Influence of Timing of Application and Chemical on Control of Bacterial Speck of Tomato. D. J. Jardine, Former Graduate Assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. C. T. Stephens, Associate Professor, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Plant Dis. 71:405-408. Accepted for publication 13 November 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0405.

Greenhouse experiments were conducted to determine the effect of timing of application of selected chemicals on control of bacterial speck on artificially inoculated plants. Streptomycin sulfate, oxytetracycline, and a copper-mancozeb complex were applied at various times before or after inoculation with Pseudomonas syringae pv. tomato. Only streptomycin provided significant control, and then only if applied within 24–48 hr of inoculation. In field studies, various antibiotic and copper compounds were applied using either a 4- or 7-day spray schedule. The efficacy of all chemicals appeared to be related to environmental conditions; significant (P = 0.05) protection was provided only when conditions for disease were limiting. Streptomycin generally provided the highest amount of control. The activity of oxytetracycline was increased by adding an adjuvant.