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Aphids on spruce

Blackman & Eastop list about 170 species of aphids  as feeding on spruces (Picea) worldwide, and provide formal identification keys.

The species below are those we have found most frequently, listed in rough order of abundance. Assistance on separating spruce from other conifers, and on differentiating the two species of spruce that we consider is given below. 

 

Elatobium abietinum (Green spruce aphid)

Apterae of Elatobium abietinum are pale to dark green, sometimes with a partial wax bloom giving the appearance of two darker green longitudinal stripes (see pictures below). The siphunculi are cylindrical, long, thin, pale and tend to be slightly s-curved. They are up to 2.5 times the length of the cauda which is pale and pointed. The body length of Elatobium abietinum apterae is 1.0-2.0 mm.

 

Elatobium abietinum spend all year on the needles of spruce, especially Sitka spruce (Picea sitchensis) and Norway spruce (Picea abies and, much less commonly fir (Abies spp.). The green spruce aphid has an unusual life cycle in that populations often continue to feed and reproduce through the winter. In spring and early summer alates are produced in response to the changing nutritional status of the host. They then migrate to other spruce where their nymphs aestivate for the summer before resuming development in autumn. The species is native to Europe, but it has now spread to Australia, New Zealand, Chile and North America. Populations in continental Europe have a sexual stage but elsewhere overwintering is by parthenogenetic forms. Elatobium abietinum can be a serious forestry pest with colonies on spruce causing discoloration and loss of old needles, sometimes involving serious defoliation.

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Adelges abietis (Eastern spruce gall adelgid)

Identification:

The gall produced by Adelges abietis on spruce is known as a 'pineapple gall'. The mature gall (see first picture below) is usually about 15-20 mm long and ellipsoidal, albeit less than 1.5 times as long as it is wide. Spruce needles on the gall are shorter than normal. The Adelges abietis gall is only slightly paler green than a normal shoot. The slits to gall chambers are often orange-red or deep pink before opening. There are often several galls together at the base of adjacent shoots, and plant growth often continues beyond the gall. Gall chambers open in August-September.

 

The winged female (gallicola) of Adelges abietis (see second picture above) is yellow with 5-segmented antennae and five pairs of abdominal spiracles. The wingless female (pseudo-fundatrix) is yellowish-green to light green again with 5-segmented antennae.

The pineapple gall adelgid is mainly found on Norway spruce (Picea abies), but it can also occur on other Picea species including sitka spruce (Picea sitchensis) and white spruce (Picea glauca). Adelges abietis is distributed throughout Europe, and is also found in Morocco, India and North America.

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Cinara piceicola (Green-striped spruce aphid)

Identification:Apterae of Cinara piceicola have a dark brown head and thorax and pale olive-buff abdomen. In life there are two longitudinal faint greyish-green dorsal stripes and a thin white stripe between them. The dorsum is not wax powdered but the underside of the body is mealy. The siphuncular cones are usually small and rather faintly pigmented. The body length is 2.1-4.2 mm.

 

The first picture above shows an adult aptera of Cinara piceicola feeding on the stem in June. Note especially the two faint dorsal green bands, with a rather indistinct whitish line between them. The second picture below shows an alate vivipara feeding on spruce. It is similar in appearance to the apterous vivipara.

Cinara piceicola occurs on spruce (Picea spp.), especially Norway spruce, in colonies on bark of woody shoots between needle-bases in spring. They move to older branches and roots in summer. Numerous alatae are produced in May-June. Oviparae and apterous males occur from July onwards. Cinara piceicola is found in north, west and central Europe, and apparently China.

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Cinara pruinosa (Wax-bordered spruce aphid)

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. Theyu 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.

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).

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Cinara piceae (Greater black spruce bark aphid)

Apterae of Cinara piceae are uniformly jet black and are often described as "resembling the texture and shape of old droplets of tar". The anterior portion is more shiny. The spiracular openings are in a series of lateral depressions giving the abdomen a crenated appearance. The siphuncular cones are rather small with the sclerotized area usually no wider than twice the diameter of the rim. The coxae and tarsi are black. The hind femora are reddish brown and black distally. The body length is 2.1-4.2 mm. The oviparous female is dark yellowish grey with a large pericaudal wax ring present. The apterous male is small (around 3.5 mm), more elongate than other forms and is dark bluish grey with sclerotized areas shining black.

