Ring rot

Clavibacter michiganensis subsp. sepedonicum

Symptoms

• Infection in the field but disease develops during storage
• Vascular bundle ring discolours to light yellow
• Later, the vascular bundle ring becomes loosened from the tuber skin
• When pressed, a cheesy tissue is released
• Secondary dry rot and/or wet rots can also occur

Infection and spread

• Latent infected seed tubers
• The disease is spread during storage
• Infection of tubers via mechanical damage
• Contaminated equipment, walls, boxes etc. are important
• Does not survive in soil
• The disease is not transferred to neighbouring plants

Possible confusion with

• Verticillium wilt (Verticillium dahliae)
• Dry rot (Fusarium spp.)
• Brown rot (Ralstonia solanacearum)