Aphid species

We have compiled key data on important species of aphid in the UK. Each of the listed aphids below contains a description of: appearance, host plants/life cycles, pest status/damage. For some of these aphids, we compile weeky data on which we convert to graphs, as seen on the graphs page


Apple - grass aphid
Rhopalosiphum insertum

Appearance

The adult wingless form on its winter host is medium sized 2.1 - 2.6mm long, oval shaped and ranges from bright green to yellow-green, with a dark green spinal stripe. On its summer hosts it is smaller, 1.4 - 2.0mm long and more yellowish green. The two tubes (siphunculi) at the rear end are short, cylindrical and dusky to dark brown. The apical end of the siphunculi is swollen slightly and ends with a strong flange preceded by a distinct constriction. The tail (cauda) is shorter than the siphunculi and paler. The winged form on the winter host is 1.5 - 2.5mm long, but smaller on grasses at 1.6 - 2.0mm long. Some winged aphids from grasses may have five segmented antennae, instead of the normal six segments.

Host plants/Life cycle

The eggs of this species overwinter mainly on apple, but also on pears, rowan, medlar and hawthorn. The eggs hatch in April, usually coinciding with bud break, and the first generation live in the curled leaves as the buds open. Subsequently winged forms are produced which migrate to grasses during May and June, where they colonise the roots and basal parts of the stems, and are rarely noticed. The grasses infested include in particular annual meadow grass, Poa annua, but also Agropyron spp., Agrostis spp. , Festuca spp. and other Poa spp.. There is a larger summer migration during which grasses are further colonised. The final migration back to the winter hosts in September/October is the largest flight of the year for this species.

Pest status/damage

This aphid is regarded as non-damaging on apples unless present in very large numbers, which occurs only in exceptional years. It then causes curling perpendicular to the mid-rib on young leaves. Heavy infestations on apple follow summers with sufficient rainfall to maintain the continuous growth of grass, the 'green bridge' effect. It is rarely a pest on cereals, preferring pasture and wild grasses, but is known to transmit Barley yellow dwarf virus.

Bird cherry - oat aphid
Rhopalosiphum padi
Appearance
 
The adult wingless form is 1.2 - 2.4mm long and broadly oval in shape. This species is brownish olive green, with two short dark tubes (siphunculi) at the rear end surrounded by a rusty red coloured area. The apical end of the siphunculi is swollen slightly and ends with a strong flange preceded by a distinct constriction. The tail (cauda) is pale and shorter than the siphunculi. The winged form is also 1.2 - 2.4mm long with a pale to dark green abdomen.
Host plants/Life cycle
 
The eggs of this aphid overwinter on bird cherry trees, Prunus padus, and hatch from April onwards. After several generations, winged forms are produced which migrate in May/early June to numerous species of Gramineae, including all the major cereals and pasture grasses. This species tends to infest the lower leaves and stem, moving to higher leaves only when numerous. Several generations are then produced, before a summer migration away from ripening cereals to wild grasses, particularly in eastern England, but also between grasses elsewhere. The timing of the autumn migration back to P. padus to lay eggs in September - November is largely determined by decreasing day length. In this species the last migration is usually the biggest of the year. The coincidence of warmer winters and a major move to winter sown cereals, has meant a significant proportion of this aphid population in the midlands and the south overwinter as mobile stages on early sown winter cereals and grasses.
 
Pest status/damage
 
This species is a major pest on wheat, barley, oats and maize, and a minor pest on rye. It seldom gets numerous enough to cause direct feeding damage, except in some years where heavy infestations develop on maize/sweetcorn in late summer. The principal factor leading to its pest status is its role as a vector of Barley yellow dwarf virus. This aphid often provides the primary source of BYDV infection in early sown winter cereals. In mild winters secondary spread by the offspring of these autumn migrants may continue until significant frosts occur.

Black bean aphid
Aphis fabae
Appearance
 
The adult wingless form is 1.5 - 3.1mm long, usually sooty black or very dark olive green, with some individuals having distinct white waxy stripes on the upper surface of the abdomen. The two tubes (siphunculi) at the rear end are black, short and tapering slightly towards the tip. The tail (cauda) is black, blunt finger shaped and short. The antennae are about half the length of the body. The winged form is 1.3 - 2.6mm long, also very dark, with some barely discernible black cross-bars on the upper surface of the abdomen.
 
