Lepidosaphes ulmi L Mussel scale

This generally abundant scale insect is associated with a wide range of trees and shrubs. Infesta tions are of particular significance on mature, unsprayed apple trees and pear trees. The shoots and branches become encrusted with scales and heavily infested hosts are weakened.


Eggs overwinter, sheltered beneath the protective maternal scale, and hatch in late May or early June. The first-instar nymphs ('crawlers') are relatively active and crawl over the host plant for a few days before becoming sedentary. They then insert their mouthparts and begin to feed, usually on the shoots and branches but occasionally on leaves and developing fruits. They pass through three nymphal instars and reach the adult stage in late July. Eggs are laid from August onwards; the adults then die. There is one generation annually. This insect usually breeds parthenogenetically but some races reproduce sexually, with males appearing in early August.


Adult female scale 2-3 mm long, grey to yellowish-brown, elongate but mussel-shaped (see Fig. 45a). Adult female 2.5 mm long, body subelongate, with a distinct pygidium (see Fig. 45b). First-lnstar nymph pale yellowish-brown, oval.

Family COCCIDAE (soft scales)

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