Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Elatobium abietinum
(green spruce aphid)

Toolbox

Datasheet

Elatobium abietinum (green spruce aphid)

Summary

  • Last modified
  • 15 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Preferred Scientific Name
  • Elatobium abietinum
  • Preferred Common Name
  • green spruce aphid
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Arthropoda
  •       Subphylum: Uniramia
  •         Class: Insecta
  • Summary of Invasiveness
  • E. abietinum is a serious invasive pest in North America where susceptible spruce species form a major component of the native forests. Defoliation of Picea sitchensis along the Pacific coast, and of Picea englemannii, Picea glauca and Picea pungens...

Don't need the entire report?

Generate a print friendly version containing only the sections you need.

Generate report

Pictures

Top of page
PictureTitleCaptionCopyright
Adult wingless female (apterous virginopara) of E. abietinum.
TitleAdult
CaptionAdult wingless female (apterous virginopara) of E. abietinum.
CopyrightForestry Commission (UK)
Adult wingless female (apterous virginopara) of E. abietinum.
AdultAdult wingless female (apterous virginopara) of E. abietinum.Forestry Commission (UK)
Adults and nymphs (apterous virginoparae) of E. abietinum on needles of Picea sitchensis.
TitleAdults and nymphs
CaptionAdults and nymphs (apterous virginoparae) of E. abietinum on needles of Picea sitchensis.
CopyrightForestry Commission (UK)
Adults and nymphs (apterous virginoparae) of E. abietinum on needles of Picea sitchensis.
Adults and nymphsAdults and nymphs (apterous virginoparae) of E. abietinum on needles of Picea sitchensis.Forestry Commission (UK)
Shoot of Picea sitchensis showing the yellowing of older needles characteristic of attack by E. abietinum.
TitleDamage symptoms
CaptionShoot of Picea sitchensis showing the yellowing of older needles characteristic of attack by E. abietinum.
CopyrightForestry Commission (UK)
Shoot of Picea sitchensis showing the yellowing of older needles characteristic of attack by E. abietinum.
Damage symptomsShoot of Picea sitchensis showing the yellowing of older needles characteristic of attack by E. abietinum.Forestry Commission (UK)
Loss of all old and some current year needles caused by a heavy spring attack of E. abietinum.
TitleDamage symptoms
CaptionLoss of all old and some current year needles caused by a heavy spring attack of E. abietinum.
CopyrightForestry Commission (UK)
Loss of all old and some current year needles caused by a heavy spring attack of E. abietinum.
Damage symptomsLoss of all old and some current year needles caused by a heavy spring attack of E. abietinum.Forestry Commission (UK)
Defoliation of 5-year-old Picea sitchensis following attack by E. abietinum in the autumn. Banteer, Ireland, January 1973.
TitleDamage symptoms
CaptionDefoliation of 5-year-old Picea sitchensis following attack by E. abietinum in the autumn. Banteer, Ireland, January 1973.
CopyrightForestry Commission (UK)
Defoliation of 5-year-old Picea sitchensis following attack by E. abietinum in the autumn. Banteer, Ireland, January 1973.
Damage symptomsDefoliation of 5-year-old Picea sitchensis following attack by E. abietinum in the autumn. Banteer, Ireland, January 1973.Forestry Commission (UK)
Spring defoliation of 4-year-old Picea sitchensis by E. abietinum. The older needles have turned brown, the new foliage is unaffected. Lampeter, Wales, UK, May 2002.
TitleDamage symptoms
CaptionSpring defoliation of 4-year-old Picea sitchensis by E. abietinum. The older needles have turned brown, the new foliage is unaffected. Lampeter, Wales, UK, May 2002.
CopyrightForestry Commission (UK)
Spring defoliation of 4-year-old Picea sitchensis by E. abietinum. The older needles have turned brown, the new foliage is unaffected. Lampeter, Wales, UK, May 2002.
Damage symptomsSpring defoliation of 4-year-old Picea sitchensis by E. abietinum. The older needles have turned brown, the new foliage is unaffected. Lampeter, Wales, UK, May 2002.Forestry Commission (UK)
Needle browning in a shelterbelt of Picea sitchensis following attack by E. abietinum in the spring. Selkirk, Scotland, UK, September 1997.
TitleDamage symptoms
CaptionNeedle browning in a shelterbelt of Picea sitchensis following attack by E. abietinum in the spring. Selkirk, Scotland, UK, September 1997.
CopyrightForestry Commission (UK)
Needle browning in a shelterbelt of Picea sitchensis following attack by E. abietinum in the spring. Selkirk, Scotland, UK, September 1997.
Damage symptomsNeedle browning in a shelterbelt of Picea sitchensis following attack by E. abietinum in the spring. Selkirk, Scotland, UK, September 1997.Forestry Commission (UK)
Mortality of Picea englemannii following defoliation by E. abietinum in mixed-conifer forest in the Pinaleno Mountains, Arizona, USA, October 2003.
TitleDamage symptoms
CaptionMortality of Picea englemannii following defoliation by E. abietinum in mixed-conifer forest in the Pinaleno Mountains, Arizona, USA, October 2003.
CopyrightForestry Commission (UK)
Mortality of Picea englemannii following defoliation by E. abietinum in mixed-conifer forest in the Pinaleno Mountains, Arizona, USA, October 2003.
Damage symptomsMortality of Picea englemannii following defoliation by E. abietinum in mixed-conifer forest in the Pinaleno Mountains, Arizona, USA, October 2003.Forestry Commission (UK)
Life cycle of E. abietinum. The continuous lines denote the anholocycle found in maritime parts of Europe. The broken lines denote the sexual forms found in the complete holocycle. Thicker lines indicate greater abundance. (From Carter and Halldórsson, 1998.)
TitleLife cycle
CaptionLife cycle of E. abietinum. The continuous lines denote the anholocycle found in maritime parts of Europe. The broken lines denote the sexual forms found in the complete holocycle. Thicker lines indicate greater abundance. (From Carter and Halldórsson, 1998.)
CopyrightForestry Commission (UK)
Life cycle of E. abietinum. The continuous lines denote the anholocycle found in maritime parts of Europe. The broken lines denote the sexual forms found in the complete holocycle. Thicker lines indicate greater abundance. (From Carter and Halldórsson, 1998.)
Life cycleLife cycle of E. abietinum. The continuous lines denote the anholocycle found in maritime parts of Europe. The broken lines denote the sexual forms found in the complete holocycle. Thicker lines indicate greater abundance. (From Carter and Halldórsson, 1998.)Forestry Commission (UK)

Identity

Top of page

Preferred Scientific Name

  • Elatobium abietinum (Walker, 1849)

Preferred Common Name

  • green spruce aphid

Other Scientific Names

  • Aphis abietina Walker, 1849
  • Liosomaphis abietina (Walker)
  • Myzaphis abietina Van der Goot, 1913
  • Neomyzaphis abietina Theobald, 1926

International Common Names

  • French: puceron vert

Local Common Names

  • Canada: spruce aphid
  • Denmark: sitkagranlus; sitkalusen
  • Germany: Fichtenröhrenlaus; Sitkafichtenlaus; sitkalaus
  • Iceland: sitkalaus
  • Netherlands: sparreluis, groene
  • Poland: mszyca swierkowa zielona; mszycy swierkowej
  • Switzerland: Fichten Rohrenlaus; Fichtenröhrenlaus
  • USA: spruce aphid; spruce needle aphid

EPPO code

  • LIOAAB (Elatobium abietinum)

Summary of Invasiveness

Top of page E. abietinum is a serious invasive pest in North America where susceptible spruce species form a major component of the native forests. Defoliation of Picea sitchensis along the Pacific coast, and of Picea englemannii, Picea glauca and Picea pungens in the south-west, has the potential to alter forest succession and species composition, and to impact on other flora and fauna. The highly dispersive nature of the alate aphids during the flight period means that once established, E. abietinum will eventually spread throughout the forested area to the limits of its climatic tolerances.

In other parts of the world where E. abietinum is introduced, both the aphid and spruce are exotic and there is no risk of invasion into natural habitats. However, the mobility of the winged aphids and potential for rapid population increase once a stand has been colonised, means that all trees must be considered likely to be attacked at some point during their life.

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Uniramia
  •                 Class: Insecta
  •                     Order: Hemiptera
  •                         Suborder: Sternorrhyncha
  •                             Unknown: Aphidoidea
  •                                 Family: Aphididae
  •                                     Genus: Elatobium
  •                                         Species: Elatobium abietinum

Notes on Taxonomy and Nomenclature

Top of page Elatobium is a small genus of five biologically diverse, tree-feeding species within the very large aphid family Aphididae. Besides E. abietinum, which feeds on spruce (Picea spp.) in Europe and other parts of the world, the genus includes Elatobium hidaense on Salix in Japan and Kamschatica, Elatobium laricis on Larix sibirica in east Siberia, Elatobium momii on Abies firma, Picea jezoensis and Taxus cuspidata in Japan, and Elatobium trochodendri on Trochodendron aralioides in Japan (Blackman and Eastop, 1994; Carter and Halldórsson, 1998). The Japanese species were revised by Miyazaki (1971), although his concept of the genus was broader and included related aphids on Ericaceae that are now placed in the genera Ericolophium and Neoacyrthosiphon (Blackman and Eastop, 1994).

E. abietinum was first described as Aphis abietina by Francis Walker in 1849, from material collected on Norway spruce (Picea abies) in London, UK. At this time, many aphid species were being assigned to the genus Aphis, but detailed drawings of the lectotype in the collection of the Hope Department of Entomology, Oxford, UK, by Doncaster (1961) provide little doubt that this is the same species as E. abietinum (Carter and Halldórsson, 1998). Theobald (1926) proposed the new generic name Neomyzaphis, and the combination Neomyzaphis abietina remained in popular usage for many years. However, Mordvilko (1914) had assigned the generic name Elatobium to the species at an earlier date, which therefore takes precedence over Neomyzaphis. However, the name Elatobium remained largely unused until the publication of works by Cottier (1953), Doncaster (1961) and Eastop (1966).

Distribution

Top of page

E. abietinum is considered native to Europe on Picea abies and introduced elsewhere (Kloft et al., 1961, 1964; Carter and Halldórsson, 1998). In maritime countries of north-west Europe, where there are no native spruce species (e.g. Ireland, UK, Denmark, north-west France) E. abietinum has spread naturally to colonise P. abies, Picea sitchensis and other Picea spp. in all types of situations. In other parts of the world, the aphid has been introduced. In addition to the distribution list of this datasheet, E. abietinum is widespread and exotic in Belgium (J-C Gregoire, University of Brussels, Belgium, personal communication, 2004). In New Zealand, Tasmania, Iceland, Chile and other regions where there are no native spruces, the aphid is confined to commercial plantations of spruce, Christmas tree crops, spruce shelterbelts and ornamental plantings. In North America, in contrast, introduction has led to the establishment of E. abietinum in natural forests of P. sitchensis along the Pacific coast and in Picea englemannii / Picea pungens forests in the interior south-west. The aphid has spread or is spreading through large areas of these natural forests.

