This species occurs locally throughout the country. Its highest abundance is recorded where potatoes are grown in moist or excessively wet soils.

The potato tuber nematode is polyphagous, attacking 70 species of cultivated and ornamental plants as well as 65 species of soil fungi. In Poland and worldwide, besides potatoes, it also feeds on sweet potatoes, sugar beets, carrots, peanuts, onions, lily bulbs, tulips, certain weeds, and fungi as alternate hosts. Initially considered a race of Ditylenchus dipsaci (the stem nematode), detailed morphological studies by Thorn demonstrated that Ditylenchus destructor is a distinct species.

Biology

• Eggs – 0.1 mm long; a female lays about 250 eggs inside plants during her 1.5-year lifespan.
• Larvae (harmful stage) – endoparasites of tubers and plants, colorless. Larvae go through four developmental stages [L1-L4], differing in body length. The first stage typically reaches 0.5 mm. Infective larvae overwinter in plant residues and seed material. In spring, they penetrate tubers, rhizomes, or bulbs through lenticels.
• Adult – endoparasitic nematode, 0.8–1.4 mm in length. Males are smaller than females. They develop in the lower parts of stems, tuber parenchyma, and bulbs. Adults can overwinter in plant debris and do not form a true dormant stage.

Life Cycle

The potato tuber nematode develops under favorable temperature (15–20°C) and moisture (60–80% field capacity) conditions, producing several generations per year. The development of one generation takes 15–45 days, mainly depending on temperature and food availability. Infective larvae overwinter in soil on tubers, crop residues, and fungal mycelium. The nematode does not tolerate soil drying and prefers moist environments.

From May, nematodes leave infected tubers or crop residues and enter new underground plant parts (stolons, bulbs, rhizomes, and stems) through lenticels, without reaching aboveground tissues.

Distribution and Damage

Nematodes damage all underground parts of potato plants, especially tubers and stolons. Plants emerging from heavily infested seed tubers in spring are weak and may quickly die. Initial damage is difficult to detect, becoming visible later in the season on new tubers. It appears as small white spots under the skin with tiny holes where nematodes entered. Over time, the affected areas enlarge into gray-brown patches that can cover the entire tuber surface. The tissue softens, the skin collapses, darkens, dries, and cracks (see photos 2A, 2B, 2C). In severe cases, the tuber flesh becomes brown and spongy, with the skin splitting in sheets, resembling parchment. These symptoms help distinguish nematode damage from early potato blight (where the skin remains firm). Nematode feeding also facilitates secondary fungal infections, particularly fusarium and soft rot pathogens. During storage under high humidity, nematodes may migrate to adjacent healthy tubers. Crop losses due to D. destructor can reach 30–40% under heavy infestation.

Economic Threshold

Not established.

Presence of hatching nematodes (larvae and adults) can be detected through direct microscopic examination of soil, plant material, or tubers.

Control Methods

Agronomic methods (crop rotation – often ineffective due to broad host range, removal of thick-stemmed weeds from fields, crop residues, and bulbs, deep winter plowing). No potato varieties are resistant to this pest. The most effective approach is planting healthy, certified seed and chemical control. Pre-planting nematode treatments using available granular nematicides with applicators (Vydate, Nemathorin) are recommended.

Compiled by: Dr. Tomasz Erlichowski