Aphid forecasts

About the forecasts

Long-term (56 years in 2020) aphid data (from the suction-trap network) and weather data (Met Office and others) is used to forecast the date of the first aphid flights, as well as aphid abundance in spring and early summer.

The best predictor of the timing and size of aphid migration is the mean temperature in January and February. Temperatures in November/December and March/April have little apparent impact.

Although there is considerable uncertainty associated with actual first flight dates at specific sites, the forecasts provide an indication of how early or late flights will take place, compared with an ‘average’ season.

Confidence is greatest for aphid species that pass the winter in the active stages (rather than as cold-hardy eggs in diapause), as they are more susceptible to low winter temperatures and can take advantage of warm conditions

  • Bird cherry–oat aphid (Rhopalosiphum padi) and rose–grain aphid (Metopolophium dirhodum) overwinter by either method, with the proportion overwintering in the active stages increasing towards the south.
  • The peach–potato aphid (Myzus persicae) and potato aphid (Macrosiphum euphorbiae) pass winter in the active stages.
  • Grain aphid (Sitobion avenae) and mealy cabbage aphid (Brevicoryne brassicae) overwinter mainly in the active stages. However, as the latter flies later it is more difficult to predict. Therefore, for this species, the forecast also uses December temperatures.

Note: Some aphids overwinter in autumn-sown cereal crops and might present before aphid flight begins. The forecasts do not capture all variability. Interpret results with caution.

Spring 2020 commentary

The 2020/21 winter was the fifth wettest on record in Britain, with several Atlantic storms. Relatively mild conditions resulted in average January–February air temperatures being above the 30-year average: Scotland and Northern England (+0.5–1.5 oC), Kirton southwards (+2 oC) and Silwood (+2.5 oC).

In the absence of abnormal conditions this spring, generally, aphids will fly about 1–3 weeks earlier in Scotland and Northern England and about 4 weeks earlier over much of the rest of England (from the Wash southwards) than average, with Silwood potentially being about 5 weeks earlier.

Jan-Feb 2020 temperatures

Suction trap site Mean temperatures (°C)
Jan 2020 Feb 2020 Jan-Feb 2020

Dundee (D)

5.06

4.22

4.64

Gogarbank (G)

6.39

4.72

5.56

Ayr (Ay)

6.36

5.3

5.83

Newcastle (N)

6.40

5.49

5.94

Preston (P)

6.03

5.72

5.87

Kirton II (K)

6.50

6.63

6.57

Broom's Barn (BB)

6.42

6.62

6.52

Wellesbourne (We)

6.64

6.83

6.73

Hereford (H)

6.62

6.83

6.72

Rothamsted (RT)

6.36

6.40

6.38

Writtle (Wr)

6.72

7.21

 6.97

Silwood (SP)

6.88

7.30

7.09

Starcross (SX)

7.03

7.85

7.44

*Met office data currently unavailable

What the forecast tables show

  • The predicted date range of first capture, together with the position of this year's prediction out of all years of trap operation (e.g.16/52 = 16th earliest out of 52 years). Note: The actual first arrival dates are included in AHDB Aphid News.
  • The predicted numbers caught by specified dates: Cereal aphids (1 July), peach—potato aphid and potato aphid (17 June) and cabbage aphid (7 October), together with the position of this year's prediction out of all years of trap operation.