Distribution Table

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

North America

CanadaPresentPresent based on regional distribution.
-British ColumbiaWidespreadIntroduced Invasive Keen, 1952; Pillsbury, 1960; Kloft et al., 1964; Holms and Ruth, 1968; Koot, 1991; Lewis et al., 1999
-OntarioPresentIntroduced Invasive CABI/EPPO, 1986
-QuebecPresentIntroduced Invasive Kloft et al., 1964
USAPresentPresent based on regional distribution.
-AlaskaRestricted distributionIntroduced Invasive Keen, 1952; Holms and Ruth, 1968; Holsten et al., 1985; Eglitis, 1986; Koot, 1991
-ArizonaRestricted distributionIntroduced Invasive Lynch, 2002; Lynch, 2004
-CaliforniaRestricted distributionIntroduced Invasive Keen, 1952; Kloft et al., 1964; Holms and Ruth, 1968; Koot, 1991
-HawaiiPresentIntroduced Not invasive Heie, 1992
-MassachusettsRestricted distributionIntroduced Not invasive Anon., 2002
-New MexicoRestricted distributionIntroduced Invasive Lynch, 2004
-North CarolinaPresentIntroduced Invasive Fedde, 1971; Fedde, 1972
-OregonRestricted distributionIntroduced Invasive Keen, 1952; Kloft et al., 1964; Holms and Ruth, 1968; Koot, 1991
-Rhode IslandRestricted distributionIntroduced Not invasive Anon., 2002
-UtahPresentIntroduced Invasive Knowlton, 1983
-WashingtonRestricted distributionIntroduced Invasive Keen, 1952; Kloft et al., 1964; Holms and Ruth, 1968; Koot, 1991

South America

ArgentinaPresentDelfino and Binazzi, 2002
ChilePresentIntroduced Not invasive Carrillo, 1977
Falkland IslandsPresentIntroduced Not invasive Low, 1986; Carter and Halldórsson, 1998

Europe

AustriaRestricted distributionNative Not invasive Kloft et al., 1964
CroatiaPresentGotlin et al., 2002
Czech RepublicPresentHolusa et al., 2005
Czechoslovakia (former)PresentNative Not invasive Kloft et al., 1964
DenmarkWidespreadIntroduced Not invasive Bejer-Petersen, 1962; Heie, 1992; Carter and Halldórsson, 1998
Faroe IslandsPresentIntroduced Not invasive Heie, 1964; Heie, 1992
FinlandPresentNative Not invasive Heikinheimo, 1963; Kloft et al., 1964; Heie, 1992
FranceWidespreadNative Not invasive Kloft et al., 1964; Laurent, 1967; Leroy and Malphettes, 1969
GermanyWidespreadNative Not invasive von Scheller, 1963; Kloft et al., 1964; Heie, 1992
IcelandWidespreadIntroduced1959 Not invasive Heie, 1992; Carter and Halldórsson, 1998; Sigurdsson et al., 1999
IrelandWidespreadIntroduced Not invasive Theobald, 1914; Carter et al., 1987
ItalyRestricted distributionNative Not invasive Kloft et al., 1964
LatviaPresentNative Not invasive CABI/EPPO, 1986
LiechtensteinWidespreadNative Not invasive Kloft et al., 1964
NetherlandsWidespreadIntroduced Not invasive Kloft et al., 1964
NorwayWidespreadNative Not invasive Kloft et al., 1964; Heie, 1992; Carter and Halldórsson, 1998
PolandPresentNative Not invasive Kloft et al., 1964; Heie, 1992; Bartkowski, 1998
PortugalPresentIntroduced Not invasive Ilharco, 1996
Russian FederationPresentNative Not invasive Kloft et al., 1964; Heie, 1992
-Central RussiaPresentNative Not invasive Kloft et al., 1964
-Northern RussiaPresentNative Not invasive Kloft et al., 1964
SlovakiaPresentNative Not invasive Kloft et al., 1964
SwedenWidespreadNative Not invasive Ossiannilsson, 1959; Heie, 1992; Carter and Halldórsson, 1998
SwitzerlandPresentNative Not invasive Maksymov, 1961; Kloft et al., 1964; Maksymov, 1981
UKWidespreadIntroduced Not invasive Heie, 1992; Carter and Halldórsson, 1998

Oceania

AustraliaPresentPresent based on regional distribution.
-TasmaniaPresentIntroduced Not invasive Evans, 1943; Eastop, 1966
New ZealandWidespreadIntroduced Not invasive Dumbleton, 1932; Cottier, 1953; Zondag, 1983; Nicol et al., 1998

History of Introduction and Spread

Top of page For many geographically isolated parts of Europe, notably the UK and Iceland, there are no native spruce trees. Although Picea abies is thought to have been cultivated in Britain from 1548 and Picea sitchensis from 1832, it was not until the two post-war decades 1945 to 1960 that really extensive afforestation with these species took place (Carter and Halldórsson, 1998). Records of E. abietinum in Britain by the time of Theobald (1926) suggested that the aphid was already well-distributed over much of the country. The raising of planting stock in areas where infestation of the young trees could readily take place and then transporting these to remote planting sites, no doubt accelerated the spread of the aphid in the UK, and the same circumstances probably apply to other countries (Carter and Halldórsson, 1998).

In France, there was an increase in the planting of P. sitchensis between 1950 and 1960, especially in coastal areas of Brittany (Leroy and Malphettes, 1969). The widespread outbreak of E. abietinum in 1961 that affected much of Europe extended into these young plantations, and appeared to be especially damaging on poor shallow soils (Joly, 1961; Leroy and Malpettes, 1969). Since this time, the area of P. sitchensis plantations in France has increased and is now in excess of 30,000 ha. P. sitchensis plantations occur as far south as 45°N on the Millevache plateau in Limousin. E. abietinum is well distributed in these areas, but outbreaks in 1987 and 1988 were only recorded from Brittany. These outbreaks occurred on poor sites and mostly in 30- to 35-year-old stands. In Limousin, the last outbreak was recorded in 1994 near Limoges between 500 and 600 m altitude (Carter and Halldórsson, 1998).

E. abietinum is common in Belgium (J-C Gregoire, University of Brussels, Belgium, personal communication, 2004), and would be expected to occur in Luxemburg, but there are no literature records for its presence in either of these countries.

E. abietinum was first recorded in Iceland in 1959, in a nursery in Reykjavik. At the time, the nursery was used for storing imported Christmas trees. Attempts to eradicate the aphids failed and it was found in several gardens in Reykjavik in late summer and autumn 1960 (Bjarnason, 1961; Ragnarsson, 1962). During the 1960s and 1970s, the aphid spread eastwards and colonised stands of P. sitchensis and other North American spruces in south Iceland. During the 1980s, it colonised stands in east Iceland, and during the 1990s it spread west and north. E. abietinum has now been found in almost all spruce stands in the country (Ottósson, 1985; Carter and Halldórsson, 1998; Halldórsson et al., 2003). The first major outbreak of E. abietinum in Iceland occurred in the south-west in 1964. Since then, another five major outbreaks have occurred, in 1977, 1984, 1987, 1991 and 1996 (Ottósson, 1985; Blöndal, 1988). All outbreaks in Iceland have been in the late summer / autumn / early winter period, and outbreaks have never occurred after severe winters (Halldórsson, 1995).

Analyses of genetic variation suggest that E. abietinum has probably been introduced into Iceland on more than one occasion (Sigurdsson et al., 1999). Icelandic aphids are genetically most closely related to aphids from Denmark, which agrees with their assumed origin (Sigurdsson et al., 1999; Halldórsson et al., 2004). Christmas trees were imported annually from Denmark into Reykjavik from 1959 up to 1990 (Sigurdsson et al., 1999).

The first report of E. abietinum in North America was on P. sitchensis in Vancouver, British Columbia, in 1914 (Kloft et al., 1964). Extensive damage to P. sitchensis has been reported in British Columbia since 1916, and E. abietinum is now known throughout the coastal range of P. sitchensis from California to Alaska (Keen, 1952; Pillsbury, 1960; Holms and Ruth, 1968, Koot, 1991). Infestations are restricted to the coast and none have been reported inland (Koot, 1991). Severe infestations have occurred in coastal areas of the Queen Charlotte Islands since 1960, and between 1981 and 1991 there was significant damage to both natural spruce forests and ornamental trees (Koot, 1991). In most areas, E. abietinum has been a chronic pest, and outbreaks have been sporadic and difficult to predict (Wood et al., 1985; Lewis et al., 1999). However, severe defoliation has caused mortality in local areas, and in some stands up to 67% of the trees have been killed (Wood et al., 1985; Koot, 1991; Van Sickle, 1995). Seed orchards of P. sitchensis and Picea glauca have also been affected (Wood et al., 1985; Lewis et al., 1999).

A small number of E. abietinum were collected from P. glauca in Quebec in November 1962 (Kloft et al., 1964). However, the aphid could not be found in the following year and there were no further records of E. abietinum east of the Rocky Mountains until Fedde (1971, 1972) discovered the species on P. glauca in North Carolina. There were no further reports of E. abietinum in eastern North America until 2002, when severe infestations on P. glauca were reported from coastal areas of Rhode Island (mainland Rhode Island and Block Island) and Massachusetts (Cape Cod, Martha's Vineyard) (Anon., 2002).

In the interior south-west USA, E. abietinum was first found in urban Sante Fe, New Mexico, in 1976, where it has remained as an intermittent pest in the urban forest (Lynch, 2002, 2004). The first wildland outbreak in the south-west occurred over the 1989-1990 winter in the White Mountains of Arizona, when more than 100,000 acres of Picea englemannii and Picea pungens were defoliated (Lynch, 2004). These two spruce species occur naturally in high elevation, mixed-conifer forests above 2400 m in the mountains of Arizona, New Mexico and Utah, and are highly susceptible to E. abietinum. Three further outbreaks of E. abietinum occurred over the winters of 1995-1996, 1996-1997 and 1999-2000 (Lynch, 2004). The range of E. abietinum has now expanded to include the Mogollon Mountains (east of the White Mountains) and Sacramento Mountains in New Mexico, and the Pinaleno Mountains and San Francisco Peaks in Arizona. Outbreaks appear to be associated with dry winter and spring weather prior to the autumn and winter in which feeding occurs (Lynch, 2002). Despite the high elevations and potentially very cold climate, evidence to date suggests that all of the E. abietinum populations are behaving anholocyclically. The origin of the aphids present in Arizona, New Mexico and Utah is not known.

The earliest record of E. abietinum in New Zealand is that of Myers (1922), who stated that it had been killing spruce in large quantities at Taranaki (Dumbleton, 1932). Infestations in 1920 appear to have reached epidemic proportions. The aphid is now found throughout the North and South Islands, on P. abies, P. sitchensis and Picea smithiana (Dumbleton, 1932; Rawlings, 1953; Cottier, 1953; Zondag, 1983). Defoliation by E. abietinum appears to have been a contributory cause to the unhealthy condition of spruce in New Zealand up to 1929 (Dumbleton, 1932), and the aphid is still considered to be a major factor preventing spruce being used as a production forest species in New Zealand (Miller and Knowles, 1989; Nicol et al., 1998).

In Australia, E. abietinum is only known from Tasmania, where it was first recorded in 1943 (Evans, 1943).

Risk of Introduction

Top of page Due to the impact that it has had since becoming established in New Zealand and North America, E. abietinum should be of concern to those countries with plantations or natural forests containing susceptible spruce species where the aphid has not yet been introduced.

Habitat

Top of page

E. abietinum is able to disperse widely in those regions where it is present, through the activity of the alate aphids during the flight period; all spruce trees in the region have the potential to be colonised. The aphid does not show strict habitat requirements, and can attack trees of all ages, and occurs throughout its range in commercial plantations, shelterbelts and on individual trees planted in parks and gardens. Picea pungens,especially var. glauca, planted as an ornamental tree, is particularly prone to attack. E. abietinum has pest status in forest nurseries and on Picea abies grown as Christmas trees (Carter and Winter, 1998). In North America, the aphid has become abundant in natural forests of Picea sitchensis along the Pacific coast, and in natural mixed-conifer forests at high elevations in Arizona and New Mexico (Lynch, 2004).

 

Habitat List

Top of page
CategoryHabitatPresenceStatus
Littoral
Coastal areas Present, no further details Harmful (pest or invasive)
Terrestrial-managed
Cultivated / agricultural land Present, no further details Harmful (pest or invasive)
Disturbed areas Present, no further details Harmful (pest or invasive)
Managed forests, plantations and orchards Present, no further details Harmful (pest or invasive)
Managed grasslands (grazing systems) Present, no further details Harmful (pest or invasive)
Protected agriculture (e.g. glasshouse production) Present, no further details Harmful (pest or invasive)
Rail / roadsides Present, no further details Harmful (pest or invasive)
Urban / peri-urban areas Present, no further details Harmful (pest or invasive)
Terrestrial-natural
semi-natural/Cold lands / tundra Present, no further details Harmful (pest or invasive)
semi-natural/Natural forests Present, no further details Harmful (pest or invasive)
semi-natural/Natural grasslands Present, no further details Harmful (pest or invasive)
semi-natural/Riverbanks Present, no further details Harmful (pest or invasive)
semi-natural/Wetlands Present, no further details Harmful (pest or invasive)

Hosts/Species Affected

Top of page Host tree species of E. abietinum are restricted to the genus Picea (Hanson, 1951). Feeding has been reported to occur on species in other conifer genera, e.g. Abies spp., Larix sibirica, Pinus strobus, Pinus sylvestris, Pseudotsuga menziesii (Theobald, 1914; Hussey, 1952; Volkova, 1970; Szelegiewicz, 1975), but this is exceptional and may only occur during outbreaks. The number of aphids involved is usually small and the damage caused unimportant (Furniss and Carolin, 1977; Blackman and Eastop, 1994; Carter and Halldórsson, 1998). Attempts to rear E. abietinum on hosts other than Picea under laboratory conditions have usually failed (e.g. Cunliffe, 1924).

The many distribution records of E. abietinum throughout Europe, and the existence of holocyclic populations in central Europe, suggest that the native host is Picea abies (Theobald, 1914; Kloft et al., 1961, 1964; Bejer-Petersen, 1962; Carter and Halldórsson, 1998). This is supported by the fact that P. abies and other Palaearctic spruce species show less reaction to the aphid's feeding than does Picea sitchensis and other Nearctic species. The other aphid species assigned to the genus Elatobium are all from Asia, and it is also in east Asia that speciation of the genus Picea appears to have taken place. Possible exposure to an Elatobium species in this region may be the reason why the most highly resistant Picea species occur there (Carter and Halldórsson, 1998).

