Kitchen herbs used as safer, less destructive pesticides

Essential oils extracted from common kitchen herbs and spices can be used as safer, less destructive pesticides, according to research led by Murray Isman of the University of British Columbia and presented at the Fall Meeting of the American Chemical Society in Washington, D.C.

"We are exploring the potential use of natural pesticides based on plant essential oils -- commonly used in foods and beverages as flavorings," Isman said.

Isman's team has been researching the pest control properties of clove, mint, rosemary and thyme for 10 years, and has found that diluted mixtures of the essential oils from two to four of the plants can be used to both repel and kill agricultural pests. These natural pesticides have been effectively used to fight aphids and mites that would otherwise prey on spinach, strawberry and tomato crops.

The essential oils provide several major advantages over synthetic pesticides. They are significantly less toxic to farm workers and the surrounding environment than synthetic chemicals. Because they break down quickly, they are less likely to cause lasting harm to the environment or human health. Researchers also claim that insects are less likely to evolve resistance to the plant compounds.

Because they are not engineered but simply extracted from foods already deemed safe, essential oil pesticides do not need regulatory approval and can be used on organic crops.

Because the essential oils degrade so quickly in the environment, however -- lasting as little as a few hours -- they need to be applied relatively frequently. In comparison, synthetic pesticides may remain in the soil for months and resist breakdown long after this time, which is part of what makes them so dangerous. The herb and spice-based pesticides also need to be applied in larger doses than synthetic pesticides.

"They're not a panacea for pest control," Isman said. "It comes down to what's good for the environment and what's good for human health."