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Identification & Distribution:

Anoecia corni apterous fundatrices in spring on dogwood (Cornus) are dark brown or blackish. They have reduced eyes and 5-segmented antennae, whereas subsequent generations have large compound eyes and 6-segmented antennae. The siphunculi of all Anoecia corni forms are reduced to inconspicuous pores. Winged forms, both spring migrants and the sexuparae returning to Cornus in autumn, have a large black pterostigmal spot on the forewing, a white band around the top of the abdomen and a dark patch on the abdomen covering tergites 3-6. The body length of winged forms is quite variable ranging from 1.9-3.0 mm.

 

The first picture above shows two mature apterous Anoecia corni fundatrices (wingless stem mothers) with several developing nymphs. The siphunculi are reduced to pores and the antennae have only 5-segments (not visible in the picture). The winged form (shown in the second picture) above has two clear distinguishing features - a large black pterostigmal spot on the forewing, and a dark patch on the abdomen covering the posterior tergites 3-6 bordered by a white band. Both can be seen in the second picture.

It can be difficult to separate Anoecia corni from two other Anoecia species that (may) occur on dogwood. The 5th and 6th antennal segments of Anoecia corni both have secondary rhinaria (c.f. Anoecia vagans which has none on those segments). The third antennal segment of Anoecia corni has 9-17 secondary rhinaria (c.f. Anoecia major which has 13-22 secondary rhinaria on that segment).

The Anoecia corni antenna (see picture above) has secondary rhinaria on both the 5th and 6th segments, and has 14 secondary rhinaria on the third antennal segment.

In Europe Anoecia corni host alternates between dogwood (Cornus spp.) and roots of grasses (Poaceae). In eastern Asia and in areas where introduced (South Africa and North America), the dogwood-grass aphid remains all year round on grasses and some cereals.

 

Biology & Ecology:

On primary host (spring)
Overwintering eggs of Anoecia corni hatch in spring and give rise to a spring generation of fundatrices. The picture below shows developing alatiform nymphs.

These spring generations are often attended by ants.

 

The pictures above and below show common black ants (Lasius niger) attending the fundatrices and their developing alatiform (future winged) nymphs.

The alates then leave dogwood and migrate to their secondary host, the roots of grasses.

 

On secondary host (summer)

The four pictures below all show Anoecia cf. corni on its secondary host. Again they are attended by ants, most commonly by Lasius niger, but sometimes by Lasius flavus (Depa & Wojciechowski, 2008 ).

 

The second picture above shows a mixed species group of root aphids including both Anoecia corni (with the dark sclerotized dorsum) and Tetraneura ulmi  with which Anoecia species are often associated.

The apterae with the rather shiny black dorsal cuticle are typical Anoecia corni. We are unsure whether the very lightly marked alate shown in the picture below is an unusually early sexupara or is a different Anoecia species.

In late summer they produce winged migrant sexuparae (females whose offspring develop to sexual forms) which return to the primary host, dogwood.

 

On primary host (autumn)

Here they produce large numbers of pale young nymphs as shown in the picture below.

This results in a rapid build-up in numbers.

Such high numbers may attract large numbers of predators as reported by Jaskiewicz (2003)  who recorded both syrphid (hoverfly) and coccinellid (ladybird) larval predators. They apparently had little effect on the aphid population as they only built up towards the end of the season.

Some colonies are attended by ants which also reduces predation levels. The colony above was attended by the ant Lasius fuliginosus, also recorded attending Anoecia corni by Quinet et al. (1997)  .

These nymphs develop into oviparae and winged males. After mating, the oviparae lay their overwintering eggs on dogwood.

 

Damage and control

Dogwood aphid is said to lower the ornamental value of Cornus alba shrubs, especially in autumn, causing deformations, discoloration and early leaf fall. Neem oil has been suggested as an effective means of control on dogwood.

It is unclear whether Anoecia corni cause any damage to the summer host - grasses and cereals. A'Brook (1980)  has shown that the dogwood aphid can transmit barley yellow dwarf virus (BYDV) to cereals. However, levels of infestation are largely unknown. It is reported to be a minor pest of rice. Given the uncertainty of its effect on yield, it is seldom if ever controlled on cereals.

