From midsummer onwards, the catches of cereal aphids in the suction traps usually dominate the Scottish aphid bulletin and significantly affect the index that is used to estimate the vector pressure for aphid-transmitted potato viruses. Three species, the Rose-Grain aphid (Metopolophium dirhodum), the Grain aphid (Sitobion avenae) and the Bird Cherry-Oat aphid (Rhopalosiphum padi), are known to be vectors of non-persistently transmitted potato viruses (e.g. PVY) and because they can occur in high numbers in the suction traps, each individual species can make a relatively high contribution to the overall aphid vector pressure index. SASA have conducted field trials that support the role of cereal aphids, particularly the Rose-Grain aphid and the Grain aphid, in virus transmission.
As would be expected, cereal aphids are also important pests of cereal crops, causing direct damage by feeding on crops and through the transmission of viruses such as barley yellow dwarf virus (BYDV).
First flight predictions for new season 2025
Based on the mean temperatures over January and February 2025, the following first flight predictions and numbers by 1st July are provided by Rothamsted Research (found at Aphid Forecast | Insect Survey):
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Rose-Grain aphid (Metopolophium dirhodum) – 18 May for Edinburgh (75% confidence limits: 25 April – 11 June) and 29 May for Dundee (75% confidence limits: 6 May - 21 June). Total numbers by 1st July are predicted to be 40 individuals for Edinburgh (75% confidence limits: 6 to 236) and 27 for Dundee (75% confidence limits: 2 to 218).
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Grain aphid (Sitobion avenae) – 23 May for Edinburgh (75% confidence limits: 3 May – 13 June) and 31 May for Dundee (75% confidence limits: 13 May – 18 June). Total numbers by 1st July are predicted to be 24 individuals for Edinburgh (75% confidence limits: 5 to 109) and 20 for Dundee (75% confidence limits: 3 to 116).
- Bird Cherry-Oat aphid (Rhopalosiphum padi) – 11 May for Edinburgh (75% confidence limits: 21 April – 1 June) and 13 May for Dundee (75% confidence limits: 26 April – 1 June). Total numbers by 1st July are predicted to be 56 for Edinburgh (75% confidence limits: 11 to 266) and 41 for Dundee (75% confidence limits: 4 to 361).
Cereal aphids and PVY transmission in 2024 into 2025
Although there was higher than average activity early in the season, cereal aphid numbers didn't increase as expected over the summer peak season, leading to below than average catch numbers by the end of the cropping year.
It is anticipated that the incidence of plants showing mosaic symptoms in 2025 will remain relatively high. Aphid activity in 2025 is expected to be approximately one to three weeks early and could potentially lead to higher than seasonal averages. Therefore, a balanced approach to the management of non-persistent viruses and their vectors, with heightened vigilance towards aphid activity and sources of virus, will be required based on the information currently available for the 2025 summer.
Potato varieties that have been revealed by virus testing of leaf samples collected during classification inspections as particularly prone to the acquisition of PVY include King Edward, Harmony, Shepody, Maris Peer and Nicola.
Previous season - 2024 (updated with latest numbers)
Cereal aphids in 2024
The first cereal aphids of 2024 were caught in both the Edinburgh and Dundee traps on the week ending 5th May. Whilst aphid activity was initially 1-2 weeks earlier than an average season, cool wet weather limited excessive build up over June. July migrations have now peaked and do not appear to have been above average for any species.
As the Inverness trap only started trapping in April 2019, we currently report on Edinburgh and Dundee catches only.
Please note that the graphs below represent actual numbers of aphids caught in these two east coast suction traps using a log scale. Viewing population data on a log scale makes it easier to spot subtle changes in early season numbers when comparing previous years for species with high seasonal peak numbers.
Rose-Grain aphid in 2024
The first Rose-Grain aphid (Metopolophium dirhodum) was caught in the Edinburgh suction traps on 9 May, four days earlier than predicted. The first Rose-Grain aphid caught at Dundee was found on 22 May, four days after predicted.
The cumulative total until 25 Aug stands at 1354, ranking 23rd over the last 38 years of trapping.
63% of the cumulative total has been caught at Dundee; 37% were caught at Edinburgh.
Grain aphids in 2024
The first Grain aphid (Sitobion avenae) was caught in the Dundee trap on 27 May. The first Grain aphid at Edinburgh was caught on 12 May.
The cumulative total until 12 September was 871, ranking 24th over the last 38 years of trapping.
65% of this cumulative total was caught at Dundee; 35% were caught at Edinburgh.
Bird Cherry-Oat aphid in 2024
The first Bird Cherry-Oat aphid (Rhopalosiphum padi) in 2024 was caught in Dundee on 1 May. The first Bird Cherry-Oat aphid at Edinburgh was caught on 3 May.
A total of 1956 Bird Cherry-Oat aphids (Rhopalosiphum padi) were caught in the Dundee and Edinburgh suction traps to 22 September. The total catch for this species ranks 34th over the last 38 years. 48% of this cumulative total was caught at Dundee; 52% were caught at Edinburgh.
Apple-Grass aphid in 2024
The first Apple-Grass aphids (Rhopalosiphum oxyacanthae) were caught in both the Edinburgh and Dundee suction traps on 4 May.
A total of 1117 Apple-Grass aphids (Rhopalosiphum oxyacanthae) have been caught in Dundee and Edinburgh to 19 Sept, ranking 22nd over the last 38 years. Weekly totals during spring were generally below seasonal averages and the summer migration appeared to have peaked by mid-August. 31% of individuals were caught at Dundee; 69% were caught at Edinburgh.
SASA