Ten Fusarium species were identified to cause root rot on soybean in South Dakota. While F. sporotrichioides, and F. acuminatum were more prevalent, F. graminearum, F. oxysporum, F. solani, F. armeniacum, F. avenaceum, F. equiseti, F. proliferatum F. subglutinans, and F. virguliforme were less frequently found.
In the aggressiveness study under greenhouse conditions, F. proliferatum isolates caused the most severe root rot symptoms on soybean, followed by isolates of F. subglutanins, F. sporotrichioides, F. graminearum, and F. virguliforme. Among the Fusarium species causing damping-off, majority of the F. oxysporum isolates caused the most severe damping-off symptoms, followed by F. armeniacum and F. subglutanins. F. proliferatum and F. subglutanins are known to have a wide host range which includes soybean and corn.
The finding of these two Fusarium species on soybean in South Dakota is important because most soybean producers in South Dakota use a corn-soybean rotation in combination with reduced-tillage or no tillage systems, to help prevent soil erosion and increase organic matter. However, crop residue left on the soil surface of the field may favor survival of Fusarium species. While the corn-soybean rotation combined with no-tillage or reduced tillage system is followed in South Dakota, our results showing that F. proliferatum, F. subglutanins, and F. sporotrichioides are root rot pathogens aggressive on soybean suggest that corn crop residues may be an important source of inoculum for these Fusarium species.
The findings from this research suggest the need to test the effectiveness of management strategies, such as fungicide seed treatments, host resistance and cultural practices, to manage Fusarium root rot of soybean and protect yield.