Plant Parasites of Europe

leafminers, galls and fungi

gallers on Picea

Dichotomous table for gallers on Picea

by Hans Roskam

1a On above-ground part => 2

1b Young stunted plants with main root atrophied, excessively branched; broom-like occurrence of shortened lateral rootlets at nodular places. P. abies: Unidentified root eelworm

2a On or in cones => 20

2b On vegetative parts => 3

2c Old resin masses contain gall midge larvae. P. abies: Cecidomyia magna

3a On buds or young shoots => 7

3b On perennial stem parts => 4

4a Club- or spindle-shaped swellings on branches or twigs => 6

4b Cancer-like malformations on stem or thicker branches => 5

5a Local, closed tumours on P. abies: Cause unknown – ? bacterium

5b Cancer-like rimmed wounds. P. abies, sitchensis: Neonectria fuckeliana

6a Branches with club- to spindle-shaped swellings, bearing Viscum album subsp. austriacum

6b Two-year or older twigs with swellings. P. abies: Unidentified lepidopteran

7a Galls on young shoots => 8

7b Buds distinctly swollen, remaining closed; mite gall. P. abies, etc.: ? Tricetacus sp.

7c Buds distinctly swollen, shoot often deformed, fungus gall. P. abies, engelmannii, pungens: Cucurbitaria piceae

8a Galls ± locally. Originate on young shoots, may partially persist on lignified ends of twigs after inducers have left; caused by animals => 9

8b Complete young shoot stunted by a perennial mycelium, becoming almost cone-like. Needles pale, shortened and thickened, ± divaricate, densely covered with erupting golden-yellow aecia. P. abies, glauca, mariana, pungens: Chrysomyxa woroninii

= Conspicuous bending of terminal shoots, infected by a rust fungus, have been attributed to Pucciniastrum areolatum

9a Galls develop with predominant involvement of needles => 10

9b Shoot axis usually with multi-chambered swelling, up to 9 mm long and 6 mm thick, especially of the bark; if severely infected ± stunted and bent. Each chamber with inner rough wall and containing a bright red larva. P. abies: Piceacecis abietiperda

10a Conspicuous, egg-shaped to elongate cylindrical galls originating from swelling of basal needle parts; caused by aphids => 11

10b Needles of unfurling shoots densely clustered, swollen at base, vitreous, ± yellowing, then often falling prematurely; many depressions in bark often accumulated, 6–9 mm long, 4–6 mm wide. Marked stunting of growth and conspicuous basal swelling in cases of severe infestation. Larvae 2–2.5 mm, bright red; often gregariously on opened scale whorls of severely stunted shoots. P. abies: Piceacecis abietiperda

11a Gall compact, usually less than 20 mm => 14

11b Cylindrical galls on only slightly shortened spring shoots, measuring several cm => 12

12a Gall chamber without cross walls, mutually connected; the gall scales not fused, spreading at maturity => 13

12b Gall chambers separated by cross walls; mainly at base of needles; hence the mutually closely fused gall scales are surmounted with long needles. Gall with 100–150 chambers, pale green to purple, 2.5–6 (10) cm long, often one-sided, crooked. Maturity from end 6 onwards. P. abies, alcoquiana, engelmannii, mariana, orientalis, pungens, sitchensis: Gilletteella cooleyi

12c Gall similar, however, the thickened bases of the needles are not fused to axis of shoot, forming a loose structure 1–4 cm long; galled needles pale green or yellowish; adelgids only partially enclosed in gall (adult has 4 pairs of spiracles) P. sitchensis: Pineus similis

13a Galls often crooked, barrel-shaped or short conical, up to about 5 cm long, with remains of needles of variable length; scales at surface rhomboidally arranged. Mature already at beginning June. Galls ± one-sided. Mainly on P. abies, also on P. glehnii, jezoensis, koraiensis, orientalis: Pineus cembrae

13b Galls similar to previous ones, but often smaller and thinner, sometimes ± egg-shaped, with narrow- or free scales, usually on all-sides. Mature end June, beginning July. Mainly on P. orientalis, also on P. jezoensis, pungens, torano: Pineus orientalis

