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Another natural from neem.

Another Natural From Neem

Finding it in a greenhouse, you could easily mistake the young plant for a graceful ornamental fern, but it will mature into a full-sized tree. Its nut resembles a shelled peanut or a large citrus seed. Although not much to look at, neem seed has some extraordinary characteristics.

"ARS scientists have been working with neem since 1975," says James C. Locke. "Our current focus is to develop natural products from the plant that can reduce our dependency on synthetic pesticides."

And that's what they're doing at the ARS Florist and Nursery Crops Laboratory in Beltsville, Maryland.

Locke, a plant pathologist, entomologist Hiram E. Larew (formerly with ARS, now with the Agency for International Development), and James F. Walter, an engineer from W.R. Grace & Company, have teamed up to discover a new use for neem seed oil. They've found it can harmlessly control rust on beans and snapdragons and powdery mildew on numerous ornamentals without harming the plants.

Although neem seed extracts are being used as a botanical insecticide, this is the first time the seed's oil has been used successfully against fungal plant pathogens.

Locke says they emulsified extracted neem seed oil in water and used it as a full coverage spray, then subjected the plants to powdery mildew or rust. "We had success with applications containing as little as 0.25 percent oil," Locke says.

"We've been working on this project for about 2 years now. We've actually been using a byproduct from the production of the neem insecticide that the firm of W.R. Grace is marketing," Locke says. "The most exceptional characteristic of this oil is its ability to exhibit both insecticidal and fungicidal properties."

"We don't really know how the oil-water mixture works since the neem oil doesn't contain azadirachtin, the insecticidal compound found in the seed," Locke says.

But work it does. J. Rennie Stavely, of ARS' Microbiology and Plant Pathology Laboratory, reports the compound was nearly 100 percent effective against bean rust in greenhouse tests. Although its performance was not quite as dramatic in the field, the spray worked well enough to be economically feasible.

And when compared with commercially available petroleum-based horticultural oils, the neem-derived fungicide was more effective against both bean and snapdragon rusts.

PHOTO : Plant pathologist James Locke displays neem seeds oil, a source of natural insecticide and fungicide.
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Author:Stanley, Doris
Publication:Agricultural Research
Date:Jun 1, 1991
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