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The Tasmanian Naturalist 142 (2020)
61
Impact of the jewel beetle Cyrioides imperialis
(Fabricius, 1801) (Coleoptera: Buprestidae) on
Banksia marginata revegetation at Seymour,
Tasmania
Karen Richards¹, Chris P. Spencer¹, David Quon² & Cheryl Quon²
¹65 Sinclair Avenue, Moonah, Tasmania 7009
²“Templestowe” 48 Macquarie Street, Seymour, Tasmania 7215
spenric@gmail.com
Cyrioides imperialis (Fabricius, 1801) is
the largest jewel beetle occurring in
Tasmania. The species is widespread
across the Australian eastern region
where it is reported to be host-
specic to the Banksia genus, earning
it the vernacular name banksia borer
(Tepper 1887, French 1900). Records
do, however, exist of the species
utilising Leptospermum spp. (Williams
1977; Williams & Williams 1983 in
Hawkeswood 2007). The beetle is
black and boldly patterned with yellow
transverse bands and/or patches.
This apparently aposematic colouring,
though striking, serves as a surprisingly
effective camouage amongst banksia
foliage. As with the majority of
Tasmanian jewel beetles, activity of
adult C. imperialis is limited to the
warmer months, December to March,
peaking on calm sunny days in January
and February when emergent beetles y
to, and feed on, B. marginata leaves and
shoots. Mating takes place amongst the
foliage, then fertilised females descend
and oviposit in bark ssures on the
lower trunk or root bole (Plate 1).
In Tasmania, the effect of C. imperialis
on sapling B. marginata has been
reported by Richards & Spencer (2018);
that study presented a detailed account
of larval activity and evidence that a
single larva may kill a juvenile tree, but
it also noted that more mature trees
appear unaffected, despite the presence
of multiple larvae. In his 1900 book
A Handbook of the Destructive Insects of
Victoria, Charles French, the government
entomologist of the period, portrays C.
imperialis [as Cyria] as a destructive pest
and advocates for control measures
(French 1900). However, his suggested
control method was to treat the tree with
a poisonous substance via the hole from
which the beetle had emerged, clearly an
ineffective practice!
This study reports the impact of C.
imperialis on 10–13-year-old B. marginata
revegetation on “Templestowe”, a 100-
acre former sheep grazing property at
The Tasmanian Naturalist 142 (2020
62
Seymour, on Tasmania’s east coast. In
2003 the land was purchased by David and
Cheryl Quon, who had a conservation
covenant applied to the property and
undertook a revegetation project with
the aim of providing a wildlife corridor
connecting the Douglas-Apsley National
Park to the reserve on Seymour Point,
via Doctors Creek and “Templestowe”.
Planting commenced in 2005 with the
establishment of 800–1000 saplings,
mainly eucalypt species, planted at 2 m
intervals on the south-western property
boundary. A grant obtained in 2007
allowed the planting of a further 4000
trees, 250 of which were B. marginata, by
conservation volunteers; this effort was
repeated in 2008. Additional planting of
1500 assorted tree species was continued
by the owners over the subsequent
years. Plants were tube stock grown
by Pulchella Nursery, generally from
seed of local provenance, apart from
the initial planting of eucalypts which
were sourced from the former Forestry
Tasmania’s Perth nursery.
“Templestowe” was surveyed in early
January 2020 by Janet Smith and
Karen Richards for the Department
of Primary Industries, Parks, Water
and Environment’s Private Land
Conservation Program, which involves
ongoing monitoring of wetland
vegetation communities on covenanted
land. Karen augmented the survey with
an invertebrate inventory and alerted
the owners to the presence of damage
caused by C. imperialis.
On the day of the survey it was still,
23°C and overcast with smoke haze
from a nearby bushre. Immediately
inside the property gate KR noted and
photographed a dead 20 cm diameter
Plate 1. Ovipositing female Cyrioides imperialis.
The Tasmanian Naturalist 142 (2020)
63
B. marginata (Plate 2) containing at least
13 C. imperialis emergence holes on the
lower trunk and an exposed root; an
adjacent banksia also had 8 emergence
holes on the trunk and was dying. There
were additional dying B. marginata trees
that did not display emergence holes.
Cyrioides imperialis were active and within
10 minutes, 6 individuals were observed
on 3 trees in close proximity to the gate,
including multiple ovipositing females.
Upon consultation, David and Cheryl
recalled rst noticing dead B. marginata
in 2018 near the main gate, in an area
containing 12 banksias with average
trunk diameters of 20 cm. By May 2020,
30% of these 13-year-old trees were
dead and displayed 4–13 emergence
holes. One dead tree, however, had
no holes and was obviously not the
victim of beetle attack and more likely
to have died from disease or lack of
water. A monitoring project aimed at
better assessing the impact of beetle
infestation on B. marginata regeneration
at “Templestowe” was initiated by KR
and CS in June 2020, the main results of
which will be reported separately.
