Blackleg/seed piece decay (Erwinia carotovora subsp. atroseptica)

Blackleg/seed piece decay: biology

Blackleg bacteria are carried on seed tubers and can live on roots of several crops and weeds. They probably do not survive more than one year in soil. They spread from diseased to healthy tubers to healthy tubers during seed cutting and are spread from cull piles into crops and from plant to plant by insects, such as flies. Wet soil and low temperatures favor infection and spread.

Blackleg can cause heavy yield losses in crops and may lead to severe storage decay with poor harvesting practices. Seed piece decay causes gaps in young plant stands. Shoots of older plants may wilt and turn yellow. Stem bases turn grey to black before the shoot dies. Blackleg bacteria can cause tuber rot, starting form the stem end, but this is not always associated with foliar symptoms. Soft decayed areas of tubers are sharply distinct from healthy tissue.