Chemistry of Neem for Organic Farming
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.
For Protecting Crops
Neem is quite effective against army worm, one of the most devastating pests of food crops in the western hemisphere. Azadirachtin in extremely low concentrations - a mere 10 mg per hectare - inhibits the pests.
Neem extract is useful against leaf - miner, a serious pest in parts of North America. Neem seed extract works as well as available commercial synthetic pesticides. It has been approved by the US environmental protection agency for use on Leaf Miners.
Neem is extremely useful as an anti-feedant and ovi-positional repellent for protection of crops like tobacco, groundnut, cotton and sweet potato from the damages caused by tobacco caterpillar or tobacco cutworm, a serious polyphagous pest of several crops in India.
Experiments have shown that neem is also effective against fruit flies. Med fly, one of the most damaging horticulture pests, can be controlled by spraying Neem solution under fruit trees. Neem has an advantage over the currently used pesticides. Whereas conventional pesticides kill fruit flies as well as thrips, internal parasites, Neem products on the other hand leave the biological-control organisms unaffected; they only kill fruit flies. This reduces, in fact, eliminates adverse, unintended effects.
De-oiled Neem cake ( the residual remaining after the oil has been pressed out of the seeds) and Neem oil are quite effective against rice pests. Five applications of a 25% oil emulsion sprayed with an ultra low-volume applicator can protect rice crops against brown plant hoppers. Neem products greatly reduce the tungo virus transmission efficiency of green leaf hopper in rice.
For Protecting Stored Crops
One of the traditional uses of Neem in Asia has been for controlling pests of stored products. Farmers usually mix Neem leaves with grain before keeping it in storage for several months. Neem leaves, oil or extracts act as repellent against several insects such as weevils, flour beetles, bean-seed beetles and potato moths. Treatment of jute sack by Neem oil or azadirachtin-rich-products prevents the penetration of pests like weevils and flour beetles. Neem oil destroys bean-seed beetles (bruchids) - a variety of insects mostly attacking legumes - at the egg-stage itself. A mixture of Neem leaves and clay and cow-dung develops pest resistant property so it can be used to make bins for storage of grain.
Preperation 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 ke rnel 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 cake powder is added. One ml of emulsifier is added to one litre of water. The emulsifier helps the extract to stick well to 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 Cake extract
100 gms of Neem cake is required for 1 litre of water. The Neem cake is put in a muslin pouch and soaked in water. It is soaked overnight before use in the morning. It is then filtered and emulsifier is added -1-ml for 1-litre of water. It can then be used for spraying.
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.