VIEW ARTICLE

Ecology and Epidemiology

Effects of Tillage and Cropping System on Incidence and Severity of Southern Stem Canker of Soybean. Craig S. Rothrock, Department of Plant Pathology, University of Georgia, Georgia Experiment Station, Experiment 30212; Thomas W. Hobbs(2), and Daniel V. Phillips(3). (2)(3)Department of Plant Pathology, University of Georgia, Georgia Experiment Station, Experiment 30212. Phytopathology 75:1156-1159. Accepted for publication 5 June 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-1156.

The effects of tillage and cropping system on southern stem canker of soybean, which is caused by southern isolates of Diaporthe phaseolorum var. caulivora, were examined in 1983 and 1984. Mean disease incidence increased from 1.6% of the plants in 1983 to 74.2% in 1984. No-tillage plots had greater disease incidence than conventional-tillage plots in both years. In addition, disease severity in 1984 was greater in plots that received no tillage. The pathogen was isolated more frequently from both stems and petioles of plants grown in no-tillage plots than from those grown in tillage plots. Disease severity was higher with wheat/soybean doublecropping than with soybean monoculture both years. Disease incidence and severity were positively correlated between years and between methods used to assess stem canker. Pathogen spread was limited as indicated by the positive correlation between disease incidence in plots between the 2 yr and by observed differences between disease incidence and severity in adjacent plots. The data indicate that stem canker can be reduced by tillage operations. In addition, the data demonstrate that stem canker can increase from negligible amounts to epidemic levels in 1 yr.