Host plants/Life cycle
 
This species overwinters mainly as eggs on spindle, Euonymus europaeus, and occasionally in the south in the mobile stages on leguminous weeds or winter beans. The eggs hatch from late February to early April and colonies develop on young leaves and shoots. The winged forms are produced in May/June, and these migrate to an enormous range of summer hosts. This species has been recorded on almost 300 plant species. The principal commercial crops involved are field beans, broad beans and sugar beet, as well as most forms of garden bean. Some common summer wild hosts include docks, poppies, goosefoot and fat hen. Breeding continues throughout the summer, and further winged forms are produced in response to crowding, and these spread within crops and invade new crops. The populations usually peak in July/August, and are often noticeably attended by ants. In autumn A. fabae migrates back to E. europaeus and winter eggs are laid.
 
Pest status/damage
 
This species is a major pest on beans and sugar beet, occasionally at an epidemic scale, principally by causing direct feeding damage. The plants lose vigour, flowers are damaged and pod development in beans may be retarded or even prevented. Spring sown field beans can be damaged severely with considerable loss of yield. However, winter and early sown spring crops are less likely to be seriously affected, because plants are well established and flowering has finished before the aphid attack starts. In sugar beet very dense colonies can develop during the summer, causing significant wilting and poor growth. This species is known to transmit more than 30 viruses, mainly of the non-persistent variety. Large populations can cause significant secondary spread, even when it did not provide the initial primary infection. A by-product of such large colonies of aphid is contamination of the plant surface with sticky secretions, which promote the growth of sooty moulds. This superficial damage can reduce the sales value of the horticultural bean crops.
Blackberry - cereal aphid
Sitobion fragariae
 
Appearance
 
The adult wingless form is 1.6 - 3.0mm long, and spindle shaped. It is dirty yellowish green with small brown intersegmental markings on the upper surface of the abdomen. The two tubes (siphunculi) at the rear end are long and usually entirely black, just occasionally having paler bases when found on Rubus spp.. A pale tail (cauda) is about half as long or less than the siphunculi. The antennae are about the same length as the body, with the segments closest to the head paler than the rest. The winged form is 2.0 - 3.0mm long, yellowish green, with very distinct dark intersegmental ornamentation.
 
Host plants/Life cycle
 
The eggs of this species overwinter on blackberry, raspberry and wild roses. The eggs hatch in February/March, the young nymphs feeding on the tips of the breaking buds. Colonies gradually build up, and in June/July winged individuals migrate to cereals, pasture grasses, cultivated and wild grasses. It may be found in small numbers on the ears of wheat, but is much less common than S. avenae. Its preferred wild hosts are Holcus spp., especially creeping soft grass (H. mollis) and yorkshire fog (H. lanatus). The autumn return migration to its overwintering host, blackberry, is noticeably late, taking place in October and into early November.
 
Pest status/damage
 
This species is regarded as a minor pest on cereals, usually found on the ears, but rarely numerous. It is much less important than the grain aphid S. avenae. Indeed S. fragariae is more associated with wild grasses than crops. This aphid is capable of transmitting Barley yellow dwarf virus, but is not thought to constitute a threat because of its low numbers. Heavy infestations on the spring growth of blackberry can cause severe leaf curling.

Blackcurrant - sowthistle aphid
Hyperomyzus lactucae
 
Appearance
 
The adult wingless form is medium sized, about 2.0 - 3.2mm long, and broadly spindle shaped. These aphids are an opaque green, with pale legs, siphunculi and cauda, but the tips of the antennal segments are dark. The two tubes (siphunculi) at the rear end are pale, medium to long and distinctly swollen. The tail (cauda) is shorter than the siphunculi, finger shaped with a somewhat blunt ending. The winged form is a very similar size, but has a rather broken central dark patch on the upper surface of the abdomen. The antennae are black, and the legs and siphunculi are a medium pigmented brown. The tail remains a pale colour.
 
Host plants/Life cycle
 
The eggs of this species overwinter on Ribes spp., in particular blackcurrants, but occasionally other species including redcurrants. The eggs hatch in March and early April, spring colonies developing in the apices of young shoots. Few winged forms develop in the second generation, but more appear in the third generation and these migrate in late May/June to Sonchus spp., especially sowthistle. On sowthistle, colonies reproduce and build up, and can be found on the upper parts of stems and on the inflorescences. There is evidence to suggest some migration between the summer hosts in July and August. The return migration to Ribes spp., takes place in September and October.
 
Pest status/damage
 
The species causes problems primarily on its winter host, blackcurrant. Colonies found on currants cause leaves to curl downward, stunting young growth. It is also common for leaves to acquire yellow spots resulting from aphids feeding. This species is a proven vector of some 12 non-persistent and semi-persistent viruses, but none apparently infect currants. It is known to have the ability to transmit the persistent virus, Lettuce necrotic yellows virus, but does not colonise lettuce!
 
