Down Garden Services

BLACKLEG ON POTATO

( Erwinia caratovora )

Blackrot affected plant looks pale and weak

Base of stem blackened and falls over

Blackleg is caused by a bacteria with many strains which also infect stored potatoes, carrots, bulbs, and damaged plant tissue, causing Soft Rot by dissolving the cell walls. When it affects potato crops, the foliage turns yellow, the base of the stems turn black and rot, then collapse. Then it travels along the underground stems to the developing tubers which get a brown or grey, slimey rot inside. If not removed they will infect other tubers later when they are stored.

Tuber flesh rots and has a distinctive smell.

It is more prevelant during periods of increased temperature and humidity. There is no treatment so prevention is the only measure that can be taken.

Use certified 'seed' potatoes which should be free of the disease. If infection occurs remove all affected stems and tubers - including the original 'seed' tuber which is most likely the source. Try to remove all of the tubers from the ground at harvest as any diseased ones will carry it to over to following crops. Also rotate crops to reduce the chances carryover. Space well when planting to improve the air flow around the stems. When harvesting check tubers for pinkish-brown blemishes which indicate underlying, developing rot. Store at low temperatues, eg. in clamps outside. If storing indoors use crates or stout cardboard boxes which can be regularly inspected.

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