Blackleg and soft rot

What you see

The stem base turns inky black and slimy, the plant yellows and collapses. In store, tubers turn to a wet cream-coloured mush with a sharp, unmistakable smell. There is no fungal growth - just wet decay.

Conditions

Wet, cold, poorly drained soil at planting, and any bruising of tubers. The bacteria are usually already inside the seed potato and only express themselves when the soil is waterlogged.

Treatment

Remove affected plants immediately with the seed tuber. In store, sort out and discard every soft tuber - one rotting potato will take a whole sack with it.

Prevention

Buy certified seed potatoes. Do not cut seed tubers in wet conditions. Plant into warm, well-drained ground. Cure the harvested crop in the dry for a fortnight before storing, and store cool, dark and airy.

Months: April, May, June, October, November

Plants

Potato

Remedies

Not recorded — the field is blank rather than guessed.

The thing people get wrong

The smell is the diagnosis - nothing else in the garden smells like bacterial soft rot. And it is worth knowing this is imported, not acquired: the bacteria came in on the seed potato you planted. Saving your own seed from a crop that had any blackleg guarantees you the same problem, larger, next year.