伊詩曼表示，天然殺蟲劑的好處是不需要經過冗長與繁複監管部門的批准，並且隨處可得。另外一個優點是，昆蟲不太容易發展出抗藥性 -- 能夠擺脫一次性有效的毒素。此外，天然殺蟲劑對常與農藥接觸的高風險農場工人也比較安全。
Common kitchen spices such as rosemary, thyme, clove, and mint, nick-named "killer spices," are proving effective as pesticides in organic agriculture's battle against insects as the industry tries to meet the growing demand for fruits and vegetables that are free of toxic chemicals.
In a study presented Sunday at the opening day of the American Chemical Society's national meeting in Washington, scientists from the University of British Columbia presented new research into what they are calling "essential oil pesticides."
"We are exploring the potential use of natural pesticides based on plant essential oils - commonly used in foods and beverages as flavorings," said study presenter Murray Isman, PhD, a professor of agroecology at UBC.
"We are developing insecticides, miticides, fungicides and herbicides using various plant essential oils as the active ingredients," he said.
The new pesticides are generally a mixture of small amounts of two to four different spices diluted in water. Some kill insects, while others repel them.
Research indicates that the spicy oils act by interfering with insects' nervous systems or by breaching their cell membranes, causing death.
To their credit, the natural pesticides do not require extensive regulatory approval and are readily available. An additional advantage is that insects are less likely to evolve resistance - the ability to shrug off once-effective toxins - Isman says. They are also safer for farm workers, who are at high risk for pesticide exposure, he says.
But there are also drawbacks to using the new pesticides. 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 the 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.
According to the U.S. Environmental Protection Agency, at least one pesticide product is used indoors by 75 percent of U.S. households each year and that 80 percent of the average person's exposure to pesticides occurs indoors.
Other scientists are exploring the insect-fighting potential of lavender, basil, bergamot, patchouli oil, and at least a dozen other oils from exotic plant sources in China.