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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. We cover the aphid galls first and then the free-living species, listing each species in rough order of abundance with the commonest first. Assistance on separating spruce from other conifers, and on differentiating Norwegian spruce (Picea abies) from Sitka spruce (Picea sitchensis) is given below.

 

Adelges abietis (Eastern spruce gall adelgid)

The Adelges abietis gall on spruce, known as a 'pineapple gall', (see first picture below) is ellipsoidal with its length less than 1.5 times the width and usually about 15-20 mm in length. The spruce needles on the gall are shorter than normal and are a slightly paler green than on 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 gall. The gall is initiated by the pseudo-fundatrix (not pictured) which is yellowish-green to light green with 5-segmented antennae. The offspring of the pseudo-fundatrix which live inside the gall (see second picture below) are a yellowish orange and are densely waxed. The gall chambers open in August-September to release the gallicolae.

The Adelges abietis gallicola (see third picture above) is yellow with 5-segmented antennae and five pairs of abdominal spiracles. The eggs laid by the gallicolae hatch to give 'crawlers' which overwinter close to buds, and then mature in spring to the wingless pseudo-fundatrices

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

The Adelges cooleyi gall (see first picture below) is elongated, more than 1.5 times as long as wide, and often curved with the needles slightly shorter than usual (cf. Adelges laricis & Adelges abietis which have globular or ellipsoidal galls, less than 1.5 times as long as wide, and with needles much shorter than usual). Adelges cooleyi galls are highly variable in colour: yellow-green, pink, red or even deep purple. The gall is initiated in spring by the fundatrix which feeds on sap and matures, inducing a swelling of the bud into a gall. At maturity she produces a cluster of eggs which hatch to give brownish nymphs which crawl into the developing gall. The galls release winged females, the gallicolae (see second picture below) which migrate to Douglas fir. The gallicolae of Adelges cooleyi have reddish brown to purplish black abdomens and reddish brown wing veins , and are somewhat larger when originating on spruce (length 1.7-2.5 mm) than on Douglas fir (length 1.2-1.7 mm). Antennal segments III and IV are carrot shaped, and have slit-like rhinaria. The rhinaria extend slightly more than half way round, but do not occupy more than 25% of the length of the segment (cf. Adelges nordmannianae where the rhinarium on III is almost half the length of the segment and extends more than half way round it).

The eggs of the gallicolae hatch out to give apterous exules and these overwinter on fir. These develop the following spring when they become covered in white woolly wax (see third picture above). The offspring of mature exules develop to give both wingless and winged forms, and the winged forms migrate back to spruce. Their offspring develop to males and females, and the mated females lay eggs. These hatch to give young fundatrices which overwinter on the spruce buds.

The cooley spruce gall adelgid typically has a two year life cycle alternating between spruce (Picea sitchensis, Picea pungens, Picea engelmannii) and Douglas fir (Pseudotsuga menziesii, Pseudotsuga 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 gallicola 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. Antennal segments IV and V of the gallicola do not have deep constrictions at the articulating surfaces, so that segments III to V appear fused. The rhinarium on segment III is narrow and angular. Each rhinarium extends at least half way round the circumference of its segment. The gallicolae migrate to larch where they lay eggs.

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

The eggs hatch to give blackish-grey apterous sistens females which on maturity lay large clusters of eggs. These develop to give wingless and winged exules which are covered in white woolly wax (see third picture above). 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. The winged females migrate back to spruce and lay eggs which develop to sexual forms. After mating eggs are laid which hatch in autumn.