Theobald (1914, 1926) listed 14 species of Picea as food plants and recognised from observations at Kew (London, UK) that European and Asiatic species were generally damaged much less than North American species. More detailed studies on the relative susceptibility of 20 different Picea species to E. abietinum were carried out by Nichols (1987). Field observations showed that Picea species could be assigned to two distinct groups. The first group consisted of the North American species (except Picea rubens) which all supported high populations. Picea sitchensis, Picea pungens, Picea englemannii and Picea glauca were particularly susceptible. The second group contained all the Eurasian, Chinese and Japanese spruces (except Picea asperata) and supported the least number of aphids. Laboratory studies on the performance of individual aphids indicated that Eurasian spruces are intermediate in terms of resistance between North American and Asian species. The mean relative growth rate (MRGR) of individual E. abietinum on P. abies is similar to that on P. sitchensis (Fisher, 1987; Nichols, 1987), but P. abies loses fewer needles in response to attack (Parry, 1974a; Fisher, 1987; Straw and Green, 2001).

The exceptions to this general pattern of resistance and susceptibility are P. rubens and Picea breweriana, North American species that are highly resistant to attack, and Picea asperata from China that is highly susceptible (Nichols, 1987). The mechanisms underlying resistance to E. abietinum are not known, but may include variation in secondary compounds, particularly terpenes, availability of sap nutrients and anatomical differences in needle structure (Harding et al., 1998).

Growth Stages

Top of page Vegetative growing stage

Symptoms

Top of page Attack by E. abietinum results in the formation of a small yellow spot around the feeding site or band across the needle. These symptoms are characteristic and lead to the whole needle eventually turning yellow and falling from the shoot within a few weeks. Yellow spots around the feeding site develop after about 5-10 days on Picea sitchensis, but longer on Picea abies (Kloft and Ehrhardt, 1959; Parry, 1971, 1974a; Fisher, 1987). The chlorosis appears to be caused by toxic substances, possibly certain amino acids, which are injected into the needle tissues with the aphid's saliva (Kloft and Ehrhardt, 1959). Adjacent needles that have not been fed on, remain healthy and are not necessarily shed.

High densities of E. abietinum can lead to severe defoliation, but in spring and summer, because the aphid avoids the current foliage, needle loss is restricted to one-year-old and older shoots. In the autumn and winter, the aphid feeds on current as well as older needles, and high populations at this time are capable of causing complete defoliation. Attack on small P. sitchensis trees (up to 5 years old) is usually concentrated in the upper part of the canopy (Straw et al., 1998a, b), whereas on older trees, attack is usually concentrated in the lower, more shaded portions of the crown (Bevan, 1966; Parry, 1969a; Koot, 1991). Young trees up to 4 years old that have been heavily defoliated during the winter often have terminal buds that fail to break the following spring (Carter, 1977).

List of Symptoms/Signs

Top of page
SignLife StagesType
Leaves / abnormal colours
Leaves / abnormal colours
Leaves / abnormal leaf fall
Leaves / abnormal leaf fall
Leaves / external feeding
Leaves / external feeding
Leaves / honeydew or sooty mould
Leaves / honeydew or sooty mould
Leaves / yellowed or dead
Leaves / yellowed or dead
Stems / honeydew or sooty mould
Stems / honeydew or sooty mould

Biology and Ecology

Top of page Life Cycle

E. abietinum only feeds on Picea spp. and it occurs on spruce throughout the year. It shows two distinct life cycles in different parts of its range. In central and eastern Europe, where the climate is continental and the winters are very cold, it survives only as holocyclic populations. Sexual forms (oviparous females and winged males) develop in September or October and the eggs that are produced overwinter and hatch the following spring (von Scheller, 1963; Carter, 1972; Heie, 1992). The fundatrix that hatches from the egg reproduces parthenogenetically to produce a number of wingless (apterous) females that also reproduce parthenogenetically (virginoparae). Multiple generations of virginoparae are then produced over the summer until sexual forms develop again in the autumn. In contrast, in milder, maritime parts of Europe, where winters are relatively warm, and in other parts of the world, populations of E. abietinum are anholocyclic and the aphid survives the winter months as adult or immature virginoparae (von Scheller, 1963; Carter and Halldórsson, 1998). In areas with an intermediate climate, e.g. north-west Germany, both anholocyclic and holocyclic life cycles can occur together (paracyclic populations). Sexual forms and eggs are also very occasionally found in maritime areas with predominantly anholocyclic populations (Carter and Austarå, 1994; Harding and Carter, 1997).

Development and Physiology

The adults and nymphs feed on phloem sap, the stylets being inserted through the stomata (Kloft and Ehrhardt, 1959). In the spring and early summer, the aphids feed primarily on the needles of shoots produced in the previous year, or on older shoots. The new foliage is chemically protected from attack for the first few months, and is not normally colonised by the aphids before the autumn. Volatile substances (terpenes) in the epicuticular wax of the new needles initially deter E. abietinum from feeding and are sufficiently toxic to cause mortality, but these substances dissipate with time (Jackson and Dixon, 1996).

In anholocyclic populations, successive generations of virginoparae are produced throughout the year. For most of the year, these consist entirely of apterous individuals, but during the spring population peak (May-June in Europe), winged individuals (alates) are produced in large quantities. The main factor determining the production of alates is increasing day-length, modified by plant nutritional quality and crowding (Parry, 1977, 1978; Fisher, 1981; Fisher and Dixon, 1986).

Both apterous and alate virginoparae pass through four nymphal instars during development (Fisher, 1986). For apterae, development times of the different instars at 15°C are: first-instar 4.2 days, second-instar 3.4 days, third-instar 3.5 days, and fourth-instar 4.0 days. The mean development time from birth to adult is 15 days, and mean adult weight is about 0.46 mg (Fisher, 1986). The development times for alate virginoparae are similar, except that the fourth-instar stage is extended: first-instar 3.8 days, second-instar 3.7 days, third-instar 3.8 days, and fourth-instar 5.9 days. The mean development time for alate virginoparae is 17.1 days, and mean adult weight is approximately 0.55 mg (Fisher, 1986). The fourth-instar nymphs of alate virginoparae possess distinct dorsal wing buds (von Scheller, 1963).

Development times given by Cunliffe (1924), Dumbleton (1932) and Hussey (1952) are slightly different, but all agree that development of the four nymphal instars of apterous virginoparae, and the first three instars of alate virginoparae, each takes about 4-5 days at 15-16°C. These earlier authors confused the extended fourth-instar stage of alate virginoparae with the production of a fifth nymphal instar. However, this is incorrect, as explained by Fisher (1986).

Total development time, i.e. the combined length of the pre-adult stages, of apterous virginoparae has been estimated as 18-26 days in spring and summer, and 38 days in winter (Dumbleton, 1932), 18.4 days at 16°C (Hussey, 1952), and 12.4 days at 15°C (Parry, 1969b, 1974b). Similarly, total development time for alate virginoparae has been estimated as 19-21 days (Dumbleton, 1932) and 21 days (Hussey, 1952). Development times are longer at lower temperatures.

The total life span of apterous virginoparae, caged indoors on Sitka spruce (Picea sitchensis), has been estimated as 42-61 days (Dumbleton, 1932), 50 days at 16°C (Hussey, 1952), and 41 days by Parry (1969b, 1974b). For alate virginoparae, the mean length of adult life has been estimated to be 12 days (maximum = 52 days) (Dumbleton, 1932).

Reproductive Biology

The generation time for apterous virginoparae, i.e. the development time plus the period up to deposition of the first nymph after the aphid has become adult, is about 18-24 days at 15°C (Cunliffe, 1924; Hussey, 1952). The adults can produce nymphs immediately or show a pre-reproductive phase of up to 9 days depending on previous nutrition or current temperature conditions (Dumbleton, 1932). The adult virginoparae can produce a nymph every day, or every other day. Dumbleton (1932) gives a mean fertility rate of 0.5-1.0 nymphs/adult/day, and Harding et al. (1998) indicate mean fertility rates of 0.6-0.8 nymphs/adult/day.

The total number of nymphs produced per adult virginoparae is highly variable, and is influenced by conditions during adult development and after maturity has been attained. In indoor experiments on P. sitchensis, Dumbleton (1932) recorded means of 32-37 nymphs/adult (maximum = 69) for apterous virginoparae, Hussey (1952) recorded a mean 12.1 nymphs/adult, and Parry (1969b, 1974b) recorded a mean of 28.9 nymphs/adult. Alate virginoparae are probably capable of producing similar numbers of offspring (Cunliffe, 1924).

Much less is known about the development of sexual stages and oviposition in E. abietinum. Carter and Austarå (1994) were able to induce the formation of males and oviparae in anholocyclic cultures of the aphid by decreasing temperatures in the autumn under long day conditions. Individual ovipara appear to be able to lay 4-5 eggs (von Scheller, 1963). The eggs are laid singly, usually near the base of a needle, but sometimes on the shoot bark or higher up the needle (von Scheller, 1963). Occasionally, two or even up to six eggs are laid together (von Scheller, 1963; Carter and Austarå, 1994).

Phenology

In maritime parts of Europe where E. abietinum populations are anholocyclic, the numbers of aphids surviving the winter are generally low. Aphid numbers start to increase in March when temperatures exceed a development threshold of about 4°C, and population growth may become exponential if the weather is favourable (Crute and Day, 1990). This period of increase coincides with high concentrations of amino acids in the needles before bud-burst (Carter and Nichols, 1988). Aphid numbers continue to increase up to a peak in May or June, and then decline rapidly to very low densities in July and remain low for the rest of the summer (Parry, 1969a, 1974b; Day, 1984b; Crute and Day, 1990). The dramatic decline in the population after the late spring/early summer peak is caused by a reduction in fertility and increase in mortality, associated with a decrease in nutritional quality of the phloem sap following bud-burst (Parry, 1978; Day, 1984b; Fisher and Dixon, 1986; Carter and Nichols, 1988). Aphids become smaller and take longer to complete development (Day and Kidd, 1998). However, dispersal through alate production and increasing activity of natural enemies may also play a part (Parry, 1969a; Fisher and Dixon, 1986; Day and Kidd, 1998). High aphid populations also cause substantial needle fall, and in these situations numbers may also decline because of competition and lack of resources.

Alate virginoparae are produced at the time of the population peak in May and June, and disperse widely (Parry, 1973; Carter and Cole, 1977). However, the flight period is relatively short. In upland or more northerly areas, where the climate is cooler, the flight period may be delayed and extended over a longer period, but even in these areas flight activity is usually finished by August (Carter and Cole, 1977).

A very small number of aphids survive the summer, and populations do not start to build up again until September. Aphid development and reproduction rates increase in the autumn as a result of an improvement in sap quality following bud-set and the onset of dormancy in the host plant (Carter and Nichols, 1988). However, populations rarely reach high densities in the autumn in maritime parts of Europe, and the main period of damage by E. abietinum in these regions occurs in the spring.

E. abietinum shows wide variations in abundance from year to year, and from one European region to another. Populations persist even on severely defoliated trees and continue to fluctuate within a plantation from the time of establishment until the crop is felled. 'Outbreaks' are declared whenever aphid population densities exceed about 0.5 aphids per needle, usually at the early summer aphid maximum. At such densities, the aphids generate noticeable needle loss (Day and McClean, 1991; Straw et al., 1998b). High populations of this order occur around once every 3-6 years in the UK and milder parts of Denmark, and about every 20 years in colder, more inland areas of Denmark (Bejer-Petersen, 1962; Carter, 1977; Day and Kidd, 1998).

Overwintering eggs produced by holocyclic E. abietinum populations in central Europe do not hatch until April, well into the spring (von Scheller, 1963). Consequently, populations in these regions are not able to take advantage of warm interludes during winter and early spring for breeding, and do not have time to build up to high densities before the mid-summer decline in host quality. Holocyclic populations, therefore, do not show such a strong late spring/early summer peak as anholocyclic populations, and rarely cause significant damage.

In other parts of the world where E. abietinum is introduced, sexual forms have not been recorded and populations appear to be primarily or entirely anholocyclic. In New Zealand and on the Pacific coast of North America, the population dynamics of the aphid are similar to those in north-west Europe, with virginoparae overwintering and the population reaching a peak in late winter or early spring (Dumbleton, 1932; Furniss and Carolin, 1977; Nicol et al., 1998). In Iceland and at high elevations in the interior south-west USA, spring populations are lower and the aphid is most abundant in the autumn and early winter (Halldórsson, 1995; Carter and Halldórsson, 1998; Lynch, 2004).

