What is Neem?

Introduction

The Neem tree is indigenous to India. Indians have revered the neem tree for a very long time. To millions of Indians neem has miraculous powers. For centuries people of India have used neem twigs for cleaning their teeth, treated skin infection with neem leaf juice, used it as a tonic and kept away bugs with different neem extracts. It also formed part of several rituals. The tree has been used in curing so many ailments that it has been called "the village pharmacy".

Distribution

Nim or Neem, Azadirachta indica A.Juss belongs to the sub family: Meliodeae; order: Meliales. It is believed that Neem originated in Asia and Burma. However the exact origin is uncertain. Some believe it to be native to the whole Indian subcontinent whereas others are of the opinion that it belongs to dry forest areas throughout all of South and Southeast Asia including Pakistan, Philippines, Sri Lanka, Thailand, Malaysia and Indonesia.

Neem is now widely distributed in many countries of the world by cultivation. Indians migrating to African countries introduced neem into that continent. Neem grows abundantly between Somalia and Mauritania. Neem has also been introduced into Fiji Islands and from there it has spread to other South Pacific islands. Neem is also cultivated in the West Indies, Australia and some countries of Central and South America. Neem is grown in Southern Florida and is being established in Southern California and Arizona in the United States.

In India neem is seldom found in the forest. It is mostly grown as an avenue or shade tree and in variety of habitats. Neem is seldom leafless - one of the reasons why it is prized in India. The Indian subcontinent has nearly eighteen million neem trees. Most of them line the roadsides or are found clustered around markets or backyards and provide great relief from the sun. Neem grows to height of about 20 meters and a girth of 25 meters. It grows well on dry, stony, clayey and saline soils. It has a strong root system that extracts nutrients and moisture from poor soils. Neem grows up to about altitude of 1,500 meters. It can withstand high temperatures but cannot survive frost.

Agronomy

The compound leaves of neem appear smooth. However, closer examination of young leaves near the shoot apex will reveal the presence of resin secreting glands. The lower portions of the leaf stalk are covered with extra floral nectarines that attract ants. Damaged tissues of the stem secrete gum. Occasionally a milky white secretion is noticed from stems prior to flowering and production of new leaves. It is also well known that the green unripe fruits secrete milky white latex, very bitter in taste because of some limonoids, but apparently free from azadirachtin.

The neem tree flowers between January and May in India although occasional flowers can be found on trees during other months, particularly, August-September. Trees in the southwest bloom first and there is a progression in the blooming period from the south to north. Flower buds of neem open in the evening and they are more scented at night and also secrete nectar that attracts a variety of pollinators. Neem honey is very popular and this has no azadirachtin.

Neem tree takes considerable abuse. It can withstand pollarding (repeated topping at heights above 1.5m) and coppicing (repeated topping at near ground level) very well. This is possible because of the root system which is large enough to feed a full grown tree.

A neem tree normally starts fruiting after 3-5 years. In about 10 years it becomes fully productive. From the tenth year onwards it can produce upto fifty kilograms of fruits annually. It’s lifespan is about two centuries.

Neem is easily propagated by seeds. However, the seeds are viable only for about three weeks after harvest under normal conditions of storage. Stem and root cuttings can also be used to propagate neem. Neem tree grows almost anywhere in the low land tropics. Its performance is best in areas which have an annual rainfall of 400 - 1,200 mm. Even if the maximum shade temperature soars past 50 C it thrives well. However, it cannot withstand freezing or cold for long. It grows from sea level up to heights of 1000m. The tap root of this tree is nearly twice the height of the tree.

Neem grows well in dry infertile sites. It performs well even where soils are sterile, strong and shallow. Neem also grows well in acid soils. It is believed that fallen neem leaves which are slightly alkaline (pH 8.2) are good for neutralizing acidity in the soil. The neem tree however, cannot withstand water logging.

Neem grows rapidly and yield timber for five to seven year. Weeds do not affect its growth and it can dominate almost all competitions.

Chemistry of Neem

Neem plants, as do all other plants, contain several thousands of chemicals. Of special interest are the 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 to K) have been isolated, the most abundant of which is Azadirachtin-A.

The neem terpenoids are present in all parts of the plant, in the living tissues. Recently, the site of synthesis and accumulation of the neem chemicals has been identified as secretory cells. Secretory cell are most abundant in the seed kernels. The secretory cell can be seen with iodine solution. The bulk of the kernel is actually a pair of cotyledons of the seed. In general, the kernels contain about 30-40 % oil. Triterpenoid content of the kernels is about 2.5 to 3%. The azadirachtin content in the kernels may vary from 0.2 to 0.6%. Besides the terpenoids, neem also contains more than 20 sulphurous compounds responsible for the characteristic smell of crushed seeds and neem oil. The gum of neem contains different kinds of sugars.

___________________________________________________________

Neem: An Ancient Cure for a Modern World
by Julia Cornborough

The Neem tree (Azadirachta indica A. Juss.) has been known as the wonder tree for centuries in the Indian subcontinent. It has become important in the global context today because it offers answers to the major concerns facing mankind.

About the Author

Julia Thornborough, BSc, MRQA, MNBPA, TIDHA is a Clinical Aromatherapist. She trained in aromatherapy at the Tisserand Institute of Holistic Aromatherapy in London. As well as having a private practice in Dorset, she teaches aromatherapy for use at home for the Holiday Property Bond and also conducts courses for care staff in residential homes for the elderly. Her particular interest of research is the use of aromatherapy in immune related disease. She can be contacted at Linden Lea, 16 Linden Road, Swanage, Dorset, BH19 1JH


Leaves of the Neem help in the treatment of neuromuscular pains and neutralize free radicals
The Neem tree (Azadirachta indica A. Juss.) has been known as the wonder tree for centuries in the Indian subcontinent. It has become important in the global context today because it offers answers to the major concerns facing mankind.

The history of the Neem tree is inextricably linked to the history of the Indian way of life. Although the antiquity of Neem is shrouded in the mists of time, this evergreen robust looking tree has long been cherished as a symbol of health in the country of its origin. It has, for a very long time, been a friend and protector of the Indian villager. Brihat Samhita, an ancient Hindu treatise, contains a chapter of verses on plant medicines. It contains recommendations for specific trees to be planted in the vicinity of one’s house. Neem was highly recommended.

The Tree

Neem is a medium sized to large tree characterised by its short straight trunk, furrowed dark brown to grey bark, and dense rounded crowns of pinnate leaves. Native to India, Neem is widely planted and naturalised in semiarid areas throughout Asia and Africa. Neem is an evergreen of the tropics and sub-tropics. It belongs to the family Meliaccae and is a cousin of the Chinaberry. With an extensive and deep root system, the hardy Neem can grow luxuriantly even in marginal and leached soils, and thrives up to an elevation of 1500m. The Neem flowers profusely between February and May. The honey-scented white flowers, found in clusters, are a good source of nectar for bees. Neem fruits are green drupes which turn golden yellow on ripening in the months of June, July and August, in India. The kernels have about 45% oil. The termite resistant Neem timber is used as a building material, and in making furniture and farm implements. The bark yields tannin and gum. The amber hued gum is used as a dye in textiles and in traditional medicines.

Medical Properties

The medical properties of Neem have been known to Indians since time immemorial. The earliest Sanskrit medical writings refer to the benefits of Neem’s fruits, seeds, oil, leaves, roots and bark. Each has been used in the Indian Ayurvedic and Unani systems of medicines, and is now being used in the manufacture of modern day medicinals, cosmetics, toiletries and pharmaceuticals.

