| Summary: | Multiple recalls and outbreaks involving <i>Listeria monocytogenes</i>-contaminated apples have been linked to the post-harvest packing environment where this pathogen can persist in biofilms. Therefore, this study assessed <i>L. monocytogenes</i> survival on apples as affected by harvest year, apple cultivar, storage atmosphere, and growth conditions. Unwaxed Gala, Granny Smith, and Honeycrisp apples were dip-inoculated in an 8-strain <i>L. monocytogenes</i> cocktail of planktonic- or biofilm-grown cells (~6.5 log CFU/mL), dried, and then examined for numbers of <i>L. monocytogenes</i> during air or controlled atmosphere (CA) (1.5% O<sub>2</sub>, 1.5% CO<sub>2</sub>) storage at 2 °C. After 90 days, air or CA storage yielded similar <i>L. monocytogenes</i> survival (<i>p</i> > 0.05), regardless of harvest year. Populations gradually decreased with <i>L. monocytogenes</i> quantifiable in most samples after 7 months. Apple cultivar significantly impacted <i>L. monocytogenes</i> survival (<i>p</i> < 0.05) during both harvest years with greater reductions (<i>p</i> < 0.05) seen on Gala compared to Granny Smith and Honeycrisp. Biofilm-derived cells survived longer (<i>p</i> < 0.05) on <i>L. monocytogenes</i>-inoculated Gala and Honeycrisp apples compared to cells grown planktonically. These findings should aid in the development of improved <i>L. monocytogenes</i> intervention strategies for apple growers and packers.
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