The rising aphid vectored virus pressure on Scottish potatoes has prompted the SAC Association of Potato Producers to host an unprecedented summit to discuss the issue in early December. Whilst SASA are yet to publish their official statistics all indications point towards a rise in provenance aphid transmitted diseases. It is hoped that the summit will help the sector co-ordinate the response to disease threat with around 60 invitees hoped to attend.

SAC potato advisor Kyran Maloney said: “It won’t be surprising for growers to be told virus is higher than we would like. Levels of virus will likely be a talking point this year but it is important to note that the Scottish crop is still very healthy so we shouldn’t over-react. Tolerances for some seed potato grades can mean a single infected plant can mean a downgrade at inspection.”

There is pressure coming from a number of places which is pushing up the threat from aphids. Warming temperatures is allowing a greater population of aphids to over winter. The aphids in some of the yellow water traps in 2022 ran to hundreds of insects collected in 7 days where usually anything in double figures would be considered high. These patterns are more similar to areas such as Yorkshire. One Scottish trap reported 348 peach-potato aphids for a single catch last year which was a new record high. Aphid flights have been at much lower levels this season, but the legacy of transmission in 2022 will have increased the risk.

Meanwhile the chemistry to cope with the insects has been dwindling with key products such as Actara, Biscaya and Plenum WG coming off the market in recent years leaving only Insyst, Teppeki, Movento and the pyrethroid products available available to growers. There is also widespread resistance to pyrethroids in some species of aphids such as Myzus persicae (peach-potato aphids). The two biggest virus disease threats are leaf roll (caused by PLRV) and mosaics (caused by viruses such as PVY). It’s a complicated picture as although aphids spread both diseases, they do so in different ways. Aphids that colonize potato plants are the most important for leaf roll and non-colonizing aphids that are “passing though” potato crops are most important for mosaics.

Dr Maloney went on to say: “One goal of this summit is understanding the practical experience grower have gain from managing this problem in the field. There are many integrated pest management options which whould help maintain healthy crops, but we need to understand how it can be applied – which approaches work, which don’t , and most impornantly which will be practical and cost-effective for famer. We hope to use the summit as a way to find some of this out.”

This year’s cool and wetter July and August limited aphid flights and will hopefully have slowed the spread of viral diseases, and with much of the seed potato crop has already started being lifted so further challenges this year is unlikely. However, Dr Maloney is keen to explain to growers they need to be aware of regrowth which could allow late transmission of aphid vectored viruses.

Following the SACAPP summit the group plans to issue a position statement on how the sector hopes to progress a plan to combat aphid and virus spread in Scotland. Only a pro-active coordinated approach from the industry will tackle this issue – but the sector has the knowledge and skills to meet the challenge.