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Aphidinae : Myzus varians
 

 

Identification & Distribution

Spring populations of Myzus varians cause characteristic rolling and reddening of the leaves of their primary host, peach trees (see first picture below). Adult apterae are pale green or yellow-green or orange-green with conspicuously banded antennae. The terminal process of the antenna is 3.9-5.5 times longer than the base of the sixth antennal segment. On the primary host the distal halves of their siphunculi are conspicuously black (see second picture below). On the secondary host (clematis) only the tips of the siphunculi are black (see third picture below). The body length of the adult Myzus varians aptera is 1.7-2.3 mm.

First two images above copyright Alan Outen, all rights reserved.

The clarified slide mounts below are of adult viviparous female Myzus varians. The first micrograph shows an adult aptera from the primary host, the second shows an adult aptera from the secondary host (note the difference in appearance of the siphunculi). The third micrograph shows the antenna of an aptera (note the darkened distal portions of segments 3, 4, 5, 6-base and 6-tip).

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

The Myzus varians alate (see first picture below) is very dark, with a large rather fragmented dorsal abdominal black patch. The second picture below shows a clarified slide mount of an alate female.

Second image above by permission of Roger Blackman, copyright AWP all rights reserved.

Myzus varians host alternates from Prunus persica (peach) to various Clematis species, although in warmer climates anholocyclic populations may persist on either host. Spring populations cause longitudinal rolling and reddening of the leaves of peach trees. On Clematis they can build up damaging populations. The species is native to eastern Asia, but has long been found in North America. It was first recorded in Europe in 1947, and in Britain in the early 1970s. Myzus varians has subsequently spread to south west Asia where it is a serious pest of peaches.

 

Biology & Ecology

Life cycle

The overwintering eggs on peach hatch in spring. The fundatrix feeds on the young leaves inducing pseudogalls by very compact longitudinal rolling of the young leaves. Within the shelter of the pseudogall, the fundatrix produces numerous offspring (see first picture below). First and second instars are usually green but older instars often take on an orange-reddish hue (see second picture below).

Both images above copyright Alan Outen, all rights reserved.

Most of the offspring of the fundatrix develop to adult apterae (see picture below).

Image above copyright Alan Outen, all rights reserved.

In subsequent generations an increasing proportion develop to alatae some of which migrate to the secondary host clematis, although populations may persist on pear throughout the growing season (Alma & Arzone, 1983). There is also some evidence from the United States that populations may overwinter on clematis presumably anholocyclically. We have found large populations on clematis by April and May even producing alatae as early as May 2nd (see pictures below of immature alate and colony with adult alate).

The picture below shows an adult apterous vivivipara of the pale green form on clematis.

In autumn oviparae and winged males develop on peach, and after mating the oviparae deposit overwintering eggs on the stems of peach.

Interspecific competition / association

As far as we know, the pseudogall on peach is not commonly used by other aphid species, such as happens with other gall causers. We have, however, found mixed aphid species colonies on clematis (see picture below).

We can see above immatures of Myzus varians (pale green with banded antennae) together with an adult and immature of Aphis vitalbae (dark green with dark-tipped antennae) feeding on wild clematis (Clematis vitalba). Both these species are invasive to Britain. Aphis vitalbae is a southern European species that has expanded its range in recent years probably in response to climate change. Myzus varians is native to east Asia and was probably introduced to both North America and Europe through the plant trade. The yellow form of Aphis vitalbae could be confused with Myzus varians but for the antennae which are banded in Myzus varians and dark-tipped in Aphid vitalbae.

Natural enemies

INRA report four species of parasitoids as attacking Myzus varians: Aphidius colemani, Aphidius matricariae, Ephedrus plagiator and Praon volucre. We have found a few mummies of parasitized aphids (see picture below) on clematis. They most resemble the mummies produced by Aphidius colemani species, but could be one of several other Aphidius species.

