Acibenzolar is an active ingredient that stimulates plant defense systems. In 2002, IR-4 started testing acibenzolar for safety on several ornamental horticulture crops. In 2008, IR-4 continued crop safety screening after a renewed interest in bringing this active ingredient to ornamental horticulture growers. From 2002 through 2012, the IR-4 Project completed 235 trials on 63 ornamental plant genera or species examining phytotoxicity related to foliar and/or drench applications of acibenzolar. In these trials, 29 species or genera exhibited minimal or no injury after foliar applications. Based on this information, it is recommended that all but 2 of these crops be added to a list of tolerant plants when this active ingredient gains registration. While there was sufficient evidence of minimal or no injury for Dianthus sp. and Pelargonium x hortorum, a single trial for each crop did elicit moderate to severe injury. Further investigation on cultivar or species differences may be warranted.