Phytophthora Root Rot


Phytophthora root and stem rot is triggered by the oomycete Phytophthora sojae.

In seedlings, the disease can induce damping-off, a phenomenon where seedlings perish before or after soil emergence. In mature plants, the disease can instigate sudden death, even when pod production has commenced.

Daren Mueller, Iowa State University, Phytophthora root and stem rot can drastically alter the physiology of soybean plants. It damages the root system, hindering the plant's ability to absorb water and nutrients from the soil, resulting in stunted growth and diminished yield.

Additionally, the disease can produce toxins that disrupt cellular processes, leading to cell death. This can further debilitate the plant, increasing its vulnerability to other diseases and pests.

(Image Credit: Daren Mueller, Iowa State University,


How to Identify Phytophthora Root and Stem Rot

Several characteristic symptoms aid farmers and agronomists in detecting the presence of Phytophthora root and stem rot.

Phytophthora root and stem rot generally manifests through leaf wilting and yellowing. As the disease advances, dark brown discoloration appears on the stems, starting from the soil line and progressing upwards. Brown and rotting roots often signal the disease's progression, potentially leading to plant death.


Geographic Impact of Phytophthora Root and Stem Rot

Phytophthora root and stem rot thrives in regions with heavy, poorly drained soils, often coinciding with excessive rainfall or irrigation. While it can appear in any soybean-growing region, it is predominantly found in the North Central United States and parts of Canada.

Timing of Phytophthora Root and Stem Rot

The disease can strike at any point during the growing season but is most prevalent during the early stages of plant development. It can also emerge in later stages, particularly under wet and warm conditions.

How to Manage Phytophthora Root and Stem Rot

To manage Phytophthora root and stem rot in soybeans, our experts recommend purchasing treated soybean seeds. FBN® soybean seed treatments contain metalaxyl, a fungicide that is highly effective against soil-borne oomycete pathogens like Phytophthora and Pythium.


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This content was generated with the assistance of Norm℠, FBN’s artificial intelligence (AI) Ag Advisor, based on a dataset of information containing general industry best practices and research. The AI model did not use specific external sources to generate this content. Our process involves using AI to aid human subject matter experts with the initial drafting and/or refinement of content.

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