Neem fruits, seeds, oil, leaves, bark and roots have such uses as general antiseptics, antimicrobials, treatment of urinary disorders, diarrhea, fever and bronchitis, skin diseases, septic sores, infected burns, hypertension and inflammatory diseases. This is mainly due to the chemical constituents which enable Neem to protect itself from a multitude of pests by a substantial number of pesticidal ingredients. Its main chemical composition is a blend of 3 to 4 related compounds along with over 20 lesser ones, which are equally as active. The general class of these compounds is triterpenes and within this category, the most effective are the limonoids, which are abundant in Neem oil. At least nine limonoids are effective in inhibiting insect growth, especially some of the most deadly varieties found in human health and agriculture worldwide. Of these limonoids, azadirachitin has been found to be the main ingredient for fighting insects and pests, being up to 90% effective in most instances. It repels and disrupts the life cycle, however does not kill immediately, but is nonetheless one of the most effective growth and feeding deterrents ever examined. Meliantriol is another feeding inhibitor which prevents locusts chewing, and has therefore been in traditional use in India for crop protection. Nimbin and nimbidin, also found in Neem, have anti-viral properties and these have been effective in inhibiting fungal growth on humans and animals. Gedunin, a lesser limonoid, is effective in treating malaria through teas and infusion of the leaves.

Fungicides

Neem has proved effective against certain fungi that infect the human body. Such fungi are an increasing problem and have been difficult to control by synthetic fungicides. For example, in one laboratory study, conducted by Khan and Wassilew – 1987, Neem preparations showed toxicity to cultures of 14 common fungi, including members of the following genera:

• Trichophyton – an ‘athlete’s foot’ fungus that infects hair, skin and nails;
• Epidermophyton – a ‘ringworm’ that invades both skin and nails of the feet;
• Microsporum – a ‘ringworm’ that invades hair, skin and (rarely) nails;
• Trichosporon – a fungus of the intestinal tract;
• Geotrichum – a yeast like fungus that causes infections of the bronchi, lungs and mucous membranes;
• Candida – a yeast-like fungus that is part of the normal flora but can get out of control, leading to lesions in mouth (thrush), vagina, skin, hands and lungs.

Components of the Neem tree and their uses

Bark
The bark is cool, bitter, astringent, acrid and refrigerant. It is useful in tiredness, cough, fever, loss of appetite, worm infestations. It heals wounds and is also used in vomiting, skin diseases and excessive thirst. Twigs have been used as a ‘toothbrush’ and for dental care, since antiquity. Neem toothpaste has been on sale in the US and Germany for some time, and is now available here.

Leaves
According to Ayurveda, Neem leaves help in the treatment of Vatik disorders (neuromuscular pains). Neem leaves are also reported to remove toxins, purify blood and prevent damage caused by free radicals in the body by neutralising them.

A paste made with leaves is used in India for the cure of chicken pox, smallpox and warts. A poultice is effective for boils, ulcers and eczema.

Fruits
Neem fruits are bitter, purgative, antihemorrhodial and anthelmintic (vermifuge) in nature.

Flowers
The flowers are used in vitiated conditions of pitta (balancing of the body heat) and kapha (cough formation). They are astringent, anthelmintic and non toxic.

Seeds
Neem seeds are also described as anthelmintic, antileprotic (cures or prevents leprosy) and antipoisonous. Seeds, along with leaves and dry Neem cake, are an active ingredient in mosquito coils.

Oil
Neem oil, derived from crushing the seeds, is antidermatonic, a powerful vermifuge and is bitter in taste. It has a wide spectrum of action and is highly medicinal in nature. As an oil used in aromatherapy, it has been effective in the treatment of head lice in children, especially where tea tree has failed to clear up the condition. This was particularly noticeable on an outbreak of head lice, two years ago, at a school local to my practice, where I treated several children. Those with blonde to reddish hair had their head lice condition cleared up much quicker with Neem oil applied at a 3% dilution to a shampoo base, than with tea tree.

Specific uses of Neem

Skin Conditions
Neem has an almost magical effect on chronic skin conditions that fail to respond to conventional treatments. Acne, psoriasis, eczema, and ringworm are conditions that are effectively treated by a Neem preparation.

Hair and Nails
Scalp conditions like dandruff, scaling and even hair loss improve with Neem products. Yellow or brittle nails, caused by the presence of yeast or fungi, are normalised by the use of Neem.

Teeth and Gums
Neem mouth rinse is very effective in the treatment of infections, tooth decay, bleeding and sore gums. A mouthwash, using Neem oil, has been used at my practice for the treatment of mouth ulcers.

Fungi, Parasites and Viruses
Stringent laboratory condition tests have proved the efficacy of Neem in destroying fungi, parasites and viruses without killing off beneficial intestinal flora. It is very effective in the treatment of Athletes’ Foot, thrush, candida infestations and herpes.

Diabetes
Neem has been found to reduce insulin requirements by up to 50% for diabetics, without altering blood glucose levels.

Heart and Blood
A recent study showed that a Neem treatment lowered high cholesterol levels. It has also been tested, with good results, for other heart conditions.

Insects
Neem is a very effective insect repellent, without being toxic to pets and humans.

AIDS and Cancer
Tests are currently being carried out, with encouraging results. During the course of the freedom movement in India, led by Mahatma Gandhi, there was an upsurge of the ‘Swadeshi’ or nationalistic sentiment. This led to a move to encourage ‘Swadeshi’ science. Neem research in India was part of this movement. Pioneering work on the possible commercial use of Neem oil and cake was done by the Indian Institute of Science in Bangalore during the 1920s.

Mahatma Gandhi kept the tradition of Neem alive, and is known to have been a firm believer in the goodness of Neem. Dr Ekaid informed Gandhi that laboratory experiments revealed that Neem leaves contain more nutritious elements than any other similar vegetation that has been subjected to chemical analysis earlier. A Neem leaf chutney was a part of Gandhi’s everyday diet. A nutraceutical tea, now being manufactured, would surely have been Gandhi’s favourite beverage.

___________________________________________________________

Physico-composition of Fresh Neem Leaves: Neem Tea and its Uses

Tender leaves, along with black pepper, are effective in intestinal helminthiasis (parasitic infections).

An aqueous extract of tender leaves has been found to possess antiviral properties against vaccinia (viral disease in cattle), variola (smallpox), fowl pox and New Castle diseases.

Fresh mature leaves, along with the seeds of Psoralea corglifolia and Cicer arietinum are effective in leucoderma.

Studies on plasma clotting time using Russell’s viper venom have proved that the leaf extract contains a clotting inhibitor, justifying its use in the treatment of poisonous bites.

Animal-based experiments have shown that total extract of Neem leaves is a potent hepatoprotective agent.

Water extract of Neem leaves shows significant antiulcer activity and reduction in severity of gastric damage, and prevents most cell degranulation and mucus depletion.

The phosphate buffer, ether and alcoholic extracts of the leaves inhibit the activity of the micro-organism Micrococcus pyrogenes var. aureus. The essential oil possesses anti-bacterial activity. It inhibits the growth of Mycobacterium tuberculosis, Salmonella paratyphi, Salmonelbtyphi, Vibrio cholera Pacini and Klebsiella pneumonia (Schroter) Trevisan (organisms which cause typhoid, cholera and pneumonia.

Chewing fresh Neem leaves acts as a sedative and relaxant.

The Future with Neem

Poverty

Today’s exploding growth in human population is seriously depleting the world’s natural reserves and economic resources. Unless the run-away human population growth rate is slowed down, there would be little hope for raising everyone out of poverty in the developing world. Besides educational constraints, the non-availability of inexpensive methods of contraception, which do not cause trauma or aesthetic, cultural, and religious sensitivities of people, limit the success of birth regulation programs. However, recent findings indicate that some Neem derivatives may serve as affordable and widely available contraceptives. A recent controlled study in the Indian army proved the efficacy of Neem as a contraceptive.

