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Aphids on pear

Blackman & Eastop list 53 species of aphid  as feeding on Common Pear (Pyrus communis) worldwide, and provide formal identification keys. Of those aphid species, Baker (2015)  lists 30 as occurring in Britain: Anuraphis catonii, Anuraphis farfarae, Anuraphis subterranea Aphis craccivora,  Aphis fabae,  Aphis gossypii,  Aphis pomi,  Aphis solanella, Aphis spiraecola, Aulacorthum solani,  Brachycaudus cardui,  Brachycaudus helichrysi,  Brachycaudus persicae,  Dysaphis plantaginea,  Dysaphis pyri,  Eriosoma americana, Eriosoma flavum, Eriosoma lanigerum,  Eriosoma lanuginosum, Eriosoma pyricola, Macrosiphum euphorbiae,  Macrosiphum rosae,  Melanaphis pyraria,  Myzus ornatus,  Myzus persicae,  Nearctaphis bakeri, Ovatus crataegarius,  Ovatus insitus, Rhopalosiphum oxyacanthae,  Rhopalosiphum padi. 
Bell et al. (2015)  (Appendix S2) have also published an "annotated checklist of aphids present in the UK". We discuss some of the reasons for the differences between Baker's and Bell's lists in our rare aphids page. 

A number of these are more commonly found on other hosts (such as Rhopalosiphum oxyacanthae and Eriosoma lanigerum on apple) or are polyphagous (Macrosiphum euphorbiae). The species listed below are roughly in order of how often we found them. Assistance on identifying pear is given below. 

 

Melanaphis pyraria

On the primay host, the dorsal abdomen has a solid dark sclerotic shield. The hairs on the antenna and dorsal body are minute, less than half the diameter of the third antennal segment. The siphunculi are about twice their basal width. Body length is 1.3-2.1 mm.

   

Our thanks to Giuseppe Cocuzza for correcting our original misidentification of this species.

Melanaphis pyraria host alternates from its primary host pear (Pyrus) to its secondary hosts grasses (including Arrhenatherum, Poa, Holcus and Triticum). On the primary host they roll the leaves transversely or diagonal to the mid-rib. The gall may become yellowed or reddened as shown above. They may be attended by ants. On the secondary host the appearance of the aphid differs according to the particular genus of grass colonized - reddish purple on Arrhenatherum, and yellowish on Poa and Triticum.

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Dysaphis plantaginea

Dysaphis plantaginea is 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. Dysaphis plantaginea siphunculi are quite long compared to other Dysaphis species, blackish brown and tapered with flanged tips. Their cauda is dark, short and triangular. The body length of the aptera is 2.1-2.6 mm. Dysaphis plantaginea colonies are often attended by ants (below second).

 

The rosy apple aphid host alternates from apple (Malus spp.) where it forms yellowish crumpled leaf galls to plantain (Plantago) where it forms colonies along the veins on the undersides of the leaves. Aphids remain on apple until mid-summer by which time attacked shoots are stunted and twisted. Fruits from infested shoots are small and malformed. Dysaphis plantaginea occurs in Europe, Africa, much of Asia and North and South America.

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Dysaphis pyri

Adult apterae of Dysaphis pyri medium to rather large globe-shaped, brownish-red to dark brown aphids. They are thickly coated with wax meal. The antennae are pale yellow near the base, but darker towards the apex. The first 5 abdominal tergites have a double row of small dark spots. Hemispherical marginal tubercles are usually present only on abdominal tergites 1-5. The siphunculi are black and perpendicular to the body. They are 3.4-4.1 times their diameter at midpoint, and longer than the cone-shaped cauda (cauda is visible in the first image above). The adult aptera has a body length of 2.1-3.2 mm. Immature Dysaphis pyri are a pale yellowish brown, with reddish suffusion around the bases of their siphunculi. Spring migrant alates have the abdomen brownish-red with a black dorsal patch. They have 23-36 secondary rhinaria on antennal segment III, 2-10 on segment IV and 0-1 on segment V.

 

The primary host of Dysaphis pyri is common pear (Pyrus communis). Leaves and shoots are yellowed and distorted to form a pseudogall (see second picture above). After about three generations on pear, alatae are produced which migrate to the secondary hosts. These are bedstraws, especially hedge bedstraw (Galium mollugo) and cleavers (Galium aparine) and sometimes squincywort (Asperula cynanchica). Dysaphis pyri may form colonies on the roots and prostrate stems, where it is attended by ants. Dysaphis pyri is found throughout Europe, the Middle East, North Africa and Central and South Asia, and has been introduced into the USA.

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Aphis pomi

The Aphis pomi aptera (below first) is bright apple green or yellow green and is not wax-powdered. The abdominal dorsum is pale and usually entirely membranous, although rarely a small sclerite or short bar may occur on the spine of tergite 5. The fused last two rostral segments are more than 120 μm in length and marginal tubercles are present on abdominal tergites 2-4 (the latter two characters distinguish Aphis pomi from the very similar invasive Aphis spiraecola). The siphunculi and cauda are conspicuously blackish. The cauda has 10-19 hairs (rarely less than 13). The body length of an adult aptera is 1.2-2.2 mm.

Aphis pomi alates (below second) have a black thorax. The alate abdomen is green, usually with 3 pairs of weakly pigmented black lateral circular spots on the anterior abdominal segments, and a semicircular spot in front of and behind each siphunculus.

 

The green apple aphid does not host alternate. It feeds in dense colonies on the young shoots and undersides of leaves of apple (Malus spp.) and related plants including pear (Pyrus), hawthorn (Crataegus), Sorbus and Cotoneaster, causing leaf curl. Colonies are often attended by ants. Sexual forms occur in autumn and after mating the females lay sometimes large egg masses on the twigs. It is generally common and is distributed throughout Europe, north Africa, Asia eastwards to India and Pakistan, and North America.

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Rhopalosiphum oxyacanthae

Rhopalosiphum oxyacanthae apterae (see first picture below) on apple are small light green to yellow-green aphids that are elongate-oval in shape. 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 frontal tubercle about the same height as the antennal tubercles. The siphunculi are quite short - about one tenth as long as the body - and pale with dusky tips. The 5-segmented antennae are about a third the length of the body. The body length of the adult aptera on the primary host is 2.1-2.6 mm. Winged Rhopalosiphum oxyacanthae viviparae (see second picture below) have blackish head, thorax and siphunculi and a green abdomen with some brown plates and pigmentation.

 

The apple-grass aphid host alternates between apple and related species (Rosaceae: Cotoneaster, Crataegus, Malus, Pyrus, Sorbus) and the roots of various Grasses (Poaceae). It has a sexual stage in its life cycle with eggs laid on apple. The first generation in March induces curling perpendicular to the mid-rib of the young leaves of the primary host. Apple-grass aphids may be attended by ants. Winged forms migrate in late May-June to the underground parts of various grasses, but colonies may persist into summer on primary hosts. Rhopalosiphum oxyacanthae is found in Europe and Japan.

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Species of pear

The European pear (Pyrus communis) is a medium sized tree native to central and eastern Europe and parts of Asia. The leaves are alternately arranged, from 2-12 cm long, oval or lanceolate and may be glossy green or densely silvery hairy. The flowers are white, 2-4 cm diameter and have five petals. The pear fruit is a pome and may be the classic pear shape or globose depending on variety.

Acknowledgements

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