Corn leaf aphid
Rhopalosiphum maidis
 
Appearance
 
The adult wingless form is 1.0 - 2.5mm long and rather elongate with short antennae. The body is usually blue-green to almost black, and sometimes appears dusted with wax. The two tubes (siphunculi) at the rear end are short and dark, and surrounded by a dark purple area at the base of each tube. The winged form is 0.9 - 2.4mm long and dark green in colour. The two tubes at the rear end are short and dark, and surrounded at their base by a ring of dark purple colour. There are no other major abdominal markings on the upper surface.
 
Host plants/Life cycle
 
This species does not produce overwintering eggs in the UK at all. The winter is spent in the mobile stages as low numbers on winter cereals, especially barley, or wild grasses. A small summer migration and/or local redistribution finds this aphid on cereal crops, in particular barley, maize and sweet corn, and a range of some 20 wild grasses.
 
Pest status/damage
 
This species is a very minor pest in the UK, just occasionally causing a few problems on sweet corn. It is a potential, but relatively inefficient vector of Barley yellow dwarf virus. This is probably the most important aphid pest on cereals in tropical and warm temperate climates, so may become more important if temperatures continue to rise.
 

Currant - lettuce aphid
Nasonovia ribisnigri
 
Graphical data
 
Appearance
 
The adult wingless form is 1.3 - 2.7mm long, green to yellowish green, even occasionally reddish. The abdomen is shiny with a dark green to black pattern on the upper surface. There are two long tubes (siphunculi) at the rear end, with pale bases but dark tips. The tail (cauda) is pale, finger shaped and about two-thirds the length of the siphunculi. The winged form is 1.5 - 2.5mm long, with black siphunculi and antennae, and with a conspicuous black abdominal pattern.
 
Host plants/Life cycle
 
The currant - lettuce aphid overwinters in the egg stage on currant or gooseberry bushes. These eggs usually hatch in March or April, nymphs then infesting the tips of the young shoots. Colonies are formed on the developing leaves, and in May or June winged aphids migrate to lettuce and other Asteraceae (Compositae). Successive generations are produced on these summer hosts until September or October. During October and November, winged aphids migrate back to the winter hosts, where eggs are laid. In southern Britain mobile stages can survive and slowly reproduce on outdoor lettuce, chicory, hawkweed and speedwell throughout mild winters.
 
Pest status/damage
 
This species is a pest on both its winter and its summer host. On its winter hosts Ribes spp. it causes leaf curl and retardation of growth. In mid August/September it is the most important foliage aphid on lettuce. Rapid development of colonies on lettuce causes plants to become stunted and unpalatable, indeed even small numbers can contaminate plants and affect marketability. In some cases large populations on young plants may prevent 'hearting'. This species acts as a vector of Gooseberry vein-banding virus, but apparently cannot transmit Lettuce mosaic virus.
 
Damson - hop aphid
Phorodon humuli
 
Appearance
 
The adult wingless forms are small on their summer hosts, 1.1 - 1.8mm long, but medium sized on its winter hosts, 2.0 - 2.6mm long. They range from pale green to yellowish green, with darker green longitudinal stripes on the upper surface of the abdomen. The two tubes (siphunculi) at the rear end are pale, of medium length, thicker at their bases and slightly curved outwards at their tips. The tail (cauda) is short, pale and blunt. This species characteristically has a pair of sharply pointed head projections on the inside of the antennae. The winged form is 1.4 - 2.1mm long, and has a black patch of more or less fused cross bars on the upper surface of the abdomen. The projections on the head are much less developed in the winged form, and the tail more triangular and sharp.
 
Host plants/Life cycle
 
This species overwinters as eggs on Prunus spp., particularly on blackthorn, bullace, damson and plums. The eggs hatch between late February and April. After one or two generations of wingless aphids, winged forms begin appearing in the latter half of May. These winged forms migrate to the summer host, hops. This migration begins in earnest in early June and reaches a maximum in late June. It then declines and ends in late July or early August. It appears there is little movement within or between hops, and no further winged forms are produced until the autumn. A return flight to the winter hosts occurs in September and October. This species can stay on its winter host Prunus spp. throughout the summer, particularly on the sucker growth of plums.
 
Pest status/damage
 
On hops, this is the dominating pest species and is the main limiting factor to hop production. Routine pesticide application is required every year, at the very least at the beginning of the aphid flight. Heavy infestations reduce hop plant vigour and may induce defoliation. Even light infestations of the harvested hop cones can reduce their economic value. Added to this, it is able to transmit Hop mosaic carlavirus, Hop split leaf blotch virus and Hop line pattern virus. This species may also cause a little damage on plums, by curling young leaves and by transmitting Plum pox potyvirus.
 

