ARS | Publication request: Effect of copper hydroxide sprays for citrus canker control on wild type Escherichia coli

Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 10, 2011
Publication Date: February 1, 2012
Citation: Narciso, J.A., Ference, C.M., Ritenour, M., Widmer, W.W. 2012. Effect of copper hydroxide sprays for citrus canker control on wild type Escherichia coli. Letters in Applied Microbiology. 54:108-111.

Interpretive Summary: Potable water restrictions for citrus growers will damage the industry as FDA is regulating water purity to prevent food borne illness on fresh produce. This report shows that because of the addition of copper to citrus tree sprays, Escherichia coli does not survive on the leaves and fruit even if water used to mix the spray is contaminated.

Technical Abstract: Studies were performed in vitro with bacteria grown in broth and then subjected to the same copper hydroxide concentrations as are sprayed on citrus trees in Florida throughout the growing season. Studies were also undertaken with grapefruit leaves and the survival of Escherichia coli (E. coli) on them with and without copper. In the laboratory (in vitro), exposure to copper brought about the death of E. coli in 6-9 hours depending on the pH of the solution. On the leaves, the bacteria did not survive even when copper hydroxide sprays were not added. Even in heavy contamination periods, environmental stresses and the presence of copper will eradicate these bacteria before harvest.