Aphanomyces root and hypocotyl rot

Aphanomyces root and hypocotyl rot is a devastating soil-borne disease caused by the oomycete Aphanomyces euteiches. This pathogen thrives in moist soil environments, affecting the root architecture and hypocotyl of susceptible plants. By destroying the root cortex, the pathogen limits the plant's ability to take up water and nutrients, causing severe developmental issues.

The disease primarily targets leguminous crops, with common beans, peas, and alfalfa being highly susceptible. Because the pathogen produces durable oospores, it can survive in the soil for years, making it difficult to eradicate once it becomes established in a field. Frequent cropping of host species is the main factor increasing the disease pressure.

Symptoms initially appear as yellowing of the lower foliage and stunted growth. Infected roots exhibit water-soaked, soft lesions that eventually turn dark brown or grey. As the infection progresses, the outer root tissue sloughs off, leaving only the central vascular cylinder, which leads to total plant collapse during periods of environmental stress.

Environmental conditions are critical for the development of the rot. High soil moisture, poor drainage, and soil temperatures ranging from 15 to 25 degrees Celsius create the perfect conditions for the pathogen's zoospores to migrate toward host roots. Compacted soils that trap water are particularly prone to severe outbreaks.

Management strategies focus on minimizing risk through cultural practices. Long crop rotations are essential to reduce the inoculum load in the soil. Farmers should prioritize field drainage, monitor soil conditions before planting, and avoid sowing in cool, wet soils. While some varieties show partial resistance, integrated management remains the most reliable way to mitigate economic losses.