Phytophthora Root and Stem Rot

Phytophthora root and stem rot is a significant disease in many areas where soybeans are grown. It can kill and damage seedlings and plants throughout the growing season from the time of planting nearly until harvest. With the rain and warm weather we have had in our territory it has created favorable conditions for Phytophthora root and stem rot.

For disease scouting, you are most likely to find the disease in the following places:

   – low and wet spots in a field
   – fields with high clay content
   – fields that have been in no-till for a few years
   – weedy areas that may be the result of stand reduction earlier in the season

What can you expect this to look like? In the mid to late season you can expect this to look like brown lesions that form on the roots, the roots can rot and degrade, and a dark chocolate-brown discoloration of the stem often extends from below the soil line upward into lower parts of the plant. The plant leaves turn yellow, wilt, and typically stay attached after plant death. Plants are often killed in patches or in sections of rows. In tolerant varieties, plants may be stunted but not killed. Symptoms on tolerant varieties may be restricted to root rot that results in hidden damage that may reduce yields.

How do you manage Phytophthora root and stem rot? By making the correct seed decisions, using a soybean seed treatment, and placing an importance on seed placement you can help reduce the risk of this disease. Varieties like NK’s 14-W6E3, 19-Y5E3, and 22-C4E3 are known for a strong resistance package to Phytophthora. Using a seed treatment like Warden CX not only sets your seedlings up for success it also provides extra protection against early season Phytophthora threats. When making the seed placement decisions to help protect your soybean crop it is recommended that you rotate your crop to prevent the rapid build-up of inoculum, and plant in fields with good drainage.

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