According to a recent report by the Washington based International Food Policy Research Institute, by 2020, the world will be an even more unfair place than it is at present, with food surpluses in the industrialized world and with chronic instability and food shortages in the south, particularly in African countries.

The US Academy of Sciences currently attaches very high importance to the Neem tree. The United Nations declared Neem as the “Tree of the 21st Century”.

Bioactivity

Search for environmentally safe pesticides received an impetus in early 1960s following the publication of Silent Spring by Rachel Carson in 1962. It was around this period that Indian scientists reported the feeding deterrent property of Neem seed kernel suspension against desert locust. Subsequently, several bioactive ingredients were isolated from various parts of the tree, more notable being the isolation of meliantriol and azadirachtin. These findings aroused world-wide interest in the bioactivity of the Neem tree.

The Neem seems to be a virtual designer tree – tailor-made for combating the serious problems confronting mankind today. The information being generated on it in the modern format of science continues to confirm all the ancient claims. Its mammalian safety and environmental friendliness reports are highly encouraging. Its bioactivity spectrum against the harmful organisms is ever increasing.

Neem is now widely used in America in fields ranging from pharmaceutical, health and beauty, pet care, pesticides and insecticides, and agriculture, while health and beauty and pharmaceutical products are available in Austria and Germany.

Neem products are also available in the UK and a nutraceutical tea is the newest product to come on the market.

A key advantage to using Neem, as opposed to some medical treatments and other herbs, is its compliance with the first tenet of the Hippocratic Oath taken by all physicians: “First, cause no harm.” Over thousands of years, Neem has been used by hundreds of millions of people and no hazards have been documented for normal dosages. Only at very high levels may Neem be toxic, something each of us understands can be true of anything taken internally.

References

Edeinya I. Anti-malarial activity of Nigerian Neem leaves. Trans Royal Soc Tropical Medicine. 87(4): 471. 1993.
Keimat G. Dental care compositions from Azadirachta indica. Ger Appli P. 20(38): 827.6. 1970
Charles V and Charles S. The use and efficacy of Azadirachta indica ADR and Curuma longa in scabies. Trop Geogr Med. 44(1-2): 178-81. 1992.
Khan M and Wassilew SW. The effect of raw material from the Neem tree, Neem oil, and Neem extracts on fungi pathogenic to humans. in Schmutterer and Ascher. Natural Pesticides from the Neem Tree and other Tropical Plants. International Neem Conference. Nairobi, Kenya. pp645-650. 1987.
Koul O, Isman M and Ketkar C. Properties and uses of Neem, Azadirachta indica. Can J Bot. 68: 1-11. 1989.
Saxena RC. Insecticides from Neem. in Arnason et al. Insecticides of Plant Origin. ACS Symp. Sere. 387, American Chemical Society. Washington DC. pp110-135. 1989.
Schmutterer H. Properties and potential of natural pesticides from the Neem tree, Azadirachta indica. Ann Rev Entomol. 35: 271-279. 1990.
Vietmeyer N. Neem, A Tree for Solving Global Problems. National Academy Press. Washington DC. 1992.

Neem America makes no claims about neem and its uses. This article should only be used for informational purposes.

______________________________________________________________

Neem: The Wonder Tree
Dr. Mallick F. Rahman M.

The neem tree (Azadirachta indica) is regarded as one of mother nature's gift to the world. In India , it is commonly found in house compounds in both villages and cities. Green twigs are used as toothbrushes to combat teeth decay. Its extracts have a powerful pesticidal activity and are used by both households and farmers to control a wide variety of pests (insects, fungi, bacteria, viruses, nematodes, rodents etc.). These extracts have considerable antiseptic affects and are used as a skin care agent in soaps and shampoos. The leaves are often mixed with rice and consumed as a cure all and prophylactic against bacterial and helminthic infections. Neem leaf pastes are used to repair scarred skins arising from the effects of chicken pox. Not surprisingly, many believe that the neem tree itself can ward off demons.

The pesticidal and medicinal properties of extracts from the neem tree have been exploited for at least the last 2500 years. Sanskrit texts dating back to the sixth century BC, document the microbicidal and prophylactic effects of neem extracts. Charaka in the 6th Century BC recommended the oral consumption of neem extracts to ward off pimples, leprosy and edema. Sushruta in the 5th century BC recommended the use of neem-leaf smoke for fumigation and maintenance of general hygiene. He also recommended it as a "krimihara", an agent effective against insects, grubs and maggots and detailed the ability of neem leaves to cure gangrenous and otherwise difficult to cure wounds.

The neem tree appears to be a biochemical factory producing a mixture of over 135 biologically active compounds. As a pesticide, the oil from neem seeds are believed to break the life cycle of pests and deters them from feeding and/or hatching. Studies have shown that active compounds in the oil inhibited the secretion of hormones into the blood inhibiting the moulting and reproductive function in insects.

Neem oil is known to be active on over 400 insect pests. It has for example been found to be effective against fleas, head lice, ticks, termites, plague locusts, mosquitoes and sheep blow flies. It is believed to be particularly active against chewing and sucking insects such as caterpillars and beetle larvae.

Neem extracts have also been shown to be effective against nematode pests. Neem cake, the by product from neem seed processing appears to be effective on nematodes, snails and certain fungi. The neem tree and its extracts surprisingly appear to be benign to bees and other nectar feeding insects. Seed extracts are not known to have any toxic effect on plants, mammals and birds and in fact in studies by the US EPA, no LD-50 could be established even at high doses.

These remarkable properties have attracted considerable interest from both researchers and pharmaceutical companies. This renewed interest in neem created no more than amusement in India where the beneficial properties of neem have been known for countless generations. This mood however has recently changed with Grace Horticultural Products, a unit of Grace Specialty Chemicals (USA) acquiring the patent and trademark rights to produce and sell insecticidal neem extracts. Their product, Margosan-O Concentrate, is protected under US patent No. 5124349.

In 1995, a group led by Mr. Jeremy Rifkin, president of the Foundation of Economic Trends in the US, Dr. Vandana Shiva of the Research Foundation for Science Technology and Natural Resource Policy and Professor, Nanjundaswamy of the Karnataka Rajya Ryot Sangha in India contested the decision of the US Patent and Trademark Office. They claim that the neem product has long been used as a pesticide in India and is not a new invention as claimed under the patent. They claim that Grace's patent does not satisfy the criterion that the invention must not be obvious to one of ordinary skill in the art. They assert that the Grace process only slightly differs from that used by farmers in India.

Grace on the other hand claims that its patent relates to a formulation based on neem-seed extract. They assert their formulation overcomes the problems associated with the instability of azadirachtin, the primary active pesticidal ingredient from the plant, in traditionally used water or alcohol based emulsions. Further the awarding of patents based on the purification or modification of naturally occurring substances is not new. For example, in 1979, the US Court of Customs and Patent Appeals reversed a decision by the Patent and Trademark Office to award a patent for a compound purified from strawberries. In fact, more than 40 patents have already been award for inventions relating to a compound found in neem seeds alone.

Regardless of its outcome, the legal battle ensuing between Grace and its opponents will have significant ramifications for the natural products industry. Rifkin and partners assert that the patent and other similar patents will mean that "indigenous populations around the world will be excluded from freely using many of the local biological resources that have been carefully developed and nurtured over hundreds of years". It has even been claimed that in a worst case scenarios that indigenous farmers would have to pay royalties to carry on their centuries-old farming practices. Unfortunately the latter argument fails to consider that no universal patent exists and as such Grace's patent is not valid in India. Indian farmers can thus choose to pay a premium for Grace's formulation or continue to produce their own.

