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Spices provide eco-friendly pesticides for organic fruits and veggies

Mention rosemary, thyme, clove, and mint and most people think of a delicious meal. Think bigger … acres bigger.

Mention rosemary, thyme, clove, and mint and most people think of a delicious meal. Think bigger … acres bigger.

Natural pesticides made of spices show promise as an eco-friendly way to fight insects that destroy organic food crops. Shown is Dr. Murray Isman of the University of British Columbia. Advertisement

These well-known spices are now becoming organic agriculture’s key
weapons against insect pests as the industry tries to satisfy demands
for fruits and veggies among the growing portion of consumers who want
food produced in more natural ways.

In a study presented recently at the American Chemical Society’s 238th
National Meeting, Canadian scientists reported new research on
essential oil pesticides, also known as killer spices. These substances
are 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.

Over the past decade, Dr. Murray Isman of the University of British
Columbia and his colleagues have 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 Dr. Isman. “They’re still only a small piece of the
insecticide market, but they’re growing and gaining momentum.”

The natural pesticides have several advantages. Unlike conventional
pesticides, these killer spices do not require extensive regulatory
approval and are readily available. An additional advantage is that
insects are less likely to evolve resistance — the ability to shrug off
once-effective toxins — Dr. Isman says. They’re also safer for farm
workers, who are at high risk for pesticide exposure, he notes.

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, Dr. Isman says. Researchers are now seeking ways of
making the natural pesticides longer lasting and more potent, he notes.

“They’re not a panacea for pest control,” cautions Dr. Isman.
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, Dr. Isman notes.

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.