We need to stop bugs at the border

In September 2022, I had just arrived in New York from West Virginia, on my way back to Australia. I opened my suitcase and out crawled three brown marmorated stink bugs, insects that are serious invasive pests. These bugs damage crops and trees in summer and are nuisance pests in houses in winter. They are so bad that they are one of Australia’s 42 national priority plant pests — a list that no one wants to be on.

I didn’t mean to pack them, of course — apparently they had crept into my West Virginia bedroom and secreted themselves in my wardrobe. In my wardrobe! Where my clothes were! That were now in my suitcase! Which I just as easily could have been opening in Australia as in New York.

This was horrifying, especially for me, a senior entomologist who specifically studies invasive insects. I am still mortified by the thought of nearly bringing brown marmorated stink bugs to Australia.

I would have been far from alone. Insects have inadvertently moved with humans for as long as humans have been moving: Think of the pubic lice, grain weevils, bed bugs, cockroaches, mosquitos and rat fleas that accompanied early voyagers. As global transportation expanded, so did the translocation of these unwanted passengers. As we traded plants between countries and continents, we broke geographic barriers that had existed for millions of years, and provided rich new habitats and food sources for insects, away from their usual competitors and enemies back home.

Today, there are over 7,000 accidentally introduced insect species living outside their native range. While only a small proportion cause damage, they are estimated to cost at least $70 billion per year. One of these, the Asia-native emerald ash borer, is among the top 10 worst invasive species, which include vertebrates and weeds (another list no one wants to be on). In the two decades since its arrival in the US — probably in imported wood packaging — it has killed tens of millions of ash trees.

The rate of invasive species entering nations shows no signs of slowing; it might be speeding up.

Just because insect invasions are rising doesn’t necessarily mean nations are bad at biosecurity: Failures are far more evident than successes, which are harder to quantify and largely go unseen. Globally, there are plenty of mitigation measures designed to reduce risks. These include pre-border regulations that balance the economics of trade against the risk of introducing new species (Australia’s import requirements for off-shore fumigation in brown marmorated stink bug’s hitchhiking season, for example, delayed the delivery of my new car last year). There are border inspections, including using sniffer dogs and acoustic devices that can hear burrowing insects; treatments at the border; and post-border surveillance and eradication measures.

So, a lot is done. But it is also true that people were largely oblivious to this problem for far too long. Stringent biosecurity measures are relatively recent, and in some countries, biosecurity is still inadequate. Europe is predicted to receive the most new invasive species over the next 25 years, and there are documented gaps in its biosecurity measures. Plants often aren’t inspected as they cross land borders, for example, which can facilitate insect invasions.

In biosecurity circles we say that “invasion begets invasion”: The more regions in which a species is invasive, the more regions from which it can spread. Countries with limited biosecurity capacity become risks to those with stricter biosecurity. So this is everyone’s problem.

I have colleagues working to strengthen biosecurity in Australia’s neighboring countries for everyone’s benefit: They’re working with the Australian Centre for International Agriculture Research, and the United Nations’ Food and Agriculture Organization, to improve biosecurity in southeast Asia and Africa. Many other countries would similarly benefit from greater international cooperation.

There are a lot of good education and citizen science projects making people aware of the impacts of invasive species. One-quarter of Australia’s most recent forest pest invasions were detected by members of the public. Community engagement is a key pillar of our new national forest pest surveillance program, designed to enhance early detection of invasive species. The more of this, the better.

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Of course, risk prediction is imperfect — some insects aren’t pests in their country of origin, making it hard to predict their impact elsewhere; others weren’t even known to science until they became invasive. And there are forces that are hard to control, such as smuggling or the willful introduction of exotic insects or their hosts. For example, a sap-sucking insect called giant pine scale was intentionally introduced to pine trees in the Mediterranean, because bees feed on that insect’s honeydew to make valuable pine honey. But the giant pine scale is now killing trees, especially with the extra strain of climate change.

And then there are accidents, by even the best-intentioned.

When I finally arrived back in Brisbane, I opened my suitcase with trepidation and a can of bug spray in hand, and shook out my clothing with the windows closed. I’m not going to be ground zero for a brown marmorated stink bug incursion. Not this time, anyway. Now we just need everyone to do their part.