Bird cherry–oat aphid forecast

Site

First capture in suction trap

Numbers to 1 July 2020

Prediction date range

(75% confidence limits)

Ranking

Predicted

Predicted range

(75% confidence limits)

Ranking

Dundee

(25 April - 7 June)

=18/51

55

(5 - 534)

16/50

Gogarbank

(22 April - 25 May)

=14/52

79

(15 - 405)

16/52

Ayr

(16 April - 25 May)

8/41

47

(11-185)

11/38

Newcastle

(17 April - 30 May)

=14/52

63

(10 - 375)

12/51

Preston

(23 March - 6 May)

10/45

143

(31 - 645)

7/45

Kirton

(16 February - 7 April)

3/41

897

(198 - 4049)

6/41

Broom's Barn

(17 March - 26 April)

9/53

528

(111 - 2498)

10/53

Wellesbourne

(4 February - 23 April)

3/16

15

(1 - 106)

6/13

Hereford

(10 February - 21 May)

10/49

223

(34 - 1427)

10/49

Rothamsted

(25 March - 1 May)

6/53

315

(68 - 1446)

10/53

Writtle

(19 February - 21 April)

=6/46

1015

(221-4639)

6/46

Silwood Park

(28 February - 27 April)

5/42

682

(168 - 2756)

5/40

Starcross

(3 January - 3 April)

11/51

1271

(281 - 5735)

6/49

Grain aphid forecast

Site

First capture in suction trap

Numbers to 1 July 2020

Prediction date range

(75% confidence limits)

Ranking

Predicted

Predicted range

(75% confidence limits)

Ranking

Dundee

(7 May - 14 June)

16/51

37

(5 - 222)

=15/50

Gogarbank

(24 April - 4 June)

10/52

58

(12 - 273)

14/52

Ayr

(28 April - 3 June)

=8/41

29

(5 - 141)

10/38

Newcastle

(27 April - 30 May)

=6/52

60

(12 - 293)

8/51

Preston

(17 April - 14 May)

8/45

250

(49 - 1251)

8/45

Kirton

(1 April - 5 May)

6/41

187

(23 - 1458)

14/41

Broom's Barn

(1 April - 2 May)

=5/53

399

(53 - 2932)

11/53

Wellesbourne

(1 February - 27 May)

=3/15

14

(4 - 44)

5/12

Hereford

(2 April - 7 May)

=4/49

404

(59 - 2719)

10/49

Rothamsted

(31 March - 4 May)

7/53

254

(40 - 1585)

18/53

Writtle

(8 March - 28 April)

=8/46

375

(49 - 2804)

16/46

Silwood Park

(30 March - 1 May)

3/41

465

(60 - 3548)

12/39

Starcross

(2 March - 28 April)

7/51

408

(89 - 1868)

15/49

Rose–grain aphid forecast

Site

First capture in suction trap

Numbers to 1 July 2020

Prediction date range

(75% confidence limits)

Ranking

Predicted

Predicted range

(75% confidence limits)

Ranking

Dundee

(29 April - 16 June)

=19/51

36

(3 - 326)

22/50

Gogarbank

(16 April - 5 June)

14/52

70

(10 - 448)

16/52

Ayr

(13 April - 31 May)

10/39

30

(9 - 90)

9/37

Newcastle

(26 April - 4 June)

11/52

42

(9 - 190)

=10/51

Preston

(23 March - 11 May)

=7/46

177

(42 - 741)

11/45

Kirton

(23 March - 6 May)

5/41

351

(38 - 3149)

10/41

Broom's Barn

(13 March - 24 May)

8/53

396

(65 - 2369)

14/53

Wellesbourne

(4 March - 3 May)

3/16

8

(0 - 73)

12/12

Hereford

(11 April - 26 May)

=12/49

239

(37 - 1530)

12/49

Rothamsted

(29 March - 12 May)

9/53

145

(25 - 824)

20/53

Writtle

(19 February - 1 May)

11/46

272

(53 – 1378)

16/46

Silwood Park

(28 February - 20 April)

4/42

97

(24 - 386)

12/40

Starcross

(25 January - 14 April)

8/50

277

(67 - 1133)

=14/49

Peach—potato aphid forecast

Site

First capture in suction trap

Numbers to 17 June 2020

Prediction date range

(75% confidence limits)

Ranking

Predicted

Predicted range

(75% confidence limits)

Ranking

Dundee

(6 May - 27 June)

