Purpose: The aim of this study was to determine the microbial dispersal due to bird droppings on tomato plants in the field.
Methods: Four experimental tomato fields, planted and maintained at typical commercial standards, were visited at least twice while fruit were mature (10 visits), and surveyed for contamination with bird droppings. Mature fruit with visible bird droppings, fruit not visually contaminated but within 30 cm of the contamination, fruit on the same plant but more than 30 cm from the contamination, and fruit on the adjacent plants were evaluated for aerobic plate count (APC), coliforms, generic E. coli, and Salmonella. Control fruit were collected from a plant ca. 10 feet away that had no visible bird droppings. Significant differences were determined using the Student’s t-Test with Bonferroni correction.
Results: Salmonella was isolated from 1/356 samples, collected from fruit on a plant adjacent to a plant contaminated with bird droppings. Populations of coliforms and APC (ca. 2.5 and 7.0 log MPN/tomato, respectively) were not significantly different between contaminated and control fruit (P=0.35 and P=0.07, respectively). Generic E. coli was higher (P=0.008) on contaminated fruit (0.5 ± 0.9 log MPN/tomato) than control fruit (0.1 ± 0.2 log MPN/tomato). Generic E. coli on tomatoes within 30 cm of contaminated fruit (0.1 ± 0.3 log MPN/tomato) was not significantly different than the controls (P=0.37).
Significance: Prevalence of Salmonella on Florida tomatoes was <1%. Enumeration of samples for generic E. coli suggest that these microbial populations are not dispersed in high numbers by bird droppings beyond visually contaminated tomatoes.