Monitoring vegetables while they are growing is crucial to preventing contamination with harmful bacteria such as E. coli and Salmonella, say plant pathologists who are members of The American Phytopathological Society.

There have been outbreaks of E. coli and Salmonella for at least the past decade, but the incidences of vegetable contamination are increasing in frequency.

"We've studied plant pathogens on plants for a long time, but haven't studied human pathogens on plants until recently," says Jeri D. Barak, research microbiologist with the U.S. Department of Agriculture's Agricultural Research Service in Albany, Calif. "What we've found up to this point is that most contamination is occurring while the plants are still growing in the field. The most successful way to prevent contamination of fresh produce is to intervene before the harvest, not after."

Her research has shown that pathogens like Salmonella use specific genes to colonize plants, creating an active interaction with the plant surface.

"When this happens, the bacteria become almost inseparable from the vegetable," she says. Barak and other APS members will present their latest food safety research at a symposium titled "Cross Domain: Emerging Threats to Plants, Humans and Our Food Supply, " July 30 from 1 to 5 p.m.

The meeting will held in conjunction with the The American Phytopathological Society and the Society of Nematologists, July 28-Aug. 1, at the Town and Country Resort and Convention Center in San Diego.