POTATO DISEASE RING ROT
Ring rot potato disease is caused by the bacterium Clavibacter michiganense subsp. sepedonicus. The bacteria which cause ring rot are persistent in storages, bags, bins, and on equipment.
The bacteria can infect seed and cause drastic losses in the field.
Severe ring rot potato disease can result in wilting of leaves and stems along with yellowing and death of leaves.
Lower leaves usually wilt first, are slightly rolled at the margins, and are paler green than healthy leaves. As wilting progresses, leaf tissues between veins become yellow. In the later stages of disease, margins of lower leaves die and become brittle and eventually entire stems yellow and die.
Ring rot potato tuber Symptoms
The first sign of ring rot in tubers is the appearance of a light, creamy-yellow to brown discoloration of the vascular ring at the stem end. When the freshly cut tuber is squeezed, a creamy-yellow or light brown exudates (scrud) will appear.
In more advanced stages, the entire vascular ring will rot with cavities extending to the center of the tuber.
The outer surface of such tubers will sometimes be cracked and depressed. Secondary soft rot bacteria may invade these tubers.
The only way bacteria persist under field conditions is in plant debris and cull tubers.
Therefore, disease loss due to residual bacteria in the soil will be minimal if plant and tuber debris is destroyed during the winter or rotational period.
Certified or foundation seed has a zero tolerance for ring rot potato disease. Therefore, any significant amount of ring rot must originate from home grown seed, contaminated equipment or storage facilities, or volunteer plants in the field.