Environmental Requirements

Winter temperatures have a major influence on the population dynamics of E. abietinum. The number of aphids surviving the winter is a key factor determining population numbers in the following spring and whether peak populations will be high enough to cause significant damage (Day and Kidd, 1998). The main cause of mortality over the winter is freezing temperatures. The adults and nymphs of E. abietinum can survive temperatures as low as -15°C to -18°C when detached from needles (Powell, 1974; Powell and Parry, 1976). However, when feeding on the host plant most aphids are killed at temperatures of -10 to -12°C, because of ice nucleation in the phloem sap which spreads to the gut contents (Powell, 1974; Halldórsson et al., 2001). The supercooling point of sap is higher than that of the aphids, and aphids on the plant freeze when the sap freezes. In contrast, unfed first-instar nymphs that do not have sap in the gut are able to survive temperatures below -20°C (Carter, 1972; Powell, 1974; Halldórsson et al., 2001). The eggs produced by holocyclic populations can withstand temperatures as low as -30°C (Carter and Austarå, 1994).

Appreciable numbers of E. abietinum also die at temperatures of -7 to -8°C before actual freezing takes place, and prolonged periods at relatively low, but non-lethal temperatures are known to have a considerable negative influence on E. abietinum populations (Carter, 1972; Powell and Parry, 1976). In this sense E. abietinum can be classed as a moderately chill-tolerant species (sensu Bale, 1993). Aphids may die as a result of low temperature before freezing takes place although many survive until the supercooling point is reached. Air humidity is also influential: freezing droplets causing the growth of rime ice crystals markedly increases mortality at the same or even at higher sub-zero temperatures (Carter, 1972).

The fact that many individuals die at temperatures of -7 to -8°C is reflected in relationships between E. abietinum populations and climate. Field observations in Denmark and Britain show that outbreaks of E. abietinum do not occur in the following spring if temperatures during the winter fall below -7 or -8°C (Bejer-Petersen, 1962; Carter, 1972; Day and Crute, 1990). Two or more mild winters in succession appear to be necessary for the build up of high E. abietinum populations (Carter, 1972; Maksymov, 1981; Carter and Nichols, 1988). However, E. abietinum outbreaks do not occur after every mild winter. Populations of the aphid in Europe are also influenced by strong density-dependent processes, driven either through interactions with the host-plant or by the action of natural enemy populations (Zhou et al., 1997; Day and Kidd, 1998). A key feature of the aphid's dynamics is a tendency for high populations in one year to be followed by low populations in the next. One consequence of this is that E. abietinum outbreaks in Europe tend to be short-lived, lasting just 1 year.

Genetics

2n=18 (Blackman and Eastop, 1994).

Nicol et al. (1998) compared the genetic variation of E. abietinum populations in New Zealand and Europe using RAPD-PCR analysis. Genetic variation in New Zealand was extremely limited, consisting of only one genotype, whereas European populations were genetically diverse. The lack of genetic variation in New Zealand is probably due to a very limited founder population, continued isolation and lack of sexual reproduction.

Studies on the genetic diversity of E. abietinum in Iceland by Sigurdsson et al. (1999), using RAPD analysis, indicated that Icelandic aphids comprise two polymorphic populations, one in the east and the other in the west of the country. Further analyses by Halldórsson et al. (2004) showed that populations of E. abietinum in north-west Europe could be divided into three major geographical groups: (1) UK and north-west France; (2) Denmark and Iceland; and (3) Norway. Significant levels of gene flow were detected both within and between sites, and between geographic regions, especially between the UK and France. Both Sigurdsson et al. (1999) and Halldórsson et al. (2004) demonstrated a close relationship between E. abietinum in Iceland and aphids from Denmark, indicating a Danish origin for the aphids in Iceland.

Associations

In Europe, there are no obvious associations between E. abietinum and other insect pests, diseases or syndromes. Large numbers of E. abietinum produce copious amounts of honeydew, but despite this, ants do not attend the aphid.

In natural spruce forests in Arizona and other parts of the interior south-west USA, Picea englemannii and Picea pungens, severely defoliated by E. abietinum, are susceptible to attack from the spruce bark beetle, Dendroctonus rufipennis, which may increase rates of tree mortality (Lynch, 2002, 2004). Mortality rates are also higher if defoliated trees are infected with dwarf mistletoe, Arceuthobium microcarpum. Severe defoliation and mistletoe infection results in almost 70% mortality (Lynch, 2004).

Natural enemies

Top of page
Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Adalia bipunctata Predator Adults/Nymphs
Adalia decempunctata Predator Adults/Nymphs
Alloxysta macrophadna Parasite
Alloxysta victrix Parasite
Anatis ocellata Predator Adults/Nymphs
Aphelinus Parasite
Aphidecta obliterata Predator Adults/Nymphs
Aphidius ervi Parasite
Aphidius picipes Parasite
Aphidius rhopalosiphi Parasite
Athous subfuscus Predator Adults/Nymphs
Cantharis livida Predator Adults/Nymphs
Cantharis obscura Predator Adults/Nymphs
Cantharis rustica Predator Adults/Nymphs
Coccinella septempunctata Predator Adults/Nymphs
Coccinella undecimpunctata Predator Adults/Nymphs
Conidiobolus coronatus Pathogen Adults/Nymphs
Conidiobolus obscurus Pathogen Adults/Nymphs
Dendrocerus carpenteri Parasite
Ephedrus koponeni Parasite Adults/Nymphs
Erynia phalloides Pathogen Adults/Nymphs
Hemerobius atrifrons Predator Adults/Nymphs
Hemerobius micans Predator Adults/Nymphs
Hemerobius stigma Predator Adults/Nymphs
Lysaphidus schimitsckeki Parasite Adults/Nymphs
Melanostoma fasciatum Predator
Myzia oblongoguttata Predator Adults/Nymphs
Neozygites fresenii Pathogen Adults/Nymphs
Pandora neoaphidis Pathogen Adults/Nymphs
Phaenoglyphis villosa Parasite
Praon flavinode Parasite Adults/Nymphs
Praon volucre Parasite
Xanthopimpla pedator Parasite Pupae

Notes on Natural Enemies

Top of page E. abietinum is attacked by a wide range of generalist aphid predators, that includes ladybirds (Coccinellidae), hoverflies (Syrphidae), lacewings (Neuroptera), birds (tits, Parus spp. and goldcrest, Regulus regulus) and even bats (Theobald, 1914; Hussey, 1952; Börner and Heinze, 1957; von Scheller, 1958, 1963; Ohnesorge, 1959; Bejer-Petersen, 1962; Austarå et al., 1997, 1998). However, the number of actual species of predator that can be confirmed as feeding on E. abietinum is relatively small, because the majority of records from the field refer only to particular species or types of predator being abundant on heavily aphid-infested trees, and not necessarily feeding on the aphids, and few predators have been the subject of feeding trials under laboratory conditions. There is also very little information on the impact of natural enemies on E. abietinum populations in the field. The only quantitative assessment of impact is by Leather and Owuor (1996) and this is rather limited in scope. However, modelling studies by Crute and Day (1990) and Leather and Kidd (1998) suggest that larval coccinellids, syrphid flies and perhaps also hemerobiids are possibly important in suppressing E. abietinum populations in late summer and autumn.

The most important coccinellid predator of E. abietinum in spruce plantations in the UK is the larch ladybird, Aphidecta obliterata. This species is a conifer specialist, and the adults and larvae also feed on Adelges spp. on Douglas-fir, and aphids on other conifers (von Scheller, 1963; Parry, 1980). Brown and Clark (1959), Amman (1966), Parry (1980, 1992) and Leather and Kidd (1998) describe aspects of its biology and ecology. Other coccinellids that have frequently been found on P. sitchensis infested with E. abietinum in Europe are adults and larvae of Anatis ocellata, Coccinella septempunctata, Coccinella undecimpunctata, Myzia oblongoguttata, Adalia decempunctata and Adalia bipunctata (von Scheller, 1958, 1963; Bejer-Petersen, 1962; Austarå et al., 1997). Leather and Owuor (1996) give consumption rates of A. bipunctata feeding on E. abietinum on P. abies.

Other beetle predators of E. abietinum include species of Cantharidae, several of which are known to feed on aphids (Frazer, 1988). Von Scheller (1958) found three Cantharis spp. commonly with E. abietinum, and Rhagonycha lignosa has been recorded in great numbers from E. abietinum-attacked trees in the UK (Austarå et al., 1998). Von Scheller (1958) also records the click beetle Athous subfuscus as feeding on E. abietinum.

Lacewing larvae, particularly larvae of brown lacewings (Hemerobiidae) and larvae of syrphid flies were the most abundant aphid predators in the canopy of P. sitchensis in Northern Ireland, UK, especially when sampling was conducted at night when the larvae were most active (Crute and Day, 1990). The main lacewing species was Hemerobius micans. Larvae of Hemerobius atrifrons have been observed feeding voraciously on E. abietinum in Norway (Austarå et al., 1998).

Spiders (Araneidae) have been considered as very likely contributors to E. abietinum mortality due to high numbers of aphid cadavers observed in webs (von Scheller, 1958; Bejer-Petersen, 1962), but neither species nor quantifications of impact have been given. Harvestmen (Opiliones) have also been suggested as predators (Theobald, 1914).

Records of parasitoids of E. abietinum are much less frequent than records of predators, and are restricted to Europe. Hanson (1951) mentions the importance of parasitoids in controlling E. abietinum, and Hussey (1952) observed up to 15% parasitism of E. abietinum populations during late summer. However, other authors report much lower parasitism rates and, generally, it appears that parasitism rarely exceeds 10% (von Scheller, 1963; Parry, 1969a; Leather and Kidd, 1998). Several species of hymenopteran parasitoids have been reared from mummies of E. abietinum: Ephedrus koponeni (Halme, 1992), Lysaphidus schimitsheki (von Scheller, 1963; Mackauer and Stary, 1967; Stary, 1973), Praon flavinode (Fulmek, in von Scheller, 1963), and several hyperparasitoid species (Austarå et al., 1997, 1998). E. koponeni appears to be specialised on E. abietinum, but has only been recorded on E. abietinum in Finland (Halme, 1992).

E. abietinum is killed by a number of insect pathogenic fungi, all from Zygomycotina Entomophthorales. Day (1984b, 1986) recorded significant mortality in Northern Ireland caused by Entomophthora planchoniana, and Austarå et al. (1997, 1998) recorded this species and five other species from various locations in the UK, Denmark, Norway and Iceland. Neozygites fresenii was found in all countries, and in Norway and Iceland it was the only pathogen isolated. In Iceland, infection varied between 0 and 19.8% amongst aphids collected in October and November 1994, whereas in the following month only two out of 3577 aphids were infected (Austarå et al., 1998). In contrast, in Denmark and the UK, infection levels never exceeded a few percent. E. planchoniana, N. fresenii and two of the other pathogens isolated from E. abietinum (Conidiobolus obscurus and Erynia neoaphidis) are common pathogens of aphids in annual crops, and the fifth species (Conidiobolus coronatus [Boudierella coronata]) is a generalist pathogen found attacking a range of insect species (Austarå et al., 1998). Zoophthora phalloides, which was recorded from E. abietinum in Denmark, is also found in annual cropping systems, but is relatively rare (Keller, 1991). This species may be more specifically adapted to forest ecosystems (Austarå et al., 1998).

Means of Movement and Dispersal

Top of page Natural Dispersal

In areas where E. abietinum is established, short- and long-distance dispersal is achieved primarily through the activity of alate virginoparae during the flight period. Active flight, wind-assisted movement and dispersal by convective air currents effectively distribute the aphid throughout the spruce-growing area within a region each year.

Movement in Trade

The aphid can only survive on green foliage, so movement in trade is restricted to the supply and distribution of living shoot material, e.g. nursery plants, Christmas trees and cut foliage. The rearing of spruce transplants in nurseries and their transport to remote areas for planting probably assisted initial colonisation of spruce forests in the UK and may have been a factor in the establishment of E. abietinum in other countries (Carter and Halldórsson, 1998). E. abietinum appears to have been introduced into Iceland on Christmas trees imported from Denmark (Sigurdsson et al., 1999). Introduction into New Zealand was probably on live trees imported from North America or the UK (Nicol et al., 1998).

