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Cinara pruinosa

Wax-bordered Spruce Aphid

On this page: Identification & Distribution  Biology & Ecology  Damage & Control 

Identification & Distribution:

In life, apterae of Cinara pruinosa are dark green or brown, sometimes with a bronze metallic tinge. They are often wax-powdered along the sides of the dorsum and on the underside of the body. Immature forms may or may not be wax powdered. They have prominent black siphuncular cones. The legs and body are conspicuously hairy.

The adults of Cinara pruinosa usually have blotchy blackish markings in a pattern resembling the letter omega on tergites 1-3 . There are sometimes further blackish marking between and in front of the siphuncular cones. The legs are pale except for the apical one third of the femora, and the bases and distal halves of the tibiae and tarsi. The hairs on the outer side of the hind tibia are quite long, with all or many of them exceeding 0.12mm and much more than 0.6 times the width of hind tibia at its midpoint. The tibial hairs are pale or dusky usually with unpigmented bases.

The second tarsal segment is shorter than the maximum diameter of the cones. The two terminal segments of the rostrum are 1.1-1.5 times longer than the second tarsal segment. The body length is 2.4-5.0 mm.

Oviparae are somewhat smaller than the viviparae and have a pericaudal wax ring. Both alate and apterous males have been recorded (the latter possibly in error).

Cinara pruinosa occurs in small colonies on the woody twigs of Spruce (Picea spp.) in spring, but later found at base of trunk and on roots in ant shelters. Oviparae and alate males occur in September-October, but anholocyclic overwintering on roots also occurs. Throughout most of Europe eastward to Turkey, and in North America (where often recorded as palmerae).

 

Biology & Ecology:

Eggs of the wax-bordered spruce aphid are laid on the bark of younger twigs, although Pintera (1966)  reports that some apterae overwinter on the roots in chambers specially prepared by ants. Carter & Maslen (1982)  report that alates occur from June till August, and that their progeny develop on roots or the base of the trunk of spruce trees. However, we have found apterae & nymphs on the branches of spruce in March, August and October. One such colony found in March is shown below.

Note that these immatures have no wax dorsally. They were reared through to adults to check identification, providing the freshly marked specimen of Cinara pruinosa shown in the identification section (above top left). There is some evidence that populations respond favourably to use of fertilizer in nursery spruce trees. Wellenstein (1960)  reported that when 5-year-old potted Spruce, artificially infected with Cinara pruinosa, were fertilized with nitrogen, calcium, potassium, phosphorus, or trace elements, aphid populations on nitrogen and calcium-fed plants increased rapidly and then quickly declined. On potassium and phosphorus-fed plants the increase was slower, but greater and more lasting.

 

We have sometimes found Cinara pruinosa to be attended by southern wood ants (Formica rufa) as can be seen in the pictures above and below. Binazzi & Scheurer (2009)  reported that Cinara pruinosa is optionally dependent on ants.

In Sweden mixed populations of Cinara piceicola and Cinara pruinosa are attended by the wood ant Formica aquilonia. Johansson & Gibb (2012)  compared clear-cuts (leaving 5-10 trees/ ha), middle-aged and mature spruce-dominated stands of boreal forest for the quality and quantity of aphid honeydew obtained by these ants. Wood ants harvested less honeydew in clear-cuts which contributed to a reduction in size and abundance of wood ant workers and mounds.

Sometimes, however, Cinara pruinosa is not attended by ants. The only unattended colony we have found appeared quite different with heavy wax powdering of all the colony - to such an extent that we originally misidentified the colony below as belonging to another species, namely Cinara costata. This picture shows a group of fourth instar nymphs.

Where the species is attended by ants we have found neither predators nor parasites. Where it was unattended, we found potential predators present near the aphid colonies - specifically of the larch ladybird (Aphidecta obliterata) shown below.

When Aphidecta was put on a branch with aphids, it rapidly started devouring them. This does not prove that it is an important or even frequent predator, but it certainly shows that it will eat them when hungry!

 

Damage and control

The wax-bordered spruce aphid often lives in mixed species colonies. The picture below on the left shows a green colour form of Cinara pruinosa (the aphid with the prominent black siphuncular cones)- despite being an adult, unusually it has no wax dorsally. On the right are an ovipara (with pericaudal wax ring) and two apterae of Cinara piceicola on spruce in October.

These mixed species colonies are usually ant-attended so one needs to assess the effect on growth of having both the aphids and the ants. Usually the growth of deciduous trees responds positively to wood ant - aphid mutualism as the ants destroy many harmful herbivores. In contrast, wood ant-aphid mutualism has been shown to suppress the growth of Scots pine. This may be because unlike deciduous trees, conifers have relatively few defoliating insects. Kilpelainen (2003)  found that wood ant-aphid mutualism was associated with a clear positive but non-significant height growth response in individual 5-year-old Norway spruce seedlings, but had a small significant negative effect on the stem growth of individual fast-growing 30-year-old Norway spruces. They concluded that effects at the stand level were negligible, because only a small number of trees were heavily infested.

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

  •  Binazzi, A. & Scheurer, S. (2009). Atlas of the honeydew producing conifer aphids of Europe. Aracne. 132 pp. Introduction 

  •  Carter, C.R. & Maslen, N.R. (1982). Conifer Lachnids. Forestry Commission Bulletin No. 58, 75pp.

  •  Johansson, T. & Gibb, H. (2012). Forestry alters foraging efficiency and crop contents of aphid-tending red wood ants, Formica aquilonia. PLoS ONE 7 (3):e32817.  Full text 

  •  Kilpelainen, J. et al. (2009). Does the mutualism between wood ants (Formica rufa group) and Cinara aphids affect Norway spruce growth? Forest Ecology and Management 257 238-243. Abstract 

  •  Pintera, A. (1966). Revision of the genus Cinara Curt. (Aphidoidea, Lachnidae) in Middle Europe. Acta entomologica bohemoslavika 63, 281-321.

  •  Wellenstein, G. (1960). Ergebnisse vierjahriger Untersuchungen uber die Steigerung der Waldbienentracht. (Four years' results of trials to increase the honey harvest from the forest.) Zeitschrift fur Angewandte Entomologie 47 (1), 32-41.