The fresh produce industry is facing major changes in production practices due to the implementation of the FDA Food Safety Modernization Act (FSMA). Within the new rules the standards associated with water quality are among the most contested by industry associations. Current guidelines require water that will be in direct contact with the crop, to meet specific microbiological thresholds based on the 2012-EPA recreational water standards. Alternative provisions to comply with these rules have also been allowed by FDA when water cannot meet these standards. One of these options considers a microbial die-off rate of 0.5 log per day that may occur naturally between irrigation and harvest events as a safe alternative practice. Despite this potentially useful provision, there needs to be science-based information supporting this option, especially on cilantro and strawberry for which few or no further disinfection steps are commercially available after harvest and where large volumes of surface or well water are used for frost protection (strawberry) and overhead irrigation (cilantro). This research focuses on optimizing the existing knowledge in microbial die-off of avirulent and pathogenic EHEC- STEC microorganisms to determine whether the proposed microbial die-off rate is a safe farm practice to follow when using water that cannot meet the EPA microbial standards.