Early season aphid activity in 2025
Prolonged exposure to low winter temperatures is known to have lethal and sub-lethal effects on populations of Myzus persicae which, in Scotland, overwinters as larvae or apterous adults. Poor over-winter survival delays the build-up of populations of this species in the forthcoming growing season. SASA uses the mean temperature for December - February to predict when M. persicae will become active in the summer. This differs from the method used by Rothamsted who use Jan/Feb mean temperatures, explaining the slight difference in predicted dates.
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) – ranking 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 in 2025 is 29 May at Edinburgh (75% confidence limits: 8 May - 18 June) and 1 June at Dundee (75% confidence limits: 5 May - 27 June). Average first catch dates are 14 June 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.
NB. Following the closure of Higgins, the Elgin suction trap did not operate in either 2017 or 2018. A new suction trap site at the Scottish Government Farm at Knocknagael, south of Inverness was operational from 2019. It is still a little early to assess how to best utilise these data.
First flights 2025
Warm conditions over April and May have likely expedited aphid development and migration beyond our prediction's expectations with most arrival dates appearing to be about 3-4 weeks earlier than predicted. The first Peach-potato aphid (Myzus persicae) of 2025 has been caught at Edinburgh on 20 April , with a second individual caught on 28 April, again at Edinburgh– this is around 8 weeks earlier than average and 6 weeks before predicted.
In 2024, the first M. persicae at Edinburgh was recorded on 13 May, thirty-two days earlier than the average date of first catch and fourteen days earlier than predicted. The first M. persicae at Dundee was recorded on 15 May, twenty-seven days earlier than the average date and nine days earlier than predicted. The first arrival dates for both were within the 75% confidence limits of predictions.
The predictions for the potato aphid Macrosiphum euphorbiae, the rose-grain aphid Metopolophium dirhodum and the grain aphid Sitobion avenae are provided by Rothamsted Research (found at Aphid Forecast | Insect Survey) and are based on mean temperatures over January and February 2025 (Table 1).
Table 1 – First flight predictions for 2025
| 2025 Prediction | 75% Confidence Limits | 2024 Obs'n | 2025 Obs'n | |
| Edinburgh | ||||
| Myzus persicae | 29 May | 8 May – 18 June | 13 May | 20 April |
| Macrosiphum euphorbiae | 16 May | 15 May – 27 June | 18 May | 30 April |
| Metopolophium dirhodum | 18 May | 25 April – 11 June | 9 May | w/b 17 Mar |
| Sitobion avenae | 23 May | 3 May – 12 June | 12 May | 05 May |
| Dundee | ||||
| Myzus persicae | 1 June | 5 May – 27 June | 15 May | - |
| Macrosiphum euphorbiae | 25 May | 2 May – 18 June | 17 May | 06 May |
| Metopolophium dirhodum | 29 May | 6 May – 21 June | 22 May | 21 April |
| Sitobion avenae | 31 May | 13 May – 18 June | 27 May | - |
The warmer than average temperatures over winter 2024-25 indicate that the first flights of M. persicae should be 2-3 weeks earlier than on average. Based on the Rothamsted predictions, first flights of other important vector species are expected to be about average. Consequently, population levels have the potential to develop to levels that could threaten the virus health of seed crops. The prediction for the total of M. persicae caught by 31 July is 38 at Dundee (75% confidence limits: 19 - 228) and 32 at Edinburgh (75% confidence limits: 9 -111).
Therefore, populations of M. persicae are likely to be about average during the growing season for potatoes in 2025. 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.
SASA