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Strawberry tree aphidOn 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 sometimes mottled with reddish anteriorly . Their antennal tubercles have smooth divergent inner faces. 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 (cf. Macrosiphum euphorbiae and Macrosiphum rosae on rose, and cf. Aulacorthum solani on Arbutus, all of which have tapering, non-swollen siphunculi). The first two images below show Wahlgreniella nervata ssp. arbuti from strawberry tree (Arbutus). The second three images show Wahlgreniella nervata ssp. nervata from rose (Rosa).
Winged viviparae of Wahlgreniella nervata (see third picture above) have a green abdomen with variably developed dark dorsal cross-bands, sometimes coalescing into an irregular patch.
There are two subspecies (or divergent clones of the same species):
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 apparently living parthenogenetically on their respective hosts.
The immatures below are of Wahlgreniella nervata arbuti and were living on their presumed secondary host, strawberry tree.
Sampling over several years has confirmed that that strawberry tree populations in Britain continue 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.
Then in in January 2019 we found flourishing populations of Wahlgreniella nervata nervata on roses in an East Sussex village.
In a Hampshire village, we also found Wahlgreniella on another host in the Rosaceae, namely Pyracantha (see picture below). As far as we can tell, Wahlgreniella nervata has not previously been recorded from Pyracantha.
Natural enemies take a heavy toll of Wahlgreniella nervata. Several syrphid larvae (see first picture below) were found preying on populations on strawberry tree.
Parasitoids had also been active (see second picture above), but we were unable to determine the identity of the primary parasitoid, as only hyperparasitoids emerged.
Another group of natural enemies is pathogenic fungi (e.g. Neozygites fresenii, Beauveria bassiana, Lecanicillium lecanii) which commonly attack and kill aphids. The fungus grows in the aphids haemolymph, soon killing the aphid.
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.