In the southeast US, tomatoes (Solanum lycopersicum) and bell pepper (Capsicum annuum) are typically staked and trellised and grown using plastic mulch for weed control. The Produce Safety Rule that is part of the Food Safety Modernization Act requires that fruit from tomato and pepper be declared non-harvestable if they fall to the ground or contact the ground through drooping while attached to the plant before harvest. The objective of this study was to quantify percent transfer from plastic mulch inoculated with Escherichia coli with green fluorescent protein (GFP) to pepper and tomato fruit making ground contact in spring and fall growing seasons. E. coli GFP was spot inoculated on plastic mulch in the field using ten - 10 µL drops (100 uL total) at approximately 7 log CFU/mL and allowed to dry for at least 1 h before fruit contact. In the spring season, white and black colored plastic mulch were compared and in the fall season, reused (second crop) plastic mulch and new white plastic mulch were compared. Fruit contacted the ground by drooping (remained attached to the plant) with a contact time of 1 h or 24 h as well as contact through dropping fruit at heights of 30 cm, 60 cm, and 120 cm (n=9 per treatment). After inoculum was allowed to dry on the plastic mulch, the E. coli population was reduced an average of 2.8 and 4.8 log CFU/mL, in the spring and fall seasons, respectively. In both seasons all dropped peppers had significantly different percent transfer than dropped tomatoes, while drooping fruit were not significantly different between the two commodities. In the fall, dropped fruit on new plastic had significantly greater bacterial transfer than fruit which was dropped on reused plastic for both tomato and pepper. No significant differences were obtained between drooping duration treatments or between the different height of dropping in either season. There was relatively low transfer overall from both drooping and dropping of fruit on inoculated plastic mulch, regardless of crop or season. Further, in this inoculated study, results suggest that there was a significant reduction in E. coli populations in a field setting after a short period of exposure to the natural environment.
