Myth busted: There’s no such thing as pesticide-free produce |

Myth busted: There’s no such thing as pesticide-free produce

Curt Swift
Free Press Gardening Columnist

Aphids. There are a lot more aphids this year than in years past due to the stress of last fall and the harshness of this past winter. Plants under stress signal their stress by giving off volatile chemicals attracting aphids as well as other insects. In addition to giving off organic volatiles, stressed plants produce compounds that provide aphids the compounds necessary to increase their body size and the number of baby aphids they give birth to.

Unlike many other insects, aphids give live birth and their baby aphids are already pregnant with the next generation of aphids. As a result of the improved nutrition of the aphids due to plant stress and live birth, the population of aphids can increase astronomically. That is what is happening this year. To control aphids, many commercial pest control professionals and gardeners apply a pesticide.

The other day I was visiting with Oli at Café V on Fifth and Belford. I stop there on occasion for a vanilla latte and we started talking about gardening and pesticides. Oli mentioned the number of people growing their own vegetables so they could eat healthy, pesticide-free food. When people grow their own fruits and vegetables, they can decide what to use to control pests like aphids. It might be a synthetic product or it could be a biological insecticide. In both cases that product is still a pesticide.

Many people use the word pesticide to mean insecticide, meaning something that kills insects. When you break pesticide into its component parts you have pest and cide. Cide means to kill. The meaning of pest is obvious. Rodents can be pests when they feed on the grains in your pantry; mites can be pests when they feed on John’s juniper trees; and aphids are pests when they attack your pine tree. Even nematodes can be pests when they feed on the leaves and stems in your alfalfa field. Many different pests exist. Even a fungus like powdery mildew is considered a pest. Thus, the term pesticide means a material used to manage a pest, not just insects.

While the correct meaning of the word pesticide means to kill pests, the Environmental Protection Agency uses a wider definition. To them pesticide means anything that prevents, mitigates or destroys a pest. The spray of lavender hydrosol you use in your hotel room to repel bedbugs is considered a pesticide yet hydrosol is a combination of water and volatile organic compounds distilled from the plant. Nothing can be more natural. Bacillus thuringiensis (Bt) is a natural and common bacterium used to kill cabbage worms, web worms, and other insect pests. Many people believe all pesticides are synthetic but they are wrong. They can be synthetic or natural. The diatomaceous earth added to grain bins to kill insects feeding on the grain is, in this case, used as a pesticide.

Gardeners often say they want to purchase pesticide-free fruits, vegetables and herbs. What they really mean is they don’t want to purchase food products that have been treated with a synthetically-manufactured pesticide. Almost every fruit, vegetable and herb you purchase has been treated with a pesticide. Many gardeners will use spinosad, an organic-approved pesticide for insect control. Or, they might use pyrethrum, an insecticide obtained from the dried flower heads of a chrysanthemum. They might use diatomaceous earth as a dust to kill insects. Other gardeners spray their pumpkin and squash plants with a natural product called potassium bicarbonate to control powdery mildew? Even sodium bicarbonate when used on plants to kill powdery mildew is considered a pesticide. Sodium bicarbonate, also known as baking soda, is used in toothpaste so how toxic can it be? And it is natural. Some gardeners use wood ash or lime to control caterpillars on their cabbage or aphids on their broccoli. Those natural compounds used in this manner are pesticides.

When people tell me all pesticides are bad and should never be used, I wonder if they really know what a pesticide is. The GMO-free organic corn gluten they use for weed control, the antibiotic their doctor might prescribe for an infection, and the salt they use to kill weeds in their asparagus patch are all pesticides. When you talk about pesticides, take the time to explain your definition. The term pesticide means different things to different people. It is a lot like the word “organic,” which has different meanings for different people.

Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at or check out his blog at He owns Swift Horticultural Consulting and High Altitude Lavender.

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