THE UK seed potato sector loses an estimated £18m from potato viruses annually – a cost that could be dramatically reduced by one small change to spray programmes, according to research and commercial trials conducted in Holland.

The findings from five years’ worth of trials with the Interagro adjuvant, Banka, has shown an increase in virus control of 18% when applied with a pyrethroid insecticide up to and including tuber initiation.

The work, conducted by Holland Fyto, also recorded an average improvement in potato yields of 0.89t/ha which translates into an estimated margin gain of £178/ha (based on a potato price of £200 per tonne).

“With resistance to pyrethroid insecticides now widespread, coupled with the succession of relatively mild winters encouraging survival of a higher number of aphids, the need for some positive news is likely to be highly welcome,” said Interagro’s product manager, Sarah Ferrie.

The UK’s estimated 17,000ha of seed plantings is vulnerable to two key viruses within four weeks of planting, both are transmitted by aphids – potato leaf roll virus (PLRV) and the protyviruses, including potato virus Y (PVY). This is a big vulnerability for the sector, given that virus-free status of seed is fundamental to both the national and export markets, pointed out Ms Ferrie.

PVYN (veinal necrosis strain) and recombinant PVYNTN (N-tuber necrosis) are key viruses for both UK and The Netherlands with the peach potato aphid being the major aphid vector. "Growers must take a zero-tolerance approach to prevent virus transmission to avoid rejection by seed crop inspectors," she said.

The Dutch Banka trials clearly showed a reliable improvement in virus control from the addition of it in each of the five years tested and demonstrated improved reliability over mineral oils, excellent crop safety and improved rainfastness of 30 minutes, helping to maintain tight spray intervals in marginal weather.

“The trials also logged a tuber number gain with Banka, versus a substantial loss using mineral oil Olie-H, not currently registered here in the UK," she pointed out.

“Growers involved in the Dutch trials observed that crops treated with Banka were more resistant to haulm collapse following torrential rain, a disadvantage typically experienced when using high dose mineral oil. Growers really appreciated the very low dose, 0.1% v/v Banka versus 2.1% Olie-H.

"At a water volume of 300 l/ha, that means the grower applies 0.3 l/ha Banka versus 6.25 l/ha mineral oil and is therefore much more efficient for growers,” she argued.

"We recommend Banka for application in tank-mix with all leading potato pyrethroid insecticides and fungicides at inclusion rates of just 0.075-0.1% by volume up to and including tuber initiation.

"The Dutch trials were based on treatments applied at 80% crop emergence with Sumicidin Super (25g/l esfenvalerate), applied weekly over 10 weeks in a mancozeb-free programme. All applications were made using a 75% drift-reduction nozzle, the Teejet Airmix 110-04."