Rhizoctonia Root and Crown Rot

Rhizoctonia solani

 

Identification

  • Rhizoctonia root and crown rot is the most common root disease of sugarbeets in the US
  • Rhizoctonia is a fungus

 

Detection

  • Sudden wilting of leaves
  • Noticed late in growing season during final cultivation or later
  • Disease typically runs down the beet row
  • Several black lesions will appear on the root
  • As the disease progresses, these lesions may grow together and cover the entire surface of the root
  • This dry rot has a sickly sweet odor that is produced from rotting beets
  • Sugarbeet roots remain firm until the plant dies, unless bacteria enters
  • The inside of the root will appear white and healthy until advanced stages of decay, when it turns brown and the root rots completely
  • A dark brown to black discoloration of the youngest leaves and petioles near the center of the crown often are observed
  • Symptoms include chlorosis of the leaves and sudden wilting with many leaves turning black and dying around the crown
 

Cause of Infection

  • Over winters in soil and in plant tissue
  • In the spring and summer it resumes growth and infects through leaf petioles, crowns, or roots
  • Over hilling of plants with cultivation often aggravates the disease
  • Favors warmer or hot temperatures
 

Beet Damage

  • Root and crown tissue rot
  • Adjacent roots become infected and can die
  • Up to a 50% loss is possible
  • Infected roots may lower quality if found in beet sample
 

Control

  • Cultural control (less dirt on crown)
  • Tillage (Without hilling) and fertilizing to promote good growth
  • Crop rotation with corn and small grains (no beans or potatoes)
  • Plant resistant varieties