Of the 400–500 B. marginata planted on
the property, approximately 50% had
visible emergence holes of C. imperialis
and the cerambycid Tragocerus spencii
Hope, 1834. Most of these trees had
three or fewer C. imperialis emergence
Plate 2. Dead Banksia marginata on the “Templestowe” property.
Insert: Cyrioides imperialis emergence holes.
The Tasmanian Naturalist 142 (2020
64
holes, but some trees displayed as many
as 20 on their lower trunk and exposed
root surfaces. Despite the beetle activity,
the majority of the trees appeared
healthy and were not exhibiting signs of
stress e.g. foliar yellowing.
Previous research at Cleveland (Richards
& Spencer 2018) suggested that C.
imperialis favoured younger banksias,
while the large cerambycid Paroplites
australis (Erichson, 1842) typically
infested dead or dying mature trees.
The observations at Seymour appear to
support these ndings. While T. spencii
also appears to favour younger trees, and
may be a contributing factor in banksia
decline, it is less likely to cause tree death
as it attacks the upper stem or branches
and not the lignotuber (Richards &
Spencer 2019).
The nearest naturally occurring stand
of banksia trees is along the eastern
boundary of the property. In this stand
the trees are mature, several with trunk
diameters approaching 70 cm. Many
of the trees exhibit emergence holes
of P. australis (Plate 3) and C. imperialis;
however, the latter are all very old and
disgured by trunk growth, indicating
that the species is no longer active at
the site. Approximately 100 B. marginata
were planted near this location in
2007–8 and all remain healthy, with no
obvious emergence holes. This sector
of “Templestowe” adjoins the coastal
strip of the Seymour Conservation Area
and Seymour Swamp; both areas have
numerous healthy mature B. marginata,
many of which also show evidence of
attack from the beetles, but few trees are
senescing. Despite the age and overall
health of these trees, no natural banksia
regeneration was recorded and evidence
of re, thought essential for banksia
regeneration, was not observed at these
locations.
Cyrioides imperialis are heavy, cumbersome
yers and are not manoeuvrable;
consequently they tend to mostly visit
trees on the outer edge of plantings
leaving internal banksias untouched.
Unfortunately, many of the banksia trees
inside the new stands are now heavily
overshadowed by vigorously growing
Plate 3. Emergence holes of Paroplites australis (left); Cyrioides imperialis (centre);
Tragocerus spencii (right). Scale button = 10 mm.
The Tasmanian Naturalist 142 (2020)
65
eucalypts and are succumbing to a
lack of light. Additionally, the mature
banksias adjacent to “Templestowe”,
while currently mostly healthy and
not impacted by C. imperialis, are of a
similar age; they will become senescent
in the near future, and the stands will
disappear without intervention to ensure
regeneration in these areas.
At rst it seemed likely that the
density of C. imperialis on the property
might prove to be a barrier to the
establishment of B. marginata plantings;
however, it now appears that many of
the surviving banksias are approaching
a size where they are less attractive to
ovipositing C. imperialis, and indeed
many of the trees are already past
this point. Any future planting of B.
marginata in the Seymour area is likely
to be impacted by these insects but, as
with the “Templestowe” plantings, trees
planted in optimal conditions will grow
quickly and the majority will survive the
insect attack.
References
French, C. (1900). A Handbook of the
Destructive Insects of Victoria, with Notes
on the Methods to be Adopted to Check and
Extirpate them. Part III. Government
Printer, Melbourne.
Hawksewood, T. (2007). A review of the
biology and a new larval host plant for
Cyrioides imperialis (Fabricius, 1801)
(Coleoptera: Buprestidae). Calodema
Supplementary Paper No. 25 (2007): 1–3.
Richards, K. & Spencer, C.P. (2019). A
new larval host plant for Tragocerus
spencii Hope, 1834 (Coleoptera:
Cerambycidae) in Tasmania. The
Tasmanian Naturalist 141: 120–124.
Richards, K. & Spencer, C.P. (2018).
Exploitation of sapling Banksia
marginata by Cyrioides imperialis
(Fabricius, 1801) (Coleoptera:
Buprestidae) in Tasmania. The
Tasmanian Naturalist 140: 27–32.
Tepper, J.G.O. (1887). Common Native
Insects of South Australia. A Popular
Guide to South Australian Entomology.
Part 1. Coleoptera or beetles. E.S.
Wigg & Son, Adelaide.
Williams, G.A. (1977). A list of
Buprestidae (Coleoptera) collected
from Leptospermum avescens Sm. at East
Minto, New South Wales. Australian
Entomological Magazine 3: 81–82.
Williams, G.A. & Williams, T. (1983). A
list of Buprestidae (Coleoptera) of the
Sydney basin, NSW, with adult food
plant records and biological notes
on food plant associations. Australian
Entomological Magazine 9: 81–93.
The Tasmanian Naturalist 142 (2020
66