Biology Reference
In-Depth Information
58
59
58
Colony of citrus whitefly (
Dialeurodes citri
).
59
Colony of phillyrea whitefly (
Siphoninus phillyreae
) on
underside of leaf of
Phillyrea
.
Dialeurodes citri
(Ashmead) (
58
)
Citrus whitefly
This polyphagous species is mainly a problem in citrus
orchards, but is also found on certain other hosts,
including ornamentals such as ash (
Fraxinus excelsior
),
Forsythia
,
Gardenia
, lilac (
Syringa
), Persian lilac
(
Melia azedarach
) and privet (
Ligustrum vulgare
). Of
East Asian origin, and first noted in Europe (Italy and
southern France) in the 1950s.
Pealius azaleae
(Baker & Moles)
Azalea whitefly
Adults of this widely distributed but local pest of
evergreen azalea, especially
Rhododendron mucronatum
and
R. simsii
, appear during the early summer. They
congregate on the underside of the leaves, where eggs
are laid, and make short flights if disturbed. Nymphs are
light green and scale-like. They develop on the underside
of the leaves from late summer onwards, overwintering
and completing their development in the spring. There
is one generation annually. The nymphs excrete
considerable quantities of honeydew, and the leaves
of infested plants commonly become coated and
discoloured by sooty moulds. Infestations are reported
from various parts of the world, including Australasia,
Europe (e.g. Belgium, England, Germany, France, Italy
and the Netherlands) and Japan.
DESCRIPTION
Adult:
1.2-1.4 mm long; creamy white, coated with
white wax.
Egg:
0.2-0.3 mm long; oval and pale
yellow, with a pedicel.
Nymph:
up to 1.5 mm long; pale
greenish yellow, flat, oval and scale-like.
Pseudo-pupa:
1.2-1.5 mm long; flat, oval and scale-like.
LIFE HISTORY
Adults, which first appear in April or May, are short-
lived, each surviving for about 10 days. Eggs are laid in
batches on the underside of young leaves and hatch
1-4 weeks later, depending on temperature. The scale-
like immature stages feed on the underside of leaves for
3-4 weeks; they then enter a quiescent pseudo-pupal
stage which lasts anything from 2 to 42 weeks or more.
Infestations are often very heavy, with several hundred
individuals clustered on a single leaf. The pest
overwinters as either third- or fourth-instar nymphs.
Under favourable conditions, there are four generations
annually.
Siphoninus phillyreae
(Haliday) (
59
)
Phillyrea whitefly
A locally common but minor pest of mock privet
(
Phillyrea latifolia
); also occurs on ash (
Fraxinus
excelsior
). Widely distributed in mainland Europe but
absent from northerly areas; in the British Isles confined
mainly to southern England. Present in parts of North
Africa and Asia.
DESCRIPTION
Adult:
1 mm long; yellow, marked with grey; fore
wings mainly white but somewhat smoky basally.
Egg:
0.3
0.1 mm; oblong, with a short stalk; yellow to
brownish.
Nymph:
elliptical to oval; brownish, with a
fringe of white waxy plates; profusely dusted with
white, powdery wax.
Pseudo-pupa:
1.0
×
DAMAGE
Hosts are weakened by heavy, persistent infestations.
However, sooty moulds, which accumulate on honeydew
excreted by this pest, tend to be more significant; they
affect the quality and appearance of ornamentals.
0.7 mm;
brown to brownish black; elliptical, with a distinctive
white waxen rim.
×
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