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Aphids on hazel (Corylus)

On this page: Species lists Corylobium avellanae Myzocallis coryli

Aphids on hazel

Blackman & Eastop list about 17 species of aphids as feeding on hazel species worldwide, and provides formal identification keys for aphids on Corylus.

Baker (2015) lists 2 of these species as occurring in Britain: Corylobium avellanae and Myzocallis coryli.

We show both of these species below, the most common first. Assistance on identifying hazel is given below.

 

Myzocallis coryli (Small hazel aphid)

Immature morphs (see first picture below) have the body hairs, and sometimes a few basal antennal hairs, capitate and very much longer than those of adult viviparae. Winged adult viviparae of Myzocallis coryli (see second picture below) are pale yellow to yellowish white. Their antennae are ringed with black, with a terminal process that is 2.05-2.55 times the length of the basal part of antennal segment 6. The forewing has a black spot at the base of the pterostigma. The body length of Myzocallis coryli alates is 1.3-2.2 mm.

Myzocallis coryli oviparae are orange-yellow in colour, but when examined in alcohol they appear quite pale. Like the immatures, the oviparae have long capitate hairs.

The hazel aphid lives on the undersides of leaves of hazel (Corylus species). Like Myzocallis carpini, it may become abundant when its host is used for hedging. Myzocallis coryli is found in Europe, south-west Asia, north Africa, Japan, New Zealand, western North America, and South America.

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Corylobium avellanae (Large hazel aphid)

Corylobium avellanae apterae are usually yellowish-green (see first picture below) but in one form the aphid is mottled with red (see second picture below). The antennae are pale with dark tips to the segments and black apices. The dorsum is granulate with numerous small cuticular structures (best seen in picture in alcohol below) and 6-8 low conical tubercles per segment, each with one or two long thick capitate hairs. The siphunculi are long, thin and tapering, 4.2-5.5 times the length of the cauda. The body length of Corylobium avellanae apterae is 1.7-2.9 mm.

The alate (see first picture below) has the head and thorax brown, and the abdomen green or dirty red, with marginal sclerites, and intersegmental pleural sclerites or crossbars. The dorsum is not granulate. The body hairs are short and thin and not capitate. The siphunculi of the alate are 0.27-0.32 times the body length.

The large hazel aphid does not host alternate but spends its entire life cycle on hazel (Corylus avellana). Sexual forms occur in autumn and overwintering eggs are laid on hazel. It mainly feeds on the fast growing shoots and only rarely on the leaves, which are utilized by another species - Myzocallis coryli. Corylobium avellanae is distributed over most of Europe east to Ukraine and Russia and west Asia. It has recently been found in Canada.

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Species of hazel

We cover two species of hazel, common hazel (Corylus avellana) and the filbert (Corylus maxima). The common hazel is a shrub or small tree that is native to Europe and western Asia. The leaves are rounded and softly hairy and have a double serrate edge. Hazel is common in woods and hedgerows, and is also cultivated for the nuts.

 

Second image copyright Eric in SF [ CC BY-SA 3.0 ]

The filbert is a closely related species which is native to southeastern europe and southwestern Asia. The purple-leaved garden variety of filbert 'purpurea' (see second picture above) is commonly grown in Britain as an ornamental.

Variety 'purpurea' is quite often heavily infested with the small hazel aphid Myzocallis coryli as in the picture above.

Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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

  • Dixon, A.F.G. & Thieme, T. (2007). Aphids on deciduous trees. Naturalist's Handbooks 29. Richmond