Potato leafroll virus is becoming an entrenched challenge for Scottish seed growers, with producers calling for tighter control of volunteer potatoes and a review of bare isolation strips.
The issue was discussed at Potatoes in Practice during a panel chaired by Andy Stephen, chair of the Scottish Society for Crop Research Potato Committee.
Ryan Torrie, a high-grade seed grower in Aberdeenshire, said leafroll had become the biggest virus threat to his business since 2018.
The business grows around 350 acres of high-grade seed potatoes across 35 varieties.
“Leafroll has been the biggest impact on us over the past six, seven or eight years,” he said. “Since 2018, the levels have been ramping up.
“If we cannot keep it clean at the high-grade seed stage, what chance does everyone else have?”
Ryan said aphid levels had been lower than expected this season, particularly without the June spike seen in previous years. He said companion crops were among measures being tested to cut the exposed bare ground that can attract aphids as potatoes emerge.
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“We are trying to create a more confusing picture for aphids by reducing how much bare ground there is within the crop,” he said.
Alistair Melrose, who grows around 700 acres of mainly seed potatoes across Perthshire and Angus, said leafroll remained the principal virus issue in pre-basic crops.
“Where you did not have to rogue crops in the past, you do now because the virus is always there,” he said.
His business has moved pre-basic production to higher ground and keeps multiplication chains short to reduce risk. It is also increasing control of volunteer potatoes between crops.
“We will go back between crops and spray two or three times to make sure the volunteer potatoes are controlled,” he said. “It is easier to deal with them in the cereal crop than in the seed crop.”
Jamie Harrison, whose family farm in north Norfolk produces ware and seed potatoes, said disease pressure was made harder by the concentration of potato production in the region.
“Norfolk is heavily concentrated in ware potatoes, so finding isolation for seed production is challenging,” he said.
He said Potato virus Y had been a more significant challenge in ware crops, but warned that hotter summers and milder winters could make aphid-borne virus harder to manage across the sector.
“With climate change, hotter summers and milder winters, the aphid problem is not going to go away,” he said.
The panel agreed that volunteers, also known as groundkeepers, could act as a virus reservoir. Growers also raised concerns that mandatory bare isolation strips may attract aphids, although any changes would need to preserve clear separation between varieties for inspection and certification.
The session’s message was that there was no single solution to leafroll. Clean seed, short multiplication chains, aphid monitoring, crop hygiene and strong volunteer control will all be needed to manage the risk.
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