The Neem Tree (Azadirachta indica A. juss) and its derivatives have great relevance in organic farming practices. This remarkable tree has been identified as a renewable resource for home grown agro-chemicals and nutrients which are bio – degradable, non-toxic and effective.
Long before synthetic chemicals and commercial insecticides and fertilizers were available, Neem derivatives were used in Indian villages to protect and nourish crops. Scientific research has shown that Neem extracts can influence nearly 300 species of insects.
It is significant that some of these pests are resistant to pesticides, or are inherently difficult to control with conventional pesticides. (floral thrips, diamond back moth and several leaf miners). Most Neem products belong to the category of medium to broad spectrum pesticides, i.e., they are effective over a wide range of pests.
Using neem derivatives for managing pests is a non-violent approach to controlling pests. Neem products work by intervening at several stages of the insect’s life. They may not kill the pest instantaneously but incapacitate it in several ways. Neem very subtly employs effects such as repellence, feeding and ovipositional deterrence, growth inhibition, mating disruption, chemo-sterilization, etc. These are now considered far more desirable than a quick knock-down in integrated pest management programs as they reduce the risk of exposing pests’ natural enemies to poisoned food or starvation.
The action of Neem products fulfills all priorities among environmental objectives. This unique tree is perhaps the most significant example of how nature can combine diverse functions i.e., the action of de-oiled Neem cake as a pesticide cum fertiliser.
Chemistry of Neem for Organic Farming:
Ladybird beetle nymphs
Neem plants, as do all other plants, contain several thousands of chemicals. Of special interest are terpenoids that are unique to Neem and some related members of this family. More than a hundred terpenoids are known from different parts of the Neem plant. Of its biological constituents, the most active and well studied compound is Azadirachtin. However in most traditional preparations of Neem as pesticide or medicine, a mixture of Neem chemicals are present and provide the active principles. Several different kinds of azadirachtin (A-K) have been isolated, the most abundant of which is Azadirachtin-A.
The Neem terpenoids are present in almost all parts of the plant, in the living tissues. Recently, the site of synthesis and accumulation of Neem chemicals has been identified as secretory cells. Secretory cells are most abundant in the seed kernels.
Preparation of Neem products for Organic Farming:
Neem is attracting world wide attention in recent decades mainly due to its bioactive ingredients that find increasing use in modern crop and grain protection. Described here are some easy methods by which the Neem extracts can be prepared by the farmer himself:
Neem Kernel Extract:50g of Neem kernel is required for use in 1 litre of water. The Neem kernel is pounded gently. It should be pounded in such a way that no oil comes out. The outer coat is removed before pounding, this is used as a manure. If pounded with seed coat 1 ½ times (75g) seeds is required. The seeds that are used for preparation of Neem kernel extract should be at least 3 months old and should not be used after 8-10 months. Before 3 months or after 8 months, the azadirachtin quantity is quite low in the seed and hence it cannot efficiently be used for pest control. The pounded Neem kernel powder is gathered in a muslin pouch and this is soaked overnight in the water. The pouch is squeezed and the extract is filtered. To the filtrate, an emulsifier like teepol, sandovit, soap oil or soap nut shell powder is added. One ml of emulsifier is added to one litre of water. The emulsifier helps the extract to spread well on the leaf surface.
Neem Leaf Extract:For 5 litres of water, 1 kg of green neem leaf is required. Since the quantity of leaves required for preparation of this extract is quite high (nearly 80 kg are required for 1 hectare) this can be used for nursery and kitchen gardens. The leaves are soaked overnight in water. The next day the leaves are grounds and the extract is filtered. The extract is beneficial against leaf eating caterpillars, grubs, locusts and grasshoppers. To the extract, emulsifier is added as mentioned in kernel extract.
Neem Oil Spray:
30 ml Neem oil is added to 1 litre of water and stirred well. To this emulsifier is added (1ml/1litre). It is very essential to add the emulsifier and mix properly. This should be used immediately before the oil droplets start floating. A knapsack sprayer is better for Neem oil spraying in preference to a hand sprayer.
Spraying should be undertaken in the morning or late in the evening. During hot conditions the frequency of spraying should be more. In winter spraying once in 10 days and in rainy season, every day spraying is recommended.
Insects lay eggs on the underside of the leaves. Hence it is important to spray on the underside of the leaves as well.
While using a powder sprayer reduce the quantity of spraying to half. It is better to use low concentration of extracts frequently. Each acre of land can be sprayed with 60 litres of ready to use solution.