Wednesday, February 9, 2011

Neem Tree

What is neem?
The neem tree (Azadirachta indica) is native to tropical South East Asia. It is
fast growing, can survive drought and poor soil and keeps its leaves all year
round. It is a tall tree, up to 30 metres high, with leafy spreading branches.
Many white flowers which smell of honey appear for the first time when the tree
is 2 to 3 years old, and the tree bears fruit after 3 to 5 years. The ripe fruit are
about 2 centimetres (cm) long and oval shaped. Inside the fruit there is a lightcoloured seed about 1.5 cm long

How does neem grow?
Rainfall and altitude
Neem trees can be grown in areas which have between 400 millimetres (mm)
and 1500mm of rain each year. It performs best at an altitude of less than
1,500 metres.
Neem trees will survive very hot temperatures, up to 44°C and as low as 4°C.
Some people report neem trees surviving light frost.
The seeds of neem do not live long and are usually planted as soon as possible
after the fruit ripens and usually within three months. To help the seeds live
longer the fruit pulp should be removed by hand and the seeds dried in the
shade to a level of 15 to 20% moisture content. If the seeds have been properly
air dried they should survive for up to twelve months in a refrigerator at 4°C.

How can neem be used?
Although it has many uses, the most important use for neem products is to fight
against crop pests and diseases. Worldwide approximately one third of crops
in the field and in storage are lost to pests each year. The worst affected are
maize and rice in Africa and Asia. The main focus of this booklet is to describe
how neem can be used to help combat and overcome these problems.

How do neem extracts control pests?
Neem extracts contain a natural chemical called azadirachtin. The substance is
found in all parts of the tree. The leaves are used effectively, though the chemical
is much more concentrated in the fruit, especially in the seeds.
Neem extracts do not usually kill insect pests immediately. They change the
feeding or life cycle of the insect until it is no longer able to live or have young.
This might mean that the neem extract takes a long time to work if the pest
attack is severe. Other insects will avoid a plant treated with neem extracts.
When neem products are exposed to light they begin to lose their ability to
control pests. For this reason the commercial neem based insecticide,
Margosan-O, that is sold in the USA, contains a sunscreen. Neem based
pesticides are suitable for use in developing countries because the useful
chemicals can be easily removed from the neem without the use of expensive
and complicated equipment.

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