Killer Spices Double as Natural Pesticides

Rosemary, thyme, clove and mint have the power to kill or repel insects.

They don't work nearly as well as conventional chemical pesticides, but they don't have the negative environmental repercussions -- and scientists are working on developing more effective spice-based pesticide concoctions.

A team of researchers at the University of British Columbia has spent the past decade investigating the potential of these spices, and the researchers presented their findings Sunday at an American Chemical Society conference in Washington D.C.

Typically the natural pesticides are made from a mixture of two or more spices. The mixtures are non-toxic, pose no threat to farm workers, and require little or no regulatory approval. Furthermore, insects are less likely to develop resistance to them the way they do to conventional chemical pesticides.

But the spice mixtures have to be used in massive quantities to be effective, and they have the unfortunate habit of quickly degrading in sunlight or evaporating -- some within a few hours of application. Lead researcher Professor Murray Isman said his team is exploring ways to fix these problems.

But in the meantime, Isman said, spice-based pesticides have worked well for many organic crops, such as strawberries, tomatoes and spinach. These natural pesticides, he said, are "still only a small piece of the insecticide market, but they're growing and gaining momentum."