Potato Cyst Nematodes
Globodera rostochiensis and Globodera pallida
Causative agent and transmission
Nematodes or very small worms (< 1 mm) visible to the naked eye during growth in the form of small balls attached to the plant roots. These balls are yellow in Globodera rostochiensis and white in Globodera pallida.
Description of symptoms on crops
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During the growth period, the presence of potato nematode cysts on the plot is expressed by "patches" or roughly circular areas with low growth.
The observation of plants uprooted from these patches during tuber development reveals the presence of white or yellow females and brown cysts on the root system.
Storage and transmission
The cyst is the result of the transformation of the female after fertilisation. It can contain more than 1,000 larvae and is therefore the essential feature ensuring that the nematode is preserved and dispersed.
Surrounded with a very thick wall, it is very resistant to low temperatures and can remain alive in the soil for many years (viability can reach 15 to 20 years in our regions).
Being of small size, these cysts can be easily mistaken for soil particles. They are conveyed from one plot to another with farm implements/machinery, on tractor wheels or any other soil transport agent (shoes, run-off, etc.).
These parasites are classified as quarantine-regulated and must undergo compulsory control procedures.
Since no curative control method is 100% reliable, preventive measures must be used : planting in an unaffected (or tested) plot, use of certified seed, long crop rotations (minimum of four years), eliminate regrowths in the plots, etc.
Numerous varieties of all types are resistant to G. rostochiensis (possibility of damage but no cysts formation). Some starchy varieties have a double resistance (G. rostochiensis and G. pallida).