Plant Trade

Top of page
Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Leaves adults; eggs; nymphs Yes Pest or symptoms usually visible to the naked eye
Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Growing medium accompanying plants
Roots
Seedlings/Micropropagated plants
Stems (above ground)/Shoots/Trunks/Branches
True seeds (inc. grain)
Wood

Wood Packaging

Top of page
Wood Packaging not known to carry the pest in trade/transport
Loose wood packing material
Non-wood
Processed or treated wood
Solid wood packing material with bark
Solid wood packing material without bark

Impact Summary

Top of page
CategoryImpact
Forestry production Negative
Forestry production Negative
Native fauna Negative
Native fauna Negative
Native flora Negative
Native flora Negative
Rare/protected species Negative
Rare/protected species Negative

Impact

Top of page The importance of E. abietinum as a forest pest in Europe and most other areas lies in its ability to cause extensive defoliation, especially of Picea sitchensis, and the effect that defoliation may have on shoot growth and dry matter production. Severe defoliation of P. sitchensis during the spring or early summer reduces height increment in the year of attack by 20-60%, and further reductions in height increment may occur in the following and subsequent years (Carter, 1977; Carter and Nichols, 1988; Seaby and Mowat, 1993; Thomas and Miller, 1994). The reduction in diameter increment may be similar after heavy defoliation (Thomas and Miller, 1994). Orlund and Austarå (1996) found that severe defoliation of 34-year-old P. sitchensis in Norway reduced diameter increments for 7-8 years. The mean reduction in diameter increment over this period was 18.5% for trees that were 15 cm diameter at breast height (dbh), and 40.5% for trees that were 20 cm dbh. The maximum reduction in diameter increment occurred 4-5 years after attack, and increments had still not returned to normal by the end of the study period.

The impact of moderate defoliation by E. abietinum in the spring on 4-year-old P. sitchensis has been described by Straw et al. (1998b, 2000, 2002). Height increment of defoliated trees was reduced by 22% in the year of attack, by 11% in the following year, and by 6% in the third year, when compared with undefoliated trees. At the end of the third year, defoliated trees were, on average, 10% shorter than undefoliated trees. Stem diameter and volume increments were not reduced in the year in which defoliation took place, but were reduced in the following year, by 12% and 24%, respectively (Straw et al., 2000). There was no reduction in diameter and volume increments in the third year. The immediate reduction in height increment in the year of attack was caused by a direct effect of aphids on shoot extension growth in the spring, whereas the decrease in diameter and volume increment in the following year was caused by a delayed reduction in needle size (Straw et al., 2002).

Defoliation during the autumn may have a greater impact than defoliation during the spring (Carter, 1977). However, the only quantitative estimates of impact following autumn defoliation are those given by Halldórsson et al. (2003) from studies in Iceland. Moderate defoliation of P. sitchensis at one site in south-east Iceland during 1986-1987 and 1990-1991 reduced total height and diameter growth over the period 1987-2000 by 16% and 17%, respectively. Severe defoliation reduced both height and diameter growth by 37%. By 2000, when the trees were 40 years old, trees that had been lightly, moderately and severely defoliated in 1991 were, on average, 9.0, 8.1 and 7.2 metres tall, respectively.

In Europe, E. abietinum rarely kills trees and its main effect is to reduce increment. The inability of E. abietinum to attack the new needles before the autumn (see Development and Physiology section under Biology and Ecology), means that trees always carry some foliage after spring or early summer infestation, or soon regain foliage after autumn or winter attack. This is usually enough to ensure that the trees survive and recover. The death of large or small trees may occur under exceptional conditions, e.g. after complete defoliation in autumn and winter when the trees have been left bare for several months, or when spring attack coincides with a severe frost that kills the new growth, but in Europe this is a rare phenomenon (Bevan, 1966; Straw et al., 1998a). The risk of mortality is higher for small, not fully established trees on difficult sites and when defoliation is followed by drought stress.

In North America and New Zealand, defoliation by E. abietinum has caused significant tree mortality. The large number of Picea englemannii and Picea pungens trees killed by E. abietinum in the interior south-west USA is likely to have a significant economic impact, although as yet this impact has not been quantified. Damage by E. abietinum has been considered to be a major factor preventing spruce being used as a production species in New Zealand, limiting options for commercial forestry and potential yields (Miller and Knowles, 1989; Nicol et al., 1998).

E. abietinum can defoliate spruce over considerable areas. Carter (1972, 1977) indicated that 37,700 ha of P. sitchensis were defoliated by E. abietinum in western parts of Britain in 1971, which was equivalent to 15% of the total area planted with P. sitchensis at the time. Koot (1991) reported that more than 5000 ha of P. sitchensis were defoliated by E. abietinum on the west coast of Canada in 1981, and Lynch (2002) estimated that E. abietinum defoliated 57,000 ha of P. englemannii and P. pungens in Arizona in 1999-2000. Large areas of P. sitchensis and Picea abies have been defoliated in Europe in other years (e.g. in 1957), but the actual area defoliated or number of trees affected were not estimated at the time (Carter and Halldórsson, 1998). Variation in defoliation by E. abietinum has been related to differences in local climate and type of planting (Ohnesorge, 1961), elevation (Joly, 1961) and soils (Leroy and Malphettes, 1969).

E. abietinum has pest status in the production of P. abies Christmas trees in Europe, and in the growing of spruce trees for ornamental purposes, particularly blue spruce (P. pungens var. glauca). Seed orchards of P. glauca in British Columbia are also frequently defoliated (Harding et al., 1998). Aphid control in these situations will also carry a significant economic cost.

Economic Impact

Top of page The importance of E. abietinum as a forest pest in Europe and most other areas lies in its ability to cause extensive defoliation, especially of Picea sitchensis, and the effect that defoliation may have on shoot growth and dry matter production. Severe defoliation of P. sitchensis during the spring or early summer reduces height increment in the year of attack by 20-60%, and further reductions in height increment may occur in the following and subsequent years (Carter, 1977; Carter and Nichols, 1988; Seaby and Mowat, 1993; Thomas and Miller, 1994). The reduction in diameter increment may be similar after heavy defoliation (Thomas and Miller, 1994). Orlund and Austarå (1996) found that severe defoliation of 34-year-old P. sitchensis in Norway reduced diameter increments for 7-8 years. The mean reduction in diameter increment over this period was 18.5% for trees that were 15 cm diameter at breast height (dbh), and 40.5% for trees that were 20 cm dbh. The maximum reduction in diameter increment occurred 4-5 years after attack, and increments had still not returned to normal by the end of the study period.

The impact of moderate defoliation by E. abietinum in the spring on 4-year-old P. sitchensis has been described by Straw et al. (1998b, 2000, 2002). Height increment of defoliated trees was reduced by 22% in the year of attack, by 11% in the following year, and by 6% in the third year, when compared with undefoliated trees. At the end of the third year, defoliated trees were, on average, 10% shorter than undefoliated trees. Stem diameter and volume increments were not reduced in the year in which defoliation took place, but were reduced in the following year, by 12% and 24%, respectively (Straw et al., 2000). There was no reduction in diameter and volume increments in the third year. The immediate reduction in height increment in the year of attack was caused by a direct effect of aphids on shoot extension growth in the spring, whereas the decrease in diameter and volume increment in the following year was caused by a delayed reduction in needle size (Straw et al., 2002).

Defoliation during the autumn may have a greater impact than defoliation during the spring (Carter, 1977). However, the only quantitative estimates of impact following autumn defoliation are those given by Halldórsson et al. (2003) from studies in Iceland. Moderate defoliation of P. sitchensis at one site in south-east Iceland during 1986-1987 and 1990-1991 reduced total height and diameter growth over the period 1987-2000 by 16% and 17%, respectively. Severe defoliation reduced both height and diameter growth by 37%. By 2000, when the trees were 40 years old, trees that had been lightly, moderately and severely defoliated in 1991 were, on average, 9.0, 8.1 and 7.2 metres tall, respectively.

In Europe, E. abietinum rarely kills trees and its main effect is to reduce increment. The inability of E. abietinum to attack the new needles before the autumn (see Development and Physiology section under Biology and Ecology), means that trees always carry some foliage after spring or early summer infestation, or soon regain foliage after autumn or winter attack. This is usually enough to ensure that the trees survive and recover. The death of large or small trees may occur under exceptional conditions, e.g. after complete defoliation in autumn and winter when the trees have been left bare for several months, or when spring attack coincides with a severe frost that kills the new growth, but in Europe this is a rare phenomenon (Bevan, 1966; Straw et al., 1998a). The risk of mortality is higher for small, not fully established trees on difficult sites and when defoliation is followed by drought stress.

In North America and New Zealand, defoliation by E. abietinum has caused significant tree mortality. The large number of Picea englemannii and Picea pungens trees killed by E. abietinum in the interior south-west USA is likely to have a significant economic impact, although as yet this impact has not been quantified. Damage by E. abietinum has been considered to be a major factor preventing spruce being used as a production species in New Zealand, limiting options for commercial forestry and potential yields (Miller and Knowles, 1989; Nicol et al., 1998).

E. abietinum can defoliate spruce over considerable areas. Carter (1972, 1977) indicated that 37,700 ha of P. sitchensis were defoliated by E. abietinum in western parts of Britain in 1971, which was equivalent to 15% of the total area planted with P. sitchensis at the time. Koot (1991) reported that more than 5000 ha of P. sitchensis were defoliated by E. abietinum on the west coast of Canada in 1981, and Lynch (2002) estimated that E. abietinum defoliated 57,000 ha of P. englemannii and P. pungens in Arizona in 1999-2000. Large areas of P. sitchensis and Picea abies have been defoliated in Europe in other years (e.g. in 1957), but the actual area defoliated or number of trees affected were not estimated at the time (Carter and Halldórsson, 1998). Variation in defoliation by E. abietinum has been related to differences in local climate and type of planting (Ohnesorge, 1961), elevation (Joly, 1961) and soils (Leroy and Malphettes, 1969).

E. abietinum has pest status in the production of P. abies Christmas trees in Europe, and in the growing of spruce trees for ornamental purposes, particularly blue spruce (P. pungens var. glauca). Seed orchards of P. glauca in British Columbia are also frequently defoliated (Harding et al., 1998). Aphid control in these situations will also carry a significant economic cost.

Environmental Impact

Top of page Defoliation by E. abietinum, in common with defoliation by other insect pests, influences short- and long-term nutrient cycling in forest stands (Pedersen, 1992; Pedersen and Bille-Hansen, 1999; Stadler et al., 2001). Nutrient availability may be increased in the short-term, but over longer periods defoliation may result in a net loss of nutrients lost from the stand (Pedersen, 1992).

Tree mortality in relatively dry areas such as Arizona is of concern because it increases the amount of dry fuel material in the forest and increases the risk of wildfire (Lynch, 2004). This may become an important issue during prolonged periods of drought.

Impact: Biodiversity

Top of page In the interior south-west USA, E. abietinum is a new invasive pest in native, high elevation spruce forests and, on its own or in combination with other factors, is causing the death of large numbers of Picea englemannii and Picea pungens. Complete defoliation of spruce over wide areas has led to 28-42% mortality of more severely defoliated trees and almost total mortality of regenerating seedlings and young saplings (Lynch, 2002, 2004). P. englemannii is more severely defoliated and suffers greater mortality than P. pungens. The mortality caused by E. abietinum in these forests is changing natural disturbance regimes and tree population dynamics, and in the long-term, will cause a shift in species composition of the mixed-conifer forests toward Abies and other non-spruce species (Lynch, 2004). Extensive mortality of spruce in the more isolated mountain ranges of Arizona and New Mexico also poses a threat to rare and endemic elements of the native fauna, e.g. certain species and subspecies of squirrels, which are dependent on spruce in these relict conifer forests.

Threatened Species

Top of page
Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Tamiasciurus hudsonicus grahamensis (Mount Graham red squirrel)USA ESA listing as endangered species USA ESA listing as endangered speciesArizonaEcosystem change / habitat alterationUS Fish and Wildlife Service, 2007

Social Impact

Top of page Old growth stands of P. sitchensis in coastal areas of Queen Charlotte Islands, British Colombia, have a high landscape and amenity value, and the death of such stands following defoliation by E. abietinum has an impact on public use of forest land (Pillsbury, 1960).

Detection and Inspection

Top of page In Europe, the first signs that aphids are present are most frequently seen in early spring, although they may also be seen as early as September when the trees are dormant. Individual needles here and there will be yellow or show a yellow band across them where the aphid has been feeding. The best way to see the aphid is to turn the shoot over and examine the underside of the yellowing needles. Placing a sheet of plain white paper under the foliage and rapping the branches with a stick will usually dislodge some aphids if they are present.

Similarities to Other Species/Conditions

Top of page Conifer spider mite, Oligonychus ununguis also causes discoloration, death and needle fall on spruce in mainland Europe, UK, and New Zealand, and damage caused by the mite has been confused with that caused by E. abietinum in the past (Dumbleton, 1932; von Scheller, 1963). However, mite damage is more frequent on small trees in dry situations, and on Christmas trees (Carter and Winter, 1998). The mites suck sap from the epidermal and cortical cells, and damaged needles have a yellow speckled (not banded) appearance at first. Later the foliage turns bronze. This change develops from the centre of the tree's crown outward, and affects needles on the current shoots last. It is most noticeable in late summer or autumn (UK). Severely damaged needles may fall from the shoot. Close examination with a hand-lens or dissecting microscope will reveal tiny orange-brown to grey spider mites (0.2-0.5mm) and orange-brown to reddish eggs on the shoots. The mites spin silk webbing across the needles, but this is only obviously visible when very large numbers are present. The mite overwinters as eggs on the current shoots, mainly clustered on the bark close to the terminal bud. The eggs hatch in April to mid-May (in the UK) and damage develops as populations increase through the summer. O. ununguis also occurs on many other conifer species (Strouts and Winter, 1994; Carter and Winter, 1998).