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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Adelges nordmannianae (Silver fir woolly adelgid)

Adelges nordmannianae induces terminal galls (see first picture below) on its primary host, oriental spruce (Picea orientalis). The galls are 2-15 mm long, globular, pinkish, strawberry-like when young, but later becoming greenish with red or purple coloration at the bases and tips of scales. The gallicola of Adelges nordmannianae which develops in the gall (not pictured) has the body and wings at first greenish, darkening in a few days. The antennae have large rhinaria on segments IV and V which extend half the length of the segment, or even more in the case of segment IV. Segment V is much narrower than the other segments and distinctly cigar-shaped. The rhinarium on III is almost half the length of the segment and extends more than half way round it. Adult body length is 1.1-1.54 mm, body width is 0.55-0.66 mm. The secondary host is fir (Abies). Nymphs overwinter on fir and on maturing deposit clusters of brownish-orange eggs. These hatch at bud-burst and the reddish brown 'crawlers' disperse over the young needles (see second picture below).

First image above of gall, copyright Peter Voboril, CC-BY-NC-SA 3.0 ee, Wikimedia Commons

The first instar larva of the sistens morph (the overwintering neosistens stage) is the stage often used for identification purposes. The wax pore plates on the inner margins of meso-- and metathoracic spinal sclerites contain numerous small rounded pits, arranged in 2-4 areas, the most central area containing 7-12 pits. The total number of pits in the central areas of the spinal wax pore plates of the meso- and metathorax together with abdominal tergites I-III (i.e. 10 central areas) is 57-104 (cf. Adelges piceae which has 18-63 pits in the 10 central areas). There are then several parthenogenetic generations of multiplication with both apterae and alatae produced. The third picture above shows mainly immature alatae (unwaxed) and a few apterae (waxed).

Where the primary host is present (Caucasus mountains in Russia & Turkey), Adelges nordmannianae has a two year life cycle, host alternating between its primary host, oriental spruce (Picea orientalis), and its secondary host, Nordmann fir (Abies nordmanniana). On its primary host it produces small rounded terminal galls. The winged forms that emerge from the galls migrate to fir where it has a series of parthenogenetic generations. The adelgid has been introduced to much of Europe, North America and New Zealand where it is anholocyclic on a variety of secondary hosts, including Nordmann fir and silver fir (Abies alba).

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Elatobium abietinum (Green spruce aphid)

Elatobium abietinum (Green spruce aphid)

Apterae of Elatobium abietinum are pale to dark green (see first picture below), sometimes with a partial wax bloom. 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. Elatobium abietinum can be a serious forestry pest with colonies on spruce causing discoloration and loss of old needles (see second picture above), sometimes causing serious defoliation.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.

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Cinara piceicola (Green-striped spruce aphid)

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 wax stripe between them (see first picture below). The dorsum is not wax powdered, but the underside of the body is mealy. The abdomen of the aptera has sclerotized areas on the dorsum consisting of a transverse segmented band on segments I-III and a broad cross band on VIII (see first picture below and first micrograph below that). A key distinguishing characteristic of Cinara piceicola is that the hairs on the outer side of the hind tibiae are all short - less than 0.12 mm long (cf. most other spruce feeding aphids in which all, or many, of those hairs are long, often greatly exceeding 0.12 mm.) The siphuncular cones are usually small and rather faintly pigmented (cf. Cinara pruinosa which have prominent black siphuncular cones). The body length of the adult aptera is 2.1-4.2 mm.

Beware: Cinara piceicola often form mixed species colonies with Cinara pruinosa so, to distinguish them, look carefully at the length of hairs on the tibia and the colour of siphunculi on adults.

The ovipararous female is rather small (at least compared to the vivipara) and is greyish or orange-brown. In life the ovipara has a prominent pericaudal wax ring (see below).