Glasshouse - potato aphid
Aulacorthum solani
 
Appearance
 
The adult wingless form is 1.5 - 3.0mm long and has a pear-shaped body. It appears shiny and can be variable. It can be whitish green or yellow, in which case there is a bright green or rust coloured spot at the base of each siphunculus. It can also be uniformly dull green or greenish brown. The legs are long with dark knee joints. There are two tubes (siphunculi) at the rear, which are long with black tips flared at the very end. The antennae have dark joints and are slightly longer than the body. The winged form looks quite different, with much darker antennae, legs and siphunculi. It has a variably developed pattern of transverse dark bars on the upper surface of the abdomen. The winged form is also 1.5 - 3.0mm long.
 
Host plants/Life cycle
 
This aphid has the unusual ability of overwintering as eggs on many different host plant species. However, the majority of the population overwinters in the mobile stages, particularly on potato sprouts in stores/chitting houses and on many plants under glass. Winged adults migrate in late spring and start colonies that reach a peak in July. This species is extremely polyphagous, colonising over 200 plant species, including both dicotyledons and monocotyledons, but not Gramineae. There is a very small autumn migration back to winter hosts.
 
Pest status/damage
 
This species is a minor pest on field crops, especially potatoes, but rarely causes significant direct feeding damage. Although it has the ability to vector about 40 viruses, both persistent and non-persistent, its relatively poor transmission efficiency makes it unimportant as a virus carrier in the field. However, this aphid's importance increases when found on protected crops and glasshouse plants. It is a problem particularly on ornamentals, bulbs (especially tulips) and a wide range of 'house' plants.
 
Grain aphid
Sitobion avenae
 
Graphical data
 
Appearance
 
The adult wingless form is 1.3 - 3.3mm long, and broadly spindle-shaped. It ranges from yellowish green to a dirty reddish brown. It has black antennae and two black tubes (siphunculi) at the rear end, which are a little longer than (1.1-1.6 times) the pale rather pointed tail (cauda). The winged form is 1.6 - 2.9mm long and similarly coloured, with distinct dark intersegmental markings on the upper surface of the abdomen.
 
Host plants/Life cycle
 
This species spends its entire year on cereals and grasses. Only a small proportion of the population overwinters as eggs on Gramineae, and these hatch in March. The majority of the population overwinters as mobile stages on wild grasses or winter cereals and can develop rapidly in warm springs. Colonies of wingless aphids develop on the flag and upper leaves of cereals, then move to emerging ears, especially on wheat. Winged forms usually fly in late May/June, and the resulting colonies rarely become numerous before late June. In continuing hot dry conditions, these colonies can increase quickly. Winged forms continue to be produced throughout the summer in response to increasing population density and declining food quality, moving to re-infest crops or other grasses. It is from these that a comparatively small autumn migration arises, which infests early sown winter cereals as well as wild grasses.
 
Pest status/damage
 
This species is a major pest on wheat, a moderate pest on barley and oats, and a minor pest on maize. It causes direct feeding damage through May, June and early July, from the flag leaf to dough ripe stages (GS37 - 85). When present on crops before the flowering stage, it reduces the number of grains in the ear. After flowering to the end of grain filling, it reduces directly the size of the grain. This species also has pest status in winter-sown cereals in September/October, and throughout mild winters up to GS31, as a virus vector of Barley yellow dwarf virus. It is more cold - hardy than R. padi, and thus more significant in the secondary spread of BYDV in winter cereals.

Green spruce aphid
Elatobium abietinum
Appearance
 
The adult wingless form is 1.0 - 2.0mm long, pale green with two darker green longitudinal stripes on the upper surface of the abdomen. The two tubes (siphunculi) at the rear end are cylindrical, long, thin and pale, with a tendency to be slightly 's-curved' and with a well developed apical flange. The siphunculi can be up to 2.5 times the length of the tail (cauda), which is pale and pointed. The winged form is 1.6 - 2.1mm long and green, with little or no abdominal markings on the upper surface.
 
Host plants/Life cycle
 
This species spends all year on Picea spp., particularly sitka spruce (P. sitchensis), but also norway spruce (P. abies) and blue spruce (P. pungens), and much less commonly on firs (Abies spp.). In the UK this aphid overwinters in the mobile stages, and in mild winters it continues to feed and reproduce. It is quite rare in the UK for this species to overwinter as an egg, as it does more commonly in continental Europe. The aphids are often difficult to see because the body colour matches closely that of the needles on which they feed. Winged forms are produced in spring and early summer in response to the changing nutritional status of the host plant. They then migrate from late April to July to other Picea spp., where they spend the summer as non-feeding immature nymphs, awaiting the return of more favourable feeding conditions in autumn.
 
