Plant Parasites of Europe

leafminers, galls and fungi

gallers on Prunus

Dichotomous table for gallers on Prunus

by Hans Roskam

1a On above-ground parts => 3

1b On roots or root collar => 2

2a Roots with small elongated or nodule-shaped swellings. P. domestica, persica: cf. Meloidogyne hapla

2b Pea-, walnut- up to even fist-size proliferations on root collar, also on basal root- or stem parts. P. amygdalus, armeniaca, avium, cerasifera, domestica, insititia, mahaleb, persica: Agrobacterium tumefaciens

3a On flowers or fruits => 52

3b On vegetative parts => 4

4a Malformations not bush- or broom-like => 7

4b Conspicuous witches’ brooms or mistletoe gall => 5

5a Witches’ brooms => 6

5b Upper stem parts or older branches with spindle-, club-, or nodule-shaped swellings bearing: Viscum album

6a Conspicuous, occasionally even up to 3 m large, perennial witches’ brooms. Basal part of twigs distinctly swollen, deflected downwards and then growing steeply erect. Leaves variously swollen, bladder-like, leaf blades hardly thickened; on underside usually covered with a grey-white pubescence of asci when the fungus has matured. On P. avium, less frequent on P. cerasus, fruticosa, and some close foreign cherries: Taphrina wiesneri

6b Similar, usually less substantial, only exceptionally up to 1 m large, perennial witches’ brooms on P. cerasifera, domestica, insititia, spinosa, ussuriensis: Taphrina pruni

= Witches’ brooms also occur occasionally on species belonging to the subgen. Euprunus, especially on P. spinosa, without verified causers

6c On P. armeniaca: Taphrina armeniacae

= Taphrina insititiae is also able to cause witches’ brooms on Prunus species. The mycelium develops intercellularly in the branches and leaves

7a On shoot ends, buds or on leaves => 16

7b On younger or older shoot axis => 8

8a On green shoots or thin twigs => 10

8b On stronger stem parts => 9

9a Bark with localised thickenings, cancer-like proliferations and exuding gum. Prunus spp.: Enarmonia formosana

= From similar cancer-like bark necrosis has also been described the sac fungus Phomopsis prunorum

= Cancers on P. avium are also caused by viruses.

9b Closed, or later on opening, variously shaped Nectria cancers, which often result in stronger bending of younger stems, sometimes occurring on older stems in large numbers. P. serotina: Neonectria ditissima

9c Smooth bark of variously aged stems with small irregular rimmed depressions, which contain a scale, up to 1.6 mm long. P. avium, domestica, dulcis, persica: Epidiaspis leperii

9d Woolly apple aphid on cancers of stem and branches. P. domestica: Eriosoma lanigerum

10a On annual, still green shoots => 12

10b On thin, wooden, two- to a few years old twigs => 11

11a Rotund galls, up to about 2 mm long, at first green, then often dark-red, eventually ± browned, single or usually clustered on veins of bud scales or leaves of 2 years old shoots. P. amygdalus, domestica, insititia, armeniaca: Acalitus phloeocoptes

11b Similar galls on P. spinosa: Acalitus prunispinosae

11c Single or several globular to irregular oblong proliferations, mainly one-sided with cracked or rugose, often gum covered surface; on two- to a few years old twigs. P. armeniaca, persica: Stigmina carpophila

11d Rotund to spindle-shaped swelling often at base of side stems. Inside is a yellow lepidopteran caterpillar with contrasting head. P. padus: Argyresthia semifusca

12a Stem with cup-shaped, nodular or bulge-like malformations > 13

12b Shoot tip covered by dense, white mycelium, variously extending to leaves. P. persica: Podosphaera pannosa

13a Malformations smaller than 5 mm => 14

13b Malformations larger than 5 mm, elongate spindle-shaped swellings => 15

14a Green axis with small, almost cup-shaped protuberances. P. padus, avium, communis, domestica, dulcis, mahaleb, spinosa: Phyllocoptes eupadi

14b Small nodular protuberances, often with several along the axis. Prunus spp.: Stephanitis pyri