Cinara piceicola occurs on spruce (Picea species), 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)

Live apterae of Cinara pruinosa are brown or dark green, sometimes with a bronze metallic tinge. They may have waxed patches along the sides of the dorsum (see first picture below) or such patches may be reduced or absent (see second picture below) (cf. Cinara costata which are wax covered to a greater or lesser extent, with deposits of wax on surrounding twigs). The adults of Cinara pruinosa usually have blotchy blackish markings in a pattern resembling the letter omega (Ω) on tergites 1-3. The two terminal segments of the rostrum are 1.1-1.5 times longer than the second tarsal segment. The legs are conspicuously hairy, with long hairs on the outer side of the hind tibia, all or many of the hairs exceeding 0.12 mm (cf. Cinara piceicola which has only short hairs on the outer side of the hind tibia - less than 0.12 mm long). The tibiae are pale except for the apical one third of the femora, and the bases and distal halves of the tibiae and tarsi. The second tarsal segment is shorter than the maximum diameter of the cones.Cinara pruinosa adults have prominent black siphuncular cones (cf. Cinara piceicola which have usually small and rather faintly pigmented siphuncular cones). The body length of Cinara pruinosa apterae is 2.4-5.0 mm.

The Cinara pruinosa alate (see third picture above) is brown or green with a pattern of white wax spots down the midline and along the sides of the dorsum.

Cinara pruinosa oviparae are somewhat smaller than the viviparae and have a pericaudal wax ring (see picture below in life cycle section). 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 species) 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. Cinara pruinosa is found throughout most of Europe eastward to Turkey, and in North America (where it is often recorded as Cinara 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 (their thoracic area) is shiny, whilst the abdomen is largely unsclerotised, indicating that the dark body colour is subcuticular. 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 of Cinara piceae is 4.5-6.7 mm.

Guest image (above-right), Copyright Ian Dawson, all rights reserved.

The alate (above, second and below, first) is similar in colouration to apterae. The forewings are broad and are tinted with a pale grey suffusion. The pigmented pterostigma extends almost half the length of the subcosta. The oviparous female (pictured below under 'Life cycle') 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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Cinara costata (Mealy spruce aphid)

Cinara costata apterae are usually wax-covered; young adults have characteristic sausage-shaped rings of wax on the dorsal cuticle (see first picture below). Under the wax they are light brown or yellow-brown, sometimes with a dull metallic golden sheen, and with a pair of wax-covered dark bottle-green dorsal longitudinal stripes which sometimes coalesce at about the level of the siphuncular cones. The rather uniform yellow-brown ground colour is good identification characteristic for unwaxed colonies. The terminal rostral segments (R IV+V) are longer than the second segment of the hind tarsus (HTII), and HTII is shorter than maximum diameter of the large dark prominent siphuncular cones (cf. Cinara pilicornis which has R IV+V shorter than HTII, and HTII is longer than the maximum diameter of the small, rather pale siphuncular cones). The prominent siphuncular cones are dark brown and usually spaced three or more diameters apart (cf. Cinara pruinosa which has the prominent blackish siphuncular cones two diameters or less apart). The body length of adult Cinara costata apterae is 2.7-3.8 mm.

Both images above copyright Anders Albrecht under a Creative Commons Attribution 3.0 Unported License.

Cinara costata alatae have characteristically pigmented forewings with a dark area near the apex and another one near the middle of the posterior border of the wing. The medial vein is only once-branched. The oviparae have their hind tibiae thickened with numerous pseudosensoria.

The mealy spruce aphid forms small colonies (see second picture above) on smaller woody twigs on lower branches of Spruces (Picea species). These twigs also receive a deposit of mealy wax and the aphids are not usually attended by ants. Oviparae and males occur in the northern hemisphere in October. Cinara costata occurs in Europe, east Asia, Australia, Greenland, Canada and USA.

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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 three species of spruce: Norwegian spruce (Picea abies), Sitka spruce (Picea sitchensis) and Oriental spruce (Picea orientalis).

  • The branches of Norwegian spruce (see picture below) 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).

First image above by Ivar Leidus - Own work, CC BY-SA 3.0 ee

  • The upper branches of Sitka spruce (shown 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.

  • The branches of Oriental spruce (shown below) are all ascending, but do not form a strong conical silhouette. The leaves are needle-like and, at 6-8 mm long, the shortest of any spruce. The cones are red to purple when young, maturing to dark brown and have stiff, smoothly rounded scales.

Third image above Zefram - Own work, CC BY-SA 3.0 ee

Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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.