Cinara piceae forms large colonies in spring on the undersides of older branches and on trunks of Spruce (Picea spp.). Numerous alatae are produced in May-June. The oviparae appear in September-October, move to the current year's growth and lay wax-dusted eggs on needles. They often move to ground level or the roots in summer. They are found throughout Europe and in the Far East, and may vary greatly in abundance from year to year.

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Adelges cooleyi (Cooley spruce gall adelgid, Douglas fir adelgid)

On spruce trees (Picea) Adelges cooleyi is most commonly identified by the gall it produces: which is elongated (it is more than 1.5 times as long as it is wide) and is often curved with long needles protruding from it. Adelges cooleyi galls are highly variable in colour, yellow-green, pink, red or even deep purple (see first picture below).

 

First image courtesy of Whitney Cranshaw, Colorado State University / copyright Bugwood.org  (CC BY 3.0 US ).
 
Second image by permission of Claude Pilon  copyright all rights reserved.

Winged females of Adelges cooleyi are reddish brown to purplish black (see second picture above). They are somewhat larger when originating on spruce (length 1.7-2.5 mm) than on Douglas fir (length 1.2-1.7 mm.). On Douglas fir the most commonly seen morph is the apterous exule which is covered in white woolly wax.

The cooley spruce gall adelgid typically has a two year life cycle alternating between spruce (Picea sitchensis, Picea pungens, P. engelmanii) and Douglas fir (Pseudotsuga menziesii, P. macrocarpa). Host alternation is sometimes lost and the species remains on one host all year round. For example a form in Canada remains on Picea glauca) and forms in Europe and California remain on Pseudotsuga. Adelges cooleyi is native to western North America, but is now found throughout Europe and North America.

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Adelges laricis (Larch adelgid, Larch woolly aphid)

Adelges laricis galls on spruce (see first picture below) are waxy, creamy and relatively small. These galls mature in June-July. The winged female of Adelges laricis (see second picture below) which matures on spruce is greyish to blackish, with a body length of 1.9-2.0 mm. The winged female that matures on larch is dark green, with a greyish-green head and thorax and a body length of 1.0-1.5 mm (see second picture below).

 

First image courtesy AfroBrazilian under a Creative Commons Attribution-Share Alike 3.0 Unported license.

On larch the most commonly seen morph is the apterous exule which is covered in white woolly wax.

The larch adelgid host alternates between the primary host Picea (spruce) and the secondary host Larix (larch). The larch adelgid was originally found in central Europe, but Adelges laricis is now widespread throughout that continent and has been introduced to North America.

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Species of spruce

Spruces all have a woody peg at the base of every needle which is a useful identification aid, the picture below shows the woody peg at the base of two needles pulled off their branch. We cover two species of spruce, Norwegian spruce (Picea abies) and Sitka spruce (Picea sitchensis).

 

The branches of Norwegian spruce are in regular horizontal whirls ascending towards the crown to form a strong conical silhouette. The needles are 1.5cm in length, stiff, pointed, dark green with fine white speckled lines. Needles grow on all sides of the shoot; the upper needles point forward; the needles beneath part to reveal the twig. The cones are red brown and pendulous (12-15cm).

The upper branches of Sitka spruce (see picture below) are ascending, but the lower branches rise and then arch widely over and down. Branchlets are dense and hanging. Needles are 2-3cm in length, slender, sharply pointed, hard and stiff, green above with two bright blue-white bands beneath. The needles grow straight out flat from the shoot with the upper needles pressed down close to the shoot along its centre. From a distance the foliage appears blue-grey. The cones are distinctive, cylindrical, pale green in summer but ripening into pale creamy-brown cones; each with thin, papery scales that have a crinkly, toothed edge.

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

  •  Blackman, R.L. & Eastop, V.F. Aphids on the world's plants An online identification and information guide. Full text 

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

  •  Heie, O.E. (1980-1995). The Aphidoidea, Hemiptera, of Fennoscandia and Denmark. (Fauna Entomologica Scandinavica) E.J. Brill, London.