Neem in Agriculture

In agriculture, neem oil, fruit and the different by products such as seed cake are used as biopesticides, fungicides and organic manures. Scientists foresee that neem tree will create a new era in the pest control and thereby solve other ecological problems affecting the globe. Recently, a number of agro-chemical businesses have realized the potential of neem and there has been a growing interest towards neem as an organic alternative to industrial pesticides.

Neem as Bio-pesticide

The importance of neem as bio-pesticide was realized by the modern scientific community, as early as 1959, when a German scientist in Sudan found that neem was the only tree that remained green during a desert locust plague. Literatures confirm that neem can effectively get rid of over 200 pest species that affects plants. The pesticidal characteristics of neem is largely attributable to Azadirachtin found in the neem extracts which is a growth regulator and as well as a powerful feeding and ovipositional deterrent. Azadirachtin is non-volatile and an insect cannot prevent it by smell but has to taste it, in order to respond to it. A taste of azadirachtin stimulates at least one ‘deterrent neuron’ in insects which show an anti-feedant response. The strength of ‘deterrent neuron’ responses has been correlated with the strength of anti-feedant responses. Neem oil can also suffocate mites, whiteflies, aphids and other types of soft bodied insects on contact. So it is clear that neem does not kill on contact, rather it inhibits feeding and reproduction of the pests. These multiple modes of action make it unlikely that insects and plant pathogens can develop resistance to neem. Also certain pest such as floral thrips, diamond back moth and several leaf miners which develop resistance to the inorganic pesticides or that are inherently difficult to control with conventional pesticides are effectively controlled or managed with neem.

The Emulsifiable Concentrate (EC) of neem

The emulsifiable concentrate (EC) of Neem prepared mostly from the Neem oil is used as the pesticide of choice in organic agriculture. It belongs to the category of medium to broad spectrum pesticides. Among the other known botanical pesticides such as Rotenone and Pyrethrins, neem is found to be superior due to a number of reasons. It is also compatible with a list of other synthetic pesticides, which enables its usage as a component of Integration pest management (IPM). Below are the reasons to explain why neem seems to be best and non-replacable component of IPM

  • Neem pesticide is a natural product, absolutely non toxic, 100% biodegradable and eco friendly.
  • It is suited for mixing with other synthetic pesticide and in fact enhances their action.
  • None or lesser quantity of synthetic pesticides needs to be used, thereby reducing the environmental load.
  • Several synthetic pesticides being single chemical compounds cause easy development of resistant species of pests. Neem consists of several compounds hence development of resistance is impossible.
  • Neem does not destroy natural predators and parasites of pests thereby allowing these natural enemies to keep a check on the pest population.
  • Neem also has systemic action and seedlings can absorb and accumulate the neem compounds to make the whole plant pest resistant.
  • Neem has a broad spectrum of action active on more than 200 species of pests.
  • Neem is harmless to non target and beneficial organisms like pollinators, honey bees, mammals and other vertebrates.

How Neem works as a pesticide

As an insect growth regulator: It is a very interesting property of neem products and unique in nature, since it works on juvenile hormone. The insect larva feeds when it grows and it sheds the old skin and again starts growing. This particular shedding of old skin is the phenomenon of ecdysis or moulting is governed by an enzyme ecdysone. When the neem components, especially Azadirachtin enter into the body of larvae, the activity of ecdysone is suppressed and the larva fails to moult, remains in the larval stage and ultimately dies. If the concentration of Azadirachtin is not sufficient, the larva manages to enter the pupal stage but dies at this stage and if the concentration is still less the adult emerging from the pupa is 100 % malformed, absolutely sterile without any capacity for reproduction.

As a feeding deterrent: The most important property of neem is feeding deterrence. When an insect larva sits on the leaf, the larva is hungry and it wants to feed on the leaf. This particular trigger of feeding is given through the maxillary glands give a trigger, peristalsis in the alimentary canal is speeded up, the larva feels hungry and its starts feeding on the surface of the leaf. When the leaf is treated with neem product, because of the presence of Azadirachtin, Salanin and Melandriol there is an anti – peristaltic wave in the alimentary canal and this produces something similar to vomiting sensation in the insect. Because of this sensation the insect does not feed on the neem treated surface. Its ability to swallow is also blocked.

As an ovipositional Deterrent: Another way in which neem reduces pests is not by allowing the female to deposits eggs. This property is known as Ovipositional deterrence, and comes in very handy when the seeds in storage are coated with neem Kernel powder and neem oil. The seeds or grains obtained from the market are already infested with some insects. Even these grains could be treated with neem seed kernel extract or neem oil; after this treatment the insects will not feed on them. There will be no further damage to the already damaged grains and at the same time when the female comes to the egg laying period of its life cycle, egg laying is prevented.

Other pesticidal activity includes : (1) The formation of chitin (exoskeleton) is also inhibited. (2) Mating as well as sexual communication is disrupted. (3) Larvae and adults of insects are repelled. (4) Adults are sterilized. (5) Larvae and adults are poisoned.

