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Clearing Vegetation around Crops has no Effect on Pathogens

August 12, 2015

cropA new study by scientists at the University of California has found that the practice of removing wild vegetation from around edible crops does not decrease the presence of food-borne pathogens. Clearing started largely as a response to the 2006 outbreak of E.coli in North America associated with pre-packaged spinach.

Researchers looked at 250,000 test results from fresh produce, irrigation waters and rodents between 2007 and 2013. The 295 farms concerned were from across the United States, Mexico and Chile, with scientists combining test results with land use data to identify characteristics of the landscape surrounding agricultural fields. The results showed that there had been no decrease in pathogen rates, and in some cases the prevalence of E.coli in leafy vegetables had increased even in areas where wild vegetation had been removed. There was even some data to suggest that farmers who removed the most vegetation experienced the biggest rises in pathogenic E.coli and salmonella.

Lead author Daniel Karp said that the previous policy of blaming wildlife for the 2006 outbreak had now been proved inaccurate. “Wildlife took much of the blame for that outbreak, even though rates of E. coli in wildlife are generally very low,” he said. “Now, growers are pressured by buyers to implement practices meant to discourage wildlife from approaching fields of produce. This includes clearing bushes, plants and trees that might serve as habitat or food sources for wild animals. Our study found that this practice has not led to the reductions in E. coli and Salmonella that people were hoping for.”

The study did find, however, that the likelihood of detecting pathogenic E. coli was greater when fields were within 1.5 kilometers of grazeable land than when they were farther away.

You can view the full study HERE