Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 73

144 145

144 Colony of woolly aphid ( Eriosoma lanigerum ). 145 Gall of currant root aphid ( Eriosoma ulmi ) on leaf of Ulmus .

146

146 Colony of currant root aphid ( Eriosoma ulmi ) on roots
of Ribes .

of curled leaves, protected by flocculent masses of bluish
or whitish wax. Winged forms are reared in June and July;
these then migrate to currant and gooseberry bushes,
where colonies of greyish or pinkish-grey aphids develop
on the roots amongst masses of whitish wax. Winged
aphids return to elm in the autumn where, after a sexual
phase, eggs are eventually laid. Infested elm foliage is
severely curled and shoot growth is checked; however,
attacks, although often common in gardens, do not harm
established trees. Summer infestations on the roots of
ornamental currant, such as flowering currant ( Ribes
sanguineum ), affect growth of young plants and are of
particular importance on containerized nursery stock.

DAMAGE
Masses of flocculent wax accumulate on heavily
infested plants. This is unsightly and a particular
nuisance if infested branches overhang or lie alongside
garden paths. The aphids also induce the development
of disfiguring galls; these cause new growth to be
malformed and the wood of older branches to split.

Eriosoma ulmi (Linnaeus) ( 145-146 )
Currant root aphid
This generally common Eurasiatic species overwinters on
elm ( Ulmus ). Overwintered eggs hatch in the spring.
Colonies of greyish aphids then develop on the underside