As a result of this case, developing countries are now more concerned about the consequences of the loss in sole proprietary of a biological resource. Recently, a senior official from the Indian Council of Agricultural Research voiced his concern on the "pilfering" of traditional plant varieties from India. "The neem is ours and nobody can take it away". His claim may be a case of closing the door after the horse has bolted and is indeed somewhat curious, given that neem trees have been successfully grown in over 17 countries. They can in fact be obtained here in Singapore.

The Indian government is in the process of formulating a Plant Varieties Protection Act which will seek to protect over 2,300 currently unprotected Indian plant varieties. Whether other countries follow India's lead will certainly have a significant influence on both research and production of natural products.

Neem in Pest Control

Research has shown that neem extracts can influence nearly 200 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.

Neem products work by intervening at several stages of the life of an insect. They may not kill the pest instantaneously but incapacitate it in several other way. The precise effect of various neem extracts on an insect species is often difficult to pinpoint.

Biological Effects of Neem on Insects

It is important to understand that the action of neem products as pest control agents can be at different level and ways. This is very important since the farmer is used to the "knock-out" effect of chemical pesticides. Neem extracts do not exhibit this type of effect of pests but affect them in several other ways.

Insect Growth Regulation

It is a very interesting property of neem products and unique in nature, since it works on juvenile hormone. The insect Iarva feeds and when it grows, it sheds the old skin and again starts growing. This particular shedding of old skin is the phenomenon of ecdysis or moulting and is governed by an enzyme ecdysone. When the neem component, especially azadirachtin enter into the body of larve, the activity of ecdysone is suppressed and the Iarva fails to moult, remains in the Iarva stage and ultimately dies, If the concentration of azadirachtin is not sufficient enough, the Iarva 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.

Feeding Deterrent

The most important properly of neem is feeding deterrence. When an insect Iarva sits on the leaf, the Iarva is hungry and it wants to feed on the leaf. This particular trigger of feeding is given through the maxillary glands. When these maxillary glands give a trigger, peristalsis in the alimentary canal is speeded up, the Iarva feels hungry and it 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 a 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.

Oviposition Deterrent

Another way in which neem reduces pests is by not allowing the females to deposit eggs. This property is known as oviposition 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 prevented.
There are also other modes of action known such as -

• The formation of chitin or the hard part covering the sect(exoskeleton) is also inhibited.
• Mating as well as sexual communication is disrupted.
• Larvae and adults of insects are repelled.
• Adults are sterilized.
• Larvae and adults are poisoned.

Use of neem products does not give immediate results like chemical insecticides. Some patience is required after application of neem products.

Effect of Neem on Different Insects

It is important to understand how neem products act on the insects.

Orthoptera (Grasshoppers, Crickets, Katydids, etc.)
Neem product act as antifeedants. Several species of these insects refuse to need on plants treated with neem for several days to several weeks. Recently it has also been discovered that neem products convert the gregarious swarms of locust to solitary forms.

Homoptera (Cicadas, Aphids, Scale insects, Leafhoppers, etc.)
These insects exhibit sensitivity to neem products to varying degrees. In leafhoppers and planthoppers neem product show considerable antifeedant and growth regulating effects. Scale insects are not much affected. In some cases, the host plant may influence the degree of control; this seems to apply to some whiteflies. When neem products are used to control whiteflies if exhibits control on some crops but not on others. The ability of certain homopterous insects to carry and transmit viruses are also influenced by them products. Low doses prevent the green rice leafhopper from infecting rice fields with tungro virus.

Thysanoptera (Thrips)
Neem products are very effective in controlling thrips larve which are found in the soil. Their effect is moderate when used on the thrips and related pests found on plants. Neem oil is more effective - this could be because the oil coat suffocates these tiny creatures.

Coleptera (Beetles, Weevils)
Larvae of all kinds of beetles refuse to feed on plants treated with neem. Their growth is retared and some soft skinned ones are killed on contact.

Lepidoptea (Moths, Skippers, Millers and Butterflies)
Neem products act as growth deterrents in the case of the larvae of most lepidopterous pests. They also act as antifeedant.

Diptera(Flies)
Insects like flies, face flies, bot flies, houseflies and horn flies are affected by neem products.

Hymenoptera (Bees, Wasps, Sawflies, Ants, etc.)
Bugs like rice bugs and vegetable bugs are affected by neem products in that they exhibit antifeedant and growth deterrent properties.

Mode of Action of Neem Products on Specific Pests

This section describes the manner of action of neem solitarization of the gregarious nymphs of locusts. Doses equal to 2.5 litres / hectare prevent the juveniles from forming massive moving plagues which are extremely devastating to the crops. Through they are not killed , they become solitary, lethargic, almost motionless and are highly susceptible to predators such as birds. Grasshopper nymphs are also affected in a similar fashion.

Cockroach
Neem kills the young cockroaches. Adults are inhibited from laying eggs. It has been observed that baits which were impregnated with commercial preparations of neem seed extract retarded growth of Oriental, Brown banded and German cockroaches. Growth of first instar nymphs of all there species was retarded and they died within 10 weeks. Last instar nymphs exhibited retarded growth and died within 9 weeks.

Brown Planthopper
Neem cake is extremely successful in controlling brown planthopper and other rice pests. Neem oil is also effective. The several way in which these could be used against brown plant hoppers is discussed in detail in the appendix.

Stored Product Insect
Use of neem for controlling pests of stored products is one of the oldest traditional uses of neem in Asia. Neem products in this context basically seem to act as repellants. After treatment of jute sacks with neem oil or extracts, weevils (Sitophilus sp.) and flour beetles (Tribolium sp.) do not penetrate for several months. Stored grains are kept mostly away from sunlight and hence the degradation problem of neem products is also less. Neem oil is also very effective against pests of stored beans, cow peas and other legumes. Treatment with neem produces does not affect the germinating capacity in anyway. Neem is used to protect stored roots and tubers against potato moth. It is shown that small amount of neem extends the storage life of potatoes by three months.

Leafminers
Neem products are used very effectively against leaf miners. When the neem are added to the soil through the roots they reach the crop’s leaves and start acting on leaf miners feasting on leaves. The moulting hormones of leaf miners their own juvenile skins.

Mosquitoes
The larvae of different species of mosquitoes are affected by neem. Crushed neem seeds when thrown into pools prevented mosquitoes from breeding.

Fruit Flies
Fruit Flies are serious horticultural pests. their presence in the tropics affects dozens of delicious fruits. it has been shown that spraying dilute neem solution under fruit trees gave a 100% control of these pests. More interestingly the neem products were also compatible with the biocontrol organisms used to control fruit flies.

Nematodes
Thread worms or nematodes are highly devastating agricultural pests and also the most difficult to control. Neem products affect several types of nematodes. Aqueous extracts of dried and powdered neem have shown up to 100% mortality of nematodes from 12 hours onwards in laboratory experiments. Aqueous extracts of seed kernel and seed coat are also nematicidal. Hatching from egg masses of nematodes was reduced when they were treated with seed kernel and coat extracts. Aqueous neem cake extracts inhibit hatching of second stage juveniles. In Aligarh, India, amending soil with neem cake helped to bring down the root-knot index to zero in tomatoes. this is very important because tomatoes are highly sensitive to nematodes. Cardamom growers of South India have taken to the use of neem cake for nematode control. They incorporate 100 to 259 kg per hectare of neem for their cardamom fields every year. Nearly 3000 tonnes of neem cake are now used in the cardamom hills of India annually. It is transported and sold by pesticide dealers 250 to 300 kms away.

