Symptoms

• Ditylenchus dipsaci may develop on leaves, stems and tubers of the potato plant. Plant growth is reduced and the infected tubers have brown spots.

• Ditylenchus destructor only colonizes the underground parts of the plant. It penetrates directly into the tuber from the stolons, lenticels and eyes. No symptoms can be seen during the growing season. At harvest, lesions appear on the tuber in the form of small brown and sometimes star-shaped spots (photo 1).

When the tuber is cut open, the underlying rotten tissues have a grainy, spongy/mealy appearance (photos 2 and 3).

In storage, the nematodes (and the lesions) continue to develop within infested tubers; a mummified tuber is the final stage of infestation (photo 4).