combat PCN
Spud push to
combat PCN
POTATO growers need to adopt the same sort of measures for keeping land free from cyst nematodes as sugar beet growers do to counter the spread of rhizomania, says Harper Adams nematologist Pat Haydock following the results of a new study funded by Dow AgroSciences.
In what is said to be the first systematic survey of PCN problems on 484 farms in England and Wales, 64% of soil samples were found to be infested. Of those 92% contained G. pallida. By contrast only 33% contained G. rostochiensis.
Researcher Stephen Minnis believes growers have unwittingly selected for pallida by concentrating on varieties like Maris Piper and Cara that are fully resistant to G. rostochiensis. On land with mixed populations that has left the way clear for G. pallida, for which there are only partially resistant varieties and which is less well controlled by granules, he reasons.
"The pallida problem is far more serious than was estimated only a few years ago."
The latest survey was backed by the British Potato Council. Previous Potato Marketing Board and other surveys have always been based on farms with suspected problems and so may have over-estimated overall infestations, says Dr Haydock.
"This increase is not unexpected, based on the varieties which have been in use since the 1960s. But it is a problem that has been creeping up on us and it shows our management isnt really working.
"It is extremely worrying for the future competitiveness of the UK potato industry." Controlling the pests with granules adds £300-340/ha (£120-138/acre) to growing costs, and fumigation for severe infestations can cost half as much again, he says. In extreme cases whole crops can be lost.
The key message is that clean land is becoming increasingly valuable and growers should reinforce their efforts to keep it that way, he suggests. "That means not using home-saved seed from infested land and cleaning machinery to make sure soil isnt transferred from field to field. Growers are really going to have to adopt the same sort of measures that are used to counter the spread of rhizomania."
For growers on infested land his advice is to lengthen the intervals between potato cropping and to check which species is present so appropriate resistant varieties may be chosen.
Pallida progress
• PCN found in 64% of soils.
• 92% of those had G pallida.
• Variety choices blamed.
• Clean land needs protecting.
PALLIDAPROGRESS
• PCN found in 64% of soils.
• 92% of those had G pallida.
• Variety choices blamed.
• Clean land needs protecting.