Symptoms

There is no specific foliage symptom but in the most serious cases, there may be yellowing and then wilting of the plants.

At harvest, infected tubers are collected from localised areas (the foci of soil infection), randomly dispersed in the field.

The infected roots and tubers become covered with red-violet mycelium, which is highly characteristic (photos 1 to 4) sometimes accompanied by small black sclerotia (photo 5).

The mycelium then penetrates the tuber. The skin cracks, the flesh changes into a greyish dry rot and finally the tuber disintegrates completely (photos 6 and 7).