The Peach-Potato aphid (Myzus persicae) has traditionally been considered as the most important aphid vector of potato viruses. However, in Scotland, Peach-Potato aphids generally fly later and in far lower numbers than in warmer countries and their relative scarcity generally makes this species less of a concern to potato growers. In some years, usually following a particularly mild winter, Peach-Potato aphids can present a very high risk of virus transmission, particularly Leaf Roll, within the Scottish seed potato crop.
Prolonged exposure to low winter temperatures is known to have lethal and sub-lethal effects on populations of M. persicae which, in Scotland, overwinter as larvae or apterous adults. Poor over-winter survival delays the build-up of populations of this species in the forthcoming growing season. SASA predicts aphid activity based on the mean temperatures during the three-month period of December-February, which is a slightly different approach than that taken by Rothamsted who still use Jan/Feb mean temperatures.
First flight predictions 2025
During winter 2024-25, the mean temperatures were above the mean over the last 50 years: 5.09°C at SASA (Edinburgh; mean = 4.09°C) and 4.62°C at JHI (Dundee; mean = 3.7°C). These winter temperatures rank the 13th warmest from the last 56 years at Edinburgh and the 12th warmest from the last 58 years at Dundee. Based on these figures, the prediction for the first flight of M. persicae is 29 May at Edinburgh (75% confidence limits: 8 May to 18 June) and 1 June at Dundee (75% confidence limits: 5 May to 27 June) (Table 1). The average dates of first catch are 14 and 11 June at Edinburgh and Dundee respectively. Therefore, based on the Edinburgh met data, M. persicae activity in 2025 is expected to commence around 2-3 weeks earlier than in an average summer.
Predictions for the total of M. persicae caught by 31 July in 2025 are 32 individuals at Edinburgh (75% confidence limits: 9 to 111) and 38 at Dundee (75% confidence limits: 19 to 228). As the level of PLRV inoculum observed during 2024 continued to be above average, a high risk of leaf roll transmission in potato crops remains in place during 2025. Growers are advised to maintain vigilance and use active virus management during the growing season.
Table 1 – Myzus persicae predictions 2025
| M. persicae | Dundee | Edinburgh |
| First catch in 2025 |
- |
20 April |
| Predicted first catch in 2025 | 1 June | 29 May |
| Average date of first Catch | 14 June | 11 June |
| Total catch to 31 July 2025 |
- |
- |
| Predicted total catch to 31 July 2025 | 38 | 32 |
| Average total catch to 31 July | 47 | 36 |
Peach-potato aphids in Scotland 2025
The first peach-potato aphid of the 2025 season has been caught at Edinburgh on 20 April - this is 6 weeks earlier than predicted and 8 weeks earlier than average. This also falls outwith the limits of our 75% confidence limits, which are based solely on winter temperatures. A second individual was caught on 28 April, again at Edinburgh. The spell of warm weather over April and May has likely expedited aphid development. No peach-potato aphids have been caught at Dundee so far.
As of 11 May, 2 peach-potato aphids have been caught (both at Edinburgh), ranking 3rd when compared to the last 38 years at this point of the season.
Note the use of a logarithmic scale in the table below to allow better visualisation of lower values when compared to years with high peaks (such as 2023).
5% catch predictions – refined to a local scale.
A collaboration between scientists in the Met Office’s Vegetation-Climate Interactions group, the Rothamsted Insect Survey (RIS), University of Warwick, Defra and SASA allows further resolution of Myzus persicae activity predictions in Scotland and the rest of the U.K.
The maps below display the estimated date on which the first 5% of the annual flight of M. persicae will have occurred, using at 1km2 resolution across Scotland. As few M. persicae are caught in Scotland compared to the rest of the U.K., this correlates well with the ‘first catch’ in Scotland but it is worth noting that this is a different measurement, so ‘first flights’ and 5% will be different in areas where a larger number of individuals are caught.
As with first flight predictions there are observable differences between 2020, 2021, and 2022 due to their respective average winter temperatures. By using the HadUK-Grid dataset climate scientists can refine predictions to a more local scale which may be of particular use to growers. Note that factors such as land use and availability of host plants are not used in this predictive model.
With thanks to the Met Office for permission to use the above images. This work is the result of collaboration between scientists in the Met Office’s Vegetation-Climate Interactions group, the Rothamsted Insect Survey (RIS), University of Warwick, Defra and SASA. It utilises the most up-to-date UK climate data and aphid monitoring results from RIS sites across the UK, and combines expertise in entomology, pest risk management and climate science.
SASA