Field control of bacterial spot and bacterial speck of tomato using a plant activator

Acibenzolar-S-methyl (CGA 245704 or Actigard 50WG) is a plant activator tha t induces systemic acquired resistance (SAR) in many different crops to a n umber of pathogens. Acibenzolar-S-methyl was evaluated for management of ba cterial spot (Xanthomonas axonopodis pv. vesicatoria) and bacterial speck ( Pseudomonas syringae pv. tomato) of tomato in 15 and 7 field experiments, r espectively. Experiments were conducted over a 4-year period in Florida Ala bama, North Carolina, Ohio, and Ontario using local production systems. App lied at 35 g a.i. ha(-1), acibenzolar-S-methyl reduced foliar disease sever ity in 14 of the 15 bacterial spot and all 7 bacterial speck experiments. D isease control was similar or superior to that obtained using a standard co pper bactericide program. Acibenzolar-S-methyl also reduced bacterial fruit spot and speck incidence. Tomato yield was not affected by using the plant activator in the field when complemented with fungicides to manage foliar fungal diseases, but tomato transplant dry weight was negatively impacted. X. axonopodis pv. vesicatoria population densities on greenhouse-grown toma to transplants were reduced by acibenzolar-S-methyl treatment. Bacterial sp eck and spot population densities on leaves of field-grown plants were not dramatically affected. Acibenzolar-S-methyl can be integrated as a viable a lternative to copper-based bactericides for field management of bacterial s pot and speck, particularly where copper-resistant populations predominate.