Pemphigus phenax Borner Blunck Carrot root aphid

This species is a common but minor pest of carrot; it also forms disfiguring galls on Populus nigra Ttalica'. Heavily infested carrots are weakened and the quality (and, hence, value) of wax-contaminated roots is reduced.

BIOLOGY

Overwintered eggs on Populus hatch in the spring, and aphids move to the unfurling leaves where they induce the formation of mid-rib galls. Each gall becomes an elongate, somewhat wrinkled, reddish swelling (often tinged with yellow laterally), packed with numerous wax-secreting aphids. In summer, winged forms are produced and these migrate to carrot plants where they initiate dense colonies on the roots. The root-feeding aphids produce copious amounts of white waxen 'wool', which may carpet the ground when heavily infested plants are lifted. There is a return migration to Populus in the autumn, where winter eggs are laid on the bark, but parthenogenetic colonies may persist throughout the winter on spring-lifted carrot crops; individuals can also survive the winter in the soil.

DESCRIPTION

Aptera (on carrot) 1.6-2.5 mm long, globular, yellowish-white to pale yellow, coated with white wax (Plate 2f); antennae very short (Fig. 195b); siphunculi absent.

Family PHYLLOXERIDAE

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