Stem and Bulb Nematodes & Potato Rot Nematodes
Ditylenchus dipsaci and Ditylenchus destructor
Causative agent and transmission
Nematodes or very small worms, not forming cysts, therefore invisible to the naked eye thoughout their development cycle. They are highly polyphagous species developing on a large number of cultivated and adventive plants, monocotyledon or dicotyledone.
Description of symptoms on crops
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Ditylenchus dipsaci develops on the leaves, stems and tubers of the plant. Plant growth is reduced and the diseased tubers show brown blemishes.
Ditylenchus destructor only appears on the parts of the plant beneath the ground. It penetrates directly into the tuber from the stolons, lenticles and eyes. No symptom is visible during the growth period.
On harvesting, lesions appear on the tuber as small brown blemishes.
On the cut surface, the underlying tissues appear granular and spongy.
The blemishes grow larger and the final stage is expressed by mummification of the tuber.
Storage and transmission
The nematode passes the winter in the soil and in the remains of the roots in the form of larvae and eggs which tolerate negative temperatures, but die beyond -5°C.
Ditylenchus destructor is classified as a quarantine parasite.
These nematodes are controlled through:
- Elimination of weeds and regrowths;
- Long crop rotations (minimum of four years);
- Disinfecting the soil with chemical products (ethylene dibromide, metam-sodium).