Decline of potato cyst nematodes in Northern Ireland
Potato cyst nematodes (Globodera pallida and G. rostochiensis, both EPPO A2 quarantine pests) were first recorded in Northern Ireland in 1922. During the 1930s and early 1940s, nematodes were found as pests in gardens and allotments around cities. Intensive cropping with potatoes in fields during the 2nd World War exacerbated the problem which led to the publication of a special Order in 1945 and later amended (Potato root eelworm order). The measures prohibited potato growing in infested land. Land which has been out of potato production ('scheduled') for at least 15 years is eligible for re-sampling, and then the land is re-sampled every five years if necessary. At present in Northern Ireland, approximately 50 % of land has now been descheduled, although there is still land that has been scheduled for 50 years.
Since 1986, a survey has been carried out in scheduled fields that had been found infested by potato cyst nematodes. Over the years, it was found that nematode populations are declining. This decline is not constant in time, the greatest reduction occurs during the first six years. Population analysis could only be made in certain fields, but it was observed that 81 % of the populations were G. rostochiensis, 8 % G. pallida and 11 % were a mixture of the two species. Cysts recovered throughout the survey were of variable age, and possibly up to 25 years old. The author concluded that the procedure followed for descheduling (with a re-sampling after 15 years since the first detection) seems adequate, as a decline of populations is obtained. It is also noted that land which has been out of potato production for more than 30 years and where non-viable cysts, or cysts containing poorly discernible juveniles are observed, could also return to potato production as these populations are considered as non-viable.
Sources
Turner, S.J. (1996) Population decline of potato cyst nematodes (Globodera rostochiensis, G. pallida) in field soils in Northern Ireland.
Annals of applied Biology, 129(2), 315-322.