Reductions in Yield of Processing Tomatoes and Incidence of Bacterial Canker. R. J. Chang, Department of Plant Pathology, University of Illinois, Urbana 61801. S. M. Ries, and J. K. Pataky. Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 76:805-809. Accepted for publication 1 April 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0805.

Various incidences of systemic infection of bacterial canker, caused by Clavibacter michiganensis subsp. michiganensis, were established in field plots of tomato, Lycopersicon esculentum. In 2 yr, total fruit weight, percent maximum yield, and average fruit weight of processing tomatoes (cv. Heinz 1810) were related to incidence of systemic infection of bacterial canker 1 wk before harvest. For plants infected during clipping or seedling harvest, total fruit weight per plot decreased as much as 58 kg, maximum yield decreased as much as 46%, and average fruit weight decreased as much as 13 g when the highest incidence of systemic infection was 31–83%. Slope coefficients from regressions of maximum yield on incidence ranged from –0.5 to –0.7, indicating that yield decreased about 5–7% for each 10% increase in incidence. The percentages of green and ripe fruit also were affected significantly by the incidence of systemic infection. The percentage of green fruit decreased as much as 41% and the percentage of ripe fruit increased as much as 41% when the highest incidence of systemic infection was 31–83%. The relationships between yield, green and ripe fruit, and incidence of bacterial canker were similar for plants infected during clipping of transplants and during harvest of transplants.