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Stop Phytophthora Root and Stem Rot


While soybean farmers face different soil types and growing conditions, many share the common challenge of controlling Phytophthora root and stem rot. There are more than 50 genetic forms of this pathogen found in North America, and it survives in soil in the form of oospores for up to 5-10 years. That equates to plenty of opportunity to wreak havoc on soybean fields.

​​​​​​​​​​​​​​Phytophthora root and stem rot not only damages seedlings, but can also harm plants throughout the growing season until just before harvest. Phytophthora tends to present itself when there are wet and warm soil conditions early in the growing season. Clay and compacted soils along with poorly drained areas also tend to trigger the disease.

When Phytophthora strikes early in the season, it attacks and kills seedlings in the ground or soon after emergence. Infected stems typically appear bruised and are soft. Leaves often turn yellow and brown, and some plants may wilt and die. However, some plants can be infected early in the season and not show severe symptoms until later in the summer. 

Later in the season, the disease is usually signaled by brown lesions on roots along with a dark chocolate-brown discoloration of the stem that frequently extends from below the soil line upward into lower parts of the plant. Leaves turn yellow, wilt and typically stay attached after plant death. Soybeans diseased by Phytophthora tend to die in patches or in sections of rows.

To prevent your fields from being infected with Phytophthora, here are several management steps you can take:

  • Increase drainage and avoid soil compaction to create a field environment that reduces the likelihood of saturated soils.
  • Treat seed with the highest labeled fungicidal compounds rates.
  • In areas with a history of Phytophthora, plant resistant varieties that contain built-in tolerance. When Phytophthora-tolerant varieties are selected, plants are more likely to be stunted rather than killed, and yield damage will not be as severe.
  • Keep field records where there has been Phytophthora so you can evaluate the effectiveness of the resistant genes planted.

Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.

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