PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Steelblue sawflies
‘Spitfires’
Scientific name
Perga spp.(Order Hymenoptera). This is the largest
and commonest of the eucalyptus-feeding sawflies.
Host range
Various species of eucalypt, eg E. camaldulensis,
E. globulus, E. occidentalis, E. melliodora,
E. viminalis.
Description & damage
Only the larvae damage plants.
Adults are called ‘sawflies’ because of the
characteristic saw-like egg-laying ovipositor of the
female used for cutting plant tissues and inserting
their eggs. Adults are about 25 mm long and are of
a general steelblue colour with yellow markings on
the head and thorax. They have yellow antennae
and legs. The wings have well marked veins and
are deep yellow. In the male the upper surface of
the abdomen is covered with silvery down.
Larvae (‘spitfires’). Young larvae are
yellowish with black heads. Fully-fed larvae are
about 70 mm long, black and covered with short
white hairs. They have no prolegs on the
abdomen. They have been called ‘spitfires’
because when disturbed, they bend back their
bodies and exude from their mouths, a viscid
yellowish substance which has a strong eucalyptus
odour. At the same time they raise the tips of their
abdomens and tap up and down. Large colonies
survive better than smaller colonies and if
individuals are separated from the colony they
soon die. It has been suggested that some
individuals in the colony lead the feeding and
movement and the survival of other members is
dependent on the activities of these leaders. The
yellow exudate has a high concentration of
eucalyptus oil and can cause severe pain if it gets
in the eyes, the eyeball becomes bloodshot and is
often called ‘Christmas eye’. Medical attention is
required to ease the irritation.
Leaves. Juvenile and adult foliage attacked.
The larvae feed on the foliage and can seriously
defoliate young trees. During the day they rest
clustered together in a tightly packed mass on the
tree upon which they are feeding. At night they
wander individually over the foliage to feed and
later return to their resting place. On older trees
the damage is not usually long lasting. On small
trees larvae from a single batch of eggs can
defoliate the whole tree.
Diagnostics.
Adult sawflies which do not have a waist like
ants and wasps are not often seen.
Larvae are common, gregarious, conspicuous
and resemble large hairy caterpillars but do not
have any prolegs on the abdomen.
Chewing damage to eucalypt leaves can also
be caused by leafeating beetles and their larvae
and many caterpillars.
Adult sawfly (about x 2).
Top: Young larvae. Lower: The cuticle
of the leaf has been removed to show
the eggs laid in the leaf tissue.
Top left: Cocoon
Top right: Young larva (x 5)
Lower: Fully-fed larva (spitfire)
Fully-fed larva (spitfires),
about natural size.
Fig. 93. Steelblue sawfly (Perga spp.). PhotosNSW Dept of Industry and Investment.
Insects and allied pests - Hymenoptera (ants, bees, sawflies, wasps) 125