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Genus Myzus [Macrosiphini]

Myzus are 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 ornatus). The siphunculi are rather long, tapering, subcylindrical or clavate (=club-shaped), 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)

Myzus ascalonicus apterae are shiny brownish green to dirty yellow (cf. Myzus cymbalariae which are not shiny). The antennal tubercles have their inner faces approximately parallel in dorsal view (cf. Myzus cymbalariae and Myzus persicae which have the inner faces convergent). Their legs and antennae are pale, apart from the ends of the antennae and the tarsi. The dorsum is strongly convex in comparison with related species (best seen in the first micrograph below). The siphunculi are shorter than antennal segment III, distinctly swollen towards the apex, evenly coloured throughout and with only a very small flange (cf. Myzus persicae which has siphunculi longer than antennal segment III and dark-tipped). The siphunculi have their narrowest part thinner than, or equal in width to, the hind tibia at midlength ( (cf. Myzus cymbalariae which has the narrowest part of the stem slightly thicker than the hind tibia at midlength). The cauda is roughly triangular in shape, and short: about one third the length of the siphunculi. The body length of Myzus ascalonicus apterae is 1.1-2.2 mm.

The alate Myzus ascalonicus (see second picture above) has a large central dark patch extending over at least the central areas of abdominal tergites 3-6 or 4-6 (cf. the alate Myzus cymbalariae which has the dorsal abdominal sclerotization at least partly divided into separate segmental cross bands).

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 Myzus ascalonicus 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)

On the primary host Myzus cerasi cause the leaves to curl and produce ant-attended leaf nests (see first picture below). The adult aptera that lives in the leaf nest on the primary host is a small to medium sized aphid, shiny, very dark brown to black with a sclerotized dorsum. The legs and antennae are yellowish and black and the cauda is brown. The siphunculi are cylindrical and black with the distal part slightly curved outward. The body length of Myzus cerasi apterae is 1.8-2.6 mm.

Most populations of the black cherry-aphid host alternate migrate from cherry (Prunus cerasus, Prunus avium) as the primary host to bedstraws (Galium), eyebrights (Euphrasia) and speedwell (Veronica spp) as the secondary hosts. However, colonies can be found on cherry throughout the summer, and these are sometimes given the status of a subspecies, Myzus cerasi veronicae. Forms on Prunus cerasus and Prunus avium are also sometimes considered as different subspecies or even species. The return migration occurs in September-October. It is distributed throughout the palaearctic zone and is now almost cosmopolitan.

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Myzus certus (Pinks aphid)

Adult apterae of Myzus certus are pink to dark reddish brown (cf. Myzus dianthicola apterae which are deep yellow-green). The antennal terminal process of Myzus certus is 2.1-3.7 (usually less than 3.25) times longer than the base of antennal segment VI (cf. Myzus dianthicola which has the antennal terminal process 2.5-4.0 (usually more than 3.25) times longer than the base of antennal segment VI). The fused apical rostral segment (RIV+V) of Myzus certus is 0.87-1.28 (usually more than 0.9) times longer than the second hind tarsal segment (HTII) (cf. Myzus dianthicola which has RIV+V 0.78-0.98 (usually less than 0.9) times longer than HTII). The siphunculi are slightly swollen distally, dusky with darker apices, and 1.7-2.5 times longer than the near triangular cauda.

The alate Myzus certus has a black patch on the mid-dorsum, with black bands anterior and posterior to the patch. It has 8-20 secondary rhinaria on antennal segment III, and 0-4 on antennal segment IV.

The pinks aphid does not host alternate, but feeds on pinks, carnations (Dianthus), sweet william and other Caryophyllaceae, and on some violets (Viola tricolor). Oviparae and apterous males are produced in the autumn with eggs laid on the host plant, but there are also anholocyclic populations. The aphid can cause curling and spotting of leaves, but is not usually regarded as a significant pest. Myzus certus occurs throughout Europe, and in Iran and North America.

