Does squishing invasive lanternflies really help stop their spread?

Several states in the eastern US encourage residents to stomp on spotted lanternflies that threaten grapevines and other crops. But smooshing isn’t a long-term solution

Life 15 September 2022

Mandatory Credit: Photo by Bastiaan Slabbers/NurPhoto/Shutterstock (11782595ah) Large banner at the Philadelphia Flower Show information desk informs visitors about the invasive spotted lanternfly, as the annual event draws thousands to the Pennsylvania Convention Center, in Philadelphia, PA, on March 1, 2019. The largest flower show in the world is held annually since 1929 and is produced by Pennsylvania Horticulture Society (PHS). Woodstock's Flower Power At Philadelphia Flower Show, United States - 01 Mar 2019

Several campaigns on the east coast of the US encourage people to squash the invasive spotted lanternfly on sight

Bastiaan Slabbers/NurPhoto/Shutterstock

There is an invasive insect spreading through the mid-Atlantic US, and people are putting their foot down – literally.

States from North Carolina to New York have issued smoosh-on-sight orders encouraging residents stomp, squash and trap spotted lanternflies. One Pennsylvania resident even created an app called Squishr that allows users to compete for the most kills.

“Kill it! Squash it, smash it…just get rid of it,” that state’s agriculture department advises online. “These are called bad bugs for a reason, don’t let them take over your county next.”

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The bugs, which are native to China, got their bad reputation because of the devastation they caused in places like South Korea, which they invaded in the mid-2000s. There they munched grapes and fruit trees to the point of severe damage or death. Two years after they were first detected, they had damaged just a single hectare of grapevines in the country. By six years, they were feasting on more than 8000 hectares.

That seems good reason to be wary – but how much difference can individual efforts to stamp them out really make? And how much harm could the insects cause if we don’t halt their spread?

The striking brown and crimson insects first arrived in south-east Pennsylvania in 2014 after hitchhiking on a shipment of landscaping stones from China. In the eight years since, lanternflies (Lycorma delicatula) have spread outward in every direction, invading more than 14 states and counting.

Lanternflies use their straw-like mouthparts to suck vital nutrients from food crops like walnuts, grapes and stone fruits. As they feed, they secrete a sticky substance called honeydew that fosters the growth of a fungal disease called sooty mould on plants, which can coat leaves and prevent photosynthesis.

“I’ve seen lanternflies build to populations where you can’t even see the bark of the tree through the insect bodies,” says Emilie Swackhamer at Penn State Extension in Collegeville, Pennsylvania. “It’s unnerving because you wonder what that’s doing to the health of the tree.”

So far, lanternflies in the US have only killed grapevines, black walnut saplings and tree of heaven (Ailanthus altissima), an invasive Asian species. Though one Pennsylvania vineyard reported losing up to 90 per cent of their grape yield because of the bugs, crop losses so far have been relatively minor due to the use of effective insecticides.

“Lanternflies are not doing as much  economic damage as we thought,” says Julie Urban at Pennsylvania State University. “But who knows what’s going to happen as they expand their range?”

Researchers don’t yet know which climates lanternflies can tolerate but anticipate that they will be able to get a foothold in western states. Californian vintners are particularly worried about what the species could mean for the state’s $45 billion wine industry.

“The spotted lanternfly seems to be able to feed on just about any plant that’s available if they have to,” says Swackhamer.

Spotted Lanternfly - Lycorma delicatula; Shutterstock ID 2189428789; purchase_order: -; job: -; client: -; other: -

The spotted lanternfly (Lycorma delicatula) first arrived in the US in 2014

Shutterstock/Jay Ondreicka

Late summer to early autumn is peak breeding season for lanternflies, which will soon begin laying mud-like masses of up to 50 eggs that will hatch next spring. While the insects can fly and jump short distances, their spread has largely been aided by people who inadvertently transport eggs between states on equipment or vehicles. That is why many eastern states have been ramping up their stomp and squish campaigns.

But while these can be great for drumming up awareness, stomping the bugs to death is “not the management plan”, says Urban. Instead, she says, more effective solutions come in the form of public support for government-led insecticide treatments, careful monitoring of transport hubs and developing new ways keep the lanternfly population in check. One idea, for instance, is to expose the flies to fatal fungal pathogens that occur in their native range to control numbers in the US.

That’s not to say the squashing is totally useless. “The idea is that we can prevent it from spreading just long enough to give us a better long-term solution,” says Urban. “Even though in the big scheme of things you’re just buying a little bit of time, that little bit of time means a lot.”

For those not keen to follow squish-on-sight orders, there are alternative ways to stop the insects’ spread. Trapping lanternflies in a water bottle or using approved insecticides can help, but avoiding transporting egg masses to new locations may be most important. Thoroughly crushing the egg masses will destroy them, as will scraping them into a container with rubbing alcohol or hand sanitiser.

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