Eriophyiid needle mites (Nalepella haarlovi) can produce similar damage to O. ununguis on Picea abies and Picea sitchensis (UK), but the mites are much smaller and do not produce silk. P. abies-affected foliage appears greyish at first but then turns reddish-brown. The discoloration begins in the centre of the tree and then spreads outward. Severe infestation can lead to defoliation of the older needles. Close examination with a x10 magnification lens may reveal pale-orange spherical eggs, about twice the diameter of the silver stomata, on the needles. The elongate mites are amber and two to three times the size of the eggs, but all stages are very difficult to see in the field, and examination with a low power microscope is necessary to confirm diagnosis (Carter and Winter, 1998).

Chrysomyxa needle rust can produce chlorotic symptoms similar to those caused by E. abietinum (in mainland Europe and the UK), but the rust causes disconcertingly bright and conspicuous needle discoloration. Infection results in needles with bright-orange or yellow transverse bands, or completely discoloured needles that contrast strongly with adjacent healthy green needles. Needles infected with Chrysomyxa abietis (spruce needle rust) over the autumn and winter produce orange, elongated blister-like pustules on the underside in the spring, which release spores that infect newly developing needles; the spore-bearing needles then fall. Chrysomyxa rhododendri overwinters on rhododendron. Spores produced in the spring infect developing spruce needles. The needles produce characteristic white outgrowths on their underside in late summer. These release orange spores that re-infect rhododendron. The infected needles then fall (Strouts and Winter, 1994)

Late spring frost damage can cause needle browning and shoot death, but damage is confined to the new, recently flushed foliage. Lime- or chalk-induced chlorosis can lead to foliage yellowing, needle loss and poor growth in spruce, but in such cases discoloration is distributed generally throughout the canopy, and needles turn completely pale or yellow (and are often unusually small) and lack the distinctive yellow spots and bands typical of E. abietinum attack. Signs of infestation (individual insects, exuviae, cadavers, honeydew and sooty moulds) are absent (Strouts and Winter, 1994).

Prevention and Control

Top of page Phytosanitary Measures

Preventing infested nursery material, ornamental stock or Christmas trees from being imported into regions or countries that currently do not have the aphid is an important means of limiting the spread of E. abietinum, and is still relevant to countries such as New Zealand where the genetic base of the E. abietinum population is extremely restricted.

Cultural Control

Cultural control of E. abietinum through modification of silvicultural practices has not been explored. Unlike many lepidopteran and hymenopteran defoliators, E. abietinum does not appear to be favoured by reduced vitality of its host trees, such as that caused by drought stress, but appears to perform better on strongly growing trees. Higher rates of defoliation have been observed on the taller, more vigorous trees within stands than on shorter, slower growing individuals (Harding et al., 1998; Halldórsson et al., 2003). If this is a general phenomenon then, unlike the management of other forest pests, management of E. abietinum cannot focus on improving tree vitality through silviculture as a means to ameliorate damage (Day et al., 1998).

However, in experimental studies, even though higher populations of E. abietinum have been shown to develop on more vigorous host plants, because these plants tend to contain higher concentrations of nitrogen, rates of defoliation are lower and effects on growth are smaller than on poorly growing plants that carry fewer aphids (Wainhouse et al., 1998; Straw and Green, 2001). Poorly growing plants are less able to retain needles and suffer relatively greater growth losses. Consequently, maximising the health and vitality of trees has a role to play in minimising damage from E. abietinum, at least when defoliation is not too severe. Fertilisation may also help a crop to replace its canopy and recover normal growth more quickly after defoliation (Thomas and Miller, 1994).

Host-Plant Resistance

Variation in resistance to attack by E. abietinum has been demonstrated between spruce species (Nichols, 1987), and at the provenance (Day, 1984a; Carter and Nichols, 1988, Harding et al., 1998), family (Jensen et al., 1997; Lewis et al., 1999) and clonal levels (Harding et al., 1998; Straw and Green, 2001). Variation in resistance within provenances of Picea sitchensis is very profound, making selection of resistant plant material possible in most provenances. Studies by Jensen et al. (1997) and Harding et al. (2003) have shown that family heritability of resistance in P. sitchensis is high and that considerable realised gains (40-60%) might be expected following selection. The expression of resistance appears to be consistent over time. Resistance demonstrated amongst families of P. sitchensis 29 years after selection for the trait (Jensen et al., 1997) was still present after 40 years (Harding et al., 2003).

A highly skewed distribution of defoliation amongst families of selected P. sitchensis indicates that major genes are involved in the expression of resistance, and the genetics behind resistance may have a non-additive component (Harding et al., 2003). Skov and Wellendorf (2000) found, within two families of P. sitchensis, two to three quantitative trait loci associated with resistance that were linked to RAPD markers.

Variation in resistance to E. abietinum amongst families of P. glauca emblings has been shown to be correlated with resistance to white pine weevil (Pissodes strobi) (Lewis et al., 1999). P. glauca seedlings ranked as highly resistant to P. strobi, sustained significantly less aphid defoliation. Similarly, P. sitchensis provenances that were more resistant to feeding by the pine weevil, Hylobius abietis, in laboratory trials supported lower populations of E. abietinum in the field (Day et al., 1999).

Resistance to E. abietinum is not currently part of P. sitchensis breeding programmes, which have concentrated on improving adaptability, quality and yield (Harding et al., 1998). However, gains achieved to-date are based on field trials and unprotected trees in which the aphid is included with other normal environmental variables. Therefore, some measure of resistance will have been taken into account implicitly within these breeding programmes.

Biological Control

The influence of natural enemies in suppressing E. abietinum populations in Europe is not clear, hence the potential of the various predators, parasitoids and pathogens of the aphid to act as biocontrol agents elsewhere cannot easily be judged. The over-riding influence of climatic factors, especially freezing temperatures during the winter, on the aphid's population dynamics in Europe, and apparent relation of populations to climate elsewhere, suggests that natural enemies are less important controls on population size and that the effectiveness of biological control might be limited. However, predators may be important in reducing aphid populations during the late summer and autumn in Europe (Crute and Day, 1990; Leather and Kidd, 1998), and in years following high populations, and so some biological control might be achievable through either augmentation of resident natural enemy populations or introduction of natural enemy species to areas where they are absent. In certain regions, notably Iceland, where there appear to be relatively few natural enemies, a classical biological approach might achieve some success (Austarå et al., 1998; Leather and Kidd, 1998).

The coccinellid Aphidecta obliterata is one of the most abundant predators of E. abietinum and has potential as a biocontrol agent. It was introduced on to the North Sea island of Amrum in 1966 to control E. abietinum (Schneider, 1966), but whether this resulted in any change in the aphid population is not reported. A. obliterata has also been introduced as a biocontrol agent against Chermes piceae [Adelges piceae piceae] in the USA (Amman, 1966) and Canada (Brown and Clark, 1959), although again without any reported success.

The Californian coccinellid Hippodamia convergens was introduced into New Zealand in 1921 to combat E. abietinum and other aphids, but was not recorded subsequently on spruce (Dumbleton, 1932). A Chrysopa species of lacewing (Neuroptera) was also introduced, but this too was not recorded after it was liberated (Dumbleton, 1932).

Chemical Control

Chemical control of E. abietinum is feasible in nurseries and on Christmas trees, but large-scale control with insecticides in plantations and natural forests is uneconomic and environmentally unacceptable. Protection of Christmas trees in the UK, and in other regions of Europe with anholocyclic aphid populations, is best achieved by spraying with an insecticide in August or early September (Carter and Winter, 1998). This is after the migration period and will give protection until the next immigration of winged aphids in the following spring. Carter and Cole (1977) suggest spraying between autumn and late winter (UK), whereas both Bevan (1966) and Parry (1977) recommend early April applications for control of the spring damage.

E. abietinum is not a difficult insect to control with insecticides that have either a contact or fumigant knock-down action provided that it is carried out under appropriate spraying conditions and good coverage is achieved. The use of systemic insecticides is not recommended, as they are not readily translocated within conifers (Carter and Winter, 1998).

Parry and Rose (1983), Musau and Parry (1988), and Partridge and Borden (1997) have studied insecticide toxicity to E. abietinum. Parry and Rose (1983) analysed the toxicity of fatty acids and their potassium salts to E. abietinum. LC50 values ranged from around 0.1% to above 10%. Musau and Parry (1988) investigated the toxicity of several organophosphorus insecticides (dimethoate, fenitrothion, malathion) and Safer's insecticidal soap, saponified corn oil and sunflower oil. Although the organophosphorus compounds were more toxic, soaps were still effective under field conditions provided that appropriately higher concentrations were applied. Partridge and Borden (1997) looked at the effectiveness of neem seed extract, from the neem tree Azadirachta indica, enriched with azadirachtin, in killing E. abietinum, with a view to controlling the aphid in seed orchards in Canada. High rates of mortality were achieved on potted spruce plants, suggesting that neem could be a viable method of control.

Field Monitoring/Economic Threshold Levels

Economic thresholds have not been determined.

References

Top of page

Amman GD, 1966. Aphidecta obliterata (Coleoptera: Coccinellidae), an introduced predator of the balsam woolly aphid, Chermes piceae (Homoptera: Chermidae), established in North Carolina. Journal of Economic Entomology, 59:506-508.

Anon., 2002. Spruce aphids endanger trees. Rhode Island, USA: The Block Island Times, June 22 2002.

Austarå O, Carter C, Eilenberg J, Halldórsson G, Harding S, 1998. A conspectus of potential natural enemies found in association with the green spruce aphid in north-west European spruce plantations. In: Day KR, Halldórsson G, Harding S, Straw NA, eds. The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management. Edinburgh, UK: Forestry Commission, 53-60.

Austarå O, Carter CI, Eilenberg J, Halldórsson G, Harding S, 1997. Natural enemies of the green spruce aphid in spruce plantations in maritime North-West Europe. Icelandic Agricultural Sciences, 11:113-124.

Bale JS, 1993. Classes of insect cold hardiness. Functional Ecology, 7(6):751-753

Bartkowski J, 1998. Spruce aphid - a noxious pest of spruces in parks and gardens. Ochrona Roslin, 42(9):6-7.

Bejer-Petersen B-[Petersen, BB. ], 1962. Peak years and regulation of numbers in the aphid Neomyzaphis abietina Walker. Oikos 13 (1), (155-68). 21 refs.

Bevan D, 1966. The green Spruce aphis Elatobium (Neomyzaphis) abietinum Walker. Scottish Forestry, 20(3):193-201, + 1 photo. [9 refs.].

Bjarnason H, 1961. Straf Skograektar rikisins 1960. Arsrit Skograektarfelags Islands, 1960-1961:84-96.

Blackman RL, Eastop VF, 1994. Aphids on the world's trees: an identification and information guide. Wallingford, UK: CAB International.

Blöndal S, 1988. Skyrsla Skograektar rikisins fyrir 1987. Arsrit Skograektarfelags Islands, 1988:109-134.

Brown NR, Clark RC, 1959. Studies of predators of the Balsam woolly aphid, Adelges piceae (Ratz.) (Homoptera: Adelgidae). VI. Aphidecta obliterata (L.) (Coleoptera:Coccinellidae), an introduced predator in Eastern Canada. Repr.from Canadian Entomologist, 91(9):596-599. 8 refs. (Contr. Div. For. Biol. Dep. Agric. Can. No. 549.).

Börner C, Heinze K, 1957. Aphidina - Aphidoidea. In: Sorauer P, ed. Handbuch der Pflanzenkrankheiten, 5: 1-355, Homoptera 2. Teil. Berlin, Germany: Paul Parey.

CABI/EPPO, 1986. Elatobium abietinum (Walker). Distribution maps of pests, No. 222 (revised). Wallingford, UK: CAB International.

Carrillo L R, 1977. Aphidoidea of Chile II. Agro Sur, 5(2):109-114

Carter C, Austara O, 1994. The occurrence of males, oviparous females and eggs within anholocyclic populations of the green spruce aphid Elatobium abietinum (Walker) (Homoptera: Aphididae). Fauna Norvegica. Serie B, Norwegian Journal of Entomology, 41(2):53-58

Carter C, Halldórsson G, 1998. Origins and background to the green spruce aphid in Europe. In: Day KR, Halldórsson G, Harding S, Straw NA, eds. The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management. Edinburgh, UK: Forestry Commission, 1-10.

Carter CI, 1969. An intermediate form of Elatobium abietinum (Walker) (Hem., Aphididae) found during the winter in Scotland. Entomologist's Monthly Magazine, 105 (1262/1264), (200). [5 refs.].

