Effects of Row Spacing and Within-Row Plant Population on Rhizoctonia Aerial Blight of Soybean and Soybean Yield. G. F. Joye, Former Graduate Assistant, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803. G. T. Berggren, and D. K. Berner. Professor, and Instructor, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803. Plant Dis. 74:158-160. Accepted for publication 12 September 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0158.

Greenhouse and field experiments were conducted from 1983 to 1985 to study the influence of row spacing and within-row plant density on Rhizoctonia aerial blight (caused by Rhizoctonia solani) and yield of soybean (Glycine max). A disease rating system was developed that accounted for both disease incidence and severity. A significant negative relationship between disease and soybean seed weight and number was observed in the greenhouse. Within-row plant population had no significant effect on disease or yield. In all years, row spacings of 50 cm or more resulted in decreased disease. In 1983 and 1985, row spacing of 25 cm resulted in higher yields than row spacings of 50, 75, or 100 cm. Rhizoctonia aerial blight reduced leaf area, but higher plant populations associated with decreased row spacing more than compensated for the reduction. In 1984 the effect of row spacing on yield was reversed; wider spacing resulted in higher yield. Drought stress in 1984 may have influenced this trend. Simulations from a soybean growth model (SOYGRO) indicated that higher yields could be expected with wider row spacings during drought years.