Does E. coli persist in strawberry fields (not forever)

Irrigation water quality is one of those nagging issues for on-farm food safety and fresh produce: it’s difficult to model how persistent E. coli is and just how much of a threat is present. Or as my farmer friends say, if I’m going to lose the crop, I’m going to irrigate.

beatles-strawberry-fields-foreverA two-year field experiment was conducted in order to evaluate the persistence of generic Escherichia coli in strawberry after irrigation with naturally E. coli-contaminated surface water. Sixteen experimental plots representing actual field conditions were set, including two methods of irrigation (overhead and subsurface drip) and two mulch types (straw and plastic). Two irrigations were performed each year with water having an E. coli content varying between 460 and 2242 CFU per 100 ml. Strawberries were harvested before irrigation and 1, 4 and 24 h following irrigation. E. coli counts could not be determined in any of the 256 strawberry samples. Enrichment procedure revealed more positive samples under straw mulch (6.4%) compared to plastic mulch (4.3%), but this difference was not statistically significant (P = 0.3991). Higher strawberry contamination was also observed in overhead irrigation treatments (8.6%) compared to drip irrigation (2.1%) (P = 0.0674). The risk to detect E. coli in overhead-irrigated strawberries was 4.5-fold higher than in strawberries under drip irrigation. Four hours following irrigation, the risk to detect E. coli in fruits was 4.0-fold lower than the risk observed 1 h after irrigation. Increasing the delay to 24 h led to a 7.4-fold lower risk. In actual conditions that may be encountered in strawberry productions, this study showed a limited persistence of E. coli in strawberries following irrigation.

Persistence of Escherichia coli following irrigation of strawberry grown under four production systems: Field experiment


Mylene Genereux, Michele Grenier, Caroline Cote

Food Control, Volume 47, January 2015, Pages 103–107, DOI: 10.1016/j.foodcont.2014.06.037

Utah: Campylobacter outbreak in Saratoga Springs probably caused by cross-connecting water lines

I’m not familiar with the practice, but apparently when crews shut off the city’s irrigation lines in the fall in Saratoga Springs, Utah, some residents tap into culinary pipes, getting water for outdoor use.

Deseret News reports that the city imposed the fine for cross-connecting culinary and irrigation lines after a Campylobacter outbreak sickened dozens of residents earlier this summer. Cross-connecting can contaminate culinary water and may have caused the outbreak.

Mayor Mia Love said anyone caught cross-connecting with a previous warning will be fined $10,000, adding, "It certainly sends a message saying we’re very serious about keeping the water clean. We’re not taking it lightly."