Biology Reference
In-Depth Information
Saissetia oleae (Olivier) ( 224 )
Mediterranean black scale
A generally abundant subtropical species, attacking a
wide range of trees and shrubs, including ornamentals
such as ivy ( Hedera ), oleander ( Nerium oleander ), olive
( Olea europaea ) and Pittosporum . Originally
Palaearctic, but now virtually cosmopolitan. Widely
distributed in southern Europe.
DAMAGE
Heavily infested hosts are weakened, and shoots and
leaves may wither. Also, considerable quantities of
honeydew are excreted by the developing nymphs, and
this quickly allows sooty moulds to become established.
This is both debilitating and unsightly.
Saissetia coffeae (Walker) ( 225 )
syn. S. hemisphaericum (Targioni-Tozzetti)
Hemispherical scale
An often abundant scale in greenhouses. Infestations
occur on a wide variety of hosts, including Asparagus
plumosus, Begonia , carnation ( Dianthus caryophyllus ),
Ficus , oleander ( Nerium oleander ) and Stephanotis , and
on various ferns and orchids. Infestations rarely cause
significant damage, particularly if plants are otherwise
healthy and well-tended, but hosts are often
contaminated by honeydew upon which sooty moulds
develop. Eggs and nymphs occur at all times of the year,
even in unheated greenhouses. Reproduction is entirely
parthenogenetic. Each female deposits up to 2,000 eggs
in a tight cluster beneath her body and then dies. The
female scales are 2-3 mm across, strongly convex and
reddish brown to blackish; oval forms are larger than
rounded ones, sometimes exceeding 4 mm in length.
DESCRIPTION
Adult female (scale): up to 5 mm long and 3 mm wide;
very convex, dark brown to black, with ridges forming
a distinctive H-shaped pattern on the back. Egg: minute,
oval, whitish to pale brownish yellow. First-instar
nymph:
pinkish, elongate-oval and dorsoventrally
flattened.
LIFE HISTORY
Infestations occur on leaves, shoots and branches, each
mature female depositing up to 2,000 or more eggs. The
eggs hatch 2-3 weeks later. First-instar nymphs occur
mainly on the young shoots and underside of leaves.
Under ideal conditions the complete lifecycle lasts for
3 or 4 months, and there are two generations annually.
However, in the more northerly parts of its outdoor
range the pest completes just one generation. Although
males are known to occur, reproduction is mainly
parthenogenetic.
224
225
224 Mediterranean black scale ( Saissetia oleae ).
225 Hemispherical scale ( Saissetia coffeae ) on Encephalartos .
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