25 October 2022
Traps reveal wide geographical spread in Scotland.
PEACH potato aphids caught in suction traps at Dundee and Edinburgh have been well above the 10-year average this summer.
Data from a wider network of yellow water traps indicates peach potato aphids were being found in high numbers across a wide geographical area of Scotland, including Grampian, where vector pressure was three times the seasonal average.
Peach potato aphids are a vector of both PVY and potato leaf roll virus (PLRV) and present a significant risk to early generation seed where control is challenged by an aphid “biological arms race” and withdrawal of chemistry.
To tackle this challenge, growers need to be looking increasingly to using Integrated Pest Management (IPM) strategies alongside plant protection products to maintain quality seed.
Scottish Agronomy and McCain Potatoes, have been leading trials on IPM strategies for the seed industry, including the use of straw mulch which has had significant outcomes. In 2021, trials in Fife had very high pressure from colonising aphids, predominantly potato aphids but also from peach potato aphids. The results showed 40% control of PVYN was achieved and 59% control of PLRV from using straw mulch alone.
The result is down to aphids’ host-finding behaviour. To them the contrast between potato foliage and straw is much lower than the contrast between potato foliage and bare soil. If you are planning to use wheat straw mulch in 2023 season on early field generation seed, lay aside and store straw in the coming days.
To further improve control, we have seen an even greater response when using a straw mulch alongside mineral oils up to tuber initiation and alternating applications of systemic insecticides throughout the entire growing season. Maintaining insecticide programmes up to the point of complete haulm death is particularly important to reduce the incidence of virus late in the season. Haulm re-growth is more common in vigorous indeterminate varieties that have been flailed as the first treatment in the desiccation programme. This re-growth is particularly vulnerable to virus ingress in susceptible varieties.
For more information and to read our extended feature, see the November issue of Potato Review. You can subscribe here.