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Polyphagous aphidsSpecies Overview: Aphis fabae Aphis nasturtii Toxoptera aurantii Aulacorthum solani Brachycaudus helichrysi Macrosiphum euphorbiae Myzus ascalonicus Myzus ornatus Myzus persicae Neomyzus circumflexus
Most aphid species are restricted to a single host-plant genus. Many can only raise successful colonies on one plant species. Host alternating species are similarly-restricted regarding their primary host, but much less so regarding possible secondary hosts. A small proportion of species (1 or 2%) can raise successful colonies on many plant genera, and are considered polyphagous. A few polyphagous aphids are now serious and cosmopolitan pests. That said, the term 'polyphagous' is not clearly defined. This is partly because their host preference is anything but uniform, but also because some species are only polyphagous in parts of their geographic range. Consequently their pest status varies: some are only considered pests in the tropics. Some are pests of ornamentals, or in special environments such as greenhouses, warehouses or hydroponic farms.
Blackman & Eastop provide a key to the 35 most polyphagous aphid species worldwide: "species which occur numerous times in the host lists of many plant genera, and in some cases on plants in many different families". Their key to 23 polyphagous aphid species that feed typically on herbs or shrubs, but occasionally occur on trees, has an additional 3 species.
Of those 38 aphid species, Baker (2015) lists 25 as occurring in Britain: Acyrthosiphon malvae, Aphis (Toxoptera) aurantii, Aphis craccivora, Aphis fabae, Aphis gossypii, Aphis nasturtii, Aphis nerii, Aphis sambuci, Aphis solanella, Aphis spiraecola, Aulacorthum solani, Brachycaudus helichrysi, Macrosiphum euphorbiae, Myzus antirrhinii, Myzus ascalonicus, Myzus cymbalariae, Myzus ornatus, Myzus persicae, Neomyzus circumflexus, Pemphigus bursarius, Rhopalosiphoninus latysiphon, Rhopalosiphoninus staphyleae, Rhopalosiphum padi, Rhopalosiphum rufiabdominale and Smynthurodes betae.
Below we describe the top ten polyphagous aphids most commonly seen in Britain, grouped by genera. Note: In Britain Aphis spiraecola is rare and not considered a pest, Aphis craccivora is a minor pest mainly found in southern Britain, and Aphis nerii in Britain is only a greenhouse pest. Rhopalosiphoninus latysiphon, Rhopalosiphoninus staphyleae, Rhopalosiphum rufiabdominale and Smynthurodes betae are root / bulb / tuber aphids. Aphis solanella looks and generally behaves like Aphis fabae, Myzus antirrhinii looks rather like Myzus persicae but can form very large colonies, and Myzus cymbalariae is difficult to distinguish from Myzus ascalonicus.
The black bean aphid host alternates between spindle (Euonymus europaeus) as the primary host and many herbaceous plant species as secondary hosts. Sexual forms occur in autumn. Aphis fabae is found throughout the northern continents, and has been introduced to many tropical and subtropical countries where it may reproduce parthenogenetically all year round. In Europe there is a complex of sibling species or subspecies which can only be distinguished by their choice of secondary host coupled with transfer experiments.
The nominate subspecies Aphis fabae fabae migrates to both broad beans (Vicia faba) (pictured above first) and poppies (Papaver spp.) (pictured above second) as well as Chenopodium spp. and beet (Beta vulgaris). It will not colonise thistle (Cirsium) or black nightshade (Solanum).
Aphis fabae cirsiiacanthoidis migrates to thistle (Cirsium arvense) (pictured above first) and Aphis fabae mordvilkoi to burdock (Arctium) (pictured above second). The fourth subspecies is Aphis fabae solanella which migrates to black nightshade (Solanum nigrum).
Although one can tentatively assign Aphis fabae on the plants above to a particular subspecies, they also colonise a huge range of other plants (for example many umbellifers) which are not associated with a particular subspecies. Also some hosts such as docks (Rumex spp) seem to be acceptable to all subspecies. Lastly (just to confuse things further) what was called Aphis euonymi has now been renamed Aphis fabae evonymi, and Aphis fabae solanella has been renamed as Aphis solanella.
The buckthorn - potato aphid host alternates between common buckthorn (Rhamnus catharticus) as the primary host and many herbaceous plant species as secondary hosts, the most economically important of which is potato (Solanum tuberosum). Aphis nasturtii is now of almost world-wide distribution.
The black citrus aphid is found on the underside of leaves of Citrus, as well as Tea (Camellia), coffee (Coffea) and mango (Mangifera). Infestation in spring can be very harmful to citrus crops. In temperate countries it is a pest of ornamental Camellia bushes. Adults stridulate by rubbing tibial spines on striae of the abdomen. The distribution is now cosmopolitan.
In temperate climates most of the population overwinters as nymphs or apterae, especially on potato sprouts and on many glasshouse plants and wild species such as foxglove (Digitalis). As a result, this is often one of the first aphid species to find on young plants in the spring. The high toxicity of the saliva of the glasshouse - potato aphid may produce deformation and discoloration of leaves being fed upon. This results in direct feeding damage to potatoes and peppers. It can also be a vector of about 40 plant viruses, but its relatively poor virus transmission efficiency makes it unimportant as a virus vector in the field. Its importance is much greater in glasshouses. Its distribution is virtually cosmopolitan.
The leaf-curling plum aphid host alternates between various plum (Prunus) species (especially domestic plum and blackthorn) and a wide range of Asteraceae such as asters, chrysanthemums, yarrow and groundsel. This aphid is a serious pest on fruit trees. The populations on red clover Trifolium pratense) have been called var warei, but are not thought sufficiently distinct to warrant subspecific status.
Macrosiphum euphorbiae is a common and highly polyphagous species, which is often a pest on various crops such as potato (Solanum tuberosum), lettuce (Lactuca sativa) and beets (Beta vulgaris) as well as on numerous garden ornamentals. It is a vector of about one hundred plant viruses. It usually overwinters as viviparae, but it can produce sexual forms and eggs on rose. Aphid numbers increase rapidly from early spring, and alates spread infestations to other plants. It is an especial problem in unheated greenhouses. Macrosiphum euphorbiae was originally a North American species but was introduced to Europe about 1917 and is now cosmopolitan.
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.
The ornate aphid does not host alternate and is extremely polyphagous. It is an important pest on crucifers, cucurbits and onions and also attacks peas, soybean, strawberry and many garden ornamentals. It also feeds on some trees such as Catalpa and Prunus, often feeding away from the main veins. Myzus ornatus occurs throughout the world.
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. The aphid 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 generalist, the subspecies Myzus persicae nicotianae is a tobacco specialist.
The crescent-marked lily aphid is entirely parthenogenetic with no sexual stage in the life cycle. In temperate climates it is primarily a pest of glasshouse crops where it attacks Asparagus, Begonia, Fuchsia and many others. Heavy infestations cause direct harm to many ornamental plants, and the aphids also transmit viruses. Neomyzus circumflexus has a cosmopolitan distribution.