Acknowledgements

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994)  and Blackman & Eastop (2006)  supplemented with Blackman (1974) , Stroyan (1977) , Stroyan (1984) , Blackman & Eastop (1984) , Heie (1980-1995) , Dixon & Thieme (2007)  and Blackman (2010) . We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure  provided by Blackman & Eastop (2006).

Useful weblinks 

References

  •  A'Brook, J. & Dewar, A.M. (1980). Barley yellow dwarf virus infectivity of alate aphid vectors in west Wales. Annals of Applied Biology 96 (1), 51-58. Abstract 

  •  Depa & Wojciechowski (2008) Ant-root aphid relations in different plant associations. Polish Journal of Entomology 77, 151-163. Full text 

  •  Jaskiewicz, B (2003). Occurrence of aphids on Cornus alba. Hortorum Cultus 21 (1), 95-110. Full text 

  •  Quinet, Y. et al. (1997). Food recruitment as a component of the trunk-trail foraging behaviour of Lasius fuliginosus (Hymenoptera: Formicidae). Behavioural Processes 40 (1), 75-83. Abstract 

 

Identification requests

Mark Skevington 6/9/2014

I wonder if you could please comment on the attached photo.

I took a few of these aphids in my garden moth trap on Friday 5th Sept, and then today there were lots of them flying around the garden throughout the day. There is a lot of dogwood on a scrubby embankment adjacent to my garden. As far as I can see it is Anoecia corni, but could you please advise if there are any similar confusion species?

Image copyright Mark Skevington, all rights reserved.

Bob, Influentialpoints:

  • Your winged aphid is very likely Anoecia corni as that is much the commonest species.

    It's interesting to see it because, for some reason, this year Anoecia have been very scarce in Sussex.

    There 2 are other related species which you might get on dogwood, specifically Anoecia major and Anoecia vagans. The 3 Anoecia species can only be separated microscopically, by the numbers of rhinaria (sense organs) on the different antennal segments.

    We will soon include some detail about this on the website, once we manage to catch some more specimens to photograph.

 


 

Nigel Gilligan 15/9/2014 common dogwood-grass aphid

I found this on dogwood - it's quite infested. Am I correct in saying it's Anoecia corni?

Image copyright Nigel Gilligan, all rights reserved.

I have, as I half expected, not been able to take many images of aphids this year. Partly because I haven't seen that many at ground level, and partly because I am too busy taking images of other inverts.

(By the way, I assume that the sticky sap stuff that constantly drips from our big trees is simply the result of aphids. If so, then we must have literally millions aloft.)

Bob, Influentialpoints:

  • Your aphids are very likely Anoecia corni as that is much the commonest species.

    For some reason, this year Anoecia have been very scarce in Sussex, but other people have reported it abundant.

    There 2 are other related species which you might get on dogwood, specifically Anoecia major and Anoecia vagans. The 3 Anoecia species can only be separated microscopically, by the numbers of rhinaria (sense organs) on the different antennal segments.

    (Regarding your honeydew rain - yes, we have reached exactly the same conclusion, supported in part by the amazing numbers of wood ants we sometimes observe heading aloft!)

Nigel Gilligan 16/9/2014

And I thought it was a cert!

I have a microscope which will go up to x40, but the detail on the antennae sounds very small, so I suspect that it won't be good enough for that level of magnification. If my microscope is not good enough, can I sent an aphid to you?

Bob, Influentialpoints:

  • We've looked at [the Anoecia you sent us].

    We start with three possibles: Anoecia vagans, Anoecia corni and Anoecia major.

    The crucial characters are on the antennae shown below.

    Both the 5th and 6th antennal segments (towards the bottom-right) have secondary rhinaria (the bluey-white bar-like swellings) which rules out Anoecia vagans.

    The third antennal segment (the long one, center-top) has 14 secondary rhinaria. This is in the middle of the range for Anoecia corni (9-17) but would be at the lower end of the range for Anoecia major (13-22).

    Since Anoecia major has only so far been found on the secondary host (albeit it is expected to occur on dogwood), we conclude your specimen is Anoecia corni.