15a Extensive swellings, up to 35 mm long and 7 mm wide, yellow-green, mainly one-sided, ± curved bulge-like on P. padus: Taphrina padi

15b On P. domestica, spinosa. Similar but smaller swellings of axial parts: Taphrina pruni

15c Similar malformations on twigs of P. persica: Taphrina deformans

16a On shoot tips or leaves => 18

16b On buds of woody or almost woody young shoots => 17

17a Bud transformed into a 4–5 mm long, acute, rotund or egg-shaped, thin-walled greenish, eventually browned gall, surrounded at base by several scales. Inner wall lined with mycelium. Containing a whitish, later on yellow-red larva. P. cerasifera, domestica, fruticosa, insititia, spinosa and relatives: Asphondylia pruniperda

17b Abnormal multiplication of buds; flowers and fruits do not develop. Attacks result in the death of trees. P. dulcis, persica: Odinadiplosis amygdali

17c Discoloured swellings of stunted shoot buds up to 15 mm long. P. padus: “Anthonomus bicinctus”

17d Bud, with involvement of neighbouring stem parts, strongly swollen; galls inside fleshy. P. padus: Taphrina padi

17e Similar malformations of buds. P. spinosa: Taphrina pruni

17f Similar malformations of buds. P. fruticosa: Taphrina wiesneri

17g Malformation of buds and leaves, caused by gall mites. P. armeniaca, cerasifera, persica: Eriophyes armeniacus

18a Local; or extensive malformations on single leaves or also on many, mainly terminal leaves => 21

18b Galls on shoot tips => 19

19a Axis shortened, leaves bunched together, rolled, uneven, ± rugose and cartilaginous => 20

19b Young leaves folded as in the buds, weakly swollen and pale-green. Galls at base sometimes partially bent outwards. Containing several white larvae. P. spinosa: Unidentified gall midge

20a On P. armeniaca, avium, cerasifera, domestica, fruticosa, insititia, spinosa: Dasineura tortrix

20b White larvae develop as inquilines in same galls. P. domestica, insititia, spinosa: Dasineura sodalis

21a Various malformations caused by aphids => 39

21b Different malformations caused by other causers => 22

22a Leaf blade ± browned or curled and curved inwards, caused by mites, spittlebugs or fungi => 36

22b Leaf blade with expanded marginal rolls, folded over, pouch-like, formation of hairs or small localised protuberances => 23

23a Leaf blade with pouch-like folds or with abnormal pubescence, or localised protuberances => 26

23b Leaf margin rolled or folded over => 24

24a More or less rugose and discoloured upward roll of leaf margin => 25

24b Leaf margin largely deflected downwards. Malformation ± sickle-shaped, at first green, then discoloured yellowish. P. domestica, spinosa: Pristiphora monogyniae

25a On P. armeniaca, avium, cerasifera, domestica, fruticosa, insititia, spinosa: Dasineura tortrix

25b In similar roll of leaf margin on same host larvae of the probably inquilinous: Dasineura sodalis

26a Leaf blade with abnormal pubescence or localised protuberances => 27

26b Border of leaf blade, or leaf blade at midrib or side vein with pouch-like, downward fold. Folds (10) 20–30 (50) mm long, thickened, cartilaginous, often reddened. Eventually with narrow, opening longitudinal slit on upper side. Usually containing several orange-yellow or -red larvae. P. domestica, fruticosa, insititia, spinosa, etc.: Putoniella pruni

27a Pouch-, horn-shaped or nodular galls, or small protuberances or warts => 32

27b Leaf blade with abnormal pubescence caused by gall mites => 28

28a Erinea situated along venation or in vein axils => 30

28b Felt pubescence mainly situated freely on the leaf blade => 29

29a On P. padus, mainly on underside of leaf blade, irregular, at first grey-white, then rust-brown, erinea. Hairs short, thick, club-shaped or irregular: Eriophyes distinguendus

29b Abnormal pubescence on underside of leaves of P. amygdalus, persica: Unidentified gall mite

