Potato growers need to be wary of the build up of aphids and be prepared to treat crops if necessary, experts have advised.

Growers with seed crops need to be particularly vigilant and spray as soon as aphids are found, said the Scottish Agricultural College’s Andy Evans.

Those with ware varieties may have more leeway and should consider treatment if populations start rising, he said. “Most ware crops will tolerate a limited aphid population. The generally accepted threshold is five aphids per leaf, but the important thing is to hit them when the population is rising.

“If you go too early then there’s time for aphids to recolonise, but a more focussed and tailored approach, ideally on a field-by-field basis, will achieve the most economic control.”

But, varieties susceptible to Potato Virus Yellows (PVY) and Potato Leaf Roll Virus (PLRV) – such as Nadine and Russett Burbank – effectively have zero tolerance for aphids, he added.

Commenting on trials last year, Greenvale’s technical director, Paul Coleman, said that growers looking to control viruses such as PVY need to use anti-feedants, such as Hallmark Zeon (lambda-cyhalothrin).

“In a real field situation, where the complete crop is treated, I would expect the inclusion of Hallmark Zeon with either Plenum (pymetrozine) or Aphox (pirimicarb) to give virtually complete control in most circumstances,” he said.