Farm Forestry
Association Eucalyptus Action Group and Acacia Melanoxylon (Blackwood)
Action Group,
MAF Sustainable Farming Fund Grant 2004/2005 and 2006:
Control of Eucalypt
and Blackwood Pests with the Southern Ladybird- A Possibility?
Contact person: Dean Satchell
RD1 Kerikeri, Northland, New Zealand.
Phone (09) 407 5525
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| Cleobora
mellyi eating tortoise beetle
eggs |
Cleobora
mellyi, the southern ladybird, was introduced into New
Zealand from Tasmania
in 1977 for control of the eucalypt tortoise beetle, Paropsis
charybdis. This specialist ladybird diets on
psyllids and
tortoise beetles, pests of both blackwood (Acacia
melanoxylon)
and eucalypts. However Cleobora
has been geographically isolated in the Marlborough Sounds for twenty
five years and therefore unavailable to farm foresters as a tool for
controlling pests in their plantations.
The Eucalypt
Tortoise
Beetle
Since early last century,
eucalypt trees in New Zealand have been under siege by the tortoise
beetle Paropsis
charybdis, an
Australian beetle which at both the
larval
and adult stages has a voracious
appetite for
eucalypt foliage. In 1987 a biological control agent
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| Eucalyptus tortoise
beetle, Paropsis
charybdis |
Enoggera nassaui was introduced from Australia
in a partially successful effort to control the pest. However, in Forest
Health News 117, April 2002, it was reported that E. nassaui
is itself now under attack from
a hyperparasitoid Baeoanusia
albifunicle. B. albifunicle checks the population
growth of E.
nassaui
and prevents it from multiplying as rapidly as it has in past seasons.
This is likely to have serious consequences, since until now E.
nassaui has been the only biological
control agent effective against P. charybdis in
this country. The discovery
of a second insect, also reported in Forest
Health News 117, April 2002, a tiny wasp identified as Neopolycystus
sp., may hold some hope for
controlling P.
charybdis, as
this species, like E.
nassaui, is a
primary parasitoid of eucalypt leaf beetles such as Paropsis
spp. in Australia.
Cleobora-
the history
Australian predators and parasites of P. charybdis
have been investigated in New Zealand as potential biological control
agents since the 1930s, and in 1977 Cleobora mellyi the Southern
Ladybird was imported from
Tasmania. These were reared
 |
| Cleobora
mellyi larvae in Tasmania eating tortoise beetle eggs |
and
3000 adult Cleobora
were released in eucalypt plantations in the central North Island,
Christchurch and the Marlborough Sounds. Adults were subsequently found
overwintering under bark in the latter release area, and Cleobora
established only in the Marlborough Sounds, in a mixed Eucalyptus
and Acacia plantation.
The effect of Cleobora on P. charybdis
populations there was never determined, and work on Cleobora
was abandoned.
It is likely that Cleobora did not establish in the
other release sites because blackwoods, and therefore the most
important component of the natural diet for this ladybird, Blackwood
psyllids, were not present. At that time, only one species of
eucalypt psyllid was present in New
Zealand, Ctenarytaina
eucalypti,
the blue-gum psyllid. This psyllid is only present
on juvenile
foliage of
blue-gums. Beetles, including ladybirds and tortoise beetles are not
found on juvenile blue-gum foliage
because it is too waxy and their feet cannot grip on its surface
(confirmed by recent observations in the Marlborough Sounds where
Cleobora were not found on juvenile blue-gum foliage despite
abundant blue-gum
psyllids feeding on the foliage).
Furthermore, Paropsis
charybdis eggs, which are eaten by Cleobora, are known to be
laid in cycles, so at times Cleobora would require abundant psyllids to
feed on.
The
Forgotten Ladybird
Twenty five years later the Eucalypt Action Group confirmed
that Cleobora
is both present and abundant in the mixed blackwood/ eucalypt stand at
Maori Bay in the Marlborough Sounds. This population appear to be
effectively controlling psyllids on the Blackwoods on which they are
common. In October 2005 Richard Davies-Colley and Dean Satchell
travelled to the Marlborough Sounds to assess this population and a report was
produced.
Ladybirds have been
collected and a rearing/release program has produced and released Cleobora
in the
North island.
Eucalypts
Since the original
introduction of Cleobora
into New
Zealand , a
number of pest psyllid species have become established on eucalypts in
New Zealand including the shoot psyllids Blastopsylla
occidentalis
and Ctenarytaina
spatulata.
