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Disease Control and Pest Management

Evaluation of Chemicals and Application Methods for Control of Bacterial Wilt of Tomato Transplants. J. M. Enfinger, Former graduate student, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602; S. M. McCarter(2), and C. A. Jaworski(3). (2)Professor, Department of Plant Pathology and Plant Genetics, University of Georgia, Athens 30602; (3)Soil scientist, Federal Research, Science and Education Administration, United States Department of Agriculture, Coastal Plain Experiment Station, Tifton, GA 31794. Phytopathology 69:637-640. Accepted for publication 26 December 1978. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-637.

Chloropicrin, whether covered with a polyethylene film or sealed with water, was the only soil treatment chemical of eight evaluated that provided significant full-season control of Pseudomonas solanacearum which causes bacterial wilt of tomato. A methyl bromide-chloropicrin mixture (67–33%) and DD-MENCS (a mixture of methyl isothiocyanate, dichlopropane and dichloropropene) retarded wilt development less effectively than chloropicrin but more effectively than methyl bromide. Methyl bromide gave good control only until midseason. Metham gave poor to moderate early-season control and was more effective when injected than when applied as a drench or incorporated. Potassium N-hydroxymethyl-N-methyldithiocarbamate and sodium azide provided limited early-season control. Hexachlorophene and formaldehyde were ineffective. Chloropicrin and methyl bromide applied at one-half, full, or twice the recommended rates (chloropicrin 326 L/ha, and methyl bromide 490 kg/ha) under optimum conditions, were highly effective in reducing high populations of P. solanacearum in artificially infested soils in greenhouse tests. Results of field and greenhouse experiments indicated that: high populations of P. solanacearum are necessary for bacterial wilt development, low residual pathogen populations remaining after chemical treatment rapidly increase to disease threshold levels in the presence of tomato roots, and chloropicrin is the most promising chemical for reducing bacterial populations in fields used for transplant production.