December 13, 2018

Salmonella and Listeria Produce Field Contamination Risk Factors

Red and green bell peppers have been recalled in California for possible Salmonella contamination. That makes this study even more relevant. Applied and Environmental Microbiology has published research about identified risk factors associated with contamination of produce fields with Salmonella and Listeria monocytogenes bacteria.

Farm FieldThe study found that management practices are crucial to development of effective Good Agricultural Practices (GAPs). Twenty one produce farms in New York state were visited over a five week period for this study. Soil, draw swab, and water samples were collected. In addition, field-management practices were recorded.

They found Salmonella in 6.1% of fields, and Listeria in 18.5%. Most of the pathogen-positive water samples were from non-irrigation surface water sources. Salmonella was found in 11% of those water samples, and Listeria was found in 30%.

In addition, the scientists found that manure application within a year of harvest increased the odds of a Salmonella-positive field. Irrigation within three days of sample collection, wildlife observed in the field, and soil cultivation within seven days of sample collection also increased the likelihood of a field positive for Listeria monocytogenes. A buffer zone around the field did have a protective effect. Growers need to evaluate their GAPS with science-based evaluation and implement preventive controls that will reduce the risk of pre-harvest contamination.


  1. Isn’t the real story hear the fact that, while positive test results were obtained for several pathogens in the field, no illness outbreaks were associated?

    • Linda Larsen says:

      Well, no, the real story is that farmers using Good Agricultural Practices can reduce the risk of Salmonella and Listeria on produce. The scientists didn’t test the produce – they tested the soil and the water.

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