Purpose: To evaluate in vitro the growth kinetics of Salmonella enterica in pesticides solutions and the effect of ag-chemicals applications with contaminated water to tomatoes during field production.
Methods: The effect of temperature (10, 25 and 37 °C), organic matter in water and time of incubation (0 - 96 h) on the growth of a cocktail of S. enterica (sv. Newport, Poona and Michigan) was determined across 13 pesticides formulations labeled for fresh tomato, following a factorial design. Pesticides that showed enhanced, neutral and inhibitory effect on the growth of Salmonella were selected for application to an experimental tomato field. Mature green tomatoes, were collected 3, 7 and 12 days post inoculation and analyzed for Salmonella with and without postharvest washing with 50 mg/l of sodium hypochlorite at pH 7.0.
Results: Positive and significant correlation (P < 0.05) was found between the growth of Salmonella and the temperature, time of incubation, pesticide and water source. Cabrio, Admire, Sulfur and Success allowed growth of Salmonella while Asana, Ridomil and Intrepid reduced survival. Analysis of the strain distribution of the Salmonella cocktail after incubation in pesticide suspensions showed a greater recovery of sv. Newport, followed by Michigan and Poona. Recovery of the bacterium from the field grown tomatoes declined from 80 to 15% after 3 and 12 d of contaminated pesticide application, respectively, but no differences among pesticides were observed. Postharvest washing with NaOCl was not efficient in removing remaining Salmonella but it could minimize cross contamination.
Significance: This study provides further evidence that pesticides may support the growth of Salmonella if introduced with source water and may elevate risk during foliar contact applications beyond that of the water source alone.