Adult (center) and immature turnip aphids. (Image courtesy Alton
N. Sparks, Jr., The University of Georgia,
www.insectimages.org).
|
Turkish Plant Oils Are Lethal to Vegetable
Pest
By Luis
Pons December 20, 2004
Turnip aphids beware! Scientists at the
Agricultural Research Service and at
Anadolu University in
Eskisehir, Turkey, have found that oils from many Turkish medicinal herbs are
deadlier to the aphid pests than those currently used in biological pesticides.
Studies at two ARS laboratories in Mississippi--the
Natural
Products Utilization Laboratory in Oxford and the
Small
Fruit Research Station in Poplarville--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, which attack collards, mustard, broccoli, cabbage,
radish, tomato and zucchini, among other vegetable crops throughout the
southeastern United States.
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 at Oxford and horticulturist
James
Spiers and entomologist
Blair
Sampson at Poplarville, along with Turkish colleagues led by chemist
Nurhayat Tabanca, identified essential oils--many from wild plants--that
achieve 100-percent 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.
According to Wedge, future efforts may include collaborations with
other universities in Turkey and technology transfer of advanced bioassay
techniques for agrochemical research.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.