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Field Control of Bacterial Spot and Bacterial Speck of Tomato Using a Plant Activator

May 2001 , Volume 85 , Number  5
Pages  481 - 488

F. J. Louws , Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616 ; M. Wilson and H. L. Campbell , Department of Plant Pathology, 209 Life Sciences Building, Auburn University, Auburn, AL 36849-5409 ; D. A. Cuppels , Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, 1391 Sandford Street, London, ON, Canada N5V 4T3 ; J. B. Jones , 1453 Fifield Hall - Plant Pathology Department, P.O. Box 110680, Gainesville, FL 32611-0680 ; P. B. Shoemaker , Department of Plant Pathology, North Carolina State University, Fletcher 28732 ; and F. Sahin and S. A. Miller , Department of Plant Pathology, Ohio State University, Wooster 44691-4114

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Accepted for publication 16 January 2001.

Acibenzolar-S-methyl (CGA 245704 or Actigard 50WG) is a plant activator that induces systemic acquired resistance (SAR) in many different crops to a number of pathogens. Acibenzolar-S-methyl was evaluated for management of bacterial spot (Xanthomonas axonopodis pv. vesicatoria) and bacterial speck (Pseudomonas syringae pv. tomato) of tomato in 15 and 7 field experiments, respectively. Experiments were conducted over a 4-year period in Florida, Alabama, North Carolina, Ohio, and Ontario using local production systems. Applied at 35 g a.i. ha-1, acibenzolar-S-methyl reduced foliar disease severity in 14 of the 15 bacterial spot and all 7 bacterial speck experiments. Disease control was similar or superior to that obtained using a standard copper 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 tomato transplants were reduced by acibenzolar-S-methyl treatment. Bacterial speck and spot population densities on leaves of field-grown plants were not dramatically affected. Acibenzolar-S-methyl can be integrated as a viable alternative to copper-based bactericides for field management of bacterial spot and speck, particularly where copper-resistant populations predominate.

Additional keywords: Bion, copper hydroxide, induced resistance, Xanthomonas campestris pv. vesicatoria, Xanthomonas vesicatoria

© 2001 The American Phytopathological Society