Plant Disease March 2004
Volume 88, Number 3
The American Pathological Society (APS)
Interpretive summary

Effect of Sclerotinia Stem Rot on Yield of Soybean Inoculated at Different Growth Stages
G. A. Danielson and B. D. Nelson, Department of Plant Pathology, and T. C. Helms, Department of Plant Sciences, North Dakota State University, Fargo 58105. Plant Dis. D-2004-0112-02R, 2004. Accepted for publication 24 October 2003.

Sclerotinia stem rot is an important disease of soybean in the north-central region of the United States. To understand the impact of this disease on production, it is necessary to know the yield losses the disease can cause. This research measured the effect of Sclerotinia stem rot on seed weight, seed numbers, pod numbers, and oil and protein content of plants inoculated at two growth stages. The effects of disease on yield were variable. Disease resulted in significant seed weight loss, with reductions per diseased plant ranging from 19 to 39%. The estimated yield loss per 10% disease incidence ranged from 83 to 229 kg/ha, with an average loss of 137 kg/ha for four field experiments. A reduction in the number of seeds and pods per plant and seed oil content occurred in some, but not all, experiments. Seed protein was not affected. Inoculation at the beginning of flowering compared with 2 weeks later had a similar effect on yield.

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