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| Plant Oils lethal to vegetable pest | |
Scientists in have discovered that oils from many medicinal herbs native to Turkey are deadlier to the aphids than currently used biological pesticides. Studies at two Agricultural Research Service laboratories in found that essential oils from 17 plant species are more toxic to turnip aphids (Lipaphis pseudobrassicae) than oils of peppermint (Mentha piperita) and rosemary (Rosmarinus officinalis), which are used in the United States as organic pesticides and in broad-spectrum insecticides. The researchers evaluated essential oils from 25 plant species for toxicity to turnip aphids. The aromatic essential oils help plants attract or repel insects and fend off heat, cold and bacteria. Obtained from air-dried flowering plants, the oils are used in the pharmaceutical, agrochemical, cosmetics and food industries. Because their bioactive compounds are potentially toxic to insects and mites but relatively safe to humans and wildlife, they've recently become the focus of developers of ecologically safe pesticides. Plant pathologist David Wedge, horticulturist James Spiers and entomologist Blair Sampson from the ARS along with Turkish colleagues led by chemist Nurhayat Tabanca, identified essential oils many from wild plants that achieve 100% kill rates at much lower concentrations than peppermint and rosemary oil. The researchers found that species of Bifora, Satureja and Salvia are the more promising botanical sources of compounds for new pesticides targeting aphids. The scientists were most impressed by the wild bishop plant, Bifora radians. It yielded the least essential oil, but that oil was by far the most toxic to the aphids. For further information: www.ars.usda.gov |
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