Dung beetles and soil bacteria on farms could help suppress E. coli and other harmful pathogens, according to research.
The study published in the Journal of Applied Ecology found improved food safety may be enhanced by on‐farm biodiversity and the current view that farm simplification helps may undervalue natural resistance to human-pathogen survival.
Growers are often encouraged to remove hedgerows, ponds and other natural habitats to prevent wildlife from moving onto their farm fields and potentially spreading foodborne pathogens.
Results suggested dung beetles and soil bacteria may improve the natural suppression of human pathogens on farms, meaning insecticide use could be reduced and greater plant and insect diversity promoted. Dung beetles bury feces below ground and make it difficult for pathogens to survive.
Researchers tested a suite of hypothesized relationships between land management (farming practices and landscape context), feces-feeding community dynamics (dung beetle community mass and soil bacterial biodiversity), and ecosystem services relevant to food safety (feces removal and suppression of potential foodborne pathogens).
Matthew Jones, who led the research as part of his Ph.D. project at Washington State University, said farmers are more concerned than ever with food safety.
“If someone gets sick from produce traced back to a particular farm it can be devastating for them. As a result, many remove natural habitats from their farm fields to discourage visits by livestock or wildlife, making the farmland less hospitable to pollinators and other beneficial insects or birds,” he said.
“Wildlife and livestock are often seen as something that endangers food safety, but our research shows that reducing on-farm biodiversity might be totally counterproductive. Nature has a ‘clean-up crew’ of dung beetles and bacteria that quickly remove feces and the pathogens within them, it appears. So, it might be better to encourage these beneficial insects and microbes.”
The team surveyed beetle and soil microbial communities in 70 commercial broccoli fields spanning the U.S. West Coast from northern Washington State to southern California. Pig feces was used to attract dung beetles to see how quickly they would clean up.
Farms visited were managed using one of three systems: conventional vegetable, organic assorted vegetable and organic assorted vegetable alongside livestock production.
Organic farms attracted a range of dung beetle species that removed the feces quicker than on conventional farms. On these fields or those surrounded by pastureland, a less effective species outweighed the number of native dung beetles.
The study suggested organic farms might foster beneficial biodiversity with the potential to counterbalance any heightened food safety risks. Such farming also indirectly led to more diverse soil bacterial communities.
Several species of dung beetles and diverse communities of soil bacteria were capable of suppressing human‐pathogenic E. coli. Taxon‐rich soil microbial communities also had increasingly strong suppression of pathogenic E. coli.
Researchers exposed the three most common dung beetle species found in the field survey to pig feces contaminated with E. coli. A seven-day lab experiment revealed two species that bury feces as part of breeding behavior reduced E. coli numbers by more than 90 percent and less than 50 percent respectively over several days.
“In summary, we recommend greater consideration of food safety as an ecosystem service associated with [feces-feeding] arthropods and soil bacteria – two key components of on‐farm biodiversity that might be harmed as farms are simplified, or augmented when farms are managed to be more diverse. Indeed, farm‐safety schemes that ignore biodiversity’s benefits might inadvertently worsen, rather than mitigate, food safety risks,” said researchers.
(To sign up for a free subscription to Food Safety News, click here.)