Effect of crop rotation on soil population densities of Fusarium solani and Heterodera glycines and on the development of sudden death syndrome of soybean

Abstract

The effect of crop rotation on the development of sudden death syndrome (SDS) of soybean and on the soil population densities of Fusarium solani and the soybean cyst nematode ( Heterodera glycines) was observed for four years in a field naturally infested with both pathogens. In 1989 all plots were planted to a soybean cultivar susceptible to both pathogens (cv. Lee 74). In 1990 and 1991, the plots were planted to one of the following crops: soybean cv. Lee 74, soybean cv. Hartz 6130 (resistant to both pathogens), sorghum, fescue, or wheat (not double-cropped). In 1992 all plots were planted to soybean cv. Lee 74. The parameters measured to determine rotation effects were severity of SDS over the season, the soil population densities of both pathogens, soybean yields and soybean seed weights. Rotation to any crop except soybean significantly reduced the H. glycines population densities in 1990 and 1991. In 1991, the H. glycines population densities began to rise in the nematode-resistant soybean treatment, but were lower than those in the susceptible soybean treatment. Averaged over all years, the F. solani population densities were significantly lower when sorghum or wheat were grown than when soybean or fescue were grown. Considering the whole season, the F. solani population densities were generally the highest at harvest. Negative correlations between SDS and yield were significant, as were positive correlations between SDS and population densities of F. solani. In 1992, SDS was very low in all treatments, but yields were highest in plots planted to non-soybean crops and lowest in plots planted to the susceptible soybean.