This particular Fusarium species is different to Fusarium solani which is responsible for Sudden Death Syndrome. Sudden Death Syndrome has been found in Ontario and will most likely become more obvious in the southwest over the next few years. Fusarium wilt as the name suggests causes a wilting of the soybean plant. This wilting has often been mis-diagnosed this year as Phytophthora root rot or Phytophthora wilt. From a distance the affected plants do look to have Phytophthora root rot.
Affected plants have a wilting of the stem tips and the upper leaves are scorched.
In severe cases the leaves will dry up and drop prematurely leaving the petiole behind. The leaves usually remain attached to plants killed by Phytophthora root rot. There also is no evidence of a stem lesion or external decay does not go above the soil line as with Phytophthora. A lenthwise cut through the roots and stem will reveal a browning of the vascular tissue and pith. This may be confused with early-season brown stem rot.