Carter CI, 1972. Winter temperatures and survival of the green spruce aphid Elatobium abietinum (Walker). Forest Record, No. 84:10 pp.

Carter CI, 1977. Impact of green spruce aphid on growth: can a tree forget its past? Research and Development Paper, Forestry Commission, No. 116:8 pp.

Carter CI, Cole J, 1977. Flight regulation in the green spruce aphid (Elatobium abietinum). Annals of Applied Biology, 86(2):137-151

Carter CI, Nichols JFA, 1988. The green spruce aphid and Sitka spruce provenances in Britain. Occasional Paper, Forestry Commission, UK, No. 19:i + 7 pp.

Carter CI, Winter T, 1998. Christmas Tree Pests. London, UK: The Stationery Office. Forestry Commission, Field Book 17.

Carter CI, Wood-Baker CS, Polaszek A, 1987. Species, host plants and distribution of aphids occurring in Ireland. Irish Naturalists' Journal, 22(7):266-284

Cottier W, 1953. Aphids of New Zealand. Department of Scientific and Industrial Research Bulletin, 106:307-311.

Crute S, Day K, 1990. Understanding the impact of natural enemies on spruce aphid populations through simulation modelling. In: Watt AD, Leather SR, Hunter MD, Kidd NAC, eds. Population Dynamics of Forest Insects. Andover, UK: Intercept, 329-337.

Cunliffe N, 1924. Notes on the biology and structure of Myzaphis abietina Walker. Quarterly Journal of Forestry, 18:133-141.

Day K, 1984. Systematic differences in the population density of green spruce aphid, Elatobium abietinum in a provenance trial of Sitka spruce, Picea sitchensis. Annals of Applied Biology, 105(3):405-412

Day K, Crute S, 1990. The abundance of spruce aphids under the influence of an oceanic climate. In: Watt AD, Leather SR, Hunter MD, Kidd NAC, eds. Population Dynamics of Forest Insects. Andover, UK: Intercept, 25-33.

Day KR, 1984. The growth and decline of a population of the spruce aphid Elatobium abietinum during a three year study, and the changing pattern of fecundity, recruitment and alary polymorphism in a Northern Ireland forest. Oecologia, 64:118-124.

Day KR, 1986. Population growth and spatial patterns of spruce aphids (Elatobium abietinum) on individual trees. Journal of Applied Entomology, 102(5):505-515

Day KR, Armour HL, Henry CJ, 1999. The performance of the green spruce aphid (Elatobium abietinum Walker) on provenances of Sitka spruce (Picea sitchensis (Bong.) Carr.). Physiology and genetics of tree-phytophage interactions. International Symposium, Gujan, France, 31 August-5 September, 1997., 199-210; [Les Colloques No. 90]; 32 ref.

Day KR, Kidd NAC, 1998. Green spruce aphid population dynamics: effects of climate, weather and regulation. In: Day KR, Halldórsson G, Harding S, Straw NA, eds. The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management. Edinburgh, UK: Forestry Commission, 41-52.

Day KR, McClean SI, 1991. Influence of the green spruce aphid on defoliation and radial stem growth of Sitka spruce. Annals of Applied Biology, 119(3):415-423

Day KR, Straw NA, Harding S, 1998. Prospects for sustainable management of forests to minimise the green spruce aphid problem in Europe. In: Day KR, Halldórsson G, Harding S, Straw NA, eds. The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management. Edinburgh, UK: Forestry Commission, 97-105.

Delfino MA, Binazzi A, 2002. Conifer aphids from Argentina (Hemiptera: Aphididae). (Âfidos de coníferas en la Argentina (Hemiptera: Aphididae).) Revista de la Sociedad Entomológica Argentina, 61(3/4):27-36.

Doncaster JP, 1961. Francis Walker’s Aphids. London, UK: British Museum (Natural History).

Dumbleton LJ, 1932. Report on Spruce-Aphis investigation for the year ending December 1930. New Zealand Journal of Science and Technology, 13(4):207-220.

Eastop VF, 1966. A taxonomic study of Australian Aphidoidea. Australian Journal of Zoology,14:399-592.

Eglitis A, 1986. Spruce needle aphid. USDA Forest Service, Alaskan Region Leaflet R10-TP-3.

Evans JW, 1943. Insect pests and their control. Tasmania: HH Pimblett.

Fedde GF, 1971. The Spruce aphid, Elatobium abietinum, observed in eastern United States. Entomological News, 82:176

Fedde GF, 1972. An anomalous occurrence of the spruce aphid, Elatobium abietinum (Walker), in western North Carolina (Homoptera:Aphididae). Proceedings of the Entomological Society of Washington, 74(4):379-381

Fisher M, 1981. The control of polymorphism in the green spruce aphid Elatobium abietinum. Forestry Commission Report on Forest Research, 1981: 65-65.

Fisher M, 1986. The number of instars of alatae of the green spruce aphid, Elatobium abietinum (Walker). Forestry Commission Report on Forest Research, 1986:71-72.

Fisher M, 1987. The effect of previously infested spruce needles on the growth of the green spruce aphid, Elatobium abietinum, and the effect of the aphid on the amino acid balance of the host plant. Annals of Applied Biology, 111:33-41.

Fisher M, Dixon AFG, 1986. The role of photoperiod in the timing of dispersal in the Green spruce aphid Elatobium abietinum (Walker). Journal of Animal Ecology, 55:657-667.

Frazer BD, 1988. Predators. In: Minks AK, Harrewijn P, eds. Aphids, Their Biology, Natural Enemies and Control, Vol. B. Amsterdam, The Netherlands: Elsevier.

Furniss RL, Carolin VM, 1977. Western forest insects. USDA Miscellaneous Publication, No. 1339. Washington DC., USA; US Department of Agriculture.

Gotlin Culjak T, Igrc Barcic I, Dobrincic R, 2002. The new registered species of aphids (Hemiptera: Aphidoidea) in Croatia. Entomologia Croatica, 6(1/2):5-22.

Halldórsson G, 1995. Frostthol sitkalusar. Skograektarritid, 1995:99-101.

Halldórsson G, Benedikz T, Eggertsson EG, Oddsdóttir ES, Óskarsson H, 2003. The impact of the green spruce aphid Elatobium abietinum (Walker) on long-term growth of Sitka spruce in Iceland. Forest Ecology and Management, 181:281-287.

Halldórsson G, Docherty M, Oddsdóttir ES, Day KR, 2001. The performance of different populations of the green spruce aphid (Elatobium abietinum Walker) at different temperatures. Buvisindi, 14:75-84; 23 ref.

Halldórsson G, Sigurdsson V, Thórsson AT, Oddsdóttir ES, Sigurgeirsson A, Anamthawat-Jónsson K, 2004. Genetic diversity of the green spruce aphid (Elatobium abietinum Walker) in north-west Europe. Agricultural and Forest Entomology, 6:31-37.

Halme J, 1992. Ephedrus koponeni sp. n. from Finland. (Hymenoptera, Braconidae, Aphidiinae). Entomologica Fennica, 3:113-116.

Hanson HS, 1951. The green spruce aphis, Neomyzaphis abietina Walker. Forestry Commission Report on Forest Research, 1951:98-104.

Harding S, Carter CI, 1997. First record of males, oviparae and eggs of the green spruce aphid Elatobium abietinum (Walker) in Denmark (Hemiptera, Aphididae). Entomologiske Meddelelser, 65(4):175-178; 13 ref.

Harding S, Day KR, Armour HL, 1998. Selecting for resistance in genetically defined Sitka spruce. In: Day KR, Halldórsson G, Harding S, Straw NA, eds. The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management. Edinburgh, UK: Forestry Commission, 71-85.

Harding S, Roulund H, Wellendorf H, 2003. Consistency of resistance to attack by the green spruce aphid (Elatobium abietinum Walker) in different ontogenetic stages of Sitka spruce. Agricultural and Forest Entomology, 5(2):107-112; 31 ref.

Heie OE, 1964. A list of Danish aphids. Part 4. Entomologiske Meddelelser, 32:341-357.

Heie OE, 1992. The Aphidoidea (Hemiptera) of Fennoscandia and Denmark. IV. Leiden, Netherlands: E J Brill Scandinavian Science Press Ltd, 29-34.

Heikinheimo O, 1963. Liosomaphis abietina found in Finland. Annales Entomologici Fennici, Helsinki, 29(4):285-6. 6 refs.

Holms J, Ruth DS, 1968. Spruce aphid in British Columbia. Forest Pest Leaflet 16.

Holsten EH, Hennon PE, Werner RA, 1985. Insects and diseases of Alaskan forests. Alaska Region Report, Forest Pest Management State and Private Forestry, Forest Service, United States Department of Agriculture, No. 181:vi + 217pp.

Holusa J, Liska J, Kapitola P, Peskova V, Soukup F, 2005. Phytopathological and entomological health aspects of mountain spruce stands in the Czech Republic. (Aspekt fitopatologiczny i entomologiczny zdrowotnosci swierczyn górskich na terenie Republiki Czeskiej.) Lesne Prace Badawcze, No.2:133-138.

Hussey NW, 1952. A contribution to the bionomics of the green Spruce aphid (Neomyzaphis abietina Walker). Scottish Forestry, 6(4):121-30. 7 refs.

Ilharco FA, 1996. 2nd addition to the catalogue of the aphids of continental Portugal (Homoptera, Aphidoidea). Agronomia Lusitana, 45(1/3):5-66; 6 pp. of ref.

Jackson DL, Dixon AFG, 1996. Factors determining the distribution of the green spruce aphid, Elatobium abietinum, on young and mature needles of spruce. Ecological Entomology, 21:358-364.

Jensen JS, Harding S, Roulund H, 1997. Resistance to the green spruce aphid (Elatobium abietinum Walker) in progenies of Sitka spruce (Picea sitchensis (Bong) Carr.). Forest Ecology and Management, 97(3):207-214; 24 ref.

Joly R, 1961. The animal causes of yellowing and needle-cast of P. sitchensis and other Spruces. [Les causes animales dans le jaunissement et la chute des aiguilles de l'epicea de Sitka "Picea sitchensis" et d'autres epiceas.] Revue Forestière Française, 13(3):179-186. 12 refs.

Keen FP, 1952. Insect enemies of western forests. US Department of Agriculture, Miscellaneous Publication 273.

Keller S, 1991. Arthropod-pathogenic Entomophthorales of Switzerland. II. Erynia, Eryniopsis, Neozygites, Zoophthora and Tarichium.. Sydowia, 43:39-122

Kloft W, Ehrhardt P, 1959. Studies on the sucking activity and damage caused by N. abietina. [Untersuchungen uber Saugtatigkeit und Schadwirkung der Sitkafichtenlaus Liosomaphis abietina (Walk.) (Neomyzaphis abietina).] Phytopath. Z., 35(4):401-410. 14 refs.

Kloft W, Ehrhardt P, Kunkel H, 1961. Die Fichtenrohrenlaus Elatobium abietinum (Walk. 1849), ein endemisches Insekt der Rotfichte Picea excelsa in Europe. Waldhygiene, 4:121-125.

Kloft W, Kunkel H, Ehrhardt P, 1964. Weitere Beiträge zur Kenntis die Fichtenrohenlaus Elatobium abietinum (Walk.) unter besondere Berucksichtigung ihnen Weltverbreitung. Zeitschrift für Angewandte Entomologie, 55:160-185.

Knowlton GF, 1983. Aphids of Utah. USA: Utah State University Research Bulletin, 509.

Koot HP, 1991. Spruce Aphid. Forest Pest Leaflet No. 16. Victoria, BC: Forestry Canada.

Laurent JE, 1967. Aphididae in French forest. Bulletin de l'Ecole Nationale Superieure Agronomique de Nancy, 9(2):93-101. [4 refs.].

Leather SR, Kidd NAC, 1998. The quantitative impact of natural enemies and the prospect for biological control. In: Day KR, Halldórsson G, Harding S, Straw NA, eds. The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management. Edinburgh, UK: Forestry Commission, 61-70.

Leather SR, Owuor A, 1996. The influence of natural enemies and migration on spring populations of the green spruce aphid, Elatobium abietinum Walker (Hom., Aphididae). Journal of Applied Entomology, 120(9):529-536; 27 ref.

Leroy P, Malphettes CB, 1969. Preliminary notes on attacks by the green aphis on Sitka Spruce plantations growing on poor soil in western France. Revue Forestière Française, 21(6):547-550. [1 ref.].

Lewis KG, Alfaro RI, Andrucko D, 1999. Variation in Elatobium abietinum attack on Picea glauca and its relation to Pissodes strobi resistance. Scandinavian Journal of Forest Research, 14(4):334-340; 42 ref.

Low AJ, 1986. Tree planting in the Falkland Islands. Forestry, 59(1):59-84; 20 ref.

