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Aphids on apple

Blackman & Eastop list about 45 species of aphid  which feed on apples worldwide, mostly in the genera Aphis,  Dysaphis,  Eriosoma,  Ovatus  and Rhopalosiphum.  Of those aphid species, Baker (2015)  lists 11 as occurring in Britain: Aphis pomi,  Dysaphis anthrisci, Dysaphis brancoi, Dysaphis devecta,  Dysaphis chaerophylli, Dysaphis plantaginea,  Eriosoma lanigerum,  Macrosiphum euphorbiae,  Myzus persicae,  Ovatus crataegarius,  and Rhopalosiphum oxyacanthae.  About six of those species are commonly encountered on the orchard apple (Malus domestica) and crab apple (Malus sylvestris).

The species below are those we have found most frequently, listed in rough order of abundance. Assistance on distinguishing the two species of apple is given below. 

 

Aphis pomi (Apple aphid)

The aptera (below first) is bright apple green or yellow green and is not wax-powdered. The abdominal dorsum is pale and membranous usually without dark bands or sclerites. The siphunculi and cauda are conspicuously blackish. The body length of apterae is 1.2-2.2 mm. The alates have some variably developed dorsal bands. Colonies are often attended by ants (below second).

 

The apple aphid does not host alternate. It feeds on Apple (Malus spp.) and related plants including pear (Pyrus), hawthorn (Crataegus), and Cotoneaster. It is distributed throughout Europe, north Africa, Asia eastwards to India and Pakistan, and North America.

 

Rhopalosiphum oxyacanthae (= insertum) (Apple-Grass Aphid)

The apterae on apple are small elongate-oval light green to yellow-green aphids They have fairly well-marked dark green stripes down the centre of the back and along each side. The frontal head tubercles are low, with the median tubercle about the same height as the antennal tubercles. The siphunculi are of moderate length - about one tenth as long as the body - and pale with dusky tips. The 5-segemented antennae are about a third the length of the body. The winged viviparae have blackish head, thorax and siphunculi and a green abdomen with some brown plates and pigmentation. The body length of apterae on apple is 2.1-2.6 mm.

 

The apple-grass aphid host alternates between Apple and related species in the Rosaceae: and the roots of various Grasses (Poaceae). It has a sexual stage in its life cycle with eggs laid on Apple. The apple - grass aphid is found in Europe and Japan.

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Dysaphis plantaginea (Rosy apple aphid)

A medium-sized globe-shaped aphid which is purplish-olive-green to mauve and covered with a whitish wax pubescence (below first). The antennae of apterae are at least as long as distance from the frons to the base of the siphunculi. The aptera is without pigmentation on the abdominal tergites anterior to the siphunculi (these two characteristics enable one to differentiate Dysaphis plantaginea from members of the Dysaphis anthrisci / devecta group, which have shorter antennae and dorsal pigmentation spots anterior to the siphunculi). The siphunculi are quite long compared to other Dysaphis species, blackish brown and tapered with flanged tips. The cauda is dark, short and triangular. The body length of the aptera is 2.1-2.6 mm. Colonies are often attended by ants (below second).

 

The rosy apple aphid host lives in spring on apple (Malus spp.) where it forms yellowish crumpled leaf galls. (Spring generations of the Dysaphis anthrisci / devecta group roll and redden the lateral margins of leaves of apple.) Aphids remain on apple until mid-summer by which time attacked shoots are stunted and twisted. Fruits from infested shoots are small and malformed. Alates then migrate to the secondary host plantain (Plantago) where they form colonies along the veins. The species occurs in Europe, Africa, much of Asia and North and South America.

 

Ovatus crataegarius (Hawthorn - mint aphid)

The aptera of the hawthorn-mint aphid (below first|) is yellow-green to apple-green, sometimes mottled with darker green markings. The antennae are curved and about 1.2-1.5 times the length of the body. The pale siphunculi are 1.7-2.6 times as long as the tongue-shaped cauda. The body length of apterae ranges from 1.5-2.0 mm. The colony shown (below second) is on young hawthorn leaves.

 

The hawthorn - mint aphid host alternates from hawthorn and apple (Rosaceae) to mint (Mentha, Lamiaceae) where it can reach pest status. In warmer climates it may overwinter viviparously near the ground.

