T7-08 Evaluating the Effect of Cover Crops on the Survival and Growth Dynamics of Foodborne Bacterial Indicators in Soil and on Cantaloupes Grown Organically

Monday, July 27, 2015: 10:45 AM
C124 (Oregon Convention Center)
Neiunna Reed-Jones, University of Maryland, College Park, College Park, MD
Sasha Marine, University of Maryland, Salisbury, MD
Kathryne Everts, University of Maryland, Salisbury, MD
Shirley Micallef, University of Maryland, College Park, MD
Introduction:  Growers may minimize cantaloupe contamination with foodborne pathogens through implementation of Good Agricultural Practices (GAPs).  However GAPs focus on exclusion of foodborne pathogens and say little about the impact of production system on contamination. Cover cropping is practiced for seasonal soil protection, nutrient management and control of phytopathogens.  The impact of cover crop systems on foodborne pathogens remains unexplored.

Purpose: We assessed the survival of bacterial foodborne pathogen surrogates in five cover crop/green manure systems – rye, hairy vetch, crimson clover, rye combinations and bare ground, in the production of cantaloupe in organic and transitional-organic fields.

Methods: Cover crops arranged in a randomized complete block design were inoculated with non-pathogenic Escherichia coli and Listeria innocua using a handheld sprayer in fall 2013 and 2014. Cover crops were tilled in spring and cantaloupe ‘Arava’ and ‘Sivan’ seedlings were transplanted.  Soil and fruit samples were collected, and bacteria enumerated using an MPN method.  Data were analyzed using a mixed model with repeated measures.

Results: In fall 2013 - spring 2014, cover crop was a factor for E. coli (P = 0.043) but not for L. innocua. Both species declined over time (P < 0.0001).  In fall 2014, time was again a factor for E.coli in both organic and transitional fields (P < 0.0001), and cover crop by week was only a factor in the transitional field (P < 0.0001).  Cover crop by week was a factor for L. innocua in organic (P = 0.0018) and transitional (P < 0.0003) fields.  Bacterial survival on ‘Sivan’ varied by fruit size and green manure treatment for L. innocua; conversely, E.coli was mostly absent.  ‘Arava’ fruit weight was lower in bare ground than in hairy vetch or hairy vetch plus rye plots (P = 0.0001).

Significance: These data reveal that cover crop/green manure treatment and time may impact the survival of foodborne indicator bacteria in fields and subsequent dispersal onto cantaloupes.