This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A brush with low doses of the herbicide dicamba spurs oxalis, a weed commonly known as wood sorrel, to produce more flowers, University of Michigan researchers have discovered. The finding suggests that farmers and homeowners are inadvertently making weeds growing around the perimeter of their fields or lawns stronger, the researchers say.
The study results are published in the journal New Phytologist. "The general public uses herbicides in their lawn to kill weeds. They're not using herbicides to make the weeds do better.
They probably don't even know this is a potential side effect or something that can happen," said senior study author Regina Baucom, professor of ecology and evolutionary biology. "We wanted to study it at a fine level to figure out what it means in terms of population persistence and evolution." During the application process, dicamba has a tendency to become whisked aloft on air currents and settle in low doses on plants adjacent to the target area of the herbicide. These plants often don't receive toxic doses of the herbicide but can be affected by it.
After conducting other research that involved dicamba, the scientists noticed that plants growing where the herbicide drifted seemed to produce more flowers. Scientists first noted this phenomenon in the early 1900s, when botanists found that stress from low concentrations of toxic substances such as copper and zinc could boost growth in plants, algae and fungi. German scientists first called this a "stimulation effect," and later it became known as "hormesis." To study this trend in oxalis, the researchers, led by recent U-M graduate Anah Botran, planted a field with oxalis and exposed half of the field to low levels of dicamba.
The other half of the field acted as a control and was not treated with the herbicide. Botran, a graduate student, along with undergraduate students Olive Tatara, Elise Kanefsky and Betania Cornejo, measured the plants' growth, flower number, seed number and other measures of plant health. The first year, the plants produced more flowers in the treated half of the plot compared to the control.
The researchers also saw some evidence that the plants hit by dicamba produced more seeds in the first year. They repeated the experiment for a second year, but did not see the same increase in the number of seeds. The researchers also examined whether the oxalis that overproduced flowers passed that trait down to its descendants—meaning that the ability to produce more flowers could have evolved in the population.
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