Status report on global Neem usage - Biblioteca Nacional de Portugal

3. NEEM AS A NON-SYNTHETIC PESTICIDE
conditions for at least 1 year. Practical sizes for bags of crushed seeds are 250 g and 2 kg.
Their principal use is for water extracts in households and gardens.
The press cake is packed and handled in the same way as the crushed seeds. It is used
directly to control soil-borne pests and as a fertiliser. Normally 30 g per square metre is
added to the soil a few weeks before sowing.
The most common way of using neem oil as a pesticide is on the basis of an oil-and-water
emulsion, which needs an appropriate emulsifier. Around the world many different emulsifiers
are used. The principal ingredients are various vegetable oils and detergents. It is important
that additives are properly biodegradable so that the ecological benefits of neem are not
counteracted. Neem oil and the emulsifier have to be mixed in the right proportions to get the
ideal emulsion in water (the neem oil should not float on the water). Normally the mixture of
oil and emulsifier is used diluted to between 0.5 and 1.0 % in water. The dilution chosen
depends on the type of plant: 0.5% is used on plants with soft leaves (e.g. many vegetables);
1 % can be used on plants with hard leaves (e.g. many fruit trees and ornamentals). A third
component can be added: sodium salt, normally known and used as “baking powder”, but at
the same time it is very effective against many phytopathogenic fungi, especially mildew.
According to many users, the home-made pesticides are more effective than the formulated
neem-based pesticides. The reason is that in addition to the insecticidal effect, the raw
material has strong repellent and feeding-inhibitory effects. On the other hand the raw material
is a plant nutrient and fortifies the plants treated. Formulated neem-based pesticides do
not have these advantages. Most of the users of home-made pesticides are hobby gardeners.
After a period of time they tend to stop using any other garden additives like fertiliser
or pesticides.
- Formulated neem-based pesticides
Formulated pesticides can only be made from neem using more advanced technology and
know-how. And yet, such neem-based pesticides no longer pose any considerable or insurmountable
problems from the point of view of production. Manufacture is carried out by
laboratories in small and medium-sized companies in semi-industrial extraction plants (7, 8,
30, 31, 34, 37).
The most common raw material is dried neem seed. The neem oil is generally pressed out
and the resulting press cake is then used to make a pesticide rich in azadirachtin.
There are four stages of production:
1. Alcoholic extraction
2. Alcohol recovery
3. Purification and concentration
4. Formulation and stabilisation
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