Aphid Monitoring

The role of aphids as vectors of potato viruses is of concern to the Scottish seed potato industry. SASA operates a national network of suction traps collecting information about aphid abundance and movement, and providing advice on the risk of virus transmission and the need for aphid control.

The suction trap data contribute to a UK network of traps operated by Rothamsted Research. Weekly aphid bulletins are published by the Rothamsted Insect Survey.

The Entomology laboratory provides technical support to the Aphid Monitoring Programme, introduced into the Seed Potato Classification Scheme in 1992. This programme ensures that seed stocks on which aphids have been poorly controlled can be identified, and that subsequent classification of these stocks is dependent upon a post-harvest tuber test for the presence of viruses.

A development programme to improve our understanding of potato virus epidemiology is underway and has improved the accuracy with which virus levels in seed crops can be forecast.

See the Scottish Aphid Bulletins page for more information.

AHDB Potatoes fund 100 in-crop water traps in the major seed growing areas of Great Britain. The trap contents are analysed weekly at FERA in York, with results posted on the APHMON website. Users of the service can also sign up to receive e-mail and SMS alerts when Peach-potato aphids (Myzus persicae) are found in their region or when aphid catches in any trap in their region exceed a weekly threshold. Comparative information with previous seasons is also available.

The SASA aphid Monitoring pages are updated regularly over the growing season (usually every Friday). Interested parties can contact Fiona Highet (via 'contact us') to receive a weekly bulletin E-mail covering the main Scottish aphid headlines for the week and links to pages for more information. SASA's twitter account also reports aphid news over the growing season, again with links to relevant pages.

Aphid Bulletins

 

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The 'Scottish Aphid Bulletin' consists of a table of 21 species, mostly species of major economic significance, and a second table listing all the other 'non-bulletin' aphids caught during the week. 

SASA currently operates four suction traps located at Inverness (*new for 2019*), Ayr, Dundee and at SASA's headquarters at Gogarbank on the west side of Edinburgh. Data from each of these traps are presented as totals for the duration of each report. Only the traps at Edinburgh and Dundee are identified in 'real time' so are presented as cumulative totals and compared to previous years.

Three additional columns of data are also presented under the title of 'Cumulative Totals'. The first presents the total catch from the two traps (Edinburgh and Dundee) for the current year, up to and including the period covered by the report. The second column provides the yearly catch of aphids for the equivalent period during the previous year, i.e. 2019. The final column provides the mean cumulative catch of aphids over the same period during the previous 10 years, i.e. 2009-2018. Presenting the data in this way enables the current year's catch of any species to be viewed in the context of data from both the previous year and an average year. As the last column presents an arithmetic mean, this figure is strongly influenced by those years when the total for that particular species of aphid has been high. 

In November 2000, the historic Elgin trap ceased operation due to the sale of the site. A new Elgin trap was erected approximately 4 kilometres from the old Elgin site. This trap started collecting aphids on 16 May 2002, and discontinued in October 2016. A permanent home for the northern trap has now been identified at Knocknagael Stud Farm, Inverness. This trap started running on 18 April 2019,has been added to the bulletin and will be added to cumulative totals in due course. 

At the end of 2005, the Edinburgh trap ceased operation at the East Craigs site. It was replaced by the Gogarbank trap located 3 kilometres to the south-west of East Craigs.  The 10-year averages for Edinburgh now consist entirely of data from the new trap.

Due to time restraints, data from the Ayr trap will not be included in the Scottish aphid bulletin cumulative totals during 2019. The trap continues to run and we hope to be able to identify catches from it in real time when time allows.

SASA is extremely grateful to the organisations where the traps are sited and to the staff who collect the samples. If you require any further information, or wish to use the contents of the Scottish Aphid Bulletins in any way, please email the Zoology team.

