It's a jungle out there.

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 — 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.

A number of previous posts have discussed poisons and noxious chemicals synthesized by plants to repel or kill herbivores. It's an evolutionary arms race as old as life. Predators range from microorganisms to insects to every other large life form except perhaps carnivores since they prey on one another rather than plants.

The natural pesticides have several advantages. Unlike conventional pesticides, these "killer spices" do not require extensive regulatory approval and are readily available.

Like tax evasion, regulatory evasion is always a good thing. It's good for people to evade such predators, and good for the predators too since this provides motivation to develop ever more stringent controls, and increase budgets and staff. It's another sort of evolutionary arms race.

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.

Giving evolution a human assist.

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."

The "killer spices" aren't just limited to agricultural use. Some show promise in the home as eco-friendly toxins and repellents against mosquitoes, flies, and roaches. Unlike conventional bug sprays, which have a harsh odor, 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 notes.

See Linalool for related discussion.

Manufacturers have already 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 currently exploring the insect-fighting potential of lavender, basil, bergamot, patchouli oil, and at least a dozen other oils from exotic plant sources in China.

There's an interesting thread of history that investigates the geopolitical consequences of the spice trade of antiquity. When the subject is expanded a bit to include spices that we call drugs is becomes clearer that this is a still relevant view of the world. The spices of life, and death, rank right up there with food and sex as major issues for primates.