Listeria monocytogenes is listed by the Food and Drug Administration as a ‘pathogen of concern’ and has been singled out on both ready-to-wash and ready-to-eat produce due to its nature as a true evironmental species. The pacific apple industry, led by Washington, suffered a significant loss of income following the L. monocytogenes outbreak traced back to a California packer. The final FDA Produce Rule and Preventive Controls Rule are challenging apple packers and handlers to develop specific efficacy data for their process controls. The apple industry has an immediate need to begin the process of science-based improvements in Listeria control during packing and subsequent storage. The overall goal of the proposed studies is to comparatively assess and validate critical operating parameters for registered, commercially practical, and legally allowed sanitizer(s) against L. monocytogenes, and to further seek to verify their efficacy on multiple apple packing lines. The proposed project will develop information for apple producers about the practical efficacy of antimicrobial interventions under commercial packing conditions, resulting in tested and proven methods for spray bar intervention in fresh apples, which will fill critical gaps in the knowledge. It will be crucial for addressing L. monocytogenes safety in fresh apples.