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Genus Myzus [Macrosiphini]

Rather small to medium-sized sometimes rather flattened green, brownish or shiny black aphids. The head has well-developed, rather convergent antennal tubercles, with little evidence of a median tubercle. The antennae in apterae appear rather curved. The dorsum is uniformly sclerotic, varying from nearly colourless to deep blackish sclerotic generally without a well-defined pattern (apart from Myzus omatus). The siphunculi are rather long, tapering, subcylindrical or clavate, usually distinctly flanged. The cauda is rather acutely triangular. The alates have a solid pigmented area occupying the mid-abdominal dorsum from segments 3 to 6, and further segmental bars on 7-8 and usually on 1-2.

Myzus are mainly associated with the rose family (Rosaceae), although the Myzus genus contains three highly polyphagous species which are very important pests. Myzus persicae is the most important known vector of potato virus diseases. It attacks a great variety of secondary hosts, on which it may overwinter viviparously, but overwinters as eggs on peach. Myzus ascalonicus and Myzus ornatus are highly polyphagous species attacking a range of species. Myzus cerasi causes extensive curling of the terminal leaves of cherry and produce much honeydew .

 

Myzus ascalonicus (Shallot aphid)

The apterae are quite small and shiny pale green to dirty yellow. The legs and antennae are pale apart from the ends of the antennae and the tarsi. The siphunculi are shorter than antennal segment III, distinctly swollen towards the apex, evenly coloured throughout and with only a very small flange. The cauda is roughly triangular in shape and short, about one third the length of the siphunculi. The body length of apterae is 1.1-2.2 mm.

 

The shallot aphid does not host alternate, but is extremely polyphagous, feeding on crops such as onions, shallots, strawberries, lettuce, brassicas and potatoes and many garden ornamentals. There is no sexual stage in the life cycle and no eggs are produced. Instead the aphid is cold-hardy and overwinters in glasshouses and sheltered areas. Numbers may build up even at low temperatures in winter and spring, with alates migrating to other crops up to mid-June.

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Myzus cerasi (Black cherry aphid)

Myzus cerasi is a small to medium sized aphid. Adult apterae on the primary host are shiny, very dark brown to black with a sclerotized dorsum. The siphunculi are cylindrical and black with the distal part slightly curved outward. The legs and antennae are yellowish and black and the cauda is brown. The body length of Myzus cerasi apterae is 1.8-2.6 mm.

 

Most populations of the black cherry-aphid host alternate and have a sexual stage in the life cycle. Host alternation is between cherry (Prunus cerasus, Prunus avium) as the primary host and bedstraws (Galium), eyebrights (Euphrasia) and speedwell (Veronica spp) as the secondary hosts. However, colonies can be found on cherry throughout the summer. Forms on Prunus cerasus and Prunus avium are sometimes considered as different subspecies or even species. On the primary host Myzus cerasi cause the leaves to curl and produce leaf nests (see second picture above). It is distributed throughout the palearctic zone and now almost cosmopolitan.

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Myzus hemerocallis (Day lily aphid)

Apterae of Myzus hemerocallis are described by Blackman & Eastop (1984)  as being pale yellowish green or yellowish white. We note that whilst immatures and freshly ecdysed adults are pale yellowish green, the mature wingless adults (see picture below) sometimes have an orange-brown hue anteriorly and posteriorly - which does not seem to have been noted in the literature. Myzus hemerocallis siphunculi are tapering or cylindrical on the distal half and are more than 2.5 times as long as the cauda.

 

Unlike many other Myzus species, the Myzus hemerocallis alate (see second picture above) does not have a black dorsal abdominal patch.

The day lily aphid attacks the basal (concealed) parts of young leaves of day lily (Hemerocallis) and lily of the Nile (Agapanthus). Myzus hemerocallis is a pest of East Asian origin, but is now also widely distributed on Hemerocallis in Australia, New Zealand, N&S America, Kenya, France and the UK. It was first recorded in Britain in the year 2000. Currently the UK Food and Environment Research Agency (FERA) has fourteen records of the species (ours is the 15th) - detected in England and Wales, mostly on Hemerocallis imported from the USA (pers. comm. Chris Malumphy). Rothamsted suction traps have picked up winged adult Myzus hemerocallis in July 2002 at Starcross in Devon, and at Writtle in Essex (pers. comm. Mark Taylor via Ed Baker).