Pest status/damage
 
The heaviest damage to spruce occurs after mild winters. The old foliage develops a pale mottled discolouration during the winter, and many of these needles fall off in spring. A black sooty mould may be noticeable on the stem joints. New growth produced in the spring is unaffected, and its bright green appearance contrasts strongly with the discoloured and sparsely foliated older stems.
 
Leaf-curling plum aphid
Brachycaudus helichrysi
 
Appearance
 
The adult wingless form is 0.9 - 2.0mm long. The spring populations are very variable, ranging from yellow to green to brown, often shiny with a slight wax dusting. In the summer forms on herbaceous plants, as well as yellow and green, they can be almost white/pinkish. The two tubes (siphunculi) at the rear end are pale, very short and tapered. The tail (cauda) is pale, short and blunt. The antennae are shorter than the body with dusky tips. The winged form is 1.1 - 2.2mm long, with dark antennae, legs and siphunculi. The tail is blunt and somewhat less dark. The upper surface of the abdomen has a broad dark patch formed by more or less fused cross-bars.
 
Host plants/Life cycle
 
The overwintering eggs are laid on various Prunus spp., particularly plums (P. domestica) and damsons (P. insititia). Unusually these eggs hatch early in November/December and the subsequent nymphs then feed on dormant buds. In spring successive generations feed on young foliage, until in May winged forms migrate to numerous summer hosts. They have been recorded on some 120 plant species, with a notable preference for Compositae such as asters, chrysanthemums, yarrow and groundsel. The migration from winter host to summer host is usually complete by early July. The return migration to Prunus spp. begins in the latter half of August and continues to mid October.
 
Pest status/damage
 
This aphid is a pest on Prunus spp. cause leaves to roll up tightly perpendicular to the mid-rib, thus severely damaging leaves at a time of rapid growth, and so early as to be before natural enemies are active. This species is able to transmit a number of viruses including Plum pox virus, Cucumber mosaic virus, Dahlia mosaic virus, and a mosaic virus disease of cineraria. It is also a notable pest of glasshouse crops and house plants. Although a relatively poor vector of Potato virus Y, a non-persistent virus, it can in some years fly in such large numbers as to become an important vector even on potato crops, which it does not truly colonise. A similar role for this species has been insinuated in the sugar beet crop with respect to its infection by non-persistent Beet mosaic virus.
 

Mealy cabbage aphid
Brevicoryne brassicae
Graphical data
 
Appearance
 
The adult wingless form is 1.6 - 2.6mm long, greyish green, with a body covering of greyish white mealy wax. This species has a pair of short 'barrel' shaped tubes (siphunculi) at the rear of the abdomen, and a triangular tail (cauda). The winged form is 1.6 - 2.8mm long, with short black transverse bars on the upper side of the abdomen. The wing vein nearest the abdomen on the forewing is darker and thicker than the other veins.
 
Host plants/Life cycle
 
This aphid is restricted to herbaceous Brassicaceae (Cruciferae) throughout its life cycle, because it requires the presence of mustard oil, sinigrin, to initiate a feeding response. The shiny black eggs are placed on the stems and leaves of cruciferous crops that remain in the field through the winter e.g. oil seed rape or overwintering horticultural brassica crops. These eggs hatch sometime between February and April, producing young that feed on leaves and shoots. Winged forms produced in May-July migrate to newly planted brassica crops, where numbers can increase rapidly. An early summer peak in abundance is reached between mid-July and mid-August, followed by a population crash brought about by a range of natural agents. A further migration from mid-September to mid-October results in egg laying in October. In recent years, more of the population has spent the winter as mobile stages, not eggs. These individuals, if they survive, have a head start in warm springs over the young hatching from eggs. In this species there is considerable variation in the annual pattern of infestation.
 
Pest status/damage
 
This aphid is a major pest on broccoli, cabbage, cauliflower, kohl rabi, radish and swede. It causes serious feeding damage, leaving plants weakened and stunted, and heavily infested seedlings and young plants can wilt and die. Less serious distortion and fouling of leaf surfaces reduces marketability. It attacks oil seed rape and kale to a lesser extent, and turnips appear virtually immune. This species can transmit about twenty plant viruses, of which Cauliflower mosaic virus and Turnip mosaic virus are the most important.
Mealy plum aphid
Hyalopterus pruni
 
Appearance
 
The adult wingless form is a small to medium sized aphid 1.5 - 2.6mm long, and has an elongate shape. It is usually pale green with a fine darker green mottling. Most individuals are covered with a white wax meal. The antennae are between 0.5 - 0.75 times the body length. The two tubes (siphunculi) at the rear end are very short, thickening and growing darker towards the apex. The tail (cauda) is longer, 1.5 - 3.0 times the length of the siphunculi. The winged form is a similar size, green with white wax patches on the upper surface of the abdomen. The siphunculi are sometimes only dark on the apical third.
 