= Whitish erinea on underside of leaf blade base are caused by Eriophyes similis, normally living in marginal pouch galls

30a Erinea mostly in vein axils, variously extending onto the leaf blade => 31

30b Felt-like pubescence along the veins. Hairs resembling the normal ones. P. insititia, spinosa: Unidentified gall mite

31a Vein axil with upward protuberances; abnormal pubescence on underside. P. spinosa: Unidentified gall mite

31b Small pustules on leaf blade. P. spinosa: Unidentified gall mite

31c Brown tufts of hairs in the vein axils on underside. P. padus: Unidentified gall mite

= The polyphagous thrips Taeniothrips inconsequens, especially frequent on fruit trees, causes small, yellowish, glabrous archings in the vein axils of P. padus

32a Galls pouch-, horn-shaped or globular, caused by gall mites => 34

32b Leaf blade with small upward protuberances or with warts on underside => 33

33a Leaf blade with small protuberances on upper side, with corresponding small depressions on underside, containing flat froth-covered nymphs. P. padus: Psylla sp.

33b Leaf blades on underside with multicellular warts, up to 1 mm across, golden-yellow; also occurring on basal petioles or stems of saplings. P. spinosa: Synchytrium aureum

34a Galls mainly situated in the middle part of the leaf blade or in the vein axils, normally protruding from upperside => 35

34b Elongated oval galls up to 2 mm across, pouch-shaped mainly at margin of leaf blade, protruding strongly on underside and closed, with a weakly pubescent, bulging rimmed slit on upperside. Galls sometimes inversely situated. Of various shape, depending on the substrate, exceptionally also occurring on petioles, on young stems and even on young fruits. P. armeniaca, domestica, fruticosa, insititia: Eriophyes similis

34c Similar galls in P. spinosa: Acalitus prunispinosae

34d Hairy galls on upperside of leaf along the midrib and the veins, on the underside a small opening. P. cerasus, domestica, mahaleb, padus, spinosa: Eriophyes homophyllus

35a Gall horn-shaped on upperside, up to about 4 mm long, with exit hole on underside. Exceptionally also occurring on underside, on petiole or on young stems. P. padus: Phyllocoptes eupadi

35b Rotund or club-shaped pouch galls, up to 2 mm long and 3 mm high with exit hole on underside. Occasionally in vein axils. Exceptionally also on petioles or on young stems. P. domestica, fruticosa, insititia, spinosa: Eriophyes prunianus

= The eriophyoid mite Eriophyes similisprunianus causes protruding pouch- or finger-like galls with a pilose opening on the lower surface of the leaf blade of P. domestica, cerasifera

= Leaves of P. avium, cerasus may have tubercular- to leaf-like proliferations “enations” between the veins. Leaves often rosette-like bunched together or developing as terminal leaf tufts. Leaf blades narrowed, reduced, ± thickened, chequered mosaic-like or mottled, disfigured at margins. Recorded as virus diseases, partly also on cherry and related Prunus species

= Also a “pock disease” is induced by a virus on P. domestica.

36a Leaf blade conspicuously undulately curled or swollen, bladder-like sometimes strongly curved => 37

36b Leaf blades ± converging upwards, markedly stunted, initially mottled yellow, then browned. Mites free-living mainly on the upperside. P. armeniaca, avium, cerasifera, cerasus, domestica, mahaleb, padus, persica, triloba, etc.: Aculus fockeui

37a Conspicuous curls or ± accentuated bladder-like swellings caused by fungi => 38

37b Terminal leaves of young shoots loosely rolled inwards or strongly deflected and twisted over their tops, densely crumpled at infestation site and often deep-green. Containing a froth-covered nymph. P. avium, cerasus, domestica, padus, etc.: Philaenus spumarius

38a Usually expanded parts of leaf blades swollen, bladder-like, curled, curved or ± twisted. Swellings pale green or often intense red, with fleshy thickened, brittle tissue. Stem sometimes stunted resulting in bushy aggregations of leaves. At maturity covered mainly on underside with whitish asci. P. persica: Taphrina deformans

