Biology Reference
In-Depth Information
95
flower (
Campanula
). Apterae (
c
. 2 mm long) on rowan
are yellowish brown to yellowish green, with pale
siphunculi.
Elatobium abietinum
(Walker) (
96-97
)
Green spruce aphid
A major pest of ornamental and forest spruce (
Picea
)
trees. Spruces of North American origin are usually
more severely affected than Eurasiatic ones. Formerly
restricted to North America but now present throughout
Europe.
DESCRIPTION
Apterous female:
1.5-1.8 mm long; green, with red
eyes; siphunculi long, cauda elongate.
95
Rowan aphid (
Dysaphis sorbi
) damage to shoot of
Sorbus
aucuparia
.
LIFE HISTORY
In parts of mainland Europe which experience harsh
winters, a sexual phase occurs in the lifecycle and the
aphids overwinter in the egg stage. However, in the
British Isles and other areas with less hostile winters,
this species is almost entirely parthenogenetic, and
wingless adults and nymphs occur on spruce trees
throughout the year. These aphids are most numerous
from August to early June but details of their
development vary considerably from area to area. The
aphids feed on the underside of the needles and are very
active, often wandering along the shoots. Winged
female aphids appear from May onwards, and this
brings an end to colony development. These winged
aphids produce small numbers of nymphs, which
aestivate for several weeks before feeding and
completing their development.
96
96
Green spruce aphid (
Elatobium abietinum
) damage to
needles of
Picea
.
DAMAGE
Infestations do not occur on the new growth, but the
aphids cause extensive yellowing of the older foliage.
Severe attacks lead to distinct bronzing and premature
loss of needles. Damage occurs from September
onwards and, in mild conditions, continues to increase
throughout the winter. In many cases, however,
significant damage does not occur until the spring,
reaching a peak in May.
97
97
Green spruce aphid (
Elatobium abietinum
) damage to
branch of
Picea
.
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