Foliar Applications of Acibenzolar-S-Methyl Negatively Affect the Yield of Grafted Tomatoes in Fields Infested with Ralstonia solanacearum

Three field experiments were conducted in Florida from 2012-2014 to assess the impact of acibenzolar-S-methyl (ASM), a systemic acquired resistance inducer, applied as foliar spray or through drip-irrigation lines, on bacterial wilt incidence and yield of grafted tomatoes. The experiments were conducted in a field with race 1, biovar 1 strain of Ralstonia solanacearum, causal agent of tomato bacterial wilt. In all three experiments, the susceptible tomato variety BHN 602, grafted onto a resistant rootstock BHN 998, was compared with nongrafted BHN 602, treated with or without foliar applications of ASM and with grafted plants treated with foliar applications of ASM. In two experiments, an additional treatment of drip applications of ASM on grafted and nongrafted plants was evaluated. Grafting alone or in combination with drip applications of ASM (178.6 mu M) significantly reduced disease incidence and increased total marketable yield relative to nongrafted treatments. There were no significant differences between grafted plants with or without drip ASM applications in terms of bacterial wilt incidence or total marketable yield. However, we demonstrate for the first time that foliar ASM applications on grafted plants negatively affects the total marketable yield compared with drip ASM applications on grafted plants or nontreated grafted control.