Methods of application: Neem cake can be applied as a soil amendment, either alone or in combination with wheat straw and inorganic fertilizers. Soil drenching with aqueous extracts of seed kernel and seed coat at lower does but for more number of times (one at the time of sowing and others at monthly intervals) also reduces the number of galls in chickpea. All organic amendments including neem products are effective against plant parasitic nematodes only after a certain period of decomposition. Maximum reduction in plant parasitic nematode population is found only after 75 days of application of neem cake, though the reduction in noticed after 45 days. Bare roots of plants like tomato can be dipped in neem extracts for different periods of time. Seeds can also be soaked in aqueous extracts. When seeds are treated in this way there is reduction in the penetration of second stage juveniles. Seeds can also be coated with cake, kernel or seed coat. This is also effective against root-knot nematodes in a number of crops like chickpea and groundnut.

Snails
Neem extracts also kill snails. Aqueous solution of neem fruit results in a 100% kill of the snail, Melania scabra. These snails are vectors of lung flukes, a parasitic flatworm that encysts in the lungs of livestock, wildlife and human.

Plant Viruses
Beside the insecticidal and nematicidal properly, neem is also a promising agent for control of plant disease. Yellow vein mosaic of okra, yellow mosaic of grain legumes and leaf curl of chilli cause enormous loss. Neem oil in combination with paraffin oil greatly reduces disease incidences. Rice fields sprayed with neem oil have had significantly lower incidence of ragged-stunt virus which affects rice and is transmitted by the brown planthopper. Neem oil and custard apple oil interfere with the transmission of tungro virus, another rice pest. Neem leaf extracts have been shown to reduce transmission of tobacco mosaic treated with neem cake were significantly free of rice tungro virus.

Fungi
Neem has been demonstrated to possess antifungal activity. Fungi are constantly evolving enemies of farmers and some can reach epidemic proportions. A few of these have no cures and some can make certain crops impossible to grow. Neem oil has been shown to protect chickpea seeds against fungal diseases. Neem seeds extracted are also beneficial against fungal disease. Neem seeds extract are also beneficial leaf fungi. It prevents powdery mildew disease when sprayed before the outbreak of the disease.
Neem leaf extracts do not kill fungi. However when treated with neem leaf extracts the fungus Aspergillus flavus does not produce aflatoxin. The extracts halt the formation of substances called polyketides. It is these substances that the fungi convert the formation of aflatoxin in cotton balls.

Effect on Non - Target Species
One of the problems with the use of chemical pesticides has been their impact on "non-target" species. Often they have proved harmful to various other species in the ecosystem that could be beneficial. This section briefly reviews the information available about the effect on non-target species. This also helps us to assess how well the use of neem may be used in conjunction with other methods such as biocontrol using predators like spiders.

Earthworms
Neem leaves and seed kernels when incorporated into potting soil, which contained earthworms increased the earthworm population by 25%.

Effect on other Beneficial Insects

Neem products have proved to be remarkably benign to spiders and also other insects such as bees that pollinate crops and trees, ladybug beetles that consume aphids and also wasps which act as parasites on various crop pests. Neem products have to be ingested to be effective. Those insects which feed on plant tissues, therefore, easily succumb. However natural enemies like spiders feed only on other insects and bees feed on nectar. Hence they rarely come in contact with significant concentration of neem products.

_______________________________________________________________

Insects affected by Neem
Source: Development and Ecological Role of Neem in India

Neem has been reported to control at least 125 species of pest insects, mites and nenatodes, including 25 species of Coleoptera (beetles), 10 species of Diptera (flies), 25 species of Leptdoptera (moths) and 9 species of Orthoptera (locusts). The following is a list of some of the insects that are affected by neem products.

American Cockroach: Reduces fecundity and molts, reduces number of fertile eggs.

Bean Aphid: Reduces fecundity, disrupts molting.
Boll Weevil: Inhibits feeding.
Brown Planthopper: Inhibits feeding repellent, disrupts growth, making failures and sterility.

Cabbage Looper: Inhibits feeding
Colorado Potato Beetle: Eggs fail to hatch, larvae fail to molt with azadirachtin levels as low as 3ppm inhibits feeding.
Confused Flour Beetle: Inhibits feeding, disrupts molting, molting, toxic to larvae.
Corn Carworm: Retards growth, inhibits feeding, disrupts molting
Cowpea Weevil: Inhibits feeding, toxic.

Diamondback Moth: Strongly suppresses larvae and pupae, retards growth, inhibits feeding.

Face Fly: Retards growth, toxic
Fall Armyworm: Retards growth, repels adults, inhibits feeding, disrupts molting, toxic to larvae.
Flea: Retards growth, repels, inhibits feeding, disrupts growth, eggs fail to hatch.
Flea Beetle: Inhibits feeding.
Fire Ant: Inhibits feeding, disrupts growth.

Green Leafhopper: Inhibits feeding.
Gypsy Moth: Retards growth, inhibits feeding, disrupts growth.

Head Lice: Kills, very sensitive to neem oil - traditional use in Asia.
Horn Fly: Repels, retards growth, disrupts growth.
Housefly: Inhibits feeding, disrupts molting, repels.
House Cricket: Disrupts molting.
House Mosquito: Toxic to larvae.

Japanese Beetle: Repels, retards growth, inhibits feeding, disrupts growth.

Khapra Beetle: Inhibits feeding, disrupts molting, toxic to larvae.

Large Milkweed Bug: Toxic, disrupts growth.
Leafminer: Retards growth, inhibits feeding, disrupts molting, toxic.

Mealy Bugs: Repels, inhibits feeding.
Meditterranean Fruit Fly: Disrupts growth, toxic.
Mexican Bean Beetle: Retards growth, inhibits feeding, disrupts molting.
Migratory Locust: Stops feeding, converts gregarious nymphs into solitary forms, reduces fitness, adults cannot fly.
Milkweed Bug: Difficulty in escaping the "skin" of the last molt, disrupts molting.

Oriental Fruit Fly: Arrest pupae development, retards growth, toxic to larvae.

Pink Hollworm: Retards growth, inhibits feeding.

Red Flour Beetle: Inhibits feeding, toxic.
Rice Gall Midge: Toxic.
Rice Weevil: Inhibits feeding, disrupts growth, toxic.

Serpentine Leafminer: High pupal mortality, retards growth, inhibits feeding, disrupts molting, toxic to larvae.
Sorghum Shoot Fly: Inhibits feeding.
Spotted Cucumber Beetle: Retards growth, inhibits feeding.

Tobacco Budworm: Inhibits feeding.
Tobacco Hornworm: Inhibits feeding, disrupts growth, toxic.

Webbing Clothes Moth: Inhibits feeding, disrupts molting.
Western Thmps: Retards growth.
Whitefly: Repels, retards growth, inhibits feeding.

Yellow-fever Mosquito: Kills larvae, disrupts molting.
_______________________________________________________________

Azadirachta indica: One Tree's Arsenal Against Pests
By Kirk Howatt (Colorado State University)

ABSTRACT
The tree Azadirachta indica is native to parts of South Asia where it has been used for many things. Of primary interest to research scientists is its activity as an insecticide. Many of the tree's secondary metabolites have biological activity, but azadirachtin is considered to be of the most ecological importance. Studies have shown a wide spectrum of activity and species affected. Research has increased in the past few years as the desire for safe pest control methods increases and it becomes apparent that this tree will be able to play a role in integrated pest management systems.


INTRODUCTION
Azadirachta indica has been used for centuries as the country store of developing nations. Earliest reference to it is in Sanskrit writings that are over 4,000 years old (Larson, 1990). Parts of this tree have been used for medicine, shade, building materials, fuel, lubrication, and most of all as pesticides. It is the use of this tree as an insecticide that now draws interest from industrialized countries. It is seen as an environmentally safe alternative to synthetic pesticides. To date over 195 species of insects are affected by this trees extracts at concentrations ranging from 0.1 to 1,000 ppm, and insects that have become resistant to synthetic pesticides are controllable with these extracts (Lindquist et al., 1990; Menn, 1990).


