(Beyond Pesticides, August 20, 2009) A new study presented to the American Chemical Society last weekend shows promising results for alternative pesticides made from the essential oils of plants. Spices such as cinnamon, rosemary, thyme, clove and mint are extracted and then diluted in water to repel and sometimes kill pests. The study, Plant Essential Oils as Green Pesticides for Pest and Disease Management, was presented by Dr. Murray Isman, PhD., of the University of British Columbia at the American Chemical Society’s 238th National Meeting.
Over the past decade, Dr. Isman and colleagues tested many plant essential oils and found that they have a broad range of insecticidal activity against agricultural pests. Some spiced-based commercial products now being used by farmers have already shown success in protecting organic strawberry, spinach, and tomato crops against destructive aphids and mites, the researcher says.
“These products expand the limited arsenal of organic growers to combat pests,” explains Isman. “They’re still only a small piece of the insecticide market, but they’re growing and gaining momentum.”
These natural pesticides have several advantages. First of all, Dr. Isman says that insects are less likely to evolve resistance to these oils like they can other once-effective toxins. They’re also safer for farm workers, who are at high risk for pesticide exposure. Essential oils also do not require extensive regulatory approval and are already widely available as inexpensive ingredients for food flavorings and in perfume.
Certain plant essential oils have different qualities. In his research, Dr. Isman found that mints, thyme, rosemary, clove, citrus, have a wide range of insecticidal activity that can be utilized for integrated pest management in organic food production. Rosemary and thyme are useful for preventing against plant pathogenic fungi such as powdery mildew, while others, like clove, and citrus are toxic to other plants at certain concentrations and can be used as herbicides.
According to his research, the oils may interfere with the insect nervous system of pests, making the muscles spasm. In some cases, essential oils can disrupt an insect’s cell membranes, causing the insect’s fluids to leak, thus killing it. His research also suggests that the plant oils are most effective against small, soft-bodied bugs that suck on plant juices, such as aphids, whiteflies, and spider mites. These bugs also have large surface areas relative to their internal volume, so more of the bug is likely to come into contact with the oil, he added.
“Small, soft-bodied insects are more vulnerable to having their membranes melted or smothered by the oils,” Isman said.
Since essential oils tend to evaporate quickly and degrade rapidly in sunlight, the spice-based pesticides needs to be applied to crops more frequently than conventional pesticides. Some last only a few hours, compared to days or even months for conventional pesticides. And, because these natural pesticides are much less toxic than conventional pesticides, they will likely be applied in higher concentrations. Due to these reasons, researchers are now seeking ways of making the natural pesticides longer-lasting and more potent.
“…At the end of the day, it comes down to what’s good for the environment and what’s good for human health,” explains Dr. Isman.
Beyond its use in agriculture, research is also being done to examine the effectiveness of essential oils for use in the home as a more eco-friendly and safer approach to combating pests such as mosquitoes, flies, and roaches. Conventional bug sprays that use DEET can cause numerous health problems. These chemicals can also have a harsh odor, while these natural pesticides tend to have a pleasant, spicy aroma since many contain the same oils that are used in aromatherapy products, including cinnamon and peppermint, Isman notes.
Spice-based products are also being developed to repel ticks and fleas on dogs and cats without harming the animals. And, researchers are currently exploring the use of other spice-based products to destroy microbes, such as E. coil and Salmonella, on fruits and vegetables.
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. Funding for this study was provided by EcoSMART ®, a botanical pesticide company based in Alpharetta, Ga.
Beyond Pesticides has long been an advocate for the use of non-toxic and least toxic pesticide alternatives. Essential oils are classified as a least-toxic method for pest management, because products that are designed to kill living organisms should be treated with caution.
The concern with essential oils is its volatility and ability to vaporize into the air. It is important to remember that there is still a potential to cause harm to human and environmental health and to read labels on all products before using to make sure it does not also include any toxic pesticides, synergists or non-disclosed inert ingredients. Also, if you are chemically sensitive, you will need to carefully evaluate the product to decide whether it makes sense for you to use.
For more information on alternative ways to manage pests, please see our Alternatives Fact Sheet.
Source: The American Chemical Society
Study: Plant Essential Oils as Green Pesticides for Pest and Disease Management, Agricultural Applications in Green Chemistry, Editor(s): William M. Nelson1, Volume 887, Publication Date (Print): July 07, 2004, Copyright © 2004, American Chemical Society