Aussies warned over 'hitchhiker' bugs in backyard: 'They're sneaky'

Here's exactly what you should do if you find these 'stink bug' critters in your garden.

You'd definitely know if you provoked them, with their unmistakable stench that anyone with a sense of smell is unlikely to quickly forget.

And although they've been deemed a "nuisance pest" over the danger they could pose to the agriculture industry should their population numbers explode, many people might not know what to do if they come across the humble "stink bug".

Bronze orange bugs on a Sydney lemon tree.
Aussies this week thought they'd found brown marmorated stink bugs, but it's actually something else. Source: Facebook.

The term actually covers a handful of related species. The brown marmorated bug — a mottled brown, oval-shaped insect is the one Australians should be most concerned about. They are common on other continents and have been found in Australia at the border in imported goods multiple times, after "hitchhiking" on imported goods. They have an insatiable ability to destroy vegetable crops, fruit and trees.

Related insects — including bronze orange bugs, that also emit a smelly, pungent odour — have also been classified as pests in Australia, and can be easily confused with their more sinister cousins.

It's important to know how to how to deal with the bugs and differentiate them, as making the wrong move could cost your garden big time.

The photo above was shared in a Sydney Facebook group with a resident asking what the bugs were on her lemon and lime trees. While many were concerned the insects may have been the invasive brown marmorated bug, Dr Tom White, entomologist with the University of Sydney, identified them as bronze orange bugs.

Stink bugs: What are they?

Speaking to Yahoo News Australia, Dr White said "stink bug" is an umbrella term used to describe a wide variety of insects that produce an unpleasant odour when provoked. He said it's sometimes easy to get confused over the different types, due to a "few subtle differences" in each bug's physical appearance.

"[There are] some pretty gnarly introduced ones like the brown marmorated stink bug," Dr White told Yahoo. "But there's plenty of natives as well. Harlequin bugs and shields bugs and bronze orange bugs are really common as well — both invasive and native."

How do we tell them apart?

A quick Google search will help you to identify who is who is your backyard — as for the most part, the differences in the insect's colouring makes them fairly reasonably distinguishable — but Dr White said there's also actually a hotline you can call in Australia, where trained professionals will help you work out what kind of critter is in front of you.

"So if you take some pictures of them and save a sample, we can send them in," he said, adding that if you do see one, you should report it, as the government likes to keep track of where the invasive insects are, so they can monitor population numbers.

A brown marmorated stink bug.
The brown marmorated stink bug originated from Asia. Source: AP.

Are they dangerous? Should we kill them?

The short answer is yes — but it's important to do so in the right way, and to know what you're trying to kill first.

"We always recommend killing them in sustainable ways to manage any sort of outbreak," White said.

"So you don't want to reach for the sprays straightaway, you don't want to go right into the Mortein, or these really broad sprays that just blast all our native insects.

"You can just physically pick them off, if we're talking about your backyard, you can grab them, collect them — and especially if you're not sure exactly what species it is, so something like the marmorated — you could just whack them in a plastic bag and pop them in the freezer, and that'll kill them humanely and also get them off your plants."

With regards to the native variant, "generally we want to deter rather than kill". "They can be a nuisance to us, but they still have their place in the ecosystem, and are food for other insects," White said.

"So focus on things like physically excluding or removing them, trapping them, encouraging their natural predators, ‘rotating’ what you grow each season to mess up their life cycle. Those kinds of sustainable things, before going straight for the kill, especially with chemicals which should be last-resort."

Is the smelly acid they produce dangerous?

No! Not generally, especially not to humans anyway. It does reek though, so beware!

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How do they travel?

Having been dubbed the "hitch-hiker" bugs, you might be able to tell how they get around the place.

Though they have wings, they're "not the strongest flyers" and don't really travel long distances by air, instead, they have a more "sneaky" tactic.

"Like a lot of invasives that establish themselves and do really well, they thrive because they don't have the predators that they are used to in their natural range," White said. "They're also pretty tough to find as well — they're pretty sneaky, except when they reach pest-plague proportions. [They have] a tendency to be spread around the world by hitchhiking on the stuff that we export and import around the place — but they wouldn't be flying up and down the coast."

Should we be concerned for our crops?

The brown marmorated bugs have not yet been classified as "established" in Australia — making it all the more important to report the bugs if you think you've found one.

"The exotic brown marmorated stink bug is not found in Australia and is a pest of considerable biosecurity concern to Australia’s agricultural industries. Juveniles and adults feed on, and can severely damage, fruit and vegetable crops," the Department of Agriculture, Fisheries and Forestry said online.

To make a report call the Department’s See. Secure. Report. hotline on 1800 798 636 or complete the online reporting form.

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