THE NEEM TREE
Azadirachta indica, commonly referred to in many countries as the neem tree, is a member of the Meliaceae family. This broad-leaved evergreen can reach heights of 30 meters with a trunk girth of 2.5 meters and live for over two centuries. Its deep root system is well adapted to retrieving water and nutrients from the soil profile, but this deep root system is very sensitive to waterlogging. The neem tree thrives in hot, dry climates where shade temperatures often reach 50 degrees celsius and annual rainfall ranges from 400 to 1,200 millimeters. The tree can withstand many environmental adversities including drought and infertile, stony, shallow, or acidic soils. The neem produces ellipsoidal drupes, that are about two centimeters in length, borne on axillary clusters. These fruits contain kernels that have high concentrations of secondary metabolites (National Research Council, 1992). There is evidence, but no scientific correlation, that trees grown in climates with lower rainfall produce kernels with higher content of metabolites (Schmutterer, 1990a).

The neem tree is believed to have originated in Assam and Burma of South Asia, but other reports suggest various areas of Pakistan, Sri Lanka, Thailand, Malaysia, and Indonesia (National Research Council, 1992). The tree also grows well in other tropical and subtropical areas around the world (Verkerk et al., 1993). This is very important to commercial neem extract production so that a broad raw material base for industrial refinement can be established. Neem trees have successfully been established in Australia, Haiti, West Africa, the Dominican Republic, Ecuador, Puerto Rico, the Virgin Islands, and in the continental United States in Florida, California, Oklahoma, and Arizona (Jacobson, 1990; Schmutterer, 1990a; Verkerk et al., 1993). The trees growing in Arizona are part of a breeding and selection program aimed at developing a variety that will be frost tolerant to temperatures as low as 18 degrees below zero celsius. Such a development would allow this tree to be established in many more regions. The seed for this project was obtained from natural tree populations growing in northern India where the climate is cooler than most areas where neem grows (Jacobson, 1990).

Cultivation of the neem tree is also an important consideration as the tree is established in new regions. Very little problems arise in vegetative propagation. Transplanting seedlings, saplings, or root suckers achieves a high success rate (National Research Council, 1992). Seeds are more desirable to use when transporting a long distance for ease of packing, however, minor problems have been observed when growing these trees from seeds. It was found that dry or unripe seeds would rot in soil. Large scale establishment of neem trees required germination in sand, transplanting to clay pots after a month, and then planting in the field when the seedlings reached 30 to 45 centimeters in height (Jacobson, 1990).


NEEM CHEMISTRY
The chemicals that have pesticidal activity can most efficiently be extracted from neem seed kernels. Neem trees begin their reproductive stage at about three to five years of age but don't become fully reproductive until they are ten years old. From this time on, the tree will yield an average of about 20.5 kilograms of fruit per year, with maximum production reaching 50 kilograms per year (National Research Council, 1992). Of the fruit yield, only about ten per cent is attributed to seed kernels, and desired biologically active compounds comprise only ten grams per kilogram of kernel weight. This means that an adult neem tree will only produce about 20 grams of pesticidal compounds in a season (Schmutterer, 1990b).

Many biologically active compounds can be extracted from neem, including triterpenoids, phenolic compounds, carotenoids, steroids, and ketones. The tetranortriterpenoid azadirachtin has received the most attention as a pesticide because it is relatively abundant in neem kernels and has shown biological activity on a wide range of insects. Azadirachtin is actually a mixture of seven isomeric compounds labeled as azadirachtin-A to azadirachtin-G with azadirachtin-A being present in the highest quantity and azadirachtin-E regarded as the most effective insect growth regulator (Verkerk et al., 1993). Many other compounds have been isolated that show antifeedant activity as well as growth regulating activity on insects. Polar and non-polar extractions yield about 24 compounds other than azadirachtin that have at least some biological activity (Schmutterer, 1990b; Jacobson, 1990). This cocktail of compounds significantly reduces the chances of tolerance or resistance developing in any of the affected organisms. However, only four of the compounds in neem have been shown to be highly effective in their activity as pesticides: azadirachtin, salannin, meliantriol, and nimbin (Jacobson, 1990; National Research Council, 1992).

These compounds can be extracted by many methods. Leaching with water is the oldest method and is still used by some firms to selectively extract azadirachtin. On the other hand, most companies are using more non-polar solvents to obtain a more varied mixture of chemicals. Hexane, pentane, ethanol, methanol,
esters, and dichloromethane are used in extractions as well as mixtures of these solvents with water (Lee et al., 1988; National Research Council, 1992; Schmutterer, 1990b). Once extracted, several separation techniques are often incorporated to isolate compounds. For instance, in the isolation and identification of
7-deacetyl-17á-hydroxyazadiradione, researchers used insect bioassays to guide reverse phase HPLC fractionation, IR spectrum analysis, 13C NMR and 1H NMR spectrum analysis, and mass spectrum to determine the structure of the active compound (Lee et al., 1988).

By using laboratory techniques, it is possible to closely mimic azadirachtin as it has been identified from the neem tree. Anderson et al. (1990) and Kolb et al. (1991) each describe processes in which they synthesized roughly half of separate ends of the azadirachtin molecule. These subunits form a compound that has similar but less activity than the natural molecule. The activity of synthetic azadirachtin compares close enough to natural products to verify that azadirachtin is the primary toxic compound in neem (Verkerk et al., 1993). Because of the great number of reactions involved in each process, synthetic azadirachtin will be very costly to produce. For this reason, companies developing azadirachtin as a commercial pesticide are working with natural products. W. R. Grace & Co., NPI, and Safer Ltd. are all trying to produce low cost, yet effective, neem-based pesticides (Isman et al., 1990; Walter et al., 1990; Wood, 1990). Research is discovering that initial by-products of azadirachtin extraction have significant efficacy on pests also. Neem seed oils have detrimental effects on viruses, mites, and early larval stages of some insects, while the solid seed residue has enough residual chemical content to have activity on soilborne fungal pathogens and plant parasitic nematodes (Larew, 1990; Locke, 1990; Schmutterer, 1990b).


NEEM EFFECTS
The mode of action of neem extracts is not understood very well. It is quite possible that the different chemicals or different ratios of chemicals found in neem trees have varied effects on insects. There is also evidence given in many research studies, a few of which will be cited later, that insect species react quite differently to compounds from the neem tree.

More research has been conducted to find the primary mode of action of azadirachtin than of any other chemical in the neem tree. This is because of interest in it as a product for commercial use. Azadirachtin alone probably has several modes and sites of action (Koul, 1991). Primary of which is an interference with the neuroendocrine system in insects which controls the synthesis of ecdysone and juvenile hormone. It has been indicated by Schmutterer (1988) that interference involves the inhibition of the release of these hormones. Indication of this was an accumulation of large quantities of stainable neurosecretory material in the corpora cardiaca of Locusta migratoria. In this insect, azadirachtin regulated juvenile hormone titer to prevent vitellogenin production in females, causing sterility. This and other research has convinced many people that azadirachtin definitely has antihormonal activity. However, other evidence indicating that control of hormone concentrations is controlled indirectly leads to the conclusion that azadirachtin is not a true antihormone.

