Neem A Tree for Solving Global Problems (1992) / Chapter Skim
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6 Effects on Other Organisms
6 Effects on Other Organisms
Pages 51-59
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From page 51... ...
Certain limonoid fractions extracted from neem kernels are proving active against root-knot nematodes, the type most devastating to plants. They inhibit the larvae from emerging and the eggs from hatching, and in at least one test they have done so at concentrations in the parts-per-million range.' Water extracts of neem cake (the residue remaining after the oil has been pressed out of the seeds)
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From page 52... ...
This minute aquatic crustacean thereby reduces a source of fertilizer for the crop. Killing this tiny creature thus would indirectly boost the nitrogen available and probably increase rice yields.6 Aqueous neem-kernel extracts have killed it very effectively under laboratory conditions.7 3 Information from S
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From page 53... ...
, the standard mildew treatment in much of the world.9 In the case of bean rust, neem extracts have given 90 percent control when applied before the plants were exposed to the fungus. However, they worked poorly once rust was established.'° In addition to affecting root-knot nematodes, treating soil with neem can reduce the populations of pest fungi in the rhizosphere that attack and feed off plant roots.
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From page 54... ...
Once they are identified, cost-effective and efficient delivery systems can probably be developed to control aflatoxin synthesis by the fungus on various crops. Bhatnagar says that the results are "promising but preliminary." But if his work proves that neem is safe and effective for aflatoxin control, it may open the door to a simple, inexpensive method for protecting stored foods using locally produced materials, even in the remotest rural villages.
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From page 55... ...
Aflatoxin causes liver cancer, and under hot and humid conditions, where fungi thrive, it can form on peanuts, corn, cottonseed, and other widely eaten food crops. It is of great concern these days; it not only threatens health, it also promises economic catastrophe.
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From page 56... ...
In the first of these trials, James Locke, a plant pathologist, emulsified neem oil in water, sprayed it over various types of ornamental plants in pots, and then subjected the plants to rust or powdery mildew. "We had success with emulsions containing as little as 0.25 percent oil," Locke says.
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From page 57... ...
These tests include the following: · A trial in the Philippines where rice fields sprayed with neem oil had significantly lower incidence of the ragged-stunt virus, which affects rice and is transmitted by the brown planthopper;~4 · A second trial in the Philippines where mixtures of neem oil and custard-apple oil interfered with the transmission of tungro virus, another rice pest;~5 · Experiments in India where neem-leaf extracts reduced the transmission of tobacco mosaic, a virus that seriously affects several vegetable crops; · Field trials in the Philippines where fields treated with urea and neem cake were found to be lower in viral diseases than those treated with urea alone;'7 and · Enzyme-linked immunosorbent assays showing that rice seedlings grown in soil treated with neem cake were significantly freer of rice tungro viruses (transmitted by green rice leafhopper) than those in untreated control plots.'8 On the other hand, not all trials have been this successful.
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From page 58... ...
Earthworms In greenhouse studies, when neem leaves and seed kernels were incorporated into potting soil containing earthworms (Eisenia foetida) , the number of young worms produced increased 25 percent.20 In field trials there were no differences in the number of worms, but the average weight of each worm was highest in neem-treated plots.
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From page 59... ...
. The aphids in the neem-treated plots were actuaNy copying more parashes than were those in either the control plots or the plots treated with the insecticide pyrethrums 24 Isman al al., in press.
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