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LETTUCE

Updated 26 June 2018

Captures in suction traps in 2018

Lettuce crops may be infested by currant-lettuce ( ribisnigri), peach-potato aphid (Myzus persicae), potato aphid (Macrosiphum euphorbiae) or lettuce-root aphid (Pemphigus bursarius) and apart from lettuce-root aphid these are all recorded in catches by the network of suction traps run by the Rothamsted Survey. Currant-lettuce aphids are only ever caught in low numbers in both suction traps and water traps and appear to be ‘trap-shy’. The best way to monitor infestations of currant-lettuce aphids is to look at lettuce plants.

The tables below summarise captures of aphids in the network of Rothamsted suction traps.

Dundee Edinburgh Ayr Newcastle FERA,York Preston Kirton Barn Broom's Wellesbourne Hereford Rothamsted Writtle Ascot Wye Starcross Nasonovia ribisnigri Elgin Week ending 22-Apr 29-Apr 06-May 13-May 1 20-May 27-May 1 1 03-Jun 1 1 10-Jun 1 17-Jun 1

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Dundee Edinburgh Ayr Newcastle FERA,York Preston Kirton Barn Broom's Wellesbourne Hereford Rothamsted Writtle Ascot Wye Starcross Myzus persicae Elgin Week ending 22-Apr 29-Apr 06-May 1 13-May 1 1 4 1 2 1 20-May 1 3 27-May 1 1 5 6 8 2 03-Jun 1 2 29 5 8 25 4 18 7 10-Jun 1 1 2 3 1 42 24 6 21 2 1 12 17-Jun 1 7 9 56 15 10 8 48 1 9 28

Dundee Edinburgh Ayr Newcastle FERA,York Preston Kirton Barn Broom's Wellesbourne Hereford Rothamsted Writtle Ascot Wye Starcross Macrosiphum euphorbiae Elgin Week ending 22-Apr 29-Apr 06-May 1 2 13-May 1 1 1 20-May 1 1 1 1 27-May 1 5 1 1 2 1 5 1 5 03-Jun 5 10 1 1 1 2 2 1 1 13 10-Jun 2 1 4 2 2 4 17-Jun 1 1 2 1 1 8

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Day-degree forecasts

The graph below shows ‘day-degree forecasts’ for currant-lettuce aphid (Nasonovia ribisnigri) and lettuce-root aphid (Pemphigus bursarius). The forecasts for both aphid species are based on accumulated day-degrees (D°) from 1 February (base 4.4°C). The information was collected in projects funded by the AHDB, Defra and LINK.

In the study on currant-lettuce aphid, the mean numbers of day-degrees accumulated until the first aphid was found and until peak numbers of aphids were found were 507D° and 935D° respectively. Comparisons between observed and predicted dates showed that this forecast is likely to be accurate to within a 2-3 week period.

In the study on the lettuce-root aphid, the start of the migration of winged aphids from poplar to lettuce occurred after 672D° had been accumulated since 1 February. Monitoring data collected during the project were compared with this forecast, which was shown to give adequate early warning of the start of aphid migration.

The weather data are provided by Plantsystems and funded by Syngenta.

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1000

900

800 Cornwall

700 Nottinghamshire

C ° Yorkshire 600 Kent

Scotland degrees >4.4 degrees - 500 South Lincs Suffolk 400 Lancashire Warwick

Accumulated day Accumulated 300 Norfolk Start of currant-lettuce aphid migration 200 Peak of currant-lettuce aphid migration Start of lettuce-root aphid migration 100

0

7-Jun

5-Apr

1-Feb 8-Feb

1-Mar 8-Mar

3-May

14-Jun

12-Apr 19-Apr 26-Apr

15-Feb 22-Feb

15-Mar 22-Mar 29-Mar

17-May 24-May 31-May 10-May