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
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.
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.