Host plants/Life cycle
 
The eggs of this species overwinter on Prunus spp., mainly plums, but also peaches, apricots and almonds. The eggs hatch in April, usually by the white bud stage on plum, where colonies can build rapidly to literally 'pave' the underside of the leaves. The winged forms of this species develop later than those of the other aphid pests on plum (Brachycaudus helichrysi and Phorodon humuli), and migrate to waterside grasses and reeds from the beginning of June. The population on plum continues to increase through July, with the peak of migration occurring between early July and early August. The return migration to Prunus spp. begins in September, and is usually quite small. Some aphids of this species are known to remain on plum, the winter host, all the year round.
 
Pest status/damage
 
This aphid is only a pest on its winter hosts, in particular plums. When it occurs in large numbers on young leaves it causes significant feeding damage, but apparently does not cause leaf curling. It combines this damage with excreting honeydew onto lower leaves, which become dark with sooty moulds growing in the resulting sticky film. These fungi reduce the plant's ability to photosynthesise. This species is 'weak' vector of Plum pox potyvirus.
 

Pea aphid  
Acyrthosiphon pisum
 
Graphical data
 
Appearance
 
The adult wingless form is rather large, at 2.5 - 4.4mm long, and usually either pale green or pink. It has long slender appendages, including two long pale slender tubes (siphunculi) at the rear end and a long pale tail (cauda). The winged form is also large at 2.3 - 4.3mm long.
 
Host plants/Life cycle
 
This aphid spends all year living on leguminous plants. Eggs and active forms overwinter low down on various clovers, lucerne, sainfoin and trefoils. The eggs hatch in February and March, and winged forms are produced during May, which then migrate to peas and other legumes. Numbers usually reach a peak in late June and early July, although populations can remain noticeable on successive sowings of peas through to early autumn. There is a small autumn migration in late September back to the overwintering sites.
 
Pest status/damage
 
This aphid is generally a moderate pest on peas, only occasionally causing major damage. It causes direct feeding damage by feeding on the young growing points of peas, causing stunting, and subsequent distortion and yellowing of leaves and pods. The crops beginning to flower are most susceptible, especially if this coincides with the population peak in late June/early July. Heavy infestation on culinary peas can significantly reduce yields. This species also merits pest status because of its ability to transmit more than 30 plant viruses, in particular Pea leaf roll virus, Pea enation mosaic virus, Pea mosaic virus and Pea seed borne mosaic virus. It is also known to cause economic damage to field beans by the transmission of Bean leaf roll virus.
Peach - potato aphid
Myzus persicae
 
Graphical data
 
Appearance
 
The adult wingless form is 1.0 - 2.1mm long, and varies considerably from yellow, through all shades of green, to pink, red and almost black. The two tubes (siphunculi) at the rear end of the abdomen are medium length and slightly swollen towards darkened tips. The winged form is 1.2 - 2.5mm long, with a black central abdominal patch on the upper surface, but a pale underside.
 
Host plants/Life cycle
 
The winter host is peach, Prunus persica, which is confined to small numbers in southern Britain. So, although some eggs overwinter on peach, overwintering is usually in the mobile stages on herbaceous plants, weeds and brassicas. The summer hosts are very numerous and spread over 40 plant families, and include very many economically important plants. Winged forms start to migrate from their winter hosts to fresh summer hosts from late April to early June. Numbers reach a peak in July. However this aphid does not form dense colonies, but tends to move when crowded by walking to infest other parts of the same or neighbouring plants. Redistribution in late summer to other crops or wild herbaceous plants is followed by a return migration to winter hosts in late September and early October.
 
Pest status/damage
 
This species is regarded as a major pest on potatoes, sugar beet, lettuce, brassicas and legumes. This is the most important pest and virus vector aphid in Britain due to its wide host range and its proficiency in transmitting more than 120 plant viruses. Its behaviour in not forming dense colonies means that it rarely reaches levels causing direct feeding damage. However, its tendency to walk short distances when crowded greatly enhances its importance as a virus vector. Some of the more important viruses transmitted include Potato leaf roll virus, Beet western yellows virus, Beet mild yellowing virus, Pea enation virus and Lettuce mosaic virus. Even small numbers cannot be tolerated when producing certified seed potato crops.

