Status report on global Neem usage - Biblioteca Nacional de Portugal

• Repellent and inhibition of feeding:
3. NEEM AS A NON-SYNTHETIC PESTICIDE
Plants that have been treated with neem are no longer attractive to insects and are
avoided by them. Larvae or sedentary insects which cannot escape eat and suck on
considerably fewer leaves.
• Metamorphosis-inhibitor:
Insect larvae that chew or suck on neem-treated plants suffer irreversible damage
caused 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 or
copulate, 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 aqueous
extracts or as a basic raw material for formulated pesticides. Leaves are also used in
simple aqueous extracts to repel insects.
• Use as a nematicide
Using neem to control soil-borne pests such as nematodes is a subject that has undergone
much research and practical testing in India in particular. The most common form
of 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 and
population density of numerous phytopathogenic nematode species. There are many
indications that neem’s efficacy against nematodes is heavily dependent upon the
prevailing soil conditions.
• Use as a fungicide
Using neem against phytopathegenic fungi has not been so intensively investigated as
yet as its effects on insect pests. However, neem has been proven to be effective in the
case of certain economically important fungal diseases. The most effective preparations
are emulsions based on neem oil. It was found that fungicidal activity was due to the
mixture of several compounds (both additive and synergistic effects); single isolated
substances were not found to be effective against fungi. The addition of certain salts
such as sodium hydrogen carbonate can enhance fungicidal action against certain species
of fungi (e.g. powdery mildew).
Press cake and leaf extracts are also used against soil-borne fungal diseases.
• Use as a molluscicide
Neem is only being used to control these types of pests on a small scale. Deterrent effects
on land snails have been observed and in tropical countries neem has proven to be
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