An emergency approval has been granted for paraffin oil product Olie-H in seed potato crops, offering growers a management tool for non-persistent aphid-vectored viruses.

Non-persistently transmitted potyviruses, known as mosaic viruses, have affected British potato production for many years and currently, the dominant species is potato virus Y (PVY). PVY is most damaging in ware crops grown from infected seed and depending on the variety affected, plants can lack vigour, producing smaller and sometimes misshapen or cracked tubers.

When aphids probe the leaves of plants infected with PVY, they can pick up the virus on their stylet and transmit the disease quickly – within minutes or even seconds of probing an uninfected plant. This in contrast to persistent viruses like potato leaf roll virus (PLRV), which take much longer for an aphid to acquire and become infectious.

Non potato colonising aphids like the grain aphid and willow-carrot aphid, as well as colonising aphids, can spread PVY very quickly as they move through potato crops. This wider range of vectors and speed of transmission make PVY difficult to manage and furthermore, key vector species have developed resistance to pyrethroid insecticides.

Mineral oils

Applying mineral oils as adjuvants is a way growers can manage PVY – these work by coating the crop’s leaves with a thin film which disrupts the acquisition and transmission of virus by the aphid’s stylet.

Caroline Williams, UK potato crop manager at Certis Belchim, says until now, mineral oil products have only been permitted from emergence up to tuber initiation (BBCH 40) in seed potato crops.

This led to Horticulture Crop Protection (HCP), Seed Potato Organisation (SPO), GB Potatoes, SAC Consulting and VCS Potatoes applying for an Emergency Authorisation (EA) for the company’s paraffin oil product Olie-H for use from tuber initiation onwards.

“The application has been successful and seed growers will benefit from the proven efficacy of oils for the entire growing season in 2024, helping suppress non-persistent virus levels in seed stocks,” says Caroline.

“We recommend that Olie-H is always applied to a dry leaf and growers avoid applying it in the heat of the day. It’s also best used as part of a virus control programme containing translaminar insecticides like Teppeki and InSyst,” she adds.

VCS Potatoes agronomist Graham Tomalin has welcomed the news of the successful application. “It’s been a team effort to gather all the evidence on the risk posed by PVY in British seed production and make a case for the emergency approval.

“Olie-H is a useful addition to integrated pest management (IPM) strategies, with a broad range of measures key to lowering virus levels and maintaining good seed potato health,” he concludes.