Zeqiri & Uka (2018) reported a number of predators attacking Myzus varians namely the coccinellids Adalia bipunctata and Coccinella septempunctata, the syrphids Episyrphus balteatus, Syrphus ribesii and Syrphus vitripennis, and the chrysopid Chrysopa vulgaris. We have found the coccinellid Propylea quattuordecimpunctata predating Myzus varians (see picture below of rare orange form).

There were also some coccinellid larvae present (species unidentified).

 

Other aphids on same host

Primary hosts

Myzus varians has been recorded from at least 5 Prunus species (Prunus davidiana, Prunus glandulosa, Prunus persica, Prunus pumila, Prunus salicina).

Blackman & Eastop list 24 species of aphid as feeding on peach (Prunus persica) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 16 as occurring in Britain (Show British list).

Secondary hosts

Myzus varians has been recorded from 14 Clematis species.

Blackman & Eastop list 23 species of aphid as feeding on clematis (Clematis) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 9 as occurring in Britain (Show British list).

The only aphid recorded on Clematis armandii (third image, top of page) is Myzus varians.

 

Damage and control

Myzus varians can cause significant direct damage to peach by inducing the young leaves to form longitudinally rolled pseudogalls so reducing the photosynthetic capacity of the tree. It is also an efficient vector of the plum pox virus (PPV-M), the causative agent of Sharka disease in peaches.

Arzone (1979) described the status of Myzus varians as a pest of peach in Italy soon after the species was first reported in Europe when the infestation was spreading rapidly. The secondary host in the area was found to be Clematis alba which was present in the immediate vicinity of some orchards. Winter eggs were laid in the bark in natural cracks, damaged parts caused by hail or in oviposition slits made by the treehopper Ceresa bubalus. For control of the pest, spray treatments were recommended against the eggs in winter and against fundatrices and their offspring in spring. Of the eight aphid species found on peach, Andreev & Vasilev (2017) found Myzus persicae and Myzus varians were the most important pests in Bulgaria due to their wide distribution and high population density.

Manachini et al (2004) note that Sharka disease is one of the most important diseases of stone fruits in Europe. Their results confirmed transmission of PPV from peach to Clematis vitalba by alates of Myzus varians and also established that Clematis vitalba is a suitable alternative host for PPV-M virus serotytpe.

Penvern et al. (2010) compared various strategies for protection of peach orchards from aphids, evaluating them in terms of efficiency of control and impact on aphid natural enemies. Protection methods were identified through semi-open interviews and peach orchard pesticide records from 19 organic and conventional fruit farms in south-eastern France. Brachycaudus schwartzi and Myzus varians were the most frequently encountered aphid species, but the structures of the aphid communities were affected by protection strategies. The strategies dominated by chemical treatments gave the most effective control but with adverse effects on predators, whereas the other two mostly carried out by organic farmers gave less effective control but were less detrimental to biodiversity conservation.

Acknowledgements

We are grateful to Alan Outen (Bedfordshire Invertebrate Group) for some of the images above.

Our thanks also 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

  • Alma, A. & Arzone, A. (1983). Unpublished findings on the heterogonic cycle of Myzus varians Dav. pp 431-436 In: Atti XIII Congresso Nazionale Italiano di Entomologia Abstract

  • Andreev, R. & Vasilev, P. (2017). Aphids (Hemiptera: Aphididae) on peach trees in Bulgaria. Agricultural Sciences 9 (22), 29-36. Full text

  • Arzone, A. (1979). Afide di attualita su pesco: Myzus varians Davidson. Informatore Filopatologico 29 (8), 3-6.

  • Manachini, B. et al. (2004). On the transmissibility of PPV by Myzus varians Davidson (Homoptera:Aphididae) to Clematis vitalba L. (Ranuculaceae). Bull. OILB/SROP 27, 25-28. Full text

  • Penvern, S. et al. (2010). Peach orchard protection strategies and aphid communities: Towards an integrated agroecosystem approach. Crop Protection 29 (10), 1148-1156. Full text

  • Zeqiri, A. & Uka, R. (2018). Status of natural enemies of aphids and coccids insect pests in stone fruit trees in Tirana region, Albania. European Academic Research 6 (6), 2953-2959. Full text