 

Eriosoma lanigerum (Woolly apple aphid)

Wingless females on the secondary host are purple, red or brown and are covered in thick white flocculent wax. This is produced by distinct wax glands on the head and along the thorax and abdomen. The six segmented antennae are 0.17-0.24 times the length of the body. The body length of apterae is 1.2-2.6 mm. Winged viviparous females (fourth instar alatiform nymphs shown in the picture below left) are reddish brown with very small wax glands and consequently much less wax. Their antennae are about 0.4 times the length of the body.

 

The wingless females live in dense colonies (see picture above right) on the roots, trunk or branches of the (secondary) host apple (Malus) and related species, often causing deformation and cancer-like swellings of bark. Sexual forms appear to have been lost, and overwintering is in fissures on the lower part of the trunk and on the roots. It is a pest of apple throughout the world.

 

Species of apple

Worldwide, the Malus genus comprises perhaps 30-55 species. The two most common apple species in Britain have pedicels that are shorter than the mature fruit.

  1. Malus sylvestris (crab apple) is native to UK. It has pinkish-white flowers. Its ripe fruits are 2-2.5 cm in diameter, usually longer than their pedicel, and green or yellow-green with some red on the side exposed to the sun. The ripe fruits tend to be sour. The branches are thorny. The mature leaves, sepals, buds, shoots and the calyx are all glabrous - and the calx remains on ripe fruit. Malus sylvestris is rarer than Malus domestica, and prefers shady conditions.

  2. Malus pumila (=Malus domestica, orchard apple, cultivated apple) is introduced but naturalized. It resembes Malus sylvestris, but generally has pinker flowers, may grow higher, and bears fruit over 5 cm in diameter whose colour, when mature, is cultivar-dependent. Its branches lack thorns. The mature shoots, pedicels, leaf undersides, and the outside of the calyx are hairy - and the calx remains on ripe fruit.

    Whilst Malus pumila hybridises readily, Malus sylvestris x Malus pumila is not known in UK. However self-seeded Malus pumila, which yield small, yellowish, sour fruit, are often confused with Malus sylvestris.

    Below are mature and immature crab apples (first image), orchard apple immature fruit (second) and mature fruit (third image) showing the pedicel.

   

First image by Wehha  - Own work, CC BY-SA 3.0,  Wikimedia commons 

Stace (2010)  lists five other introduced species. These have pedicels at least as long as their mature fruit.

Two species are considered naturalized in UK.

  1. Malus x purpurea (purple crab) is a hybrid created by crossing Malus xatrosanguinea and Malus niedzwetskyana. It does not have thorny branches. Its leaves are purplish-green to purple, and hairy. The petals are deep pink. The fruit are 1.5-3.5cm in diameter, dull reddish-purple and roughly spherical.

  2. Malus hupehensis (Hupeh crab) is not thorny. Its leaves are sparsely hairy. The mature petals are white. The fruit are 1cm, red and spherical, on a 1-3cm pedicel.

The remainder are described as "street trees", and seldom self-seed.

  • Malus baccata (Siberian crab) has white petals. The leaf undersides are hairy. The fruits are red to yellow, and 1cm or less. The calyx is glabrous, and may be retained or lost - see Flora of China. 

  • Malus floribunda (Japanese crab) has pink and white petals. The fruits are >1cm and red or yellow. The calyx is deciduous, but its outside is hairy - see NY MFP. 

  • Malus x robusta (Malus baccata x Malus prunifolia) (cherry crab) has white flowers which open from pink buds, and usually have orange or yellow 1-3cm spherical fruit.

There are undoubtedly other apple species, hybrids and cultivars in UK gardens, parks and streets. Below are mature fruit of an unidentified specimen, possibly a hybrid of Malus floribunda or Malus baccata.

Acknowledgements

We especially thank Tudor Ursu, Institute of Biological Research, Romania  for much helpful assistance on the apple-species identification.

We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994)  and Blackman & Eastop (2006)  supplemented with Blackman (1974) , Stroyan (1977) , Stroyan (1984) , Blackman & Eastop (1984) , Heie (1980-1995) , Dixon & Thieme (2007)  and Blackman (2010) . We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure  provided by Blackman & Eastop (2006).

Useful weblinks 

References

  •  Blackman, R.L. & Eastop, V.F. Aphids on the world's plants An online identification and information guide. Full text 

  •  Stace, C. (2010). New Flora of the British Isles. Cambridge University Press. ISBN: 9781139486491 Google books