Publication no. D-2003-0324-01R

Soybean Cyst Nematode Reduces Soybean Yield Without Causing Obvious Aboveground Symptoms. J. Wang and T. L. Niblack, Department of Plant Microbiology and Pathology, and J. A. Tremain and W. J. Wiebold, Department of Agronomy, University of Missouri, Columbia 65211; G. L. Tylka and C. C. Marett, Department of Plant Pathology, Iowa State University, Ames 50011; G. R. Noel, USDA-ARS, Department of Crop Sciences, University of Illinois, Urbana 61801; and O. Myers and M. E. Schmidt, Department of Plant, Soil, and General Agriculture, Southern Illinois University, Carbondale 62901. Plant Dis. 87:623-628. Accepted for publication 21 October 2002. Copyright 2003 The American Phytopathological Society.

Field experiments were conducted at locations in northern and southern Illinois, central Iowa, and central Missouri from 1997 to 1999 to investigate the effects of Heterodera glycines on soybean growth, development, and yield. A wide range of infestation levels was present at all locations. Two locally adapted cultivars, one resistant to H. glycines, were grown at each location. Cultivars were planted in alternating four-row strips with 76 cm between rows. For each cultivar, 20 1-m-long single-row plots were sampled every 2 weeks starting 4 weeks after planting. Infection by H. glycines reduced plant height and leaf and stem weight on the resistant cultivars in the first 12 weeks after planting, and delayed pod and seed development 12 to 14 weeks after planting. Biomass accumulation was not reduced on the susceptible cultivars until 10 weeks after planting; reduction in pod and seed development occurred throughout the reproductive stages. Susceptible cultivars produced significantly lower yields than resistant cultivars, but the yield reductions were not accompanied by visually detectable symptoms.