=16/52

3

(0 - 10)

=9/51

Gogarbank

(3 May - 17 June)

13/52

4

(1 - 16)

=9/52

Ayr

(17 May - 5 July)

13/39

1

(0-3)

=5/38

Newcastle

(22 April - 14 June)

=9/52

8

(2 - 25)

=10/52

Preston

(7 April - 11 June)

17/45

19

(5 - 66)

=9/45

Kirton

(27 March - 1 May)

=2/41

149

(35 - 616)

5/41

Broom's Barn

(24 March - 27 April)

6/56

344

(62 - 1889)

9/56

Wellesbourne

(4 January - 26 March)

3/14

459

(63 - 3317)

5/12

Hereford

(30 March - 11 May)

4/49

95

(21 - 424)

7/49

Rothamsted

(22 March - 23 April)

4/56

190

(51 - 702)

10/56

Writtle

(5 March - 26 April)

6/46

583

(139 - 2427)

5/46

Silwood Park

(23 March - 5 May)

5/41

78

(20 - 289)

5/40

Starcross

(27 February - 1 May)

=6/51

53

(17 - 165)

10/49

Potato aphid forecast

Site

First capture in suction trap

Numbers to 17 June 2020

Prediction date range

(75% confidence limits)

Ranking

Predicted

Predicted range

(75% confidence limits)

Ranking

Dundee

(23 April - 12 June)

16/52

7

(2 - 25)

=17/51

Gogarbank

(14 April - 28 May)

10/52

27

(7 - 97)

=12/52

Ayr

(29 April - 6 June)

11/41

6

(2 - 15)

=11/39

Newcastle

(25 April - 3 June)

=7/52

10

(2 - 36)

=13/52

Preston

(20 April - 23 May)

=9/45

24

(10 - 54)

=7/45

Kirton

(28 March - 6 May)

6/41

48

(15 - 156)

4/41

Broom's Barn

(30 March - 11 May)

7/56

29

(10 - 80)

8/56

Wellesbourne

(5 April - 10 May)

2/15

31

(8 - 116)

3/12

Hereford

(5 April - 8 May)

4/49

44

(13 - 142)

10/49

Rothamsted

(2 April - 13 May)

=7/56

34

(11 - 102)

8/56

Writtle

(13 March – 25 April)

7/46

71

(24 - 204)

6/46

Silwood Park

(25 March - 28 April)

4/41

51

(16 - 164)

10/40

Starcross

(22 March - 8 May)

11/50

43

(16 - 113)

8/49

Cabbage aphid forecast

Site

First capture in suction trap

Numbers to 7 October 2020

Prediction date range

(75% confidence limits)

Ranking

Predicted

Predicted range

(75% confidence limits)

Ranking

Dundee

(30 May - 22 August)

17/49

15

(2 - 94)

16/48

Gogarbank

(5 May - 30 July)

11/49

16

(4 - 63)

11/47

Ayr

(2 June - 18 August)

7/35

4

(1 - 12)

=7/31

Newcastle

(14 May - 10 July)

9/51

18

(4 - 77)

=10/48

Preston

(15 April - 27 June)

11/45

39

(9 - 158)

10/42

Kirton

(23 March - 28 May)

1/41

352

(67 - 1834)

7/39

Broom's Barn

(17 April - 22 May)

=5/56

391

(75 - 2031)

=11/54

Wellesbourne

(15 April - 30 May)

3/14

219

(39 - 1198)

4/9

Hereford

(10 April - 22 May)

2/49

555

(98 - 3113)

=9/45

Rothamsted

(7 April - 27 May)

=3/56

194

(29 - 1264)

16/55

Writtle

(30 March - 8 May)

3/46

1202

(196 - 7352)

11/44

Silwood Park

(6 April - 29 May)

4/38

214

(32 - 1394)

7/35

Starcross

(23 March - 16 May)

6/49

226

(73 - 696)

11/43