Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 46

Aphis ilicis Kaltenbach ( 74 )
Holly aphid
Infestations of this widely distributed, greenish-black to
reddish-brown or greyish-brown aphid occur on new
shoots and young foliage of holly ( Ilex ). Attacks, which
result in significant leaf curling, tend to occur only on
young plants, on severely pruned bushes or on hedges
producing an abundance of new growth. Colonies die
out in the absence of young growth (mature foliage
apparently being unsuitable for their continued
survival). The winter is spent in the egg stage.

milkweed ( Asclepias ). Of southern European origin but
now established in many other warm parts of the world.
The aphids occur mainly on the young, succulent
growth, and very large colonies develop on the shoots
and along the midrib of expanded leaves. Direct damage
is of little significance but the aphids produce
considerable quantities of honeydew upon which sooty
moulds develop, spoiling the appearance of ornamental
hosts. The aphids are a particular problem on frequently
pruned and heavily fertilized plants that produce an
abundance of new growth. Apterae (1.5-2.6 mm long)
are bright lemon-yellow (occasionally tinged with
green), with dark legs and antennae, a black cauda and
relatively long, stout, black siphunculi.

Aphis nerii Boyer de Fonscolombe ( 75 )
Oleander aphid
Although associated mainly with oleander ( Nerium
oleander ), this entirely parthenogenetic aphid also
infests other Apocynaceae, including Chinese dregea
( Dregea sinensis ), as well as plants such as Citrus and

Aphis newtoni Theobald ( 76-77 )
Iris aphid
This dark green to brownish-black aphid is recorded
only from various countries in north-western Europe,
including England, Germany, the Netherlands and
Scandinavia, where it is associated with Iris . Large
numbers often build up on the lower parts of leaves
and, later, on the young inflorescences. Colonies are
commonly attended by ants and are sometimes
protected by ant-built earthen canopies.

74

Aphis pomi Degeer ( 78 )
Green apple aphid
Infestations of this generally common aphid often
occur on Cotoneaster , crab-apple ( Malus ), firethorn
( Pyracantha ), hawthorn ( Crataegus ), medlar ( Mespilus
germanica ), rowan ( Sorbus aucuparia ) and other
species of Sorbus , but they are of greater significance
on apple trees. Heavy attacks on ornamentals occur
most commonly from June or July onwards. Dense ant-
attended colonies develop on the underside of leaves
and on the new shoots. The aphids (1.3-2.3 mm long)
are bright green or yellowish green, with short antennae
and black or dark brown siphunculi. They excrete
quantities of honeydew, and foliage and shoots soon
become blackened by the accumulation of sooty
moulds. Heavy summer infestations cause leaf curl and
check the growth of new shoots. Damage to nursery
stock may be considerable, but attacks on established
trees and shrubs are usually of little or no importance.

74 Colony of holly aphid ( Aphis ilicis ).

75

Aphis sambuci Linnaeus ( 79 )
Elder aphid
Widespread and often abundant on elder ( Sambucus ),
including ornamental forms. In spring, dense, ant-
attended colonies develop on the young shoots,
infestations being most common on bushes growing in
suburban areas. In July there is a migration of winged

75 Colony of oleander aphid ( Aphis nerii ).