Managing Bacterial Speck and Spot of Tomato with Acibenzolar-S-Methyl in Virginia

Abstract

On the Eastern Shore of Virginia, copper compounds, which have been used for controlling bacterial disease on tomato, have been associated with pesticide run-off from commercial tomato production with copper toxicity causing losses in clam nurseries. The objective of this study was to identify and evaluate a replacement for copper that was safer for the environment and could provide effective management of bacterial diseases of tomato. Acibenzolar-S-methyl (Actigard 50 WG), a plant activator that induces systemic acquired resistance (SAR), was compared to the standard bactericide (copper hydroxide + mancozeb) for controlling Xanthomonas axonopodis pv. vesicatoria and Pseudomonas syringae pv. tomato. Plots were established in grower fields in a randomized complete block design with four replications. Acibenzolar-S-methyl, at a rate of 10.5-g a.i./ha was equal to or better than the standard copper-based bactericide for controlling bacterial speck and spot, with no adverse affect on yield. Replacing copper with acibenzolar-S-methyl would effectively eliminate the need for copper bactericides. In environmentally sensitive areas where copper toxicity can be a problem, acibenzolar-S-methyl can providean effective alternative for the management of bacterial speck and bacterial spot on tomato. Accepted for publication 26 January 2002. Published 20 February 2002.