How to Use Neem as a Natural Pesticide
Contents
Other Names
En: neem, Indian lilac, Fr: azadira d'Inde, margousier, azidarac, azadira Pt: margosa (Goa) Es: margosa, nim De: Niembaum Hindi: neem, nimb Burmese: tamar, tamarkha Urdu: nim, neem Punjabi: neem Tamil: vembu, veppan Sanskrit: nimba, nimbou, arishtha (reliever of sickness) Sindhi: nimmu Sri Lanka: kohomba Farsi: azad darakht i hindi (free tree of India), nib Malay: veppa Singapore: kohumba, nimba Indonesia: mindi Nigeria: dongoyaro Kiswahili: mwarubaini (muarobaini)
Description
Among Neem's many benefits, the one that is most immediately practical is the control of farm and household pests.
Some entomologists now conclude that neem has such remarkable powers for controlling insects that it will usher in a new era in safe, natural pesticides: neem compounds usually leave the pests alive for some time, but so repelled, debilitated, or hormonally disrupted that crops, people, and animals are protected.
Extracts from its extremely bitter seeds and leaves may, in fact, be the ideal insecticides: they attack many pestiferous species; they seem to leave people, animals, and beneficial insects unharmed; they are biodegradable; and they appear unlikely to quickly lose their potency to a buildup of genetic resistance in the pests.
For centuries, India's farmers have known that the Neem trees withstand the periodic infestations of locusts. Neem extracts applied to vegetable crops repel locusts (Heinrich Schmutterer, 1962).
Like most plants, neem deploys internal chemical defences to protect itself against leaf- chewing insects. Its chemical weapons are extraordinary, however.
Neem contains several active ingredients, and they act in different ways under different circumstances.
These compounds bear no resemblance to the chemicals in today's synthetic insecticides. Chemically, they are distant relatives of steroidal compounds, which include cortisone, birth-control pills, and many valuable pharmaceuticals. Composed only of carbon, hydrogen, and oxygen, they have no atoms of chlorine, phosphorus, sulfur, or nitrogen (such as are commonly found in synthetic pesticides). Their mode of action is thus also quite different.
Neem products are unique in that (at least for most insects) they are not outright killers. Instead, they alter an insect's behavior or life processes in ways that can be extremely subtle. Eventually, however, the insect can no longer feed or breed or metamorphose, and can cause no further damage.
For example, one outstanding neem component, azadirachtin, disrupts the metamorphosis of insect larvae.
By inhibiting molting, it keeps the larvae from developing into pupae, and they die without producing a new generation. In addition, azadirachtin is frequently so repugnant to insects that scores of different leaf-chewing species - even ones that normally strip everything living from plants - will starve to death rather than touch plants that carry traces of it.
Another neem substance, salannin, is a similarly powerful repellent.
It also stops many insects from touching even the plants they normally find most delectable. Indeed, it deters certain biting insects more effectively than the synthetic chemical called "DEET" (N,N-diethy- lm-toluamide), which is now found in hundreds of consumer insect repellents.
These pesticidal "cocktails," containing 4 major and perhaps 20 minor active compounds, can be astonishingly effective. In concentrations of less than one-tenth of a part per million, they affect certain insects dramatically. In trials in The Gambia, for example, these crude neem extracts compared favorably with the synthetic insecticide malathion in their effects on some of the pests of vegetable crops. In Nigeria, they equaled the effectiveness of DDT, Dieldrin, and other insecticides. And elsewhere in the world these plant products have often showed results as good as those of standard pesticides.
Although pests can become tolerant to a single toxic chemical such as malathion, it seems unlikely that they can develop genetic resistance to neem's complex blend of compounds - many functioning quite differently and on different parts of an insect's life cycle and physiology:For example, even after being exposed to neem for 35 successive generations, diamondback moths remained as susceptible as they had been at the beginning.
Another valuable quality is that some neem compounds act as systemic agents in certain plant species.
That is, they are absorbed by, and transported throughout, the plants. In such cases, aqueous neem extracts can merely be sprinkled on the soil. The ingredients are then absorbed by the roots, pass up through the stems, and perfuse the upper parts of the plant. In this way, crops become protected from within. In trials, the leaves and stems of wheat, barley, rice, sugarcane, tomatoes, cotton, and chrysanthemums have been protected from certain types of damaging insects for 10 weeks in this way.Because systemic materials are inside the plant, they cannot be washed off by rain.
Pest toxicity
In tests over the last decade, entomologists have found that neem materials can affect more than 200 insect species as well as some mites, nematodes, fungi, bacteria, and even a few viruses. The tests have included several dozen serious farm and household pests
- Mexican bean beetles,
- Colorado potato beetles,
- locusts, grasshoppers,
- tobacco budworms,
- and six species of cockroaches, for example.
Success has also been reported on:
- cotton and tobacco pests in India, Israel, and the United States;
- cabbage pests in Togo, Dominican Republic, and Mauritius;
- rice pests in the Philippines;
- coffee bugs in Kenya.
- Neem products have protected stored corn, sorghum, beans, and other foods against pests for up to 10 months in some very sophisticated controlled experiments and field trials.
- Neem extracts will protect Soybeans from the Japanese beetles: In one test in Ohio, soybeans sprayed with neem extract stayed untouched for up to 14 days, untreated plants in the same field were chewed to pieces by various species of insects, seemingly overnight
Receipes
To obtain the insecticide from Neem is simple (at least in principle). The leaves or seeds are merely crushed and steeped in water, alcohol, or other solvents. For some purposes, the resulting extracts can be used without further refinement.
For example, grind 1kg of nuts from the neem fruit, mix the powder with 15 litres of water and leave to soak for 24 hours.
Links
Link to Fourthway's poster "How to make a natural pesticide": http://www.fourthway.co.uk/posters/pages/pesticide.html
Related articles
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- What to Do with Neem Seeds
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