Metopolophium dirhodum

Identification & Distribution:

The adult apterae of Metopolophium dirhodum are medium-sized spindle-shaped aphids which range from green to yellowish green, with a brighter green longitudinal mid-dorsal stripe (see pictures below) (cf. Metopolophium albidum, which has no green spinal stripe). The antennae are about 0.75 times the body length, and are mainly pale apart from the apices of segments III-V, and parts of segment 6 which are dusky or black (cf. Metopolophium albidum, which has antennae that become progressively darker from the base to the apex). The apical rostral segment (RIV+V) is 0.61-0.72 times the length of the second hind tarsal segment (HTII) (cf. Metopolophium tenerum, which has RIV+V 0.92-1.10 times longer than HTII; and cf. Metopolophium fasciatum on Arrhenatherum which has RIV+V 0.65-0.78 times longer than HTII ). The siphunculi are long and pale, with slightly dusky tips and are 1.3-1.9 times longer than the cauda (cf. Metopolophium fasciatum on Arrhenatherum which has siphunculi 1.7-2.0 times longer than the cauda). The cauda is pale. The body length of Metopolophium dirhodum apterae is 1.6-2.9 mm.

Guest image(s) by permission of Roger Blackman copyright AWP all rights reserved.

The rose - grain aphid host alternates from rose (Rosa species) as the primary host in spring and early summer to cereals and grasses, especially wheat, barley and maize, as the secondary host. In mild winters they may overwinter on grasses parthenogenetically. Large numbers on cereals can cause economic damage. Metopolophium dirhodum also transmit maize mosaic virus and barley yellow dwarf virus.

Biology & Ecology

Life cycle

Overwintering eggs laid on rose hatch in March to give fundatrices in April (see picture below of large fundatrix with offspring).

Alatae develop in the second and third generations which then migrate to the secondary hosts, grasses and cereals.

Populations then increase greatly on the secondary hosts probably reaching a peak in June-July.

The return migration of gynoparae to rose occurs in October-November, and their offspring develop to oviparae (see pictures below).

The oviparae of Metopolophium dirhodum on rose are whitish, pale yellow or pink. Those shown above were found on the undersides of rose leaves in late October and November. After mating, the oviparae lay overwintering eggs on the rose stems.

Other aphids on same host:

Primary hosts

• Metopolophium dirhodum has been recorded on 45 species within the Rosa genus (the genus contains perhaps a hundred species, plus hybrids thereof).

  Blackman & Eastop list 61 species of aphid as feeding on plants in the Rosa genus worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 24 as occurring in Britain (Show British list).

• Blackman & Eastop (1984) list thirty-or-so species of aphids that feed on cultivated 'roses', worldwide (Show World list). Of those aphid species, Baker (2015) lists 12 as occurring in Britain (Show British list).

Secondary hosts

• Metopolophium dirhodum has been recorded on 7 Triticum species (Triticum aestivum, Triticum compactum, Triticum dicoccum, Triticum durum, Triticum spelta, Triticum turanicum, Triticum turgidum). Several species of the Triticum genus are grown as 'wheat' the most common of which is Triticum aestivum.

  Blackman & Eastop list 60 species of aphid as feeding on 'common wheat' (Triticum aestivum) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 30 as occurring in Britain (Show British list).

• Metopolophium dirhodum has been recorded on 11 species of Hordeum.

  Blackman & Eastop list 47 species of aphid as feeding on barley (Hordeum vulgare) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 26 as occurring in Britain (Show British list).

• Metopolophium dirhodum has been recorded on 1 species of Zea.

  Blackman & Eastop list 47 species of aphid as feeding on maize (Zea mays) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 23 as occurring in Britain (Show British list).

• Metopolophium dirhodum have been recorded on only 1 species of Oryza: Oryza sativa (Asian rice). No aphid species are listed on Oryza glaberrima (African rice).

  Blackman & Eastop list 34 species of aphid as feeding on rice (Oryza sativa) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 15 as occurring in Britain (Show British list).

Acknowledgements Our particular thanks to Roger Blackman for images of his clarified slide mounts. We also thank Hadlow College and Middle Farm, East Sussex for their kind assistance, and permission to sample. 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).

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