Lettuce growers in the desert valleys of the US Southwest will face more federal scrutiny during the winter growing season. The aim is to prevent the type of contamination with E. coli bacteria that killed 5 people and made 205 others ill this year.

The Food and Drug Administration for the first time will routinely test samples of romaine coming from the lower Colorado River area in Arizona and California, which will begin its harvest this month and continue through April.

Growers in both states also have committed to treating irrigation water drawn from canals that pass within 400 feet of cattle feedlots, and will triple the distance between their fields and the feedlots.

The FDA has implicated a feedlot from Wellton, Arizona, that housed more than 100,000 head of cattle as the most plausible source of a toxin-producing bacteria strain (known as O157:H7) that caused the outbreak that spread to 36 states last spring.

But, after an edict under President Donald Trump’s administration to ease regulation across all industries, the agency recently announced further delays in regulations that would address issues such as safety standards for water used to irrigate crops.