Mode of applications of Neem pesticide: The mode of applications, the dosages and the points to be noted during application are explained in detail in the product section of this website. However the EC formulations are mostly applied as aerial sprays. It is also applied as soil drench to some plant species which translocates it through the plant tissue. Neem can be effectively used in Hydroponics, Aeroponics, greenhouses, shade houses, ornamentals, interior-scapes, horticulture, landscapes, nurseries, turf farms, shrubs, flowering shrubs, fruits and nut trees.

Neem as a bio-fungicide :

As a fungicide, neem oil is mainly used as a preventative and when disease is just starting to show. It coats the leaf surface which in turn prevents the germination of the fungal spores. Neem oil is effective against rots, mildews, rusts, scab, leaf spot and blights.

Neem as soil conditioner and organic manure

Neem Cake, the by-product obtained in the process of cold pressing of Neem fruits and kernels is used as organic manure. It has adequate quantity of NPK in organic form for plant growth. Neem cake typically contains about 6% neem oil and min. 4% nitrogen, 0.5 % phosphorus and 0.5% potassium. Being totally botanical product it contains 100% natural NPK content and other essential micro nutrients. It is rich in both sulphur compounds and bitter limonoids. Please report to the product section of this website, to find in details the nutrients present in neem seed cake. According to research calculations, neem cake seems to make soil more fertile due to an ingredient that blocks soil bacteria from converting nitrogenous compounds into nitrogen gas. It is a nitrification inhibitor and prolongs the availability of nitrogen to both short duration and long duration crops. It also acts as a natural fertilizer with pesticidal properties. Neem cake organic manure protects plant roots from nematodes, soil grubs and white ants probably due to its content of the residual limonoids. Neem cake is widely used in India to fertilize paddy, cotton and sugarcane. It is harmless to earthworms – in fact earthworm populations are known to proliferate in plots treated with neem cake.

Neem as a fertilizer efficiency improving product

Neem is decomposed only slowly, leading to a slower release of nutrients contained in it. The slow release of nutrients is attributed to the presence to the various extractable principles in seed and cake and these extractives are used as rewarding adjuvant for nitrogenous fertilizers such as urea. It is estimated that out of the total quantity of urea applied to crops, about 50- 70% is lost in various forms, thereby reducing the availability of nitrogen to crops. There is an age old practice in India of blending neem cake with urea. When neem cake is blended with urea, it forms a fine coating and protects the loss of Nitrogen by denitrification ensuring regulated continuous availability of nitrogen for a longer period, as per the requirement of crops. Neem seed cake also stimulates the phosphorus uptake slightly but had no effect on potassium uptake.

Neem in storage control

Throughout the tropics much of the food harvested is lost during storage. More affluent farmers can and do spray their stored food crops with chemical pesticides to prevent worms, beetles and other infestations. Neem offers the impoverished farmers and even affluent farmers wanting to replace pesticides with a natural and inexpensive alternative. A light coating of neem oil or kernel powder protects stored food crops for up to twenty months from all types of infestations with no deterioration or loss of palatability. Even today in rural India, people store their grains mixed with dried neem. Neem not only protects but also prevents the further proliferation of storage pest if it has already infested the grains. The insects stop feeding on them due to the anti-feeding property neem. On the other hand, the ovipositional deterrent of neem prevents the female insects from laying the egg during its egg laying period of its life cycle.

Neem and environment

The natural insecticides, fungicides and bio-pesticides made out of neem have many advantages. Research studies indicate that they are not harmful to humans or animals. The pests will not develop resistance over generations while the beneficial insects like butterflies, ladybugs, etc are spared. The soil is enriched, and neem extracts leave no residue in the environment.

Neem’s “soft” pesticide character improves the lives of impoverished farmers throughout the tropical range of the neem tree. According to the World Health Organization, misuse or overuse of chemical pesticides result in poisoning of about 500,000 people resulting about a million illnesses and about 20,000 deaths in the Third World alone. Substituting crude neem extracts for expensive chemical controls saves both money and lives. In developing countries, most of the earnings of farmers are spent on crop protection chemicals. These results in a vicious cycle of continued debt and thereby the poverty, ill health and environmental degradation. To break this cycle and to improve the farmer’s lives, agencies such as CARE, AID and AFGRO are actively promoting the introduction and use of neem in Southeast Asia, Africa, the Caribbean and both South and Central America. The farmers are educated about the means and methods for easily making a cheap, safe and effective product that protects their crops from over 200 different insect pests.

Farmers in Mexico and Haiti and shepherds in Australia have begun switching to simple neem-based sprays from the usual synthetic chemical pest controls. This has allowed the farmers to export mangos and other fruit to the United States without the chemical residues that often stopped their shipments at inspection stations. Neem-based sprays have similarly allowed the shepherds in Australia to produce pesticide-free wool that is being sold to European buyers for a considerable premium over the standard wool impregnated with chemical pesticides. Neem extracts have been approved by the U.S. Environmental Protection Agency for use on food crops. And today more and more of the governmental agencies approve the usage of neem on food crops.

Leave a Reply

Your email address will not be published. Required fields are marked *