Recent research on potatoes showed that low levels of herbicides, which did not result in obvious damage to the plants above ground, negatively affected their underground growth, reducing yields.

Oregon researchers with the Environmental Protection Agency tested the herbicides to assess a plant’s resilience to exposures that would be assumed to be safe; levels that weren’t concentrated enough to wilt the plant’s foliage or cause any obvious signs of damage.

Seven different herbicides were tested and applied at certain times in the plant’s development – and found to affect the size and number of the potato tubers produced, according to a news release about the study by the American Society of Agronomy.

Potatoes were chosen for the project because scientists suspected that their plant structure  would provide an easy way to check on the effects of herbicide exposure a during a plant’s  reproductive cycle.

Oust, an herbicide authorized for use in ditches and road right-of-ways, was found to have a significant effect on the potato plants, causing deformed tubers and reduced yield, said lead researcher Dr. Thomas Pfleeger, a plant physiologist with the EPA.

That finding had implications for real world practices because the low levels of Oust applied simulated what can happen when a pesticide drifts into agriculture areas. If the drift occurs at a sensitive time in the plants development, the fruit of the plant can be affected, Pfleeger said.

Previous work with low levels of pesticides on cherry trees, simulating accidental or “drift” exposures, also found damage to the trees ability to reproduce and bear fruit the following season, he explained.

The takeaway message?

“People who are applying pesticides have to be very careful. They can go long distances and cause problems. And you can’t always see the damage,” he said.

The experiments also have relevance for EPA labeling practices. Currently, pesticides are tested on pre-emergent and seedling plants, to gauge their effects. Pfleeger says the Oregon experiments suggest that testing during a plant’s reproductive cycle should also be part of the chemical registration process.

Asked if the tests also raise questions about pesticide use in general, and other potential “unseen” effects, he responded that the threat to the produce-buying public would be nominal: “It’s pretty hard to get away from pesticides. They’re pretty much everywhere.”

The research by the U.S. EPA’s Western Ecology Division has been printed in the latest issue of the Journal of Environmental Quality, a peer reviewed publication put out by the American Society of Agronomy.

The article notes that American agriculture’s dependence on herbicides – a multi-billion dollar industry that annually dumps about 500 million pounds of herbicides on the land at last count – is worth evaluating because  of “potential risk are non-targeted crops, rare and endangered plant species, native plant communities, and organisms that are dependent on natural plant communities for food and shelter.”

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