Efficacy of Fosetyl-Al for Control of Some Bacterial Diseases on Ornamentals. A. R. Chase, Professor of Plant Pathology, University of Florida, Institute of Food and Agricultural Sciences, Central Florida Research and Education Center, Apopka 32703. . Plant Dis. 77:771-776. Accepted for publication 24 March 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0771.

Several factors, including pH and timing and number of applications, affect the efficacy of fosetyl-Al for controlling bacterial disease on ornamentals. Although pH may be a factor in the efficacy of fosetyl-Al for sensitive bacteria such as strains of Xanthomonas campestris pv. dieffenbachiae from Syngonium, sensitivity to pH alone cannot adequately explain the response of bacteria to exposure to fosetyl-Al in vitro. Disease control appears to be based on surface factors rather than chemical changes within the leaf tissue, since bacterial populations following leaf infiltration reach similar numbers whether plants are treated with fosetyl-Al or water. Disease control varied unpredictably when applications were made on 4- to 10-day intervals up to five times before inoculation. Results of 7 yr of testing suggest that fosetyl-Al does not give consistent or reliable control of bacterial disease on ornamentals.

Keyword(s): Erwinia spp., Pseudomonas cichorii, Xanthomonas campestris.