Microbial Carriage and Contamination of Mangoes by the Oriental Fruit Fly

Fruit flies, especially of the Family Terphritidae, are economically important pests for the horticulture industry because many species cause serious mechanical damage to a number of crops of different plant families. Studies have shown that some species of fruit flies have the potential to contaminate fruits and vegetables with enteric bacterial pathogens. However, this has not been conclusively demonstrated.

In this study, we investigated enteric bacteria carriage by Bactrocera dorsalis and its possible role in transmission of microbes into internal tissues of fruits. Fruit flies trapped using liquid protein bait, ripe mango fruits exposed to the fruit flies and controls, as well as mangoes obtained from farms with and without fly-control traps, were analyzed for microbes, such as total aerobic bacteria, total coliforms, yeast and molds, Escherichia coli and Salmonella/Shigella spp. using direct culture methods.

The results revealed that a high percentage of these insects carries pathogenic bacteria. This finding shows that, like B. cacuminata and B. tryoni, B. dorsalis also carries pathogenic microbes. It was also observed that mangoes sampled from fly-control farms had significantly lower microbial loads and proportions of fruits contaminated compared to those from farms without fly-control. Additionally, all microbial counts of internal tissues were significantly higher for exposed mangoes compared to unexposed mangoes. These data indicate that B. dorsalis contaminates not only the external but also internal tissues of mangoes.

These findings show that B. dorsalis carries pathogenic bacteria and plays a direct role in internalization of microbes in mangoes.