The effect of azadirachtin as an antihormone on juvenile hormone titer was also investigated in the variegated cutworm by Koul et al. (1991). Their goal was to either eliminate or reproduce the effect of azadirachtin on metamorphic abnormalities by artificially raising the concentrations of juvenile hormones I and II or BEPAT, a juvenile hormone esterase inhibitor. They were unable to achieve any desired outcome, but ligation experiments did indicate that the region of activity was in the head capsule. The possibility was proposed that an inhibition of the synthesis of a neurosecretory protein could alter titer levels (Koul et al., 1991). So while azadirachtin has activity on hormone levels, it may be an indirect relationship indicating
that azadirachtin is not a true antihormone. Evidence at this time is not conclusive on the matter of primary mode and site of action, and researchers involved admit that much more investigation is necessary to unwind the mystery (Schmutterer, 1988; Schmutterer, 1990a).

Other research has indicated a more direct role in the inhibition of molting. Direct cytotoxic effects on imaginal discs and epidermal cells result in primary lesions that prevent molting (Koul et al., 1991). Azadirachtin has also been proved to be a chitin synthesis inhibitor, but the role of this inhibition as the primary mode of action has not been investigated (Schmutterer, 1988).

Neem extracts have many effects on insects. The antifeedant and growth regulating effects are the most valued in pest management as these are the most intense effects on the widest range of insects. Other secondary effects that have been studied include repellency, antioviposition, sterility, fecundity reduction, loss of flying ability, disrupting sexual communication, and reducing guttural motility (National Research Council, 1992; Schmutterer, 1990a).


EFFICACY STUDIES
Research has shown that many organisms are sensitive to neem extracts. These include insects from several orders, mites, nematodes, snails, fungi, and viruses (Bhatnagar et al., 1990; Locke, 1990; National Research Council, 1992). Insect control is now the primary use of neem and has been found to be effective against insects by several methods stated earlier. The growth regulation and feeding deterrence of azadirachtin are receiving the most attention, and other effects are studied secondarily as the experiment enables. This is not so much because these responses are less important, but not as many insects show
sensitivity.

Insects have shown the most sensitivity to azadirachtin as a growth regulator. Metamorphic stages are affected in such a way that death often occurs during the molting process. These results are not only dose dependent, but also, response increases with earlier larval stages. Not all species react the same though. A few insects show no mortality or metamorphic abnormalities until the final molt to an adult insect, at which time very high rates of death are observed. Molting inhibition can be seen at very low topical and ingestion rates, one ppm. Even though this was in a laboratory, field rates are effective at rates much lower than those required to elicit other responses (Isman et al., 1990; Schmutterer, 1990b; Stark et al., 1990; Wood, 1990).

Antifeeding effects have received much attention especially in crops that suffer from excessive insect damage. Response by insects to neem extract applications varies greatly across the spectrum of sensitive insects. Even within an order this can be seen. The desert locust is believed to be the most sensitive insect to antifeedant effects of azadirachtin, but the migratory grasshopper feeds undeterred on cabbage treated with 500 ppm, a rate that would deter many other insect species. Growth reduction as a preliminary indication of food refusal can be seen at 0.1 ppm azadirachtin, but antifeedant activity often requires higher concentrations, usually over 200 ppm. In Rhodnius prolixus, antifeedant activity is observed at 600 times the amount needed to disrupt development. Gustatory and non-gustatory sensilla as well as reduced guttural motility may contribute to deterrent responses (Koul et al., 1991; Schmutterer, 1990b; Wood, 1990; Zehnder et al., 1990).

With a large number of organisms being affected by neem extracts, concern was expressed for the welfare of beneficial organisms under management programs using neem tree extracts. It has been found, however that predator and parasitoid insects are relatively unaffected when their life cycle involves exposure to neem extracts. Evidently, azadirachtin does not affect these insects in the same way or not enough chemical is taken up in their diet to cause behavioral or metamorphic abnormalities. Some parasitoids showed slight toxic affects when emerging from treated mummified hosts, but these parasitoids were likely exposed to a much higher dose than normal. Further longevity studies are warranted to determine if extracts have any effects on reproduction or alter fitness of natural enemies (Hoelmer et al., 1990).

The effects of neem on other desirable organisms have led to similar conclusions. In a study conducted by Shapiro et al. (1994), mortality of the gypsy moth was evaluated in the presence of a virus pathogen and also when the moth and virus were subject to neem treatments. Not only did the extracts have no adverse effect on viral activity but, when applied concurrently, moths died sooner. A neem product has shown no toxicity to honeybee workers at rates of 500 ppm. Earthworms actually benefit from soil application of neem by-products with increased weight gain and more progeny (Schmutterer, 1990b). And spiders, butterflies, ants, and ladybugs also show no detrimental effects from exposure to neem tree extracts (National Research Council, 1992).

APPLICATION PROBLEMS
One of the main problems of using neem treatments is the durability of azadirachtin in field conditions. The activity of neem-based products subsides rapidly, lasting four to eight days, meaning that many applications will likely be needed in a season. The primary means of this is photodegradation by ultra-violet light. But leaf pH can also affect detoxification rates, and rain can wash residue off leaf surfaces. Derivation of natural product stabilizes azadirachtin and may provide an avenue for greatly increasing its residual activity (Wood, 1990). Also, activity can be extended in plants, such as potato and tomato, that demonstrate systemic activity. This protects azadirachtin from light and through translocation enables protection of new growth which is often preferred by insects (Klocke et al., 1991, Verkerk et al., 1993).

Systemic activity in plants also relates to a greater chance of phytotoxicity. Potato, onion, cabbage, and chrysanthemum have demonstrated various types and extent of phytotoxicity. In most instances this is undesirable, but the stunting that occurs on chrysanthemums can actually take the place of plant growth regulators that are sprayed for the same effect on plants grown in greenhouses (Oetting et al., 1990; Schmutterer, 1990a).

Azadirachtin content in neem kernels and quickness of activity are further considerations in the commercialization of neem extracts. To provide a consistent product, refining kernels with similar levels of compounds is essential. On the contrary, a Canadian company discovered that samples of neem oil from Indian sources ranged from undetectable amounts, less than 50 ppm, of azadirachtin to 6,800 ppm (Isman et al., 1990). Farmers using synthetic pesticides also are used to quick acting chemicals. They may not be patient enough to wait for the activity of neem-based products to produce results (Schmutterer, 1990b).

CONCLUSION
While neem tree products have some shortcomings as a conventional alternative, they fit in well as a tool to be used in integrated pest management systems. As more and more synthetic chemicals are being pulled from the market, neem is an environmentally benign alternative. It has significant effect on pests without harming beneficial organisms. Toxicology studies have indicated it to be quite safe to mammals also (Schmutterer, 1990b). Researchers, however, still have much work ahead of them to characterize the responses of sensitive insects in the field.

REFERENCES
1. Anderson, J.C. and Ley, S.V. 1990. Chemistry of insect antifeedants from Azadirachta indica (part 7): preparation of an optically pure hydroxyacetal epoxide related to azadirachtin. Tetrahedron Letters. Vol.31: pp. 3437-3440.

2. Bhatnar, D., Zeringue, H.J. Jr., and McCormick, S.P. 1990. Neem leaf extracts inhibit aflatoxin biosynthesis in Aspergillus flavus and A. parasiticus. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 118-127.

3. Hoelmer, K.A., Osborne, L.S., and Yokomi, R.K. 1990. Effects of neem extracts on beneficial insects in greenhouse culture. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 100-105.

4. Isman, M.B., Koul, O., Lowrey, D.T., Arnason, J.T., Gagnon, D., Stewart, J.G., and Salloum, G.S. 1990. Development of a neem-based insecticide in Canada. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 32-30.

5. Jacobson, M. 1990. Review of neem research in the United States. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 4-14.

6. Klocke, J.A. and Kubo, I. 1991. Defense of plants through regulation of insect feeding behavior. Florida Entomologist. Vol.74: pp. 18-23.