 

Aphid Predictions

Early season aphid activity in 2019


Prolonged exposure to low winter temperatures are known to have lethal and sub-lethal effects on populations of M. 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.  Prior to 2011, SASA has used the mean temperatures for January and February to predict when M. persicae will become active in the summer.  In 2011, following an extremely cold December 2010, SASA predicted early season aphid activity has been based on the mean temperatures during the three-month period of December-February.  We intend to continue to use the model based on the three month period.


During winter 2018-19, the mean temperatures were well above the mean over the last 50 years:  5.1°C at SASA (Edinburgh; mean = 4.0°C) and 4.1°C at JHI (Dundee; mean = 3.7°C).  These winter temperatures rank the 9th warmest from the last 51 years at Edinburgh and the 21st warmest from the last 53 years at Dundee.  Based on these figures, the predictions for the first flight of M. persicae is 1 June at Edinburgh (average date of first catch is 14 June) and 9 June at Dundee (average date of first catch is 13 June).  Therefore, M. persicae activity in 2019 is expected to commence 1 to 2 weeks earlier than in an average summer.


In 2018, the first M. persicae at Edinburgh was recorded on 6 July, 21 days later than the average date of first catch and 15 days later than predicted. The first M. persicae at Dundee was recorded on 15 June, 1 day earlier than the average date and 8 days earlier than predicted. First arrival dates for both sites were well within the 75% confidence limits of predictions.
The predictions for the Potato aphid Macrosiphum euphorbiae, Rose-Grain aphid Metopolophium dirhodum and the Grain aphid Sitobion avenae are provided by Rothamsted Research and are based on mean temperatures over January and February 2019 (Table 1).

Table 1

  2019 Prediction 75% Confidence Limits 2018 Obs'n

2019 Obs'n

Edinburgh
Myzus persicae 1 June 8 May - 19 June 6 July 28 May
Macrosiphum euphorbiae   20 April - 3 June 25 May 24 April
Metopolophium dirhodum   22 April - 10 June 31 May 8 April
Sitobion avenae   29 April - 9 June 30 May 7 May
Dundee
Myzus persicae 9 June 14 May - 5 July 15 June 30 April
Macrosiphum euphorbiae   2 May - 20 June 24 May  1 May
Metopolophium dirhodum   7 May - 23 June 9 May 21 April
Sitobion avenae   13 May - 20 June 28 May  23 May

The moderately warm temperatures over 2018-19 winter, particularly at Edinburgh,  indicate that the first flights of M. persicae should be 1 to 2 weeks earlier than on average, and at least 1 week earlier than in 2018.  Consequently, population levels have the potential to develop to levels that could significantly threaten the virus health of seed crops.  The prediction for the total of M. persicae caught by 31 July is 24 at Dundee and 33 at Edinburgh.  The 75% confidence intervals for these predictions are 7 at the lower end for Dundee and 9 at the lower end for Edinburgh, and 81 at the upper for Dundee and 119 at Edinburgh.  Therefore, populations of M. persicae could be relatively high during the growing season for potatoes in 2019.  Therefore, given the increase in inoculum observed during 2018, there is a significant risk of further leaf roll transmission in potato crops in 2019, presenting a risk for the 2020 crop exhibiting significantly higher levels of leaf roll than the average of 5.5% predicted for 2019.

View archive aphid predictions 

Cereal Aphids

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 has recently 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).

Cereal aphids and PVY transmission in 2018

During 2018, all four dominant species of cereal aphids were caught in high numbers in the aphid traps when compared with an 'average' year.  For the period when most virus transmission is believed to occur (before 31 July), the catches of the Rose-Grain aphid ranked 8th over the last 32 years, the Bird Cherry-Oat aphid ranked 6th and the Grain aphid ranked 9th.  These are the three species most strongly associated with the transmission of the most prevalent potato virus (PVY) in Scotland. Therefore, it is anticipated that the incidence of plants showing mosaic symptoms in 2019 will be higher than the levels observed in the 2018 potato crop.  Virus management options will need to be considered should high populations of aphid vectors develop over the season.

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, Nicola.

