The results of a preliminary study conducted earlier this year by USDA pathologist Tim Gottwald and colleagues suggests canker bacteria could be spread through contact with infected fruit, even after the fruit was treated at a packinghouse, the Lakeland-based newspaper The Ledger reported Aug. 19.  Previously, mature citrus fruit was considered an unlikely vehicle for transmission.

The researchers emphasized that the study was not conclusive, and more research is scheduled to determine how the bacteria spread to uninfected fruit, The Ledger said. Still, the study could influence whether the USDA lifts the statewide ban on shipments of Florida citrus to other citrus-producing U.S. states and territories.

In the study, Gottwald mixed 107 canker-infected grapefruit in a batch of other grapefruit showing no visible symptoms. The batch was run through a simulated packinghouse that included treatment with several disinfectants, The Ledger said.

Gottwald said it was “quite a surprise” when the results showed the nonsymptomatic fruit – which had been picked from trees showing no visible signs of canker – had trace amounts of canker bacteria.

Timothy Schubert, a pathologist with the Florida Department of Agriculture and Consumer Services, noted in the article that the amount of bacteria found on the treated fruit were probably too low to cause an infection.

The researchers told The Ledger that several limitations to the study – the fact that the grapefruit were not thoroughly cleaned prior to disinfection and those without visible symptoms were not tested for canker prior to processing – would be addressed in future research.