38b Mainly in southern areas, also in GB, occur less conspicuous fleshy curls also on almond, P. amygdalus: Taphrina deformans

38c Conspicuous bladder-like galls on leaves of P. serotina; also the inflorescences may be heavily infested. Introduced from the Nearctic together with its host plant: Taphrina farlowii

38d Several leaves of developing buds are soon completely or partially ± swollen, bladder-like. Diseased leaf parts are hardly thickened, often lighter green than the healthy ones, occasionally reddened at margins. Characteristic symptoms, especially on partially infected leaves. Often on young long shoots all leaves are diseased; stems are ± elongated and thickened. At maturity of fungus the asci develop mainly on underside as an ash-grey covering. P. avium, cerasus, fruticosa: Taphrina wiesneri

38e Similar malformations lacking a reddening of diseased leaf blades. P. domestica, insititia, spinosa: Taphrina pruni

= Red midge larvae developing inside dry fruits of P. domestica containing the fungus Polystigma rubrum belong to the gall midge Dichodiplosis langeni

39a Malformation of single to several leaves on young shoots, which are not conspicuously stunted in development => 44

39b Malformation of many terminal leaves on shoots which are stunted in longitudinal growth => 40

40a Loose clusters at shoot tips => 41

40b Leaves on shoot tip often bunched together in large clusters. Leaf blades strongly curled, ± narrowly rolled inwards. P. avium, sometimes on P. serratula, yedoensis: Myzus cerasi subsp. pruniavium

41a On P. cerasus, spinosa, mahaleb => 42

41b On P. persica strong roll of the not discoloured, curled, sometimes bulging leaves, which are ± densely clustered, nest-like, on the shortened, partially swollen shoot tipL Brachycaudus schwartzi

41c Curled narrow leaf rolls of P. amygdalus, occasionally also of P. persica: Brachycaudus amygdalinus

42a On P. cerasus, spinosa => 43

42b On P. mahaleb. Several, ± stunted and disfigured leaves bunched together in loose clusters at shoot tips: Myzus lythri

43a On P. cerasus. Shoots slightly stunted, leaves weakly deflected, arched: Myzus cerasi

43b On P. spinosa. Leaves strongly curled and shoot tips densely bunched together. Aphids often occurring in masses: Brachycaudus prunicola

= Blackman (2010) furthermore distinguished the aphid Brachycaudus prunifex. Apterae are shiny dark green to black; body length 1.5‒2.4 mm. Colonies occur all-year-round on Prunus spinosa, in spring causing severe leaf curl and discoloration to new growth. There is also a record from P. cerasifera var. atropurpurea. Suggestions of a facultative host alternation to Tragopogon do not appear to be substantiated. Alate males have been collected in 9, but oviparae are not yet recorded. In GB (England, Wales), IRL, and northern F. This species has been synonymised previously with B. prunicola, which occurs on the same host throughout the rest of Eu and in C-As, but it can be distinguished from that species (and from B. schwartzi) by the longer hairs on the antennae and anterior abdominal tergite

44a Leaves with pronounced rolls and curls at margin => 50

44b Leaves only weakly rolled, swollen, bladder-like or slightly curled => 45

45a Aphids not- or only slightly powdered => 47

45b Aphids strongly to densely mealy powdered => 46

46a On P. armeniaca, domestica, insititia, spinosa. Aphid covered with dense mealy layer of wax. Leaves stunted, otherwise only weakly disfigured, slightly deflected, not curled, sometimes discoloured pale-green, occasionally marbled, later on strongly powdered by the exuded aphid wax: Hyalopterus pruni

46b On P. persica, amygdalus. Malformations and aphids similar to those of previous species: Hyalopterus amygdali

46c Aphids on the underside of the leaves, 2‒3 mm long, probably strongly resembling those of Hyalopterus amygdali. P. persica: Hyalopterus persikonus

47a Leaves only weakly swollen or arched, without conspicuous discolouration => 49

47b Leaf blade slightly to conspicuously rolled or arched, ± conspicuously discoloured or yellow spotted => 48

48a On P. padus. Fundatrices pale green; fundatrigeniae dark grey-green: Rhopalosiphum padi

