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Aphids on hazel (Corylus)

Species Overview: 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. Only 2 of these aphid species are known to occur in Britain: Corylobium avellanae  and Myzocallis coryli.  We show both of these species below, the most common first. Please refer to Blackman & Eastop  for formal identification keys and further information on aphids found worldwide on hazel. Assistance on identifying hazel is given below. 

 

Myzocallis coryli (Small hazel aphid)

Winged adult viviparae are pale yellow to yellowish white. The antennae are ringed with black, and the terminal process is 2-3 times as long as the base of the last abdominal segment. The forewing has a black spot at the base of the pterostigma. The cauda is knobbed, and the siphunculi are small, truncate cones. The body length of Myzocallis coryli alates is 1.3-2.2 mm.

 

Myzocallis coryli lives on the undersides of leaves of hazel (Corylus species). As with Myzocallis carpini,  it may become abundant when its host is used for hedging. Where hazel trees are grown commercially for the hazelnut crop as in USA and Iran, Myzocallis coryli may be a serious pest. This was tackled in the USA by classical biological control - a parasitoid was introduced from overseas. 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)

Adult viviparae may be winged or wingless. Wingless viviparae (apterae) are yellowish-green often mottled with red spots. The antennae are pale with dark tips to the segments and black apices. The dorsum is granulate with numerous small cuticular structures and 6-8 low conical tubercles per segment, each with one or two long thick capitate hairs. The terminal process is more than 4.3 times longer than the base of the last antennal segment. The siphunculi are long, thin and tapering, 4.2-5.5 times the length of the cauda. The cauda is finger-shaped. The body length of apterae is 1.7-2.9 mm. Winged viviparae have a brown head and thorax and a green or brown abdomen with cross bands.

 

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. Corylobium avellanae feeds on the fast growing shoots, 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.

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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. 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 below second, infested with hazel aphids) is commonly grown in Britain as an ornamental.

 

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 

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