Flight Risk

Invasive Australian wasps may threaten humans in one pernicious way

These wasps have experts seriously worried.

We've all heard some version of this story. A bird hits an airplane, potentially leading to a serious accident. The phenomenon is so well-known it even has its own name: bird strike.

But it turns out there's another critter causing trouble and even threatening flight safety at Brisbane Airport in Australia.

In a new study, researchers find evidence to suggest an invasive wasp species originally hailing from South America may be able to damage a crucial component of a plane's hardware — potentially endangering those who fly on board.

The study was published Wednesday in the journal PLOS ONE.

A hidden threat — Following several serious wasp-related safety incidents involving aircraft in recent years, the Brisbane Airport Corporation commissioned the researchers to investigate. Their goal was to not only identify the wasp species, but also uncover any patterns in its nesting habitats.

Keyhole wasps (Pachodynerus nasidens) are a super-invader, spreading from their home in South America throughout the world, although they tend to stick to tropical climates. And they have made it to Australia, too.

The researchers found these wasps form nests in the pitot probes of aircrafts at the Brisbane Airport in Australia. Pitot probes are critical tools to monitor airplane speed. Debris from wasp nests blocks the probes, affecting their ability to function properly.

Keyhole wasps are known for their inventive nesting behavior.House et al (2020) PLOS ONE

What's even more alarming: wasps can build these nests fairly quickly. In August 2015, airport workers in Newcastle found a blocked probe in an aircraft arriving from Brisbane. The airplane had been on the ground in Brisbane for only half an hour.

But despite these alarming findings, co-author on the study and principal ecologist at Ecological Australia, Alan House tells Inverse flyers need not fear the wasps — even before this research, the risk was relatively low.

"I think it is fair to say that for the 5 or so years between the wasp setting up home in Brisbane and our research flying was riskier; but now that additional risk is lower. Flying is safe!"

Location location location —To get a sense of where the wasps were making their nests at the airport, scientists constructed replica pitot probes using 3D-printing technology and installed them at four different locations around the airport. They monitored these probes between February 2016 and April 2019.

They also created traps to try to lure female wasps away from the aircrafts and possibly reduce nesting.

Over the study period, they discovered 93 nests completely blocking the dummy pitot probes.

The hot summer months appear to be especially suitable conditions for the pests, which created most of their nests during this time.

The researchers also discovered that wasps prefer probes with openings larger than 2.5 millimeters, and that the wasps gravitated towards one particular aircraft — the Boeing 737.

But the most significant factor in determining the likelihood of wasp nests: location. The researchers found the majority of the nests near one grassy section of the airport, which could help airport workers understand where planes need to avoid.

The dummy probes used by the researchers in their study.House et al (2020) PLOS ONE

Pest control — House hopes these findings can shed light on a generally overlooked flight safety issue and generate further recommendations about how best to control — or destroy — the wasp population in airports. But finding a solution isn't that easy.

"The simplest management response is to cover the probes as soon as possible after planes arrive at the gate. This prevents the wasp from getting in," House says. "However, this can lead to other issues to do with aircraft maintenance processes that can cause an even greater risk, such as forgetting to take the covers off."

Instead, airport officials can establish a protocol for covering and removing the probes, House says.

"Management of the environment could also reduce risk — for instance, paving all the grassed areas in an airport precinct would remove habitat for the prey species the wasps rely on, but would result in a pretty harsh environment," House says.

He also recommends using traps for pest control, which has had some success already at the Brisbane Airport.

"Eradication is, of course, the gold standard, but is expensive and not guaranteed to last — if this wasp can cross the Pacific once, it can do it again," House says.

Expert invaders — Even though they are embedding in the bodies of planes, it is unlikely these wasps will travel between countries this way.

"The wasp can’t be transported as larvae in the probes, for two reasons — the plane would register an airspeed anomaly and the pilots would return to land, and second, probes are heated in flight to prevent icing up, so anything inside gets cooked," House says.

But if the wasp population gets out of control, other forms of transport could help bring this wasp to new regions in Australia, where it will undoubtedly wreak further havoc.

"Aircraft are not the only piece of mobile plant that these guys could hitch a ride on: trucks, ships, cars all have cavities that the keyhole wasp could use. It certainly is a worry that this thing could spread to other airports in Australia," House says.

Yet, armed with this new information, researchers are optimistic that aviation experts can take appropriate next steps to stop the spread of the invasive wasps.

So, don't worry — you can rest easy before heading out to your next vacation in Brisbane. Probably.

"The [flight] risk is extremely low. This is because we now know more about the behavior of the keyhole wasp and what airports and airlines can do to reduce the risk. However, the risk will not be entirely eliminated whilst there is a breeding population at Brisbane Airport," House says.

Abstract: The keyhole wasp (Pachodynerusnasidens Latreille1812), a mud-nesting wasp native to South and Central America and the Caribbean, is a relatively recent(2010) arrival in Australia. In its native range it is known to use manmade cavities to construct nests. A series of serious safety incidents Brisbane Airport related to the obstruction of vital air speed measuring pitot probes on aircraft possibly caused by mud-nesting wasps, prompted an assessment of risk. An experiment was designed to determine the species responsible, the types of aircraft most affected, the seasonal patternof potential risk and the spatial distribution of risk on the airport. A series of replica pitot probes were constructed using 3D-printing tech-nology, representing aircraft with high numbers of movements (landings and take-offs), and mounted at four locations at the airport. Probes were monitored for 39 months. Probes blocked by mud nesting wasps were retrieved and incubated in meshbags. Emerging wasps were identified to species. Results show that all nests in probes were made by P.nasidens, and peak nesting occurs in the summer months. Nesting success (as proportion of nests with live adult emergents) was optimal between 24 and 31 C and that probes with apertures of more than 3 mm diameter are preferred. Not all areas on the airport are affected equally, with the majority of nests constructed in one area.The proportion of grassed areas within 1000m of probes was a significant predictor of nesting, and probe volume may determine the sex of emerging wasps.
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