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SHIELD BUGS: (Stink bugs) : Bronze Orange Bug, Glossy Shield Bug, Gum Tree Shield Bug, Australasian Green Shield Bug

Shield Bugs


Bronze Orange Bug

Adult Bronze Orange Shield Bug

Scientific Name : Musgraveia sulciventris

(episodic infestations)

When and where in yard : Found on two of our citrus trees in back corner of yard – the Lemonade Tree (hybrid mandarin x lemon) and the native Finger Lime. Infestations of over fifty bugs at different life/colour stage occurred in spring/summer.

Adult showing gland from which stink chemical squirted.

Observations: Adults are quite hefty and long at around 25mm The nymphs I photographed would be 3rd -5th instars and measure 15-20mm. The first time our citrus trees were infested with these destructive stink bugs I googled how to get rid of them. Following advice on the internet I donned rubber gloves and put on sunglasses for protection then I painstakingly and prickingly (the Finger Lime has mean thorns) picked off each shield bug I could reach. Protection is necessary because of the shield bug’s defence mechanism , that is, their ability to squirt a chemical at their attackers from a gland on the underside of the thorax (blue arrow). We discovered this chemical had an unpleasant (but not overpowering) waxy off-citrus sort of smell. We flicked the removed bugs into a tub of soapy water to drown them. This may seem macabre but better than generalised pesticide sprays which, apparently, are often ineffective against stink bugs anyway. Another solution is to use a vacuum (preferably old or with a bag so you can throw the stink away) to suck them off the trees but we’ve only got an upright – so not exactly a workable proposition for us.

Stink bug chemical staining my hand

After a few weeks the shield bugs began to increase in numbers again as new nymphs hatched. However this time, stupidly, I grabbed the garden gloves. Bad mistake. I picked off the stinkbugs for an hour or so. It wasn’t till I finished and removed my sturdy, but non-waterproof, gloves that I realise my hands had been badly stained by the stinky liquid exudate. The irony was, that had I had bare hands I would’ve realised straight away the effect of the chemical on my skin. There was absolutely no sign on my gloves of the brown stain. As it was, I had a dark, now-tingling stain on my hands which had accumulated over the last hour. Lesson learned – garden gloves are porous. My fingers continued to tingle for a few days as a result of the chemical ‘burn’. The stain persisted for a few weeks until finally the top layer of skin sloughed off. On the upside, we appeared to have defeated that particular infestation of bronze orange bugs.

I have several photos of the three ‘colour’ stages of the bronze orange bug: Green– newly hatched nymphs and early instars are more difficult to see because of their light green colouring. Orange –The later instars (4-5th instar) are a bright orange and are the easiest to see and remove. Although far from my favourite True Bug (Order Hemiptera) I’ve used the orange nymph as the header image due to its quite spectacular appearance. Black/bronze adults (top image) are large and sturdy and have the ability to fly or drop to the ground when you approach to grab them.

Our Finger Lime tree seems to have recovered well from the most recent infestation around 4 months ago and we had a bumper crop during February-March. But the Lemonade tree is still struggling, the fruit is discoloured and dropping early – possibly there is an unidentified secondary pest taking hold of the stressed tree.

Fun (and not-so-fun facts) : Bronze Orange bugs suck the sap and juices from flowers, fruit and shoots of citrus trees. They are native in origin but their population has spread and increased to pest proportions due to plantings of edible citrus. Certainly their natural range is far to the north of Wollongong (where we live). One of Musgraveia sulciventris native hosts is the Australian Finger Lime. Possibly that is why my Finger Lime tree coped so much better with an infestation. Maybe it has developed greater resistance or better recovery strategies. The female Bronze Orange Bug lays 10-14 pale green spherical eggs on the underside of the citrus leaves. These hatch into small green nymphs around late winter. I’ll check our citrus around August next year to see if I can photograph these eggs and nymphs (first instars) – although the gardener side of me doesn’t really want to find any.

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Glossy Shield Bug

Glossy Shield Bug on Twiggy Myrtle Spring 2017

Other Common Names: Brown Soldier Bug

Scientific Name: Cermatulus nasalis

(Only seen once 2017)

When and where in yard : Only sighted once in Nov 2017 on Twiggy Myrtle (low shrub).

Observations: About 20mm long. In my photo the Glossy Shield Bug seems to be sucking nectar from the myrtle flower. The T.E.R.R.A.I.N website (NZ) reports that the early nymph instars of the Glossy Shield Bug can feed on plant juices while the later nymphs and adults are only predators. The long mouthparts and the stout beak at the end are designed to stab soft-bodied insects such as caterpillars and suck out their body fluids. However, my photo seems to indicate that even adults continue to complement diet with plant juices.

