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The upshot is that most Scottish seed crops will emerge from late May into an onslaught of aphid pressure. “Aphid and virus control measures will need to take account of this and apply new knowledge from research and resistance monitoring,” he advises.

Ongoing Potato Council funded research has shown that in Scotland cereal aphids are the main vectors of non-persistent viruses and the rose-grain aphid is the number one vector of PVA and PVYⁿ. The project has also identified that mineral oils represent an untapped method for controlling non-persistent viruses.

Last year Scottish Agronomy looked further into the implications of these findings. They compared efficacy of aphicide programmes comprising mineral oils, the neonicotinoid Biscaya (thiacloprid) and other insecticides, which varied according to how early Biscaya was introduced.

Eric says the programme where Biscaya was used early – at the second and fourth sprays – produced the best result, restricting PVA + PVV incidence to 0.41%. “It seems Biscaya’s OD (oil dispersion) formulation had a useful effect on non-colonisers. Compared with other aphicides that target colonisers, this gives it an edge in programmes. The focus has to be on non-colonisers but we mustn’t forget peach-potato aphids.”

Seed growers have been living with MACE resistance to pirimicarb in peach-potato aphids for some years. But it now appears that the strains which dominate UK populations have also developed a new form of resistance to pyrethroids described as super-kdr. This suspicion arose from tests by Rothamsted Research on field samples last year but Eric suspects it’s been around for some time.

“If this mutation is confirmed it’s important to realise that super-kdr can confer up to 500 fold resistance. We tested pyrethroids on peach-potato aphids two years ago and they survived, so we have been working on the precautionary principle that they have it.“

Based on Scottish Agronomy’s research, the key principles Eric advocates this year are: “Begin with oils, then switch to pyrethroids, to control cereal aphids and other non-colonisers; introduce Biscaya early to control peach–potato aphids and bring activity against non-colonisers; follow with other modes of action to continue controlling non-colonisers.“