With excessive rain in many areas this year, Phytophthora root rot is a looming threat in soybeans.

Wet soil conditions – especially in heavy, poorly drained or compacted soils – promote disease development with the ideal temperature for infection. Additionally, the disease can be worse in fields where high levels of potash, manure or municipal sludge were applied before planting.

Phytophthora often affects plants in three phases — seed rot, seedling blight and root/stem rot. The soil borne fungus persists in soil and soybean residue, infecting roots through water films, causing severe damage and potential plant death.

Symptoms may take weeks to appear. Severe infection often leads to replanting, while surviving infected plants are less productive, with yield losses ranging from 5% to over 50%.

Improving field drainage and soil structure, as well as carefully timing planting in heavy soils or no-till systems, can help mitigate the disease. The most effective means of management is for farmers to choose soybean varieties rated for Phytophthora tolerance to protect their crops and improve yields. Seed treatments are another very effective management tool.

“Phytophthora tends to be adaptive, which is why we use multiple modes of action in our seed treatments to buy some time for resistant genes or field tolerance to kick in,” said Matt Montgomery, Pioneer Field Agronomist. “That helps us avoid late-season Phytophthora.”

Ongoing research and effective management strategies remain critical in mitigating the impact of Phytophthora root rot as it continues to threaten soybean production.

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