Purpose: A cross-sectional study was conducted to determine the associations between field management practices and the likelihood of a Salmonella or Listeria monocytogenes positive field.
Methods: Over five weeks, 21 produce farms in New York State were visited. Information about field-level management practices were recorded for 263 fields and 600 environmental samples (1 drag swab and soil sample per field, and a water sample when available) were collected and analyzed for Salmonella and L. monocytogenes. Management practices were evaluated by logistic regression analysis for their association with the likelihood of a pathogen positive field, defined by a soil or drag swab sample from a field testing culture positive for the respective pathogen.
Results: Salmonella and L. monocytogenes were detected in 6.1% and 17.5% of fields (n=263), respectively. Additionally, Salmonella and L. monocytogenes were detected in 11% and 30% of water samples collected (n=74), respectively; the majority of positive samples were from surface water within 50 m of a field. Manure application within a year was observed to increase the odds of a Salmonella positive field 15 times, when compared to a field where manure was applied more than a year ago, or not at all. Presence of a buffer zone (at least 10 m) was shown to decrease the likelihood of a Salmonella positive field (odds ratio,[OR]0.2). Irrigation (within 3d, [OR]7.2), wildlife presence (within 3d, [OR]6.0), and soil cultivation (within 7d, [OR]3.4) in the field were all identified as important management practices increasing the likelihood of an L. monocytogenes positive field.
Significance: This study has identified management practices that are associated with the likelihood of field-level pathogen contamination. These findings will help growers evaluate their current practices and implement GAPs that reduce the risk of preharvest field contamination.