New research finds the pathogen E. coli O157:H7 lives about 30
days in soils from California’s Salinas Valley — 10 days more
than in the state’s Imperial Valley or Yuma, Ariz. Lower
salinity in Salinas irrigation water is the main cause of the
difference, said Mark Ibekwe, a microbiologist with the U.S.
Department of Agriculture’s Agricultural Research Service in
Riverside, Calif. Ibekwe and three colleagues published their
findings, “Persistence of Escherichia coli O157:H7 in Major
Leafy Green Producing Soils,” in the journal Environmental
Science & Technology in October. The results were based on
laboratory-tested soil samples. Field studies of E. coli are
typically limited to nonpathogenic varieties. Increasing
salinity in Salinas water would not be realistic or beneficial
for leafy greens growers there, Ibekwe said. Nevertheless, the
research underscores the importance of keeping new pathogens
from entering the fields. “You don’t want to introduce another
variable into the farming environment that will ul