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Rhizoctonia Damping-off and Root Rot of Soybean

Causal Agent: 

Rhizoctonia solani

Symptoms and Signs: 

  • Reddish-brown, sunken lesions on hypocotyls of young seedlings
  • Damping-off, pre- and post-emergence
  • Stunted growth and chlorosis of older plants
  • Persistant sunken, reddish-brown canker on plants that survived seedling infection

Disease Cycle: 

  1. Survives in field as mycelium (filamentous fungal body) or sclerotia (mycelial ball in a melanized rind) in the soil.
  2. In warm and wet conditions, sclerotia can germinate and mycelium will infect the host. No spores are produced.
  3. Symptoms such as damping-off will occur early in the season, while surviving plants will be stunted, chlorotic and may senesce early.
  4. Mycelium and sclerotia are produced in  plant tissues and can survive in the soil for subsequent growing seasons.

Disease Management:

  • Use high quality seed
  • Use fungicide treatments with efficacy for true fungi
  • Plant varieties with partial resistance to R. solani
  • Rotate to non-hosts such as corn or wheat
  • Improve soil drainage
  • Test soil for proper pH and fertility, as over fertilization can encourage R. solani growth