Potato aphid
Macrosiphum euphorbiae
Graphical data
 
Appearance
 
The adult wingless form is large 1.7 - 3.6mm and an elongated pear shape. It ranges from light green, yellowish green to pinkish red. It often has a darker stripe down the centre of its back, especially in immature nymphs. This species has noticeably long legs, and two long tubes (siphunculi) at the rear end. The tail (cauda) is also long and finger shaped. The winged form is 1.7 - 3.4mm long, with a much less distinct central stripe. The antennae and siphunculi are darker than in the wingless forms.
 
Host plants/Life cycle
 
This species overwinters rarely as eggs on Rosa spp., but predominantly spends winter in the mobile stages on weeds, potato sprouts in stores/chitting houses, and on lettuce under glass. In early May/June winged forms are produced and migrate to potato and other crops. This aphid is highly polyphagous in the summer, feeding on over 200 plant species in more than 20 plant families. The Solanaceae, especially potato, are its preferred summer hosts. A second summer dispersal migration in July may happen if numbers are particularly high. There is only a very small migration in the autumn.
 
Pest status/damage
 
In some years this species is a major pest on potatoes and lettuce, both outdoor and indoor. It is of little importance in the field as a virus vector of potato viruses. It can cause physical damage to foliage resulting in yield loss when populations are high. Early large infestations may cause the upper leaves of some potato varieties to roll upward [false top roll]. It can transmit over 50 plant viruses, mainly of the non- persistent variety, but with less efficiency than Myzus persicae. In particular it is known to transmit Potato leaf roll virus (symptoms appear later than false top roll), Beet mild yellowing virus, Beet yellows virus and Lettuce mosaic virus. In lettuce crops small numbers can persist late into autumn and will affect marketability.
Rose - grain aphid
Metopolophium dirhodum
 
Graphical data
 
Appearance
 
The adult wingless form is 1.6 - 2.9mm long, and an elongate spindle shape. It ranges from green to yellowish green, with a distinct brighter green longitudinal mid-dorsal stripe. The antennae are pale with darker joints, and are usually about three-quarters of the body length. The two tubes (siphunculi) at the rear end are medium long and pale, with slightly dusky tips, and the tail (cauda) is pale. The winged form is 1.6 - 3.3mm long and usually has a green abdomen without markings.
 
Host plants/Life cycle
 
The overwintering eggs are laid on wild and cultivated Rosa spp. in October and November, and hatch the following spring. Colonies then develop and produce winged forms in April/early May. These migrate to grasses, especially Bromus spp., and cereals, particularly wheat, where the population can continue to breed and build to epidemic proportions in some years. Later, further winged forms are produced on cereals in response to increasing population density, and these re-infest the crop or migrate to other grasses. An autumn return migration to Rosa spp. occurs in late September/October. Rarely, but more commonly recently, this species can overwinter in the mobile stages on grasses, but is not often seen on winter cereals in the autumn.
 
Pest status/damage
 
This species is a minor pest on cereals, but just occasionally very large populations can reduce yields, particularly in wheat. Plants coming into ear (GS59) through to ripening, may have the lower leaves attacked, and if numbers build they move up to the flag leaves. The infested leaves tend to turn yellow and prematurely senesce. This aphid is a poor vector of Barley yellow dwarf virus, although in large population years it can contribute to secondary spread within fields. This species is also commonly recognised as a pest on cultivated roses in spring and early summer.

Shallot aphid
Myzus ascalonicus
 
Appearance
 
The adult wingless form is 1.1 - 2.2mm long, and shiny pale green to dirty yellow. Its appendages are all pale except for the ends of the antennae and the 'ankles/feet' which are all quite black. The two tubes (siphunculi) at the rear end are pale, short to medium in length with the apical part slightly swollen. The tail (cauda) is roughly triangular in shape and short, about a third the length of the siphunculi. The winged form is 1.3 - 2.4mm long, with a black abdominal patch on the upper surface, and some smaller separated markings on the lower surface. The siphunculi are black and again slightly swollen. It also has a black tail.
 
Host plants/Life cycle
 
This species is not known to produce overwintering eggs at all, but is extremely polyphagous, having been recorded on over 200 plant species from 20 plant families. Overwintering takes place in glasshouses and other protected places such as potato stores, on onions or shallots, or swede/beet clamps. It can also pass the winter in the open on plants such as chickweed and cranesbill under hedges or similar shady spots. This aphid seems quite cold hardy and apparently thrives on etiolated plants growing in the shade, where large numbers can build up even at low temperatures. Winged forms are produced in spring, and migrate from late April through to mid June. Plants colonised in the summer are many, but include crops such as onions, shallots, strawberries, lettuce, brassicas and potatoes. It is also known to infest many economically important garden ornamentals, such as asters, chrysanthemums and polyanthus, as well as most flowers derived from bulbs. There is a small flight in mid October most years.
 
