Insecticidal properties of some spice oils
'Killer Spices' Provide Eco-friendly Pesticides For Organic Fruits And Veggies ScienceDaily (Aug. 18, 2009) Â Mention rosemary, thyme, clove, and mint and most people think of a delicious meal. Think biggerÂacres bigger. These well-known spices are now becoming organic agriculture's key weapons against insect pests as the industry tries to satisfy demands for fruits and veggies among the growing portion of consumers who want food produced in more natural ways.
In a study presented at the American Chemical Society's 238th National Meeting, scientists in Canada are reporting exciting new research on these so-called "essential oil pesticides" or "killer spices." These substances represent a relatively new class of natural insecticides that show promise as an environmentally-friendly alternative to conventional pesticides while also posing less risk to human and animal health, the researcher says.
"We are exploring the potential use of natural pesticides based on plant essential oils Â commonly used in foods and beverages as flavorings," says study presenter Murray Isman, Ph.D., of the University of British Columbia. These new pesticides are generally a mixture of tiny amounts of two to four different spices diluted in water. Some kill insects outright, while others repel them.
The natural pesticides have several advantages. Unlike conventional pesticides, these "killer spices" do not require extensive regulatory approval and are readily available. An additional advantage is that insects are less likely to evolve resistance Â the ability to shrug off once-effective toxins Â Isman says. They're also safer for farm workers, who are at high risk for pesticide exposure, he notes.
But the new pesticides also have shortcomings. Since essential oils tend to evaporate quickly and degrade rapidly in sunlight, farmers need to apply the spice-based pesticides to crops more frequently than conventional pesticides. Some last only a few hours, compared to days or even months for conventional pesticides. As these natural pesticides are generally less potent than conventional pesticides, they also must be applied in higher concentrations to achieve acceptable levels of pest control, Isman says. Researchers are now seeking ways of making the natural pesticides longer-lasting and more potent, he notes.
"They're not a panacea for pest control," cautions Isman. Conventional pesticides are still the most effective way to control caterpillars, grasshoppers, beetles and other large insects on commercial food crops, he says. "But at the end of the day, it comes down to what's good for the environment and what's good for human health."
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