Emergency application to combat key potato viruses

An emergency approval has been granted for paraffin oil product Olie-H in seed potato crops – helping growers tackle non-persistent aphid-vectored viruses.

Non-persistently transmitted potyviruses – sometimes called mosaic viruses – are the most problematic viral diseases affecting British potato production. Currently, the dominant species is potato virus Y (PVY).

PVY is most damaging in ware crops grown from infected seed (secondary infection), 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 (or mouthparts) and transmit the disease very 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, so aphids that colonise potato crops – such as the peach-potato aphid – are key to its transmission.

Rapid transmission

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 it very difficult to manage, and key vector species have developed resistance to pyrethroid insecticides – including to their rapid ‘knock-down’ action – so it has only become trickier in recent years.

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.

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

This led to an emergency application for the company’s paraffin oil product Olie-H to be used from tuber initiation onwards. Applicants were Horticulture Crop Protection, Seed Potato Organisation, GB Potatoes, SAC Consulting and VCS Potatoes.

Ms Williams said: “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.

“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.”

Welcome news

VCS Potatoes agronomist Graham Tomalin, who oversees seed potato crops across East Anglia where PVY is a significant threat, said news of the successful application was a welcome boost for growers.

“It’s been an excellent 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.”