Potato ware crop growers must look for aphid build-up and be ready to take quick action, particularly if the their variety is susceptible to the effects of Potato Virus Yellows (PVY) and Potato Leaf Roll Virus (PLRV), warns Dr Andy Evans of the Scottish Agricultural College.

Dr Evans advises all ware growers to monitor crops regularly and hit aphid populations if they start to multiply rapidly.

He advocates growers mark a number of plants across the field when they start to see aphids present, then track population development on the same plants each week.

“Most ware crops will tolerate a limited aphid population, but as soon as they start to multiply rapidly, that’s the most effective time to strike,” said Dr Evans. “If you go too early then there’s time for aphids to recolonise, but a more focused and tailored approach, ideally on a field-by-field basis, will achieve the most economic control strategy.”

Varieties such as Nadine and Russett Burbank have a zero tolerance for aphids.

Trials in a ware crop of the virus susceptible variety Nadine in Nottinghamshire, sponsored by Greenvale AP, demonstrated the value of including Hallmark Zeon for anti-feeding activity, alongside Plenum.

The six-spray strategy, between the end of July and the beginning of September, involving three sprays of Plenum plus Hallmark Zeon alternated with three applications of Dovetail, effectively halved the level of PVY and PLRV virus infection in the tubers, compared to untreated areas. Leaving out the Hallmark Zeon significantly reduced the success rate of a Plenum and Aphox based programme.

Paul Coleman, technical director at Greenvale, said: "The results from the trial are very revealing and serve to remind us that anti-feedants are required when trying to control non-persistent viruses, such as PVY.

“The aphid and virus pressure was artificially high due to the untreated parts of the trial field, which just goes to show how effective Hallmark Zeon was in reducing the incidence of PVY.”

Aphid counts in the trial, prior to the initial treatment in July, highlighted that all the Peach Potato aphid populations were present in the middle to bottom third of the crop, although the majority of other aphid species, present in far higher numbers, were located in the top third of the plants. Coleman added: “This really highlights the need to inspect crops thoroughly and identify the presence of the most important virus vectors, along with the need for good application technique that can target aphids low down in the crop canopy.”

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