Status report on global Neem usage - Biblioteca Nacional de Portugal

3. NEEM AS A NON-SYNTHETIC PESTICIDE
3. Neem as a Non-synthetic Pesticide
3.1 Historical Importance of Neem as a Non-synthetic Pesticide
In comparison to the traditional, centuries-old neem applications, the use of neem as a nonsynthetic
pesticide is a relatively new one, although one exception here is stock protection
using neem oil and leaves, which has been practised on the Indian subcontinent for many
centuries (2, 13, 15, 19).
Neem’s insect-repellent effect was first described by Indian researchers in the 1920s.
Greater recognition was granted to the observations made by the German entomologist
Heinrich Schmutterer at the end of the 1950s in Sudan who described how huge swarms of
locusts swept over the country destroying every type of plant but the neem tree. There had to
be a reason for this phenomenon and intensive research was conducted into the possible
insecticidal agents in the neem tree. Since then, numerous research projects in India, initiated
by Germany and the USA as well as some other industrialised countries, have illustrated
neem’s multifaceted potential for use as a pesticide (2, 13, 15-21, 24).
In recent years, know-how stemming from this comprehensive research into neem has increasingly
found its way into TC projects. As a result, knowledge about the neem tree and its
insecticidal properties has been disseminated in many countries throughout Africa, Asia and
Latin America. It is significant that in many countries in which neem has now been commonplace
for a long time, the potential for its usage as an environmentally friendly pesticide is
very great indeed, but by no means fully exploited (3, 5, 7, 8, 11).
3.2 How Does Neem Work?
Numerous research results have shown that neem and its components have a variety of
effects on pests (2, 13, 15-21, 24). More than 140 active principles (MORGAN 1999,
Vancouver Int. Neem Conf.) have been identified to date which occur in different parts of the
tree. The most important agents include the azadirachtin derivatives, which belong to the
group of triterpenoids. Azadirachtins are among the most effective known insecticides and
are found in greatest concentrations in the seed core (0.1 - 0.9%). 30 - 60 g azadirachtin per
hectare suffice to combat and repel the key biting and sucking pests (5, 7).
Besides its effect on insects, neem can also be used to control nematodes, phytopathogenic
fungi, spider mites and snails (2, 13, 15, 19).
Below are neem’s key forms of application as a pesticide (13, 15, 19):
• Use as an insecticide
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Neem’s usage as an insecticide is the most widespread and widely researched. Its insecticidal
effect is known to work in various ways: