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Wahlgreniella nervata

Strawberry tree aphid

Identification & Distribution  Biology & Ecology  Damage & Control 

Identification & Distribution:

Wahlgreniella nervata apterae are spindle-shaped and yellowish or green (see below first picture), sometimes mottled with reddish anteriorly (see below second picture). The femora do not have distinctly dark apices. Their siphunculi are slightly swollen rather symmetrically about their inner and outer faces, they have dark tips and a small flange. Winged viviparae of Wahlgreniella nervata have a green abdomen with variably developed dark dorsal cross-bands, sometimes coalescing into an irregular patch.

There are two subspecies:

  • Wahlgreniella nervata arbuti
    The apical segment of the rostrum is longer than 1.3 times the length of segment two of the hind tarsus. The live aphids are pale-yellowish to pale yellowish green. On Arbutus (strawberry tree) and Arctostaphylos (manzanitas and bearberries).
  • Wahlgreniella nervata nervata
    The apical segment of the rostrum is shorter than 1.3 times the length of segment two of the hind tarsus. The live aphids are dull greenish, sometimes with dark reddish mottling anteriorly. On rose (Rosa), but in culture able to live on Arbutus.

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 only found Wahlgreniella nervata arbuti in UK once, but this may have more to do with the scarcity of strawberry trees than of the aphid. The nymphs shown below came from the same well established colony as the two apterae shown above.

Predators had found the colony 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.

 

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 the tree, but there is little evidence it causes serious damage.

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

  •  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 

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