Cornell researchers have identified some agricultural management practices that can boost or reduce the risk of contamination in produce from two major foodborne pathogens.

For example, applying manure within a year of harvesting produce boosts the odds of contaminating a field with salmonella, the biggest single killer among the foodborne microbes, report the researchers. And irrigating fields within three days and cultivating fields within a week of harvest significantly raised the risk of listeria monocytogenes contamination. However, establishing a buffer zone between fields and potential pathogen reservoirs, such as livestock operations or waterways, was found to be protective against salmonella.

The study is published online in the journal Applied and Environmental Microbiology (scheduled for print in December).

“This is going to help make produce safer,” says first author Laura Strawn, a graduate student in the field of food science. “We could significantly reduce risk of contamination through changes that occur a few days before the harvest.”

Many of the risk factors were influenced by when they were applied to fields, which suggests that adjustments to current practices may reduce the potential for contamination with minimal cost to growers, says Strawn, whose co-authors include Yrjo Grohn, professor of epidemiology; and Randy Worobo and Martin Wiedmann, Cornell professors of food science.

Foodborne illness sickens an estimated 9.4 million people and kills about 1,300 annually in the United States, according to the Centers for Disease Control and Prevention. Produce accounts for nearly half the illnesses and 23 percent of the deaths.

“The research is the first to use field collected data to show the association between certain management practices and an increased or decreased likelihood of salmonella and L. monocytogenes,” says Strawn. “These findings will assist growers in evaluating their current on-farm food safety plans (e.g., ‘Good Agricultural Practices’), implementing preventive controls that reduce the risk of preharvest contamination and making more informed decisions related to field practices prior to harvest. Small changes in how produce is grown and managed could result in a large reduction of food safety risks.”

Other co-authors of the study, which can be found online, were all from Cornell and include Steven Warchocki, technician in food science; and Elizabeth Bihn, senior extension associate in food science and the Good Agricultural Practices coordinator.

The study was supported by the U.S. Department of Agriculture.