Cereal aphids in 2019

The first cereal aphids of 2019 were caught in the Scottish traps on the week ending 14th April, coming in early when compared to previous seasons. Although May's rainfall appears to be holding numbers at bay, periods of prolonged warm temperatures may lead to an increase in numbers early in the season.

As the Inverness trap has only recently started operation, we will be reporting on Edinburgh and Dundee catches only.

Please note that most of 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 numbers when comparing 2018 data to the large number of aphids caught in previous seasons.

Rose-Grain aphid in 2019

25 Rose-Grain aphids (Metopolophium dirhodum) have now been caught in the Scottish (Dundee and Edinburgh) suction traps up to 9 June, ranking 7th over the last 32 years of trapping. Between 3 and 9 June, none were caught in the Dundee trap, while six were caught at Edinburgh. The first individual of this season was caught in Edinburgh on 8 April, which is the earliest record for this species for Edinburgh in the last 32 years.

 

Grain aphid in 2019

27 Grain aphids (Sitobion avenae) have been caught in the Scottish (Edinburgh and Dundee) suction traps to 9 June, ranking 11th from the last 32 years of monitoring. The first individual was caught at Edinburgh on the 7th May; the first at Dundee was caught on the 23rd May.

 

Bird Cherry-Oat aphid in 2019

33 Bird Cherry-Oat aphids (Rhopalosiphum padi) have been caught in the Scottish (Dundee and Edinburgh) suction traps up to 9 June.  The 2019 total catch for this species now ranks 15th over the last 32 years. The first Scottish individual was caught on the 25th April in Dundee; the first in Edinburgh was caught on the 12th May.

Apple-Grass aphid in 2019

83 Apple-Grass aphids (Rhopalosiphum oxyacanthae) have been caught up to 9 June. This 2019 season total currently ranks 12th over the last 32 years. 21 of these were caught at Dundee, the rest at Edinburgh.

Peach-Potato Aphid

The Peach-Potato aphid Myzus persicae has traditionally been considered as the most important aphid vector of potato viruses. However in Scotland, Peach-Potato aphids generally fly later and in far lower numbers than in warmer countries and their relative scarcity generally makes this species less of a concern to potato growers.  In some years, usually following a particularly mild winter, Peach-Potato aphids can present a very high risk of virus transmission, particularly Leaf Roll, within the Scottish seed potato crop.

Prolonged exposure to low winter temperatures are known to have lethal and sub-lethal effects on populations of M. persicae which, in Scotland, overwinter as larvae or apterous adults.  Poor over-winter survival delays the build up of populations of this species in the forthcoming growing season.  Prior to 2011, SASA had used the mean temperatures for January and February to predict when M. persicae will become active in the summer.  In 2011, following an extremely cold December 2010, SASA predicted aphid activity based on the mean temperatures during the three-month period of December-February.  We intend to continue to use the model based on the 3 month period. 

During winter 2018-19, the mean temperatures were well above the mean over the last 50 years:  5.1°C at SASA (Edinburgh; mean = 4.0°C) and 4.1°C at JHI (Dundee; mean = 3.7°C).  These winter temperatures rank the 9th warmest from the last 51 years at Edinburgh and the 21st warmest from the last 53 years at Dundee.  Based on these figures, the predictions for the first flight of M. persicae is 1 June at Edinburgh (average date of first catch is 14 June) and 9 June at Dundee (average date of first catch is 13 June).  Therefore, M. persicae activity in 2019 is expected to commence 1-2 weeks earier than in an average summer.