Fun Facts : The Glossy Shield Bug is native to New Zealand and Australian. While most shield bugs are plant pests the Glossy Shield Bug is considered beneficial to crops for its role in controlling caterpillars and to a lesser extent aphids and other soft-bodied insects. For that reason it is important to not get it confused the Brown Mamorated Stink Bug (BMSB) – a reportable (to state agricultural departments) exotic originating from east Asia, but now, a widespread pest in Europe and USA. The BMSB poses a major biosecurity risk to a wide range of Australian crops. It is a notorious hitchhiker on goods arriving on our shores. Shipments of cars, various machinery, packaging and terracotta pots from Europe, Asia and USA have found to have harboured the BMSB. There have already been many reports of individuals and populations outside border security areas which have been subsequently subject to eradication programs. Adult BMSB and Glossy bugs are similar in size, shape and colour but two most useful differences, for me, were – the shine of the Glossy Shield Bug (indicated by the common name, of course) and the creamy crescent shaped tab between the wings of the Glossy Shield Bug. Note, that a number of images online show the Glossy Shield bug with a red/rusty colour variation but the bug in my garden was more gold/bronze.

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Gum Tree Shield Bug

On Bottlebrush (Callistemon) Feb 2019

Scientific Name: Poecilometis sp.

Notes on name: As a group the Poecilometis genera are referred to as the Gum Tree Shield Bugs as they most commonly feed off eucalypts. The Common Gum Tree Shield Bug is Poecilometis patruelis. My photo maybe this bug however I think the antennae look more like what Brisbane Insects calls The Brown Shield Bug which is only classified to genera. If anybody can type to species accurately I would love you to comment.

Only sighted on one occasion

When and where in yard : Seen resting on a newly planted Callistemon (Perth Pink). In the middle of a summer’s day.

Observations: Approximately 20 mm long and was only seen on one occasion. I couldn’t find any reference to Callistemon being a host plant for Poecilometis. As the Common name states it is usually found on eucalypts. I have no gums in the yard and the nearest is about 20 metres away.

Fun Facts: As with all shield bugs, the Gum Tree Shield nymphs goes through five instar (moult) stages. After each instar moult there is a colour change. In the case of the Gum Tree Shield Bug the instars are more deeply coloured than the adult – displaying colours such as red, orange, black and yellow.
Poecilometis eggs are generally laid underneath the bark of gums and nymphs tend to stay hidden there until they moult into the motley camouflaged adults. Adults are often seen on gum branches and trunks feeding on sap with their piercing mouthparts. I haven’t seen any reports of these been major pests, they rarely seem to be present in enough numbers to cause serious damage to Eucalyptus or other native plants. To distinguish Poecilometis from the invasive Brown Marmorated Stink Bug (see Fun Facts from entry above) the cream tab between the wings is once again useful (as with Glossy shield bug) but also the skirt around abdomen doesn’t have horizontal stripes in Gum Tree Shield Bug.

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Australasian Green Shield Bug

Australasian green shield bug on Casuarina Dec 2017

Scientific Name:Glaucias amyoti

Only one sighting in 2017

When and where in yard : On a summer evening (used flash). On Casuarina glauca (Green Wave)

Observations : Around 20mm long. Seen walking like a tightrope walker on a Casuarina ‘needle’. Once again I could find no reference to the Casuarina been a natural host plant and didn’t observe the G.amyoti feeding. I did manage to get a photo showing the mouth part which is tucked under its body. The true bugs as a group are distinguished by these rigid sucking mouth parts. There was a black spot on one side of the upper thorax. I can’t be sure what this is – possibly some disease/parasite.

Fun facts : The Australasian Green Shield Bug maybe confused with the exotic pest of pulses and cotton – the Green Vegetable Stink Bug. In fact I agonised over the identification of my bug but, in the end, the distinguishing feature of the adult Green Vegetable Bug seems to be small white spots at the top of the wing (wing insertions) which I couldn’t find on my bug. I am not the only creature which finds it hard to distinguish between the two because, unfortunately for the Australasian Bug, so do the biological control insects that have been introduced to tackle the Green Vegetable Bug. The Australasian Shield bug falls victim to introduced parastic wasps and a tachinid fly species (Trichopoda giacomellii) that have been released to control populations of GVB in cotton and pulse growing areas of NSW and Queensland. Parasitic wasps (this includes a native parasitic wasp) lay their eggs in the eggs or nymphs of the shield bugs but the introduced Tachinid fly can lay eggs on the adults. These eggs are generally laid on the wing insertions on the bugs back. Coincidentally, or not, the area of the black spot on my Australasian Green Shield Bug.

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