Population changes of the potato cyst nematode (Globodera rostochiensis) during irregular crop rotation
1999
Sedivy, J. (Vyzkumny Ustav Rostlinne Vyroby, Prague-Ruzyne (Czech Republic))
For a period of 17 years, changes in the number of potato cyst nematode (PCN) cysts in the soil and in their contents were studied in two fields with an irregular crop rotation and growing resistant and susceptible potato cultivars. The number of cysts per 100 g of soil cannot be used to estimate the degree of soil infestation with the PCN without knowing the number of viable stages in the cysts. No unequivocal negative effect of cropping resistant potato cultivars on the number of PCN cysts in the soil has been ascertained. In most years, the cropping of resistant cultivars was followed by an increased number of empty cysts in soil samples in both experimental fields. The effect of growing resistant cultivars on the number of viable eggs/larvae was negative in both fields, resulting in decreased mean numbers of viable individuals per cyst. The mean number of dead eggs/larvae per cyst was variable. The number of empty egg cases was usually higher after the harvest of a resistant potato cultivar. The numbers of empty cysts and those with dead contents increased distinctly after an application of pig manure prior to growing the resistant cultivar and in subsequent years. The mean number of cysts in the soil, and of viable stages in the cysts also declined after a crop of rye. Regular cropping of resistant potato cultivars at 3-year intervals, once interrupted by growing a susceptible plant cultivar, decreased the occurrence of viable stages of the PCN below the detectable level.
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