Scottish seed potato growers have come out strongly in defence of their production standards amid accusations of unacceptable viral infection in 2019 crops.
The SAC Association of Potato Growers meeting at Scone on January 29 heard that 62 seed crops grown in England from Scottish stock had been downgraded after field inspections as part of the certification process.
In most cases Virus Y infection was cited but there is doubt about the source of the aphid borne disease.
Dr Jon Pickup, Head of Virology and Zoology at Science and Advice for Scottish Agriculture (SASA) said he had traced 30 sister stocks which had been grown in Scotland.
These had produced 67 crops of which only six had signs of Virus Y infection, with three being downgraded from S grade to SE.
Dr Pickup said: “In 2017 we recorded the lowest ever levels of virus infections in Scottish crops. In 2018 there was something of a resurgence partly because of the loss of insecticides and partly because of high summer mean temperatures and high sunshine hours. It did mean we saw higher virus levels than predicted but our inspection regime, with two visual inspections during the season, works to extremely precise tolerances and can detect one infected plant in 10,000 or 0.01 per cent.”
SASA, which supervises the Scottish seed potato inspection scheme on behalf of Scottish Government, also has the power to order the burning down of any potato crop, including ware crops, which shows more than 10 percent virus infection.
There is also a one-year limit on using home saved seed which does not apply south of the Border.
Adrian Fox, senior plant virologist at Fera said the biggest reason for downgrading English seed crops in 2019 had been virus, and he had heard anectodal evidence of high levels of tuber cracking. This was not all due to virus infection however.
“There have been calls for tuber testing of seed crops, but it is expensive. It can certainly identify stocks with excessive virus content but cannot predict the impact on the growing crop or what virus there will be in the daughter crop.”
Dr Pickup agreed but pointed out that accuracy was limited to 0.5 per cent.
Eric Anderson, senior agronomist with Scottish Agronomy asked what consideration English growers had given to virus moving into seed crops from neighbouring ware crops or from groundkeepers. He also asked what the risk was of virus transfer by willow carrot aphid from neighbouring carrot crops.
Mr Fox agreed that groundkeepers were ‘a risk’ but more work needed to be done to before he could comment definitively on the role of willow carrot aphid as a vector.