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Myzus cymbalariae (Cymbalaria aphid)

Adult apterae of Myzus cymbalariae are matt yellowish green or yellowish brown to dark brown or deep crimson red (cf. Myzus ascalonicus which are shiny). The antennal tubercles have their inner faces apically convergent in dorsal view (cf. Myzus ascalonicus which has the inner faces approximately parallel in dorsal view). Their legs and antennae are pale, apart from the ends of the antennae and the tarsi. The dorsal cuticle is scaly (cf. Myzus ascalonicus which does not have the dorsal cuticle scaly). The siphunculi are shorter than antennal segment III, distinctly swollen towards the apex, evenly coloured throughout and with only a very small flange. The narrowest part of the stem of the siphunculi is slightly thicker than the hind tibia at midlength (cf. Myzus ascalonicus which has the narrowest part of the siphunculi equal in width or thinner than the hind tibia at midlength). The cauda is roughly triangular in shape, and short: about one third the length of the siphunculi. The body length of Myzus cymbalariae apterae is 1.2-2.0 mm.

The alate Myzus cymbalariae (see second picture above) has the dorsal abdominal sclerotization at least partly divided into separate segmental cross bands (cf. the alate Myzus ascalonicus which has a large central dark patch extending over at least the central areas of abdominal tergites 3-6 or 4-6).

The cymbalaria aphid does not host alternate, but is extremely polyphagous, feeding on a similar range of hosts to Myzus ascalonicus including Alliaceae, Caryophyllaceae, Scrophulariaceae, and Violaceae. There is no sexual stage in the life cycle and no eggs are produced. Like Myzus ascalonicus, Myzus cymbalariae was first found in Britain (in 1954), and has since spread to many parts of the world.

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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) 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 lilly 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. It has been found in Australia, New Zealand, N&S America, Kenya, France and the UK. Smith et al. (2007) give the year 2000 as the first record for the species in UK. 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)

Myzus ligustri produces a characteristic leaf roll gall on its host, privet (Ligustrum) (see first picture below). The leaves are distorted and slightly swollen with one or both margins curved downwards or rolled towards the midrib, and spotted with yellow. The apterae of Myzus ligustri are shiny greenish-yellow, often with an orange hue around the base of their siphunculi (see pictures below). Their antennae and legs are pale, apart from the joints, which are brown. The siphunculi have their distal parts brownish black, contrasting with the yellow bases, and are 2.6-3.2 times longer than the pale triangular cauda. 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. Myzus ligustri is found in Europe and has been introduced into North America.

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Myzus lythri (Loosetstrifeaphid)

Adult apterae of Myzus lythri (see first picture below) are light green to yellow. On their secondary hosts the anterior part of the body is frequently brownish, and the posterior parts reddish. The head and first two antennal segments are granular, and the cuticle is wrinkled. The antennae are 0.5-0.6 times the body length, and the antennal terminal process is 2.4-3.0 times the length of the base of the sixth abdominal segment. The antennal tubercles are low and the median frontal tubercle is broad. The pale siphunculi are cylindrical, scaly, and 2.3-2.8 times the length of the pale tongue-shaped cauda. The body length of the adult Myzus lythri aptera is 1.5-2.4 mm.

The alate of Myzus lythri (see second picture above) has a light green to yellow abdomen, with a dark patch on tergites II-VI, and marginal and postsiphuncular sclerites. The siphunculi and cauda are brown.

In central Europe Myzus lythri host alternates from mahleb cherry (Prunus mahaleb) to purple loosestrifes (Lythraceae) and willow herbs (Onagraceae). In some other parts of the world (including Russia and possibly Britain) it reproduces parthenogenetically on Lythrum species all year round. The aphid is found throughout Europe and much of Asia, and has been introduced to central Africa (Burundi) and 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, and is marked with conspicuous dark green or brownish transverse intersegmental sclerites (see first picture below). 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, constricted below the flange and 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 alate viviparous female (pictured above right) 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 (oviparae are unknown and males only recorded from India) and nearly all reproduction is parthenogenetic.

Not so long ago Myzus ornatus was a rare aphid. It was first discovered in England in 1932, but within a few years spread throughout the world - definitely one of Britain's more successful exports - even if its primary host, if such exists, may be Himalayan.

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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 length of the rather pointed cauda. The body length of Myzus persicae apterae is 1.2-2.3 mm.

The alate Myzus persicae (third picture above) 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 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. On the secondary host (clematis) only the tips of the siphunculi are black (see first picture below). Myzus varians apterae from their primary host (peach) have the distal half or more 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.

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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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