These are now very common on a wide range of eucalypt species, and an
ideal food for Cleobora.
Other recent eucalypt psyllid introductions include Cardiaspina
fiscella (a serious pest of Eucalyptus saligna and E.
botryoides), Glycaspis granulata,
Eucalyptolyma maidenii, Cryptoneossa triangulata, Creiis lituratus
and Anoeconeoassa communis, all pests of eucalypts
and potential food for Cleobora.
Two more
Australian eucalypt tortoise beetles, likely food sources for Cleobora,
have also established in New Zealand since the original
introduction attempt. Trachymela
catenata has
established in the Gisborne area, and Trachymela
sloanei
first found in Auckland in 1976, has spread to other parts of the
country causing some concern for eucalypt growers.
The diversity of
these pests suggest an adequate food source for Cleobora
that was not available in 1980.
Blackwoods
Blackwood
tortoise beetle
The blackwood tortoise beetle, Dicranosterna semipunctata,
first discovered in Auckland in 1996, has become established on Acacia
melanoxylon, Tasmanian blackwood. This pest has now spread
through the top half of the North Island and is of major
concern to growers of this valuable timber.
Recent feeding trials by the Eucalyptus Action Group have shown that
both the eggs and larvae of the blackwood tortoise beetle are eaten by Cleobora.
 |
| Blackwood tortoise beetle, Dicranosterna
semipunctata |
 |
 |
| Early instar Dicranoseterna
semipunctata
larvae |
Eggs
of Dicranosterna semipunctata |
 |
| Cleobora larvae devouring Dicranosterna larvae in
captivity |
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| Dicranosterna semipunctata, the blackwood
tortoise beetle, chews its way through blackwood foliage throughout
summer |
Blackwood psyllids
Blackwood psyllids are present throughout the year, with
population
peaks in late spring, and at the completion of the growing season in
autumn. It is very likely Cleobora
will effectively control this pest
in our blackwood plantations.
 |
| Acacia psyllids
suck the sap from Blackwood leaves and shoots. These
nymphs are a
favourite food of the Cleobora ladybird. There is an
adult
psyllid in the top left corner of this photograph. |
It was noted in a recent Tasmanian study that in April,
blackwood
seedlings bordering a eucalypt plantation carried large numbers of
newly emerged Cleobora ladybirds feeding on
psyllids prior to
overwintering. The ladybirds were not found in the plantation at this
time despite some tortoise beetle eggs being available on the
plantation eucalypts. This indicates a dietry preference for psyllids.
Solutions?
It is likely Cleobora
will emerge in spring at the same time as Paropsis, when Paropsis causes the
most damage (See Paropsis
Charybdis Defoliation of Eucalyptus Stands in New Zealand's
Central North Island
pdf published in 2000). It is therefore possible that Cleobora
may
provide some level of control over Paropsis
in eucalypts, facilitated
by the presence of psyllids.
The signs are encouraging that the insect diversity required for good
levels of control of a number of insect pests by Cleobora on Eucalyptus
and Acacia
is present, and the mindset of industry is there for the
promotion of naturally sustainable biological control options.
Distribution
and release
Releases of Cleobora were made in the North Island and
Southland during 2006 and 2007 in mixed blackwood/eucalypt plantations.
We hope this is the first step towards improving the
biological control of a large number of eucalyptus and acacia pests
currently established in New Zealand, while also providing Farm
Forestry Action Group
members with
much needed experience in both this field and also building links
between supporting members, e.g. industry, farm forestry and govt
departments.
Cleobora has established in several sites in the North Island . We now
hope to study
pest/ predator dynamics, and hopefully document good control of target
pests. If you have a mixed eucalypt / blackwood or blackwood plantation
where you would like to release this ladybird please get in touch with
us.
Dean Satchell has been
working on
intensive mass rearing systems for three years and has devised
artificial diets and techniques suitable for rearing large
numbers of this beneficial insect inexpensively and easily.
last updated May 2010
Many thanks Nod Kay
for "seeding" this ladybird in our minds...
Many thanks also to Brian Richardson and John Bain of Forest Research
for supporting our application and making this possible, and also Dick
Bashford of Forestry Tasmania for all his advice and support.
Eucalyptus
Action Groups successful application 2004/2005
AMIGO
successful application 2006/2007
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