7. Kolb, H.C. and Ley, S.V. 1991. Chemistry of insect antifeedants from Azadirachta indica (part 10): synthesis of a highly functionalized decalin fragment of azadirachtin. Tetrahedron Letters. Vol.32: pp. 6187-6190.

8. Koul, O. and Isman, M.B. 1991. Effects of azadirachtin on the dietary utilization and development of the variegated cutworm Peridroma saucia. Journal of Insect Physiology. Vol.37: pp. 591-598.

9. Larew, H.G. 1990. Activity of neem seed oil against greenhouse pests. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 128-131.

10. Larson, R.O. 1990. Commercialization of the neem extract Margosan-O in a USDA collaboration. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 23-28.

11. Lee, S.M., Olsen, J.I., Schweizer, M.P., and Klocke, J.A. 1988. 7-deacetyl-17á-hydroxyazadiradione, a new limonoid insect growth inhibitor from Azadirachta indica. Phytochemistry. Vol.27: pp. 2773-2775.

12. Lindquist, R.K., Adams, A.J., Hall, F.R., and Adams I.H.H. 1990. Laboratory and greenhouse evaluations of Margosan-O against bifenthrin-resistant and -susceptible greenhouse whiteflies, Trialeurodes vaporariorum (Homoptera: Aleyrodidae). In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 91-99.

13. Locke, J.C. 1990. Activity of neem seed oil against fungal plant pathogens. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 132-136.

14. Menn, J.J. 1990. USDA interest in neem research. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 1-3.

15. National Research Council. 1992. Neem: a tree for solving global problems. National Academy Press, Washington, D.C.

16. Oetting, R.D., Sanderson, K.C., and Smith, D.A. 1990. Treatment of cuttings before shipment with neem. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 113-117.

17. Schmutterer, H. 1988. Potential of azadirachtin-containing pesticides for integrated pest control in developing and industrialized countries. Journal of Insect Physiology. Vol.34: pp. 713-719.

18. Schmutterer, H. 1990a. Future tasks of neem research in relation to agricultural needs wordwide. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 15-22.

19. Schmutterer, H. 1990b. Properties and potential of natural pesticides from the neem tree, Azadirachta indica. Annual Review of Entomology. Vol.35: pp. 271-297.

20. Shapiro, M., Robertson, J.L., and Webb, R.E. 1994. Effect of neem seed extract upon the gypsy moth (Lepidoptera: Lymantriidae) and its nuclear polyhedrosis virus. Journal of Economic Entomology. Vol.87: pp. 356-360.

21. Stark, J.D., Vargas, R.I., and Wong, T.Y. 1990. Effects of neem seed extracts on tephritid fruit flies (Diptera: Tephritidae) and their parasitoids in Hawaii. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 106-112.

22. Verkerk, R.H.J. and Wright, D.J. 1993. Biological activity of neem seed kernel extracts and synthetic azadirachtin against larvae of Plutella xylostella L. Pesticide Science. Vol.37: pp. 83-91.

23. Walter, J.F and Knauss, J.F. 1990. Developing a neem-based pest management product. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 29-31.

24. Wood, T. 1990. Efficacy of neem extracts and neem derivatives against several agricultural insect pests. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 76-84.

25. Zehnder, G.W. and Warthen, J.W. 1990. Activity of neem extract and Margosan-O for control of Colorado potato beetle in Virginia. In: Locke, J.C., and Lawson, R.H. (eds.) Proceedings of a workshop on neem's potential in pest management programs. USDA-ARS, Beltsville, MD. ARS-86, pp. 67-75.

Neem America makes no claims about neem and its uses. This article should only be used for informational purposes.

_________________________________________________________

Neem Oil: Facts and Practical Experience
By Larry Evans (Blue Pagoda Orchids)

I can only tell you of my experience with Neem Oil. I cannot recommend Neem oil because our government has not approved its use on orchids or on any plants. When I refer to Neem oil, I mean pure Neem Oil as pressed from the seeds of the Neem tree. I have never used any product with Neem oil in it. I don't know that it would be as safe as pure Neem oil.
Where does Neem oil come from? Originally it came from India. The Indian natives have been using Neem for about 3000 years as an internal remedy as well as an ingredient in tooth paste, soap, shampoo, cosmetics and skin creams.
I have never used a product in the greenhouse whose effects were as efficient and long lasting as Neem. Insecticides and fungicides that I had previously used were a short-term fix - about two weeks. And the smell was offensive and lasted for days. But it was what was available to keep a clean insect free greenhouse even if the fumes from most insecticides caused me to have allergic reactions.

Due to a long term illness, my greenhouse became a disaster area. In January, as the phalaenopsis were spiking, the mealy bugs moved in by the thousands. About 75% of the mature plants had fire ants in the pot. Scale was rampant. We had snails and slugs so big they looked dangerous. Toxic sprays did not get rid of them completely.

The first time I used Neem oil (1 oz. to 1 gallon of water + few drops of dishwashing liquid), I sprayed every plant, bench, walkway and under every bench. In a few days there was a definite improvement. I waited 2 weeks and sprayed again. I kept a close eye on the plants, no mealy bugs, scale and best of all the fire ants were gone. And no more slugs and snails. I didn't spray again for six months. I found a snail and a slug, no other 'live stock', but I decided to spray everything again. The beauty part of using Neem oil is that you don't have to wear protective clothing or special breathing equipment and there are no sickening odors. Neem oil does have an odor, best described as 'kind of like onion soup'. However, the odor only lingers for a short time.

How does Neem get rid of insects? Most insects die shortly after spraying. Those remaining become sterile and do not reproduce. I've heard a story of 2 desert locusts, 2 grape leaves and 2 bell jars. One grape leaf was sprayed with an insecticide, the other with Neem. One locust and one grape leaf were put under each bell jar. The locust ate the toxic leaf and died. The other locust refused to eat the Neem sprayed leaf and starved to death. From my experience the story could be true. I believe it is better if you can prevent the insect from eating the plant, than to let them eat the plant and then die. It takes years to lose the damaged leaves on most orchids. Flowers can be ruined before the critters will die from insecticide. I've not been disappointed with Neem Oil. I'm sure that many who read this will be sceptical because of the 'do everything' claim.

We have a cat that has grown up in the greenhouse. Neem hasn't bothered her at all. Panzie greets all comers and we certainly would not use anything that would hurt her.

We also used Neem on my daughter's dog, a Shar-pei. The dog was biting and chewing her fur and making sores and bald spots all over her coat. The veterinarian said she had hair mites. There is a treatment for this - a series of 6 dips at $65.00 per dip and only a 50% chance of a cure.

I suggested that she try using a 'Neem rinse' after bathing the dog, using a 1 oz. to 1 gallon of water. This treatment was followed for three weeks. The dog has stopped chewing herself and has grown back a full glossy coat.

It is also harmless on people. A lady in our orchid society has an allergy to mosquito bites. Living in Florida she had a problem working in her garden, fishing or taking an evening stroll. She had used spray repellents but it was difficult to use and not always satisfactory. She tried Neem oil and she swears by it.

When I use Neem oil I only mix the amount I will use within four hours. Neem is very biodegradable and will start to break down quickly. If it is kept in the refrigerator at approximately 40F the shelf life is extended. As any organic oil, it will turn rancid. How soon will depend on the storage temperature.

We have used pure Neem oil on cattleya, dendrobium, phaleanopsis, oncidiums, vanilla, vanda, peristeria, etc. We have detected no damage to any of these plants.

Have you tried Neem Oil? Drop me a note and let me know your experiences with it.

Neem America makes no claims about neem and its uses. This article should only be used for informational purposes.