Megoura viciae Buckton Vetch aphid

Minor infestations of this aphid occur on various members of the Fabaceae, including broad bean, culinary pea and vetches. Heavily infested parts of plants become discoloured, the affected tissue turning red and eventually black; damage, however, is rarely important. The aphids are also vectors of several viruses, including bean enation mosaic and bean leaf roll.

BIOLOGY

Eggs overwintering on host plants hatch in the spring from early April onwards. After about three generations of wingless forms, winged aphids are produced, and these spread infestations to other locations. Breeding continues until the autumn when populations reach their peak and, eventually, winter eggs are laid.

DESCRIPTION

Aptera 3.0-4.3 mm long, body spindle-shaped, mainly green to dark bluish-green; head, antennae, prothorax and legs black; siphunculi black and distinctly swollen; cauda black and finger-shaped (Fig. 188e).

tions also occur on grasses. Damage is rarely important, but 'outbreak' years are known in which very large populations develop and yield reductions occur. On wheat and barley, aphids developing on flag leaves from ear emergence onwards are of greatest significance; on maize and sweet corn, the aphids are of only minor importance unless very numerous. Colonies on rose bushes have little direct effect on plant growth.

BIOLOGY

This species overwinters in the egg stage on wild and cultivated rose bushes where, in spring, colonies develop on the leaves and flower buds. Winged forms are produced from April or early May onwards. These aphids migrate to cereals and grasses, where breeding continues; colonies on rose do not persist beyond June (cf. rose aphid, Macrosiphum rosae, above). On cereals, the aphids are restricted mainly to the lower leaves but, especially if numerous, they may invade the upper leaves, including the flag leaves. The aphids feed mainly beneath the leaves and, although dislodged by gusts of wind, usually remain undisturbed by rain (cf. grain aphid, Sitobion avenae, p. 120). Colony decline on Poaceae is followed by a return migration to rose, the primary host; winter eggs are laid in October and November. In mild, ideally damp situations, the aphids are capable of surviving the winter pathenogenetically on grasses.

DESCRIPTION

Aptera 1.5-3.0 mm long; body broadly spindle-shaped, pale green (rarely pink) with a dark longitudinal stripe dorsally; siphunculi long and pale; cauda broadly finger-shaped (Fig. 193a); head with divergent lateral prominences and a distinct median prominence (outline, therefore, W-shaped) (Fig. 189e).

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