'Killer Spices' Fatal to Insect Pests

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.

Dr. Murray Isman with eco-friendly pesticides made of essential oils. (Photo by Martin Dee courtesy UBC)

"We are developing insecticides, miticides, fungicides and herbicides using various plant essential oils as the active ingredients," he said.

Over the past decade, Isman and colleagues tested many plant essential oils and found that they have a broad range of insecticidal activity against agricultural pests.

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.

Some spiced-based commercial products now being used by farmers have shown success in protecting organic strawberry, spinach, and tomato crops against destructive aphids and mites, Isman says.

"These products expand the limited arsenal of organic growers to combat pests," he said. "They're still only a small piece of the insecticide market, but they're growing and gaining momentum."

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.

"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."

Some essential oil pesticides show promise in the home as eco-friendly toxins and repellents against mosquitoes, flies, and roaches. Unlike conventional bug sprays, these natural pesticides tend to have a pleasant, spicy aroma. Many contain the same oils that are used in aromatherapy products, including cinnamon and peppermint, Isman observes.

Funding for this study was provided by EcoSMART®, a botanical pesticide company based in Alpharetta, Georgia. EcoSMART Technologies sells products of this type for the agricultural, industrial and consumer markets in the United States.

Steve Bessette, president and founder of EcoSMART Technologies, says, "Most Americans don't realize that they can kill household insects like ants and roaches with botanical products. Our new aerosols and mosquito repellent are not only as effective as conventional pesticides, but they protect children and pets from harmful chemical residues," he noted.

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.

Manufacturers also have developed spice-based products that can repel ticks and fleas on dogs and cats without harming the animals. Researchers are now exploring the use of other spice-based products for use on fruits and vegetables to destroy microbes, such as E. coil and Salmonella, which cause food poisoning.

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.

Copyright Environment News Service, ENS, 2009. All rights reserved.