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Plantwise Technical Factsheet

eastern spruce gall aphid (Adelges abietis)

Host plants / species affected
Picea abies (common spruce)
Picea engelmannii (Engelmann spruce)
Picea glauca var. albertiana
Picea jezoensis (Yeddo spruce)
Picea koyamai (koyama spruce)
Picea pungens (blue spruce)
Picea rubens (red spruce)
Picea sitchensis (Sitka spruce)
List of symptoms/signs
Growing point  -  external feeding
Growing point  -  external feeding
Leaves  -  abnormal leaf fall
Leaves  -  abnormal leaf fall
Leaves  -  external feeding
Leaves  -  external feeding
Leaves  -  honeydew or sooty mould
Leaves  -  honeydew or sooty mould
Stems  -  distortion
Stems  -  distortion
Stems  -  external feeding
Stems  -  external feeding
Stems  -  galls
Stems  -  galls
Stems  -  internal feeding
Stems  -  internal feeding
Stems  -  lodging; broken stems
Stems  -  lodging; broken stems
Whole plant  -  external feeding
Whole plant  -  external feeding
Whole plant  -  internal feeding
Whole plant  -  internal feeding
Symptoms
Heavy galling reduces the vigour of the shoots, reducing the growth increment. Galled shoots often become distorted due to the action of gravity on the weakened stems, and these branches may break off in high winds (Carter, 1971). Needles on branches attacked by overwintering nymphs fall (Kolomoets, 1994). The removal of large quantities of sap reduces the vigour of infested trees (Gaumont, 1978), and results in tissue-drying and growth retardation (Kolomoets, 1994).

Prevention and control

Phytosanitary Measures

Planting material of Picea species (especially seedlings from outdoor nurseries) should be closely inspected for galls and signs of adelgid infestation such as patches of white, woolly wax before export to another country, or entry into a country from abroad.

Host-Plant Resistance

There is considerable variation in the susceptibility of Picea abies to damage by A. abietis, in which resistance is related to the presence of high levels of phenols in the tissues (Tija, 1973). The amount of phenolic glucosides in shoots was found to exceed that in galls (a favourable environment engineered by the insects) by a factor of 60 to 100 (Kraus and Spiteller, 1997). An unknown phenol with an ultraviolet spectral maximum at 272 nm in 95% ethanol was consistently present in resistant trees (Tija and Houston, 1975).

In some trees, a reaction to pseudo-fundatrix feeding (death of cells irritated by adelgid feeding in the cortical tissues of the bud base) may cause death of the young adelgids (Rohfritsch, 1981). There is evidence that resistance is heritable, and that Norwegian provenances are less susceptible to A. abietis attack than German provenances (Walberg, 1980; Mattson et al., 1999).

Host-resistance studies have been carried out in Sweden (Bjorkman, 2000), France (Rohfritsch, 1981; Mattson et al., 1999) and Norway (Walberg, 1980); also in Canada (British Colombia) by Mattson et al. (1999), and in the USA: Maine (Canavera and DiGennaro, 1979) and Ohio (Thielges and Campbell, 1971; Tija, 1973).

Biological Control

There are no records in the literature of any successful biological control programmes against A. abietis. Mitchell and Maksymov (1977) remarked that the gall may be an unexploited environment for biological control agents against adelgid populations throughout the world.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


Impact

The lack of active dispersal between trees by A. abietis results in heavy infestations building up within the canopy of an infested tree over time (Carter, 1971), weakening the trees by removing large quantities of sap (Gaumont, 1978), resulting in tissue drying and growth retardation in Ukraine (Kolomoets, 1994). Production of numerous galls drains the resources of the host tree and galling weakens the branches, which may become distorted and snap in high winds (Carter, 1971).

In the UK, A. abietis is a regular problem, as the clusters of pineapple galls it forms disfigure the shoot growth of commercially grown Picea abies as Christmas trees (Carter, 1983); tree nurseries, amenity plantings and specimen trees may also be affected (Carter, 1975).

In Europe (where A. abietis is native), the insect causes sufficient damage to spruce forests to merit chemical control efforts in Poland (Jaskiewicz et al., 2002) and Italy (Marchetti, 2003). Also, population and host-resistance studies have been carried out in Sweden (Bjorkman and Larsson, 1999; Bjorkman, 2000), Switzerland (Fluckiger et al., 1999), France (Rohfritsch, 1981; Mattson et al., 1998), former Czechoslovakia (Novak and Mensik, 1982), Norway (Walberg, 1980) and Germany (Thalenhorst, 1974). In Italy, A. abietis is one of the commonest adelgid pests of conifers; it damages young trees in nurseries, new plantations and trees in parks and gardens (Covassi and Binazzi, 1981). Damage has been reported from Ukraine (Kolomoets, 1994) and France (Gaumont, 1978).

In northeastern America, A. abietis is a common pest of Norway and white spruce, justifying chemical control measures in the past in Ohio (Campbell and Balderston, 1972; Nielsen and Balderston, 1977), Connecticut (Schread, 1971) and Pennsylvania (Cameron et al., 1973). Studies on host resistance have been carried out in Canada (British Colombia) by Mattson et al. (1999) and in the USA: Maine (Canavera and DiGennaro, 1979) and Ohio (Thielges and Campbell, 1971; Tija, 1973).

In West Virginia, USA, a pathogen causing twig necrosis of dominant and co-dominant Picea rubens was found in association with old galls of A. abietis in high-elevation stands (Audley and Skelly, 1994). A fungus, Phomopsis sp., was isolated from 14 of 43 (33%) dying adelgid-galled twigs. Subsequent seedling inoculations produced cankers in 14 of 48 (29%) attempts and the fungus was consistently re-isolated from symptomatic tissues.
 

Related treatment support
 
External factsheets
Maine Forest Service Insect and Disease Factsheets, Maine Department of Conservation, 2000, English language
Maine Forest Service Insect and Disease Factsheets, Maine Department of Conservation, 2000, English language
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