A Christmas Aphid

A few weeks ago I was contacted by a researcher from the One Show.  They were interested in the possibility of doing a festive piece about what people bring into the house with them on Christmas trees with the idea that George McGavin would shake a Christmas tree over a piece of white paper and tell the audience all about the insects that fell out;  a typical media “how gross nature” is piece.

The researcher was somewhat disappointed when I told her that being winter  that there would be relatively little hiding in the tree, especially if it was a commercially reared cut tree bought from a garden centre or other retail outlet.  Cut Christmas trees in the UK tend to be harvested from October onwards so the chances are that your tree has lain about for at least a month before you bring it into your house and by that time, any sensible winter active herbivore has long departed for fresher trees.  Although conifer trees have a large number of insect species associated with them, most of them spend the winter either off the tree or as inactive eggs hidden under the bark or as eggs actually laid inside the needles e.g. the pine sawfly Neodiprion sertifer.  You would probably find a few opportunistic spiders and possibly some mites and bark lice, but not much else unless you had a potted tree or one that had only recently been felled.  The other thing that would influence what you would find is of course what species of tree you had bought.  Gone are the days when the Christmas tree and Norway spruce (Picea abies) were one and the same.  I guess my caveating and pessimistic reply proved too much for the researcher as I never heard back from her.

The one insect I had waxed lyrical about was of course an aphid, the green spruce aphid, Elatobium abietinum to be precise.   There are a number of aphid species that make a living on spruce trees, some of them quite large and spectacular such as the greater black spruce aphid, Cinara piceae, but like most aphids, they overwinter as eggs (Leather, 1992).

The greater black spruce aphid, Cinara piceae (Photograph courtesy of http://influentialpoints.com/Gallery/Aphids_on_spruce_Picea_in_Britain.htm)

The green spruce aphid, E. abietinum or Elatobium as it is commonly known, (there is only one species in the genus), overwinters in the UK and most other parts of the world, as an adult or immature stage (nymph) (Nicol et al., 1998).

The adult is small, green and inconspicuous, and quite difficult to see unless you are actually looking for them.

The green spruce aphid, Elatobium abietinum and nymphs.

The green spruce aphid is a native of Europe and normally attacks Norway spruce.  They avoid current year needles as these tend to be distasteful to them (the chemistry of young spruce needles is pretty nasty and makes them unsuitable hosts for the aphids) and feed on the previous year and older needles.  Spruce needles, even older ones, are not particularly nutritious, so the aphid injects a toxic material in its saliva that makes the needles more nutritious by encouraging nitrogen mobilisation (Kloft & Erhardt, 1959).  Their populations build up during the spring and towards the end of May and beginning of June, they take flight and the trees seem relatively free of aphids (Bevan, 1966).  As they are so small, they are most obvious after they have gone, either by the damage they cause, premature senescence of the needles as shown in the photograph above, premature needle drop or by the presence of a large number of ladybird larvae.  When I worked for the Forestry Commission as an entomologist, I quite often received phone calls from distressed foresters who had sprayed the blue beetles damaging their spruce trees!

Although they are difficult to find during the summer months they are still there; this summer collapse of singe-host aphids is quite common (Karley et al., 2004).  In the autumn,  Elatobium populations begin to build up and as they do not overwinter as eggs, they are able to continue reproducing through the winter months (Powell & Parry, 1976). Sitka spruce, Picea sitchensis, the most commonly grown conifer in the UK, is a native of North America and as such has very low resistance to Elatobium and displays an almost hypersensitive response to the toxic saliva produced by the aphid.

If it is a particularly mild winter then the spruce trees are likely to show severe signs of damage by June and July.  After several mild winters spruce trees may end up with only current year needles present, which has a severe effect on their growth and appearance.

Branches of Sitka spruce with only current year needles present after a severe Elatobium abietinum infestation

Sitka spruce trees showing discoloured needles after attack by Elatobium abietinum.

It may be small, inconspicuous and not worth a TV appearance, but  Elatobium abietinum is now a pest with a world-wide distribution and an international reputation.

References

Bevan, D. (1966). The green spruce aphis Elatobium (Neomyzaphis) abietinum Walker. Scottish Forestry 20, 193-201.

Karley, A. J., Parker, W. E., Pitchford, J. W. &Douglas, A. E. (2004). The mid-season crash in aphid populations: why and how does it occur? Ecological  Entomology 29, 383-388.

Kloft, W. & Ehrhardt, P. (1959). Unterschungen uber Saugtatigkeit und Schadwirkung der Sitkafichtenlaus, Liosomuphis abietina (Walk.), (Neomyzaphis abietina Walk.).  Phytopathologie Zeitzschrqt 35, 401 – 410.

Leather, S. R. (1992). Aspects of aphid overwintering (Homoptera: Aphidinea: Aphididae). Entomologia Generalis 17, 101-113.

