In partnership with
Willow-carrot aphid – 9 May 2017
This species overwinters mainly as eggs on willow trees and these generally hatch in February – March.
The aphids pass through one or two generations on the willow. Winged forms are produced later and
migrate to carrot and other hosts over a five to six week period.
Willow-carrot aphid may also be present as adult or immature stages on carrot crops throughout the
winter. These mobile stages are capable of producing spring colonies rapidly, with winged forms
potentially arising earlier than those developing on willow trees. As in 2016, a population of willowcarrot aphid has overwintered on our carrots at Wellesbourne (not strawed but there for the carrot fly)
rather than on willow. However, we are also expecting our usual ‘invasion’ from willow.
It is possible that two species of parsnip aphid and Myzus persicae also transmit viruses to carrot and
thereby reduce yield (see Factsheet 07/16 Virus diseases of carrots and the report for FV 382b). The
parsnip aphids are Cavariella pastinacae and Cavariella theobaldi. There is some information on
parsnip aphids at the end of this document. Information on Myzus persicae is in the Pest
Bulletin sheets for brassica and lettuce aphids.
We have been monitoring the numbers of aphids on some young carrot plants at
Wellesbourne. They are the numbers of aphids on 3 x 0.5 m lengths of row.
Date
Winged adults
4 May
1
Wingless adults and
nymphs
3
Parasitised aphids
0
In partnership with
Captures of willow-carrot aphids in suction traps
Willow-carrot aphid (Cavariella aegopodii) is one of the species captured in the network of suction traps
run by the Rothamsted Insect Survey. The table below is from AHDB Aphid News and shows first arrivals
in each suction trap compared with 2016 and the average over the last 10 years. Counts are available
up to the week ending 30 April.
In partnership with
Starcross
Wye
Ascot
Writtle
Rothamsted
Hereford
Wellesbourne
Broom's Barn
Kirton
Preston
FERA, York
Newcastle
Ayr
Edinburgh
Dundee
1
8
1
Ascot
Wye
2
4
Starcross
1
2
Writtle
Broom's Barn
1
Rothamsted
Kirton
1
Hereford
1
3
Wellesbourne
2
Preston
FERA, York
Newcastle
Ayr
Edinburgh
Dundee
1
1
1
16
1
Starcross
3
Wye
Writtle
2
Ascot
Rothamsted
1
1
Hereford
Wellesbourne
Broom's Barn
Kirton
Preston
FERA, York
Newcastle
Ayr
Edinburgh
1
Dundee
Cavariella theobaldi
Week ending
26-Feb
05-Mar
12-Mar
19-Mar
26-Mar
02-Apr
09-Apr
16-Apr
23-Apr
30-Apr
Elgin
Cavariella pastinaceae
Week ending
26-Feb
05-Mar
12-Mar
19-Mar
26-Mar
02-Apr
09-Apr
16-Apr
23-Apr
30-Apr
1
1
Elgin
Cavariella aegopodii
Week ending
26-Feb
05-Mar
12-Mar
19-Mar
26-Mar
02-Apr
09-Apr
16-Apr
23-Apr
30-Apr
Elgin
The tables below summarise the numbers of willow-carrot aphid and two species of parsnip aphid
captured in the suction traps each week during 2017.
1
In partnership with
Day-degree forecast
The graph below shows a ‘day-degree forecast’ for willow-carrot aphid (Cavariella aegopodii).
The forecast is based on accumulated day-degrees (D°) from 1 February (base 4.4°C). Information from
the Rothamsted Suction trap captures at Wellesbourne and Kirton has been used to estimate the mean
number of D° from 1 February until the first aphid of the year is caught in a suction trap (the start of the
migration to carrot). This is after approximately 360D°.
Weather data provided by Plantsystems Limited and funded by Syngenta.
500
450
400
Accumulated day-degrees above 4.4 C
350
300
250
200
150
100
50
0
1-Feb
15-Feb
1-Mar
15-Mar
29-Mar
12-Apr
26-Apr
Cornwall
Nottinghamshire
Yorkshire
Kent
Scotland
South Lincs
Suffolk
Start of willow-carrot aphid migration
10-May
In partnership with
Parsnip aphids
Mark Taylor from the Rothamsted Insect Survey very kindly extracted their data on Cavariella
pastinacae and Cavariella theobaldi for 2015 for the suction traps in England. Both of these species
overwinter on willow, as does Cavariella aegopodii (willow-carrot aphid). Because they have similar lifecycles to C. aegopodii there is the possibility of developing a simple day-degree forecast.
2015 data
Figure 1 shows the total numbers of each species captured at the English suction trap sites in 2015. It
includes C. aegopodii and M. persicae.
Figure 2 shows the dates by which 10% of each species were captured in each suction trap (start of
migration) and Figure 3 shows the date of 50% capture (mid-point of migration). These show that
Cavariella pastinacae and Cavariella theobaldi migrate later than Cavariella aegopodii overall.
Figures 4 and 5 show captures in the suction traps at Broom’s Barn and Kirton over time.
In partnership with
2000
1800
1600
Total number
1400
1200
1000
Cavariella pastinaceae No.
Cavariella theobaldi No.
800
600
Cavariella aegopodii No.
Myzus persicae No.
400
200
0
Figure 1
Total numbers of each species captured at the English suction trap sites in 2015
including C. aegopodii and M. persicae.
In partnership with
19-Jul
09-Jul
29-Jun
19-Jun
09-Jun
Cavariella pastinaceae 10%
30-May
Cavariella theobaldi 10%
Cavariella aegopodii 10%
20-May
Myzus persicae 10%
10-May
30-Apr
20-Apr
Figure 2
Dates by which 10% of each species were captured in each suction trap (start of
migration) in 2015.
In partnership with
18-Aug
29-Jul
09-Jul
19-Jun
Cavariella pastinaceae 50%
Cavariella theobaldi 50%
Cavariella aegopodii 50%
30-May
Myzus persicae 50%
10-May
20-Apr
Figure 3
Dates by which 50% of each species were captured in each suction trap (mid-point of
migration) in 2015.
In partnership with
700
Broom's Barn 2015
600
Number per week
500
400
Cavariella pastinaceae
Cavariella theobaldi
Cavariella aegopodii
300
Myzus persicae
200
100
0
19-Apr
Figure 4
19-May
19-Jun
19-Jul
19-Aug
19-Sep
19-Oct
Captures of aphids by the suction trap at Brooms’s Barn in 2015.
In partnership with
1000
Kirton 2015
900
800
Number per week
700
600
Cavariella pastinaceae
Cavariella theobaldi
500
Cavariella aegopodii
400
Myzus persicae
300
200
100
0
19-Apr
Figure 5
19-May
19-Jun
19-Jul
19-Aug
19-Sep
Captures of aphids by the suction trap at Kirton in 2015.
19-Oct