He says the mechanism by which dung beetles kill pathogenic E. coli in manure is still poorly understood, but it could be a combination of directly killing E. coli through mastication and by simply aerating manure and creating a less hospitable environment for the bacterium to survive.
Dr. Jones also notes that a group in Korea also found antimicrobial properties built into the exoskeleton of a different species.
To validate their findings, the researchers exposed the three most common species of dung beetles found in the field survey to pig feces contaminated with E. coli. A seven-day laboratory experiment revealed that Onthophagus taurus and Onthophagus nuchicornis reduced E. coli numbers by more than 90 percent and less than 50 percent, respectively.
They also found that organic farming encouraged higher biodiversity among soil bacteria, which decreased the survival of pathogens.
“Wildlife and livestock are often seen as something that endanger food safety, but our research shows that reducing on-farm biodiversity might be totally counterproductive,” says Dr. Jones.
He says he sees no real challenges in allowing dung beetles to persist on farms. The dung beetles are naturally occurring, not purchased.
Dr. Jones says a lot of assumptions are made when putting food safety regulations on farmers without thoroughly researching the indirect effects of these regulations.
“There’s a lot more to be done regarding the co-management of food safety and conservation,” he says.
One farmer who has noticed a benefit from having dung beetles is Judith Redmond, co-owner of Full Belly Farm, Guinda, Calif., located in the northern part of the state.
“Our farm has been managed organically since 1985,” says Redmond. The 400-acre certified organic farm with 80 different crops as well as chickens, sheep, goats, and cows.
“I would expect that we have had the dung beetles for several decades at least,” she says. “The benefits, as described in the research, are that they contribute to breaking down organic materials and even possibly to reducing food safety risks.”