Globodera rostochiensis and Globodera pallida
HETDRO (G. rostochiensis)
HETDPS (G. pallida)
Heterodera rostochiensis (G. rostochiensis)
Heterodera pallida (G. pallida)
English names: Yellow Potato Cyst Nematode, Golden Potato Cyst Nematode, Golden Nematode
Nordic names: Gul Kartoffelcystenematod (DK), Keltaperuna-ankeroinen (FI), Gul potetcystenematod (NO), Gul potatiscystenematod (SE)
Estonian name: Kollane kartuli-kuduussi
G. pallida English names: White Potato Cyst Nematode, Pale Potato Cyst Nematode Nordic names: Hvid Kartoffelcystenematod (DK), Valkoperuna-ankeroinen (FI), Hvit potetcystenematod (NO), Vit potatiscystenematod (SE)
Estonian name: Valkjas kartuli-kiduuss
Major host plants
Potatoes (Solanum tuberosum) are the most important host crop for both G. rostochiensis and G. pallida. Tomatoes (Lycopersicon esculentum) and aubergines (S. melongena) are also attacked as well as other Solanum spp. Each species of Potato Cyst Nematode has several pathotypes and these differ in their ability to multiply on different potato cultivars.
Patches of poor growth occur generally in the crop, sometimes with yellowing and wilting. Even with minor symptoms on the foliage, the size of the tubers can be reduced. Mild infestation symptoms suggest the plants may be under stress from water or mineral deficiency. On heavily infested plants the cysts on the roots are clearly visible with the naked eye.
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The life cycle takes 38-48 days, depending on soil temperature. After mating, each female produces approximately 500 eggs, dies, and the cuticle of the dead female forms the cyst. Eggs remain dormant within the dead female's body (the cyst) until the proper stimulus to hatch is received (i.e. chemical stimuli released by host plant roots). Potato cyst nematode eggs can remain dormant and viable within the cyst for 30 years. Second-stage juveniles hatch when the soil temperature are warm enough (above 10°C) and under stimulus from host root exudates, they invade the roots. The juvenile undergoes three more moults to become either male or female. Females swell and break through the root surface but remain attached, being afterwards fertilized by the vermiform, actively moving males. Females are white when they protrude from the root surface and those of G. pallida remain so, but those of G. rostochiensis later pass through a golden yellow phase lasting 4-6 weeks. Later cysts of both species turn brown.
They are spread into new areas as cysts on seed potatoes, nursery stock, soil, flower bulbs. Cysts are also spread locally by wind and flood water.
Detection and inspection
The symptoms described for Glododera spp. can have many other causes and cannot be taken as proof of presence of nematodes. For positive detection it is necessary to find cysts in soil samples or females or cysts on host roots. Mature females and cysts are just visible to the naked eye and can be seen as minute white or yellow globes on the root surface. Specific identification is just possible by observation of the female colour at the appropriate stage of development, either a change from white to yellow in G. rostochiensis or prolonged white (slightly cream but no yellow phase) in G. pallida. Several methods are available for extracting juveniles or larvae from the soil, and thereafter specialist microscopical examination of juveniles, females or cyst is necessary for precise identification. Identification of pathotypes can be done by molecular laboratory methods.
Pest status and importance
Potato cyst nematodes are major pests of the potato crop in cool-temperate areas. The situation is more serious in the case of G. pallida because of the lack of resistance cultivar to this species. The estimated loss due to potato cyst nematodes could be approximately 2 t/ha of potatoes for every 20 eggs/g soil. The crop loss could be up to 80% when nematode populations are raised to very high levels by repeated cultivation of potatoes.
G. pallida is generally less common than G. rostochiensis in most of the EPPO region (with the exception of the southern part of the UK) and is absent from some countries. Therefore it deserves greater attention from a phytosanitary standpoint.
Source of information
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Author: Christiane Scheel
Editor: Elise T. Yamamoto Buch