Influence of Planting Date and Cultivar on Soybean Sudden Death Syndrome in Kentucky. D. E. Hershman, Department of Plant Pathology, University of Kentucky, Lexington 40546. J. W. Hendrix, R. E. Stuckey, P. R. Bachi, and G. Henson. Department of Plant Pathology, University of Kentucky, Lexington 40546, and University of Kentucky Cooperative Extension Service, McLean County, Calhoun 42327. Plant Dis. 74:761-766. Accepted for publication 30 April 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/PD-74-0761.

In a 3-yr study in western Kentucky, soybean (Glycine max) cultivars differed in susceptibility to soybean sudden death syndrome (SDS), and their reactions, while not always consistent, were affected by planting date. In 1987 and 1988, May plantings resulted in higher SDS levels for most cultivars than did plantings in mid-June through early July. The reverse occurred for some cultivars in 1986, and others were unaffected by planting date. While the relative SDS reactions of most cultivars were generally consistent among years, all cultivars were affected, at least moderately, in one or more plantings. Overall, cultivars resistant to the soybean cyst nematode (Heterodera glycines) were less affected by SDS than were cultivars susceptible to H. glycines; however, yields were generally not correlated (P > 0.05) with either densities of viable cysts of H. glycines at soybean harvest or SDS progress (area under the disease progress curve). Similarly, area under the disease progress curve and densities of viable cysts were poorly correlated (P > 0.5) for most planting date and cultivar combinations. The number of pods per plant was reduced as SDS severity increased from moderate to severe levels; however, mild symptom expression did not affect pod numbers. Similarly, plant height was unaffected by SDS.

Keyword(s): Fusarium solani.