Early season aphid activity 2008
The temperature during January and February is critical to aphid activity in the forthcoming growing season. The mean temperature during this period at SASA (Edinburgh) was 5.2°C, and at and SCRI (Dundee) was 4.7°C, over 1.3°C warmer than the mean temperature over the previous 40 years. The relatively mild winter indicates that the first flights of aphids will be about two to three weeks earlier than in an average year (see Table 1) and the total aphids caught before 1 August are expected to be higher than average.
Table 1
|
Edinburgh |
2008 Prediction |
75% Confidence Limits |
2008 Observation |
2007 Observation |
|
Myzus persicae |
24 May |
2 May to 16 June |
N/A |
5 May |
|
Macrosiphum euphorbiae |
8 May |
19 April to 28 May |
16 May |
19 April |
|
Dundee |
2008 Prediction |
75% Confidence Limits |
2008 Observation |
2007 Observation |
|
Myzus persicae |
2 June |
7 May to 27 June |
N/A |
9 May |
|
Macrosiphum euphorbiae |
17 May |
21 April to 12 June |
24 May |
19 April |
The 75% confidence limits quoted in Table 1 provide an estimate of the expected accuracy of the 2008 prediction, i.e. 3 times out of 4 the prediction should fall within these limits. The average date of first capture for the Peach-Potato aphid (Myzus persicae) over the last 39 years is 13 June at Edinburgh (16 June at Dundee). The mean date for catching the first Potato aphid (Macrosiphum euphorbiae) at Edinburgh is 21 May (31 May at Dundee).
Total catches of potato aphids are likely to be slightly higher than usual. The model prediction is that 34 M. persicae will be caught at Edinburgh before 1 August (75% confidence interval of 8 to 129 aphids). At Dundee, the predicted catch over the same period is 34 M. persicae (75% confidence interval of 8 to 129). If these predictions are borne out then 2008 will rank 12th out of the last 39 years in terms of the abundance of M. persicae.