Pest status/damage
 
This species is a particular pest on shallots and strawberries. It colonises strawberries in autumn, building up over winter to cause severe damage the following spring, distorting leaves and blossom, and even destroying whole crops after mild winters. This aphid is an important virus vector and is a proven transmitter of over 20 plant viruses, including Beet yellows virus, Potato leaf roll virus and a range of strawberry viruses. It seems particularly important for its ability to transfer viruses from wild overwintering hosts to crops e.g. Beet mosaic potyvirus from chickweed to sugar beet.
Sycamore aphid
Drepanosiphum platanoidis
 
Appearance
 
In this species all adult forms are winged, and range in size from 3.2 - 4.3 mm long. They have a yellow-brown head and thorax, and a pale green abdomen. The upper surface of the abdomen has up to 5 or 6 variably developed dark cross-bars. Early in the year these cross bars may be reduced or absent altogether. The two tubes (siphunculi) at the rear end are pale, long and thick, with an apical flange preceded by a ring-like constriction. The tail (cauda) is also pale and 'knobbed' in shape.
 
Host plants/Life cycle
 
This aphid spends all year on sycamore (Acer pseudoplatanus), but has also been recorded from many other Acer spp., but these are apparently only visited on a casual basis. This species overwinters as eggs placed in bark crevices and behind buds. The eggs hatch in early spring, and there is a migration in late spring/early summer. The aphids colonise the underside of the leaves of sycamore, preferring leaves principally in shade. Large numbers can build up, but never into dense colonies, always evenly spaced ('spaced-out aggregations'). The individuals sit just close enough so as to reach their neighbours with their antennae and so register any disturbance. The reproduction is low in mid summer, but an autumn flight occurs in late September/October as individuals move to the overwintering sites on branches and trunks.
 
Pest status/damage
 
This aphid is of no agricultural importance, but it can be of nuisance value for anything placed under sycamore trees. It excretes copious amounts of honeydew, which collects to form a sticky film on any surface immediately below, and can subsequently result in 'sooty' moulds growing on this sugary film.

Willow - carrot aphid
Cavariella aegopodii
Graphical data
 
Appearance
 
The adult wingless form is 1.0 - 2.6mm long, green or yellowish-green, elongate oval and somewhat flattened. There are two tubes [siphunculi] at the rear end, which are swollen towards the tips. A small outgrowth (tubercle) is present above the tail (cauda). The winged form is 1.4 - 2.7mm long, darker and more easily seen because of a black patch on the upper surface of the abdomen, formed by the fusion of three or four cross bars.
 
Host plants/Life cycle
 
This aphid principally overwinters as eggs round bud axils of willows (Salix spp.), in particular crack willow (S. fragilis) and white willow (S. alba). Eggs on willow hatch in February or March, with the young feeding first on young shoots, then on foliage and catkins, where colonies develop. Winged forms produced in May migrate to carrot, parsnip, celery, parsley or other umbelliferous plants over a 5-6 week period, usually with a peak in early June. Late seasons can delay migration for 2-3 weeks, but generally populations on summer hosts peak in late June and then decline. Further winged generations disperse to hedgerow umbellifers, and finally back to willow in the autumn to mate and lay eggs. A small proportion in warmer areas can survive winter as mobile stages on umbelliferous plants or on carrots in field storage, e.g. under straw, and produce colonies early the following spring.
 
Pest status/damage
 
This aphid is a major pest on carrots, celery, parsnips and parsley. It often causes considerable loss of yield in carrot crops sown in April/May, but those sown in June may escape attack. Dry sunny weather late May/June favours a large-scale migration to host crops, but cold rainy weather inhibits it. The aphids infest carrots at the cotyledon stage, but can also invade older plants. When many are present the leaves may be discoloured, distorted and sometimes shiny from honeydew excretion. The plants and ground below may become covered with cast skins. This aphid is a vector of the Carrot motley dwarf virus complex, which produces a yellow mottling of the leaves and stunts the plants. It also transmits Parsnip yellow fleck virus, which can cause severe damage, stunted plants and blackening of the central core. It is also known to transmit Carrot red leaf virus, Parsnip mosaic virus and Celery mosaic virus. Damage may be confused with carrot fly attack and sometimes drought stress, which produces similar foliar symptoms.