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Myzus ligustri (Privet aphid)

The apterae of Myzus ligustri are shiny greenish-yellow. Their antennae and legs are pale, apart from the joints, which are brown. The siphunculi have their distal parts brownish black. The cauda is pale. The body length of Myzus ligustri apterae is 1.0-1.5 mm.

 

The privet aphid does not host alternate but spends all its life cycle on privet (Ligustrum ovalifolium, Ligustrum vulgare). Sexual forms are produced in November. Privet leaves are rolled longitudinally into narrow tubes and spotted with yellow. Myzus ligustri is found in Europe and has been introduced into North America.

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Myzus ornatus (Ornate aphid, Violet aphid)

The adult apterae of Myzus ornatus are somewhat dorso-ventrally flattened. The dorsum is sclerotic and granulate, dirty yellowish to yellowish green, marked with conspicuous dark green or brownish transverse intersegmental sclerites. The antennal tubercles are well developed with just a suggestion of a median frontal tubercle. The antennae are 0.5-0.6 times the body length. The siphunculi are cylindrical, slightly curved outwards and constricted below the flange. They are 2.1-2.7 times the length of the triangular cauda. Myzus ornatus is a very small aphid with a body length of only 1.0-1.7 mm.

 

The first picture above shows an apterous adult surrounded by her nymphs. The second picture above shows an apterous adult in the midst of a group of young Macrosiphum rosae The alate viviparous female has a large dark dorsal patch, not touching the marginal sclerites, with some spots and cross bands on other tergites.

The ornate aphid does not host alternate and is extremely polyphagous. It often occurs in mixed-species colonies, where it can be difficult to spot amongst other aphids. It is an important pest on crucifers, cucurbits and onions and also attacks peas, soybean, strawberry and many garden ornamentals, especially in glasshouses. It also feeds on some trees such as Catalpa and Prunus, often feeding away from the main veins. Sexual forms are extremely rare and nearly all reproduction is parthenogenetic. Myzus ornatus was first discovered in England in 1932 and within a few years spread throughout the world - definitely one of Britain's more successful exports!

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Myzus persicae (Peach-potato aphid)

The apterae of Myzus persicae are generally yellowish-green (see first picture below) but vary from whitish or pale yellowish green to mid-green, rose-pink or red (see second picture below). They are often darker in cold conditions. The antennae are 0.7-1.0 times the body length, reaching to the siphunculi. Their siphunculi are slightly swollen towards the darkened tips and are 1.9-2.5 times the lerngth of the rather pointed cauda. The body length of Myzus persicae apterae is 1.2-2.3 mm.

 

The alate Myzus persicae has a solid pigmented area occupying the mid-abdominal dorsum from segments 3 to 6, as well as further bars on adjoining segments.

The peach-potato aphid does host alternate where the primary host - peach (Prunus persica) occurs. Eggs are laid on the primary host and spring colonies curl the young leaves. However, most of the population overwinters as mobile stages on herbaceous plants and brassicas. Myzus persicae is a major pest on its summer hosts including potatoes, sugar beet, lettuce, brassicas and legumes, mainly because it transmits a number of important plant viruses. Whilst Myzus persicae is a polyphagous generalist, the subspecies Myzus persicae nicotianae is a tobacco specialist.

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Myzus varians (Peach-clematis aphid)

Adult apterae of Myzus varians (see first picture below) are pale green or yellow-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. The ends of the siphunculi are black. Apterae on peach have the distal half or more of the siphunculi black, whereas those on clematis (as pictured here) have only the tips of the siphunculi black. The body length of the adult aptera is 1.7-2.3 mm.

 

The alate is very dark, with a large dorsal abdominal black patch (second picture above shows a developing fourth instar alate).

Myzus varians host alternates from Prunus persica (peach) to various Clematis species. 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 has subsequently spread to south west Asia where it is a serious pest of peaches.

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).

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