Problem Identifier Unit Screen//v.w/ RR Template

Problem Identifier Unit Screen//v.w/ RR Template Ring Rot

Problem
Shoot tips are stunted, forming rosettes. Leaves turn yellow, then brown between the veins. Leaf margins curl upward, and stems may wilt. Stems cut at the ground level exude a creamy white ooze. Only a few stems on a plant may show symptoms. Tubers may be cracked and, when cut near the stem end, reveal a yellow to light brown ring of crumbly decay.

Analysis
This disease is caused by a bacterium (Clavibacter michiganense subsp. sepedonicum) that attacks both tubers and stems. Infected tubers are inedible. Tuber decay may be evident at harvest, or it may not develop until after several months in storage. Other rot organisms frequently invade and completely rot the tubers. Ring rot bacteria enter plants through wounds, especially those caused by cutting seed pieces before planting. They do not spread from plant to plant in the field. The bacteria survive between seasons in infected tubers and storage containers.

Solution
Discard all infected tubers and plants at the first sign of the disease. Next year, use only certified potato seed pieces for plants. Plant whole; or if you cut them, disinfect the knife between cuts by dipping it in rubbing alcohol. Disinfect storage containers with a chlorine bleach. Wash storage bags in hot water.

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