Lynch AM, 2002. Spruce aphid in high elevation habitats in the southwest US. In: Proceedings of USDA Interagency Research Forum on Gypsy Moth and Other Invasive Species, Annapolis MD, January 2002. USDA Forest Service.

Lynch AM, 2004. Fate and characteristics of Picea damaged by Elatobium abietinum (Walker) (Homoptera: Aphididae) in the White Mountains, Arizona. Western North American Naturalist, 64:7-17.

Mackauer M, Stary P, 1967. Hym., Ichneumoidea, World Aphidiidae. In: Delucchi V, Remaudiere G, eds. Index of Entomophagous Insects. 1st edn. Le Francois, Paris.

Maksymov JK, 1961. Blattlausschäden im Jahre 1961 und Auftreten der Fichtenröhrenlaus Liosomaphis abietina Walker in der Schweiz. Mitteilungen der Schweizerischen Anstalt für das forstliche Versuchswesen, 37:343-353.

Maksymov JK, 1981. Mass outbreak of the green spruce aphid, Elatobium abietinum, in Switzerland. [Die Massenvermehrung der Fichten-Rohrenlaus, Elatobium abietinum Walker, in der Schweiz.] Schweizerische Zeitschrift für Forstwesen, 132(4):267-272; 2 pl.; 6 ref.

Miller JT, Knowles FB, 1989. Introduced forest trees in New Zealand: recognition, role, and seed source. 6. The spruces. Picea sitchensis (Bong.) Carriere - Sitka spruce; Picea abies (L.) Karsten - Norway spruce; ornamental spruces. FRI Bulletin, Forest Research Institute, New Zealand, No. 124, 20 pp.; 4 col. pl.; 17 ref.

Miyazaki M, 1971. A revision of the tribe Macrosiphini of Japan (Homoptera: Aphididae, Aphidinae). Insecta Matsumurana, 34(1):247 pp.

Mordvilko A, 1914. Aphidoidea I. In: Faune de la Russie (Insecta Hemiptera), I, CLXIV.

Musau DM, Parry WH, 1988. Comparison of the potential of organophosphorus insecticides and soaps in conifer aphid control. Crop Protection, 7(4):267-272

Myers JG, 1922. The order Hemiptera in New Zealand. New Zealand Journal of Science and Technology, 5:1-12.

Nichols JFA, 1987. Damage and performance of the green spruce aphid, Elatobium abietinum on twenty spruce species. Entomologia Experimentalis et Applicata, 45(3):211-217

Nicol D, Armstrong KF, Wratten SD, Walsh PJ, Straw NA, Cameron CM, Lahmann C, Frampton CM, 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(5):537-543; 39 ref.

Ohnesorge B, 1959. The outbreak of Liosomaphis (Neomyzaphis) abietina in N.W. Germany. Forstarchiv, 30(4/5):73-78. 14 refs.

Ohnesorge B, 1961. When must we expect outbreaks of Liosomphis [Neomyzaphis] abietina. [Wann sind Schaden durch die Sitkalaus zu erwarten?] Allgemeine Forstzeitschrift, 16(27-28):408-410. 7 refs.

Orlund A, Austara O, 1996. Effects of Elatobium abietinum infestation on diameter growth of Sitka spruce. Meddelelser fra Skogforsk, 47(13):12 pp.; 15 ref.

Ossiannilsson F, 1959. Contributions to the knowledge of Swedish aphids II. Lantbrukshigskolans Annaler, 25:375-527.

Ottósson JG, 1985. Sitklaus (Elatobium abietinum Walker). Arsrit Skograektarfelags Islands, 1985:8-16.

Parry WH, 1969. A study of the relationship between defoliation of Sitka Spruce and population levels of Elatobium abietinum (Walker). Forestry, 42(1):69-82. [12 refs.].

Parry WH, 1969. Research on the green spruce aphid, Elatobium abietinum. Forestry Commission Report on Forest Research, 1969:152-154.

Parry WH, 1971. Differences in the probing behaviour of Elatobium abietinum feeding on Sitka and Norway Spruces. Annals of Applied Biology, 69(3):177-185; ORE; 6 ref.

Parry WH, 1973. Observations on the flight periods of aphids in a Sitka spruce plantation in north-eastern Scotland. Bulletin of Entomological Research, 62(3):391-399

Parry WH, 1974. Damage caused by the green spruce aphid to Norway and Sitka spruce needles. Annals of Applied Biology, 77(2):113-120

Parry WH, 1974. The effects of nitrogen levels in Sitka Spruce needles on Elatobium abietinum (Walker) populations in north-eastern Scotland. Oecologia, 15(4):305-320; ORS; 16 ref.

Parry WH, 1977. The effects of nutrition and density on the production of alate Elatobium abietinum on Sitka spruce. Oecologia, 30:367-375

Parry WH, 1978. A reappraisal of flight regulation in the green spruce aphid, Elatobium abietinum. Annals of Applied Biology, 89(1):9-14

Parry WH, 1980. Overwintering of Aphidecta obliterata (L.) (Coleoptera: Coccinellidae) in north east Scotland. Acta Oecologica, Oecologia Applicata, 1(4):307-316

Parry WH, 1992. A comparison of Aphidecta obliterata (L.) (Col., Coccinellidae) populations feeding on Elatobium abietinum (Walker) and on Adelges cooleyi (Gillette). Journal of Applied Entomology, 114(3):280-288

Parry WH, Rose R, 1983. The role of fatty acids and soaps in aphid control on conifers. Zeitschrift für Angewandte Entomologie, 96(1):16-23

Partridge MJ, Borden JH, 1997. Evaluation of neem seed extract for control of the spruce aphid, Elatobium abietinum (Walker) (Homoptera: Aphididae). Canadian Entomologist, 129(5):899-906; 33 ref.

Pedersen LB, 1992. The variation in defoliation in stands of Norway spruce, Sitka spruce and beech in relation to the stability of forest ecosystems. Dansk Skovforenings Tidsskrift, 4:210-216.

Pedersen LB, Bille-Hansen J, 1999. A comparison of litterfall and element fluxes in even aged Norway spruce, Sitka spruce and beech stands in Denmark. Forest Ecology and Management, 114(1):55-70; 60 ref.

Pillsbury RW, 1960. Three decades of five-year cycles of the spruce aphid, Neomyzaphis abietina (Wlkr.). Northwest Science, 34:106-109.

Powell W, 1974. Supercooling and the low-temperature survival of the green spruce aphid Elatobium abietinum. Annals of Applied Biology, 78(1):27-37

Powell W, Parry WH, 1976. Effects of temperature on overwintering populations of the green spruce aphid Elatobium abietinum. Annals of Applied Biology, 82(2):209-219

Ragnarsson H, 1962. Sitkalausin. Arsrit Skograektarfelags Islands, 1962:69-70.

Rawlings GB, 1953. Insect epidemics on forest trees in New Zealand. New Zealand Journal of Forestry [1954], 6(5):405-413.

Rupais A, 1989. The Aphids (Aphididea) of Latvia. Riga, Latvia: Latvian SSR Academy of Sciences.

Schneider I, 1966. Introduction of Aphidecta obliterata into the North Sea island of Amrum for the biological control of Liosomaphis abietina. Anzeiger für Schädlingskunde, 39(2):26.

Seaby DA, Mowat DJ, 1993. Growth changes in 20-year-old Sitka spruce Picea sitchensis after attack by the green spruce aphid Elatobium abietinum. Forestry (Oxford), 66(4):371-379

Sigurdsson V, Halldórsson G, Sigurgeirsson A, Thórsson T, Anamthawat-Jónsson K, 1999. Genetic differentiation of the green spruce aphid (Elatobium abietinum Walker), a recent invader to Iceland. Agricultural and Forest Entomology, 1(3):157-163; 35 ref.

Skov E, Wellendorf H, 2000. RAPD markers linked to major genes behind field resistance against the green spruce aphid Elatobium abietinum (Walker) in Picea sitchensis (Bong. (Carr.)). Forest Genetics, 7(3):233-246; 38 ref.

Stadler B, Mnller T, Sheppard L, Crossley A, 2001. Effects of Elatobium abietinum on nutrient fluxes in Sitka spruce canopies receiving elevated nitrogen and sulphur deposition. Agricultural and Forest Entomology, 3(4):253-261; 42 ref.

Stary P, 1973. A review of the Aphidius-species (Hymenoptera, Aphidiidae) of Europe. Annotationes Zoologicae et Botanicae, 84:1-85.

Straw NA, Fielding NJ, Green G, Coggan A, 1998. The impact of green spruce aphid, Elatobium abietinum (Walker), on the growth of young Sitka spruce in Hafren Forest, Wales: pattern of defoliation and effect on shoot growth. Forest Ecology and Management, 104(1/3):209-225; 44 ref.

Straw NA, Fielding NJ, Green G, Price J, 2000. The impact of green spruce aphid, Elatobium abietinum (Walker), and root aphids on the growth of young Sitka spruce in Hafren forest, Wales: effects on height, diameter and volume. Forest Ecology and Management, 134(1/3):97-109; 37 ref.

Straw NA, Fielding NJ, Green G, Price J, 2002. The impact of green spruce aphid, Elatobium abietinum (Walker), on the growth of young Sitka spruce in Hafren forest, Wales: delayed effects on needle size limit wood production. Forest Ecology and Management, 157(1/3):267-283; 44 ref.

Straw NA, Green G, 2001. Interactions between green spruce aphid (Elatobium abietinum (Walker)) and Norway and Sitka spruce under high and low nutrient conditions. Agricultural and Forest Entomology, 3(4):263-274; 38 ref.

Straw NA, Halldórsson G, Benedikz T, 1998. Damage sustained by individual trees: empirical studies on the impact of the green spruce aphid. In: Day KR, Halldórsson G, Harding S, Straw NA, eds. The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management. Edinburgh, UK: Forestry Commission, 15-31.

Strouts RG, Winter TG, 1994. Diagnosis of ill-health in trees. London, UK; HMSO, x + 307 pp.

Szelegiewicz H, 1975. A mass appearance of Sitka spruce aphid - Elatobium abietinum (Homoptera, Aphidodea) in parks and open spaces in Warsaw. Polskie Pismo Entomologiczne, 45(3/4):597-599

Theobald FV, 1914. Notes on the green spruce aphis (Aphis abietina Walker). Annals of Applied Biology, 1:23-36.

Theobald FV, 1926. The Plant Lice or Aphididae of Great Britain Volume 1. London, UK: Headley Brothers, 262-272.

Thomas RC, Miller HG, 1994. The interaction of green spruce aphid and fertilizer applications on the growth of Sitka spruce. Forestry (Oxford), 67(4):329-341

US Fish and Wildlife Service, 2007. In: Mount Graham Red Squirrel (Tamiasciurus hudsonicus grahamensis). 5-Year Review: Summary and Evaluation. US Fish and Wildlife Service, 24 pp.

Van Sickle GA, 1995. Forest insect pests in the Pacific and Yukon region. In: Armstrong JA, Ives WGH, eds. Forest Insect Pests in Canada. Ottawa, Canada: Natural Resources Canada, Canadian Forest Service, 73-89.

Volkova LM, 1970. Aphidinea. In: Roshkov AS, ed. Pests of Siberian Larch. Jerusalem, Israel: Program for Scientific Translations, 41-55.

von Scheller HD, 1958. Die Massenvermehrung der Sitkafichtenlaus Elatobium (=Liosomaphis) abietina Walk. in Nordwestdeutschland. Anzeiger für Schädlingskunde, 31:85-88.

von Scheller HD, 1963. Zur Biologie und Schadwirkung der Nadelholzspinnmilbe Oligonychus ununguis Jacobi und der Sitkafichtenlaus Liosomaphis abietina Walker (Hom. Aphid.). Zeitschrift für Angewandte Entomologie, 51:258-284.

Wainhouse D, Ashburner R, Ward E, Rose J, 1998. The effect of variation in light and nitrogen on growth and defence in young Sitka Spruce. Functional Ecology, 12(4):561-572; [62 ref].

Walker F, 1849. Description of aphides. Annals and Magazine of Natural History, 3:301-302.

Wood CS, Sickle GA van, Shore TL, 1985. Forest insect and disease conditions British Columbia & Yukon 1984. Information Report, Pacific Forest Research Centre, Canada, No. BC-X-259:32pp.

Zhou X, Perry JN, Woiwood IP, Harrington R, Bale JS, Clark SJ, 1997. Detecting chaotic dynamics of insect populations from long-term survey data. Ecological Entomology, 22:231-241.

Zondag R, 1983. Elatobium abietinum (Walker) (Hemiptera: Aphididae). Spruce aphid. Forest and Timber Insects in New Zealand, No. 54:4 pp.

Distribution Maps

Top of page
You can pan and zoom the map
Save map