Nicol, D., Armstrong, K. F., Wratten, S. D., Walsh, P. J., Straw, N., Cameron, C. M., Lahmann, C. & Frampton, C. M. (1998). Genetic diversity of an introduced pest, the green spruce aphid Elatobium abietinum (Hemiptera: Aphididae) in New Zealand and the United Kingdom. Bulletin of Entomological Research 88, 537-543.

Powell, W. & Parry, W. H. (1976). Effects of temperature on overwintering populations of the green spruce aphid, Elatobium abietinum.  Annals of Applied Biology 82, 209-219.

Sullivan, C.R. (1965) Laboratory and field investigations on the ability of eggs of the European Pine Sawfly, Neodiprion sertifer (Geoffroy) to withstand low winter temperatures.  Canadian Entomologist, 97, 978-993

 

Postscript

During the 1980s when ‘Acid Rain’ was very much in the news, Elatobium damage was often mistaken as a symptom of acid rain in the UK.

 

Vive La France! The BES crosses La Manche

This year the AGM of the British Ecological Society  (BES) was a joint affair with the Société Française d’Écologie (SFE) and was held in Lille in northern France just over an hour away from London by Eurostar.  Given our love of France and in my wife’s case, Christmas markets, there was no way I was not going to attend this landmark meeting especially as the BES were willing to pay my registration fee in recognition of my role as an Associate Editor of the Journal of Animal Ecology.   My mother-in-law is also a keen fan of Christmas markets so she decided to come along and keep Gill company.

We left London on a later train than originally planned (strike action in Brussels) and arrived in Lille mid –afternoon Monday to find that our hotel was a good 4 km away from the railway station and almost as far away from the Grand Palais where the conference was being held.  Luckily my mother-in-law, although almost 86, is very spry and took the longish walk in her stride.  We eventually found the hotel, on the way being amused by an Irish pub with a very non-Irish name 😉

An unusual name for an Irish Pub

Being a Monday in France, not much was open but we eventually found somewhere to eat for a reasonable price, and amusingly were served by an English waiter!

As the conference registration didn’t start until Tuesday evening we spent most of the day sight-seeing and bumping into fellow delegates.

 

     

The Christmas market was, however, somewhat disappointing, especially for those of us who were at the BES Birmingham meeting a couple of years ago.

The very small Christmas Market

The damp weather was also a bit off-putting.  This was when I started to regret my decision to opt for a comfortable well-worn pair of Desert Boots with holes in the soles instead of a new pair.

Wet, cold feet

The state of my feet inspired me to tweet an appropriate Haiku 😉

 

Wet Pavements in Lille

Desert boots are great,

except when soles are holey;

then rain means wet feet

 

The BES and SFE did a great job – a very full programme kept us occupied from Wednesday 10^th until late afternoon of Friday 12^th December.  (Gill and my mother-in-law managed to get to Brussels and Arras for their Christmas markets).  My only gripe was that because it was such a popular meeting (over 1100 delegates) that there were a huge number of sessions (62) so I missed a lot of talks that I wanted to hear.  This is why in some ways I much prefer smaller conferences such as the Royal Entomological Society annual meetings where there are generally only two parallel sessions.  I have long ago given up trying to session- hop, so confined myself to the plenaries and complete sessions such as the Agricultural Ecology, Pest & Pesticides session, where one of my favourite talks was given by Victoria Wickens from the University of Reading on local and landscape effects on aphids and their natural enemies; she was supported in the audience by her identical twin, Jennifer (also a PhD student at Reading and who spoke later in the Plant-Pollinator Interactions session).  I first meet Jennifer and Victoria at the BES AGM in Leeds when they were MSc students and student helpers.  It was only towards the end of that conference that I realised that there were actually two of them 😉

With careful planning I managed to fit in the Urban Ecology session, the Ecology & Society session, the symposium session on plant-insect-microbe interactions, and a session on herbivory.  There were a lot of really good talks and I learnt a lot. I made sure that I attended the Friday morning talk by Grrl Scientist who spoke about the use of social media and crowd funding in ecology.  I was somewhat embarrassed (and flattered) to have my blog publicly cited as an example of what other ecologists should be doing.  It was lucky that it was dark in the auditorium as I was blushing rather a lot.

The influence of the SFE was definitely felt; the catering was much, much better than we normally get at the normal BES meetings and it was great to see so many French ecologists.

  

and the free beer at lunch time was a welcome innovation that went down very well with the English delegates 😉

The organisers of the meeting next year in Edinburgh must be feeling somewhat nervous 😉

 

Very many thanks to the BES and SFE and their local organisers for putting on such a splendid meeting; a veritable scientific and gastronomic delight.

The infamous Desert boots – back home and ready to be  put to rest!