14a Galls mainly terminally and on all-sides, strawberry- or pineapple-like; scales glabrous on outside, needles not- or only slightly protruding. Top of gall with or without tuft => 16

14b Gall predominantly one-sided at base of new shoots, surmounted by the ± stunted tip of shoot, often deflected from growth direction; ± egg-shaped, 15–25 (30) mm long, green. Scales usually very short pubescent, especially on the often reddened exit slits; provided with longer needles => 15

15a Galls mature mid to end June. Aphid host alternating. P. abies, occasionally on P. engelmannii, glauca, koraiensis, mariana, obovata, omorika, orientalis, pungens, sitchensis, smithiana: Sacchiphantes viridis

15b Similar galls, mainly mature in August. Aphid anholocyclic, no host alternation. P. abies and forms; occasionally on P. engelmannii, glauca, jezoensis, koyamae, mariana, omorika, orientalis, pungens, schrenkiana, sitchensis, smithiana:
Sacchiphantes abietis

16a Galls on P. abies and related species => 18

16b Galls only on P. orientalis => 17

17a Galls occupy the complete lateral shoots; ± blunt conical or cone-like, up to 22 mm long, chambered, strawberry-coloured, with minute, broad stub-shaped remains of needles but no tufts: Dreyfusia nordmannianae and/ or Dreyfusia merkeri

17b Galls similar, rotund to oblong, 6–20 x 8–15 mm, dull bluish to dark green, appearing weakly frosted, chambered. Develop from lateral shoots. Needles already in the galled buds, running ahead to the normal ones, transformed into narrow scales, ± fused at base. Tips of scales present only as remains of the regularly patterned, always tuft-less gall. Mature mid-June, beginning August: Dreyfusia prelli

18a Many galls ± egg-shaped, up to hazelnut size, pale green or whitish; scales partially provided with stub-shaped, distinctly recognisable needle stumps. Usually on top of shaded lanky lateral shoots, only exceptionally surmounted by a tuft of needles or a short atrophied shoot => 19

18b Galls on lateral buds of shoots wild strawberry-size, green, lacking tuft of needles. Scales on chambers fused, endings blunt-pyramidal. Picea spp.: Aphrastasia pectinatae

19a Aphid holocyclic, migrating to Larix decidua. Galls mature in June. Picea spp.: Adelges laricis

19b Galls similar, but mature in late-summer, August-October. Aphid especially biologically distinct from the previous one, anholocyclic, not alternating. P. abies, glauca, pungens, sitchensis: Adelges tardus

19c In similar galls, P. abies, live the following closely related species: Adelges tardoides and/ or, P. abies, glauca, jezoensis, mariana, pungens, sitchensis: Adelges lapponicus

20a On cone scales => 21

20b Seeds narrowed, oblong, acuminate, ± twisted and bent, discoloured. Wings of seed absent, seed often falling prematurely. Containing a yellow- to orange-red larva. P. abies, glauca, obovata, pungens: Plemeliella abietina

21a Warts bearing aecia at base of scales => 22

21b Inside the scales with 1–3 weak, ± wart-shaped, lighter swellings. Cone remains closed for a longer time. Each gall containing a single red larva, often many per cone. P. abies, glauca, omorika, pungens: Kaltenbachiola strobi

= Gall midge larvae develop inside the growing cones; damaging the basal part of the scale where the resin mass arise. P. abies: Resseliella ingrica

= The introduction of the N-Am gall midge Resseliella conicola on P. sitchensis has been reported

22a All scales of a cone at first covered on upper side with small warts caused by many, clustered, rough-walled, brown aecia, which become exposed, also in disfigured cones, during dry weather in summer. P. abies: Pucciniastrum areolatum

22b Outside of scale, usually at both sides of the midrib with two to several, swellings up to pea-size, sometimes with coalescing flat aecia. P. abies, engelmannii, glauca, mariana, obovata, pungens, rubens: Chrysomyxa pyrolae

22b Bisexual cones, observed in many Picea species are teratomata, and cannot be attributed to parasitic agents

Last modified 30.iii.2020