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Wahlgreniella nervata

Strawberry tree aphid

On this page: Identification & Distribution Biology & Ecology Other aphids on the same host Damage & Control

Identification & Distribution:

Wahlgreniella nervata apterae are spindle-shaped and yellowish or green (see below first picture ssp. arbuti & second picture ssp. nervata), sometimes mottled with reddish anteriorly (see below third picture). The antennal tubercles have their inner faces divergent and smooth. The femora do not have distinctly dark apices. Their siphunculi are slightly swollen rather symmetrically about their inner and outer faces, and have dark tips and a small flange.

Winged viviparae of Wahlgreniella nervata (not pictured) have a green abdomen with variably developed dark dorsal cross-bands, sometimes coalescing into an irregular patch.

The clarified slide mounts below are of adult viviparous female Wahlgreniella nervata nervata : wingless, and winged.

Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.

There are two subspecies (or divergent clones of the same species):

  1. Wahlgreniella nervata arbuti
    The apical segment of the rostrum (RIV+V) is longer than 1.3 times the length of segment two of the hind tarsus (HTII). The apterae in spring and summer are shining yellowish green. Aptera body length is 2.1-2.9 mm. On Arbutus (strawberry tree) and Arctostaphylos (manzanitas and bearberries), but in culture able to live on rose.
  2. Wahlgreniella nervata nervata
    RIV+V is shorter than 1.3 times the length of HTII. The apterae in spring and summer are pale green to dull mid-green. Aptera body length is 1.4-2.5 mm. This subspecies lives on rose (Rosa) but, in culture, able to live on strawberry tree.

In North America Wahlgreniella nervata apparently host alternates between rose (Rosa) and ericaceous plants (mainly strawberry tree, Arbutus), although the host alternation has not yet been experimentally verified. Parthenogenetic populations on both Rosa and Arbutus have been introduced into Europe, and are treated as separate subspecies. Wahlgreniella nervata is considered an invasive species, having been reported from Damask rose in Turkey (Barjadze, 2011), and as a new pest of rose in India (Joshi et al., 2014).

 

Biology & Ecology:

We have found both of the subspecies of Wahlgreniella nervata in Britain. The immatures shown below are of Wahlgreniella nervata nervata and were living on rose.

These immatures are of Wahlgreniella nervata arbuti and were living on strawberry tree.

Predators had found the colony on strawberry tree and there were several syrphid larvae present (see picture below).

 

Parasitoids had also been active (see picture of mummy below), but we were unable to determine the identity of the primary parasitoid, as only hyperparasitoids emerged.

Sampling over three years has confirmed that that the strawberry tree population continues to reproduce parthenogenetically through the winter, at least during mild weather. The picture below shows some immatures found on January 31st 2017 in the midst of winter.

A few days later some of these had matured to adult apterae.

 

Other aphids on same host:

 

Damage and control

The strawberry tree is grown as an ornamental tree, and the fruits may be used to make preserves.

The strawberry tree aphid is one of the very few pests of this tree, but there is little evidence it causes serious damage.

Acknowledgements

We especially thank Middle Farm, East Sussex for their kind assistance, and permission to sample.

Our particular thanks to Roger Blackman for images of his clarified slide mounts.

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

  • Barjadze, S. et al. (2014). Note on Wahlgreniella nervata (Gillette, 1908) (Hemiptera: Aphididae): a new pest of Damask rose in Turkey. Phytoparasitica 39 (3), 239-241. Abstract

  • Blackman, R.L. (2010). Aphids - Aphidinae (Macrosiphini). Handbooks for the identification of British insects 2(7). Royal Entomological Society, London.

  • Blackman, R.L. & Eastop, V.F. (1984). Aphids on the world's crops: an identification guide. J. Wiley & Sons, Chichester, UK.

  • Joshi, S. et al. (2014). Wahlgreniella nervata (Hemiptera: Aphididae), a new pest of rose in India. Florida Entomologist 97 (1), 162-167. Full text