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How Yorkshire seed potato growers are tackling virus

Virus has dominated potato industry headlines recently, as levels of non-persistent PVYN, in particular, have increased dramatically. Certis talks to two differing Yorkshire Highland Seed Potato Growers’ Association members to see how they are minimising infection risk. In this first case study, Certis talks to Andrew Johnston, seed manager, Wolds Produce Ltd

Andrew Johnston, seed manager, Wolds Produce Ltd

Wolds Produce Ltd was set up in 2006, primarily as a supplier of crisping and ware potatoes, but has evolved and added seed production into its remit not long after.

Seed manager Andrew Johnston now oversees some 400ha of seed crops across 24 contracted growers, from high-grade production on the Black Isle peninsula in Scotland, right down to Gloucestershire in England.

He’s seen potyvirus become the main issue for seed producers over the last three years, with the difficult 2018 a watershed moment for many, particularly in Yorkshire.

A hot and dry summer saw high aphid numbers and with largely unirrigated seed crops progressing slowly, they remained susceptible to infection for longer than expected.

Andrew says this showed that the available insecticide armoury now provides a relatively thin line of defence, with many growers not having enough applications to protect crops through to burndown.

“Unfortunately, the stable door was left open, but there has been a huge amount of learning about [its management] since.

“An optimistic view is that most of those involved in the seed trade, from growers to seed houses and merchants to agronomists have now come up with ways of reducing virus risk.”

Wolds Produce Ltd has a zero tolerance for virus in input stocks and varieties that are more susceptible to virus will not be multiplied more than once in Yorkshire before being sold for use in ware production.

For other varieties that are multiplied more than once, regular crop inspections, sometimes on a weekly basis, in-field rapid tests, post-burndown pre-harvest growing on tests and testing tubers from store are measures used to detect virus infection.

Timely and effective burndown is also a priority to ensure crops don’t run on too long and regrowth is minimal, reducing primary aphid-borne virus spread at the end of the growing period.

“If you take a relaxed attitude towards burndown and don’t go back to check crops once the job is done, that’s when it can come back to bite you,” notes Andrew.

Yellow water trap data is analysed to monitor activity of the various aphid species that spread persistent and non-persistent viruses.

Andrew says once he sees upturn in numbers of colonising species, such as the peach potato aphid, seed crops get a full programme consisting of the “Rolls Royce” systemic products.

These include Insyst (acetamiprid), Teppeki (flonicamid) and Movento (spirotetramat), although Movento can’t be used until after flowering in varieties that produce flowers.

He adds that growers should have a plan of how applications of these products will be spaced out across the season, within label guidelines and restrictions, to offer the best protection against aphids and virus.

However, flexibility to shuffle these “trump cards” can be necessary where aphid monitoring data and crop inspections inform growers that applications need pulling forward.

“I’d much rather use these systemics in the first half of the season if needed, rather than hold them back and find out you have high levels of virus in the crop.”

Read the second case study in the series here