Can the inclusion of uniconazole improve the effectiveness of acibenzolar-S-methyl in managing bacterial speck (Pseudomonas syringae pv. tomato) and bacterial spot (Xanthomonas gardneri) in tomato?

There are reports of acibenzolar-S-methyl (ASM) having host fitness costs and variable levels of control of bacterial speck ( Pseudomonas syringae pv. tomato ) and bacterial spot ( Xanthomonas gardneri ) in tomato ( Solanum lycopersicum ). The plant growth regulator uniconazole (UNI) is associated with alleviating abiotic stress symptoms, and was tested as an additive to ASM to see if it would reduce ASM-associated fitness costs and improve the consistency of disease control. Field applied ASM (fASM) plus greenhouse applied UNI (gUNI) was less consistent than fASM alone, as the combination reduced disease incidence in only two of three years versus fASM alone that reduced disease incidence in three of three years. However, fASM alone never increased total yield compared to the non-treated control, whereas fASM+gUNI increased it in one of three years, which was not associated with changes in disease intensity or relative chlorophyll levels. Greenhouse applied ASM (gASM) plus gUNI reduced disease incidence in one of three years, whereas gASM alone was never effective. This is the first report that gASM can result in long term disease control reducing disease severity up to 13 weeks post-application, indicating long-term effects of gASM are possible. The lack of improved consistency for disease control or improved yield with ASM combined with UNI compared to ASM alone indicates that other additives need to be tested. Also, further research is needed to discover why the ASM + UNI combination did provide improvements under certain field conditions.