48b Similar malformations causing yellow and red spots on the deflected bladder-like inflated leaves. P. padus: Myzus padellus

48c On P. persica, nana, serotina; variously shaped minor leaf archings or -rolls, which are ± brightened: Myzus persicae

48d Leaves of P. persica are tightly rolled longitudinally: Myzus varians

49a Aphid shining dark red to dark-brown or black. On P. domestica. Leaves slightly deflected, not rolled. Brachycaudus persicae subsp. semisubterraneus

49b Aphid pale green to yellowish green, rather shiny, with three darker green dorsal longitudinal stripes. On P. domestica, fruticosa, insititia, spinosa, mahaleb, ? padus, serotina, etc. Leaves only weakly arched. The apterous aphids inhabit the leaf underside, also the complete shoot: Phorodon humuli

50a On. P. domestica, spinosa and close cherries => 51

50b On P. mahaleb. Leaves in spring with yellowish discoloured, bladder-like-rugose rolls, with walls clearly thickened and ± brittle: Roepkea marchali

51a Aphid 0.9–2.0 mm long, usually pale-green; siphunculi pale, very short, 1/11 to 1/15 times body length. Tip of rostrum not reaching the metacoxae. Leaves narrowly rolled and strongly curled, shoots often ± leaning: Brachycaudus helichrysi

51b Aphid about 2.2 mm long, pale-green with dorsal cuticle sclerotic and often brownish, fundatrices brownish-red. Adults usually with dark pigmented back. Siphunculi mainly brown, 1/6 to 1/8 times body length in fundatrigeniae [viviparous parthenogenetic wingless female aphid produced by a fundatrix and giving rise to further wingless forms or to migrants]. Leaves in spring narrow and curled or rolled, converging, bleaching after departure of aphids. Shoots sometimes ± stunted. P. domestica, spinosa; sometimes P. avium. armeniaca: Brachycaudus cardui

51c Very closely related, and often mixed with foregoing: Brachycaudus cardui subsp. lateralis

52a Malformations on ovaries and fruits => 54

52b Malformations of flowers => 53

52c Abnormal multiplication of buds; flowers and fruits do not develop. Attacks result in the death of trees. P. dulcis, persica: Odinadiplosis amygdali

53a The slightly enlarged corolla remains in bud condition. Receptacle, ovary and base of stamens ± clearly swollen. Larvae jumping, single or several. P. domestica, mahaleb, spinosa: Contarinia pruniflorum

53b Flowers disfigured, unopened. The corolla, which soon dies, arches roof-like over generative parts and receptacle and sometimes regenerating tissue is eaten by yellowish, brown-headed, larvae. P. padus, also mahaleb, avium, etc.: Anthonomus humeralis

53c Flowers disfigured, unopened. P. spinosa: Anthonomus rufus

54a Ovary completely transformed into a tube-like, hollow gall => 56

54b Fruit with localised swellings or ovary galled, including other organs of flower bud or flower => 55

55a Localised pale-green hypertrophies on fruits, also ± reddish discoloured, usually rotund. P. persica: Taphrina deformans

55b Ovaries or young fruits, flowers, flower buds variously disfigured and swollen. P. cerasifera: Taphrina wiesneri

55c Midge larvae develop in fruits of P. cerasus which were damaged by puncture holes of the weevil Anthonomus rectirostris: Lasioptera cerasiphera

= The fruit fly Rhagoletis cerasi has been recorded from from cherries; introduced from N-Am is R. cingulata in fruits of P. serotina.

56a Fruit distinctly enlarged, hollow, at first pale green, then dark coloured. At maturity the fungus is covered with an expanded grey layer of asci. P. cerasifera, domestica, insititia, salicina, serotina, spinosa: Taphrina pruni

56b Ovaries or young fruits transformed into elongate tube-shaped, terminally acuminate, greenish galls, which are black and hollow after sporulating. P. padus: Taphrina padi

56c Similar galls on other hosts belonging to the subgenus Padus: Taphrina confusa

Last modified 24.viii.2020