Effect of cultivars and irrigation waters on persistence of indicator bacteria on lettuce grown in high tunnel

Effect of irrigation with groundwater (GW), primary‐treated wastewater (PTWW), secondary‐treated wastewater (STWW), and roof‐collected rainwater (RCR) on the microbial quality of lettuce cultivars “Annapolis,” “Celinet,” and “Coastline” grown in high tunnel was investigated. Lettuce plants were spray irrigated with irrigation waters once a week for 2 weeks and analyzed for indicator and pathogenic bacteria. PTWW irrigation resulted in the highest Escherichia coli recovery on the lettuce plants (4.7 log MPN/g) as compared to irrigation with other three waters on 0 day postirrigation (dpi). Lettuce cultivars affected the bacterial die‐off rate, where E. coli populations reduced the most by 1.5 log MPN/g on “Annapolis” lettuce on 2 dpi. The STWW and RCR irrigation did not significantly influence indicator bacterial populations on lettuce as compared to GW irrigation. The STWW and RCR containing low populations of indicator bacteria may be suitable for lettuce irrigation in Mid‐Atlantic area without affecting its microbial quality.