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Genus MetopolophiumRose - grass aphidsOn this page: Genus Metopolophium Metopolophium albidum Metopolophium dirhodum
Metopolophium are medium to large aphids, the adult viviparae of which may be winged or wingless. Wingless adults have rather low, divergent antennal tubercles, and a rather distinct, though lower, median tubercle. The antennae of apterae are shorter than or about the same length as the body. Antennal and dorsal body hairs are very short and blunt. The rostrum is short as is the apical segment (RIV+V). The abdominal dorsum is sclerotic, wrinkled or papillated (=with nipple-like projections). Their siphunculi are cylindrical, rather expanded at the base, pale, not reticulated apically, and with a small to moderate apical flange. The cauda is elongate and rather blunt. Wingless forms are not usually pigmented, but winged forms may be. Some Metopolophium species host alternate between rose (Rosaceae) and many species of grasses (Poaceae). They commonly have a sexual stage in the life cycle, overwintering as eggs. However, some species spend the whole year on grasses, and overwinter viviparously.
The body colour of adult apterae of Metopolophium albidum varies from pale straw-yellow (see first picture below) to pale yellowish green. The adult has no green spinal stripe (cf. Metopolophium dirhodum and Metopolophium fasciatum which both have a green spinal stripe), but sometimes has green spots at the bases of the siphunculi. The antennae become progressively darker from the base to the apex (cf. Metopolophium dirhodum which has the apices of antennal segments darker than the bases of the succeeding segments). The terminal process is entirely dark and the base of antennal segment VI is 1.20-1.62 times longer than the second hind tarsal segment (HTII). The siphunculi are about 1.7 times the length of the cauda and 0.25-0.36 times the length of the hind tibia. The body length of adult apterae is 1.9-2.7 mm.
Alatae have a pale greenish yellow abdomen, a brownish orange head and a pale greenish yellow abdomen. The marginal and intersegmental sclerites are pale and there are sometimes faint cross bands. Immatures are a shiny greenish-yellow. Metopolophium albidum feeds year round on false oat grass (Arrhenatherum elatius). The feeding damage is characteristic, with red and yellow streaky discolouration of the grass blades (see second picture above). Sexual forms have been found in the Netherlands and fundatrices in Britain, but parthenogenetic overwintering is also common.
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 rostrum 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.
The alate (see second picture above) has a pale yellow-green abdomen with darker green markings and sometimes some indistinct brownish cross-bars on anterior tergites (see picture below). The rose - grain aphid host alternates from rose (Rosa sp) 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.
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