Organic pesticides: Not an oxymoron

by Maureen Langlois

It may seem counterintuitive, but foods that are grown to organic standards can contain commercially manufactured pesticides.

A U.S. Department of Agriculture survey of produce that found nearly 20 percent of organic lettuce tested positive for pesticide residues.

... Jeff Gillman, a professor of nursery management at the University of Minnesota, has written about organic practices for lay readers. He said:

When people are buying organic food, they often make the incorrect assumption that there are no pesticides. It's true that organic production often uses fewer dangerous chemicals, but certain pesticides are allowed.

...a key factor in chemicals being cleared for use on organic crops is whether they occur naturally.

The USDA maintains an official list of substances that can and can't be used for organic farming. Other potent natural extracts that have been approved for use as pesticides include pyrethrin, derived from chrysanthemums, and azadirachtin, from the Asian neem tree, which was also detected on some samples of organic lettuce.All three of these substances are considered slightly toxic by the EPA.

Synthetic compounds can also make it onto the list as pesticides, if they are relatively nontoxic combinations that include minerals or natural elements, such as copper or sulfur. But some naturally occuring substances, such as nicotine and arsenic are off limits.

Are naturally derived pesticides less toxic than synthetic ones?

The answer depends a lot on the dosage, says Gillman. "To control fire blight on the same acre of land," he explains, "I could use a tiny amount of a potent synthetic that has proved safe over the last 50 years, or a much larger amount of an organic pesticide." He demurs on saying which is better, saying, "I want people to know that there are definitely tradeoffs."

The seeming contradiction between organic labeling and potentially harmful pesticide practices may lie in the relative leniency of the USDA organic guidelines, Gillman says. Various organic certification agencies, such as the Oregon Tilth, have tighter rules. (Check out this roundup of acceptable and forbidden pesticides.)

Gillman says just because an organic farmer used some authorized chemicals is no reason to shun the food. But it's important for consumers to know what's going on. For him, the answer to the ambiguity around organic labeling is to go local. "I go to the farmers market and talk to the growers to see who is serious about reducing pesticide use," he says. "I'd rather buy food from someone who used Roundup once than someone who uses organic pesticides all the time."

...full article...NPR