The warmer than average temperatures over 2018-19 winter indicate that the first flights of M. persicae should be about 1-2 weeks earlier than on average, and 2-3 weeks earlier than in 2018.  Consequently, populations have the potential to develop to levels that could significantly threaten the virus health of seed crops.  The prediction for the total of M. persicae caught by 31 July is 24 at Dundee and 33 at Edinburgh.  The 75% confidence intervals for these predictions are 7 at the lower end for Dundee and 9 at the lower end for Edinburgh, and 81 at the upper for Dundee and 119 at Edinburgh.  Therefore, populations of M. persicae could be relatively high during the growing season for potatoes in 2019.  Therefore, given the increase in inoculum observed during 2018, there is a significant risk of further leaf roll transmission in potato crops in 2019, presenting a risk for the 2020 crop exhibiting significantly higher levels of leaf roll than the average of 5.5% predicted for 2018. 

Table

 M. persicae Dundee Edinburgh
First catch in 2019 30 April 28 May
1st catch prediction 2019 9 June 1 June
Mean date of first Catch 13 June 14 June
Catch to 9 June 2019 8 1
Predicted catch to 31 July 2018 24 33
Mean catch to 31 July 41 34

Peach-Potato aphids in 2019

A total of six peach-potato aphids were caught in two of the Scottish suction traps between the 3 and 9 June, with five in Dundee and one in the new Inverness trap.

As of 9 June 2019, a total of 8 Peach-Potato aphids have been caught in the Dundee trap and 1 in the Edinburgh trap. The combined total ranks 6th when compared to the previous 32 years. 

The first individual at Dundee was caught more than six weeks earlier than average, and 40 days earlier than predicted. This lies outwith (earlier than) the 75% confidence limits for both SASA and Rothamsted's prediction models. 

The first individual at Edinburgh  was caught on the 28 May, just over two weeks earlier than average and four days earlier than predicted (lying well within the confidence ranges).

 

 

Potato Aphid


The Potato aphid Macrosiphum euphorbiae is often the most numerous of the five or six species of aphids that regularly colonize potato crops in Scotland. It is also a potential aphid vector of non-persistent potato viruses (e.g. PVY, PVA).

As with Peach-Potato aphids Myzus persicae, early season predictions made following the 2018-2019 winter indicated that Potato aphid flights should be earlier than in an average year.  Therefore, total catches of Potato aphids may be relatively high and consequently the risk of virus transmission within potato crops colonised by Potato aphids have the potential to be higher than average. However, environmental conditions over the early summer do influence population development, and growers should monitor how the populations of this species develop over the season.

Table

 M. euphorbiae Dundee Edinburgh
First catch 2019 1 May 24 April
First catch prediction 2019 (75% confidence limits) 2 May - 20 June 20 April - 3 June
Mean date of first catch 1 June 24 May
Catch to 9 June 2019 2 8
Predicted catch to 31 July 2018 N/A N/A
Mean catch to 31 July 73 57

 

Potato aphids in 2019

A total of 10 potato aphids were caught up to 9 June, ranking 23rd out of the last 32 years. The first individual of this species was caught at Edinburgh on 24 April, one month earlier than average.

Summary & Outlook

Inspection of the 2018 Scottish seed potato crop revealed an incidence of crops containing virus affected plants of 9.4% of the total area entered for classification (up from 4.8% in 2017). 

The incidence of mosaic symptoms (i.e. excluding leaf roll) increased to 7.3% from 4.5% in 2017.  Within this 7.3%, the incidence of PVY was recorded as having increased from 3.6% to 6.9%, contrary to the decline to 2.8% that we predicted in March 2018.  Without the Elgin trap operating in 2017 and 2018 we are relying on a revised model, based on catches from just the Dundee and Edinburgh suction traps, using the three most abundant cereal aphids which have been most closely linked with PVY transmission in Scotland, to provide a prediction of 8.0% in 2019. 

The incidence of crops containing any leaf roll increased from 0.25% in 2017 to 3.1% in 2018. This exceeded predictions based on models using data from both Dundee and Edinburgh suction traps. Following moderately high activity of Myzus persicae in 2018, a further increase in the level of leaf roll to 6.5% is expected for the 2019 crop based on data from Dundee where the activity of this species was high in 2018 and to 4.5% based on data from Edinburgh where Myzus persicae activity was relatively lower in 2018.