Herbs show promise as pesticides

The essential oils of herbs like rosemary, thyme, clove and mint have a broad range of insecticidal activity. Researchers at the Univ. of British Columbia have found herb-based insecticides can kill pests outright or repel them. The pesticides are usually a mixture of 2-4 different herbs diluted in water. Some growers are already using spice-based commercial products to control aphids and mites on organic crops such as strawberries, spinach and tomatoes. “We are exploring the potential use of natural pesticides based on plant essential oils — commonly used in foods and beverages as flavorings,” said Univ. of British Columbia professor Murray Isman. The natural pesticides have several advantages: they don’t require extensive regulatory approval; they are readily available; insects are less likely to evolve resistance to them and they are safer for workers. Disadvantages of these natural compounds include: essential oils tend to evaporate quickly and degrade rapidly in sunlight; they are generally less potent than conventional pesticides and may need to be applied in higher concentrations to achieve satisfactory control.