A recent UK survey of potato cyst nematode (PCN) has identified a fall in the area of land affected by the pest, but a significant shift in populations on areas that remain infested, since the last assessment was carried out in 1999.
The survey, conducted by Kasia Dybal of Harper Adams University as part of a AHDB Potatoes PhD Studentship, showed almost half (48 per cent) of the soils tested in 2016 were found to be infested with PCN.
This was lower than the previous figure of 64 per cent, possibly due to the increase in potato varieties carrying the H1 resistance to Globodera rostochiensis, according to Dr Matthew Back of Harper Adams University.
He said: “The widespread use of varieties with high resistance to G. rostochiensis, possibly combined with the adoption of better management, including longer rotations, adoption of better practices and integrated management techniques, has led to an overall decline in the area infested.”
Six out of the 10 most popular varieties in the UK, including the most widely grown, Maris Piper, had resistance scores of eight or nine to that species, he added. “But it means we are left with more G. pallida as a result.”
In the 1999 survey, pure G. pallida accounted for 67 per cent of infestations, G. rostochiensis for 25 per cent and a mix of the species for 8 per cent.
In 2016, almost 90 per cent of infested sites contained pure G. pallida. The remaining 10 per cent were split between pure G. rostochiensis and a mix of the two species.
This was potentially bad news for the fresh potato sector, said Dr Back. “Varietal resistance is a key component of PCN management. The processing sector has access to quite a few resistant varieties, but very few options are available for the ware sector. Of the top 10 varieties, two score three for resistance and the rest just two.”
The eventual aim is to produce a map of PCN distribution around the country highlighting regional differences in populations to help growers optimise variety selection.