The emerald ash borer may be pretty, but it's also one of the greatest known threats to North American forests. Thankfully, help is at hand in the form of fake, but sexy-looking, ash borer models that kill any borer male that tries to get too friendly.
In the 12 years since the emerald ash borer (Agrilus planipennis) was discovered, the beetle has swept 24 US states and two Canadian provinces, killing tens of millions of trees in the process. Like so many invasive species, the trees in the borer’s home range have natural defenses, but American ash trees are unprotected—except, perhaps, for helpful woodpeckers snacking on them.
Professor Akhlesh Lakhtakia of Pennsylvania State University is part of a team that has produced electrified female beetle imitators, which zap any males that try to mate with them. “We coated a dead female beetle with a vapor of nickel and used the ‘nickelized’ shell to fabricate two matching molds in the shape of the resting beetle,” says Lakhtakia. “Pressing a structurally colored plastic sheet between the two molds while simultaneously applying heat, we cast numerous replicas or decoys."
In information you may not have wanted to know, Lakhtakia vouches for the authenticity of the lethal beetle sex toys, saying, “The finished bioreplicated decoys retained the surface texture of the beetle at the nanoscale.”
Justin George, USDA-Agricultural Research Service. The texturing of emerald ash borers reflects light in ways invisible to humans, but attractive to fellow beetles.
A quick coating of metallic green paint and the Penn State team have been able to produce a product that fools even the most discerning male beetle. In the Proceedings of the National Academy of Sciences, they announce that the males really are discriminating, choosing a dead female or an advanced decoy over simpler 3D-printed decoys lacking authentically-textured skin.
Even the best borer mannequins didn’t hold the males’ attentions for long, but a quick touch-down was enough to electrocute and trap them.
The borer reproduces in such numbers even an army of plastic sirens could not stop the plague. However, lead author Michael Domingue says, “Early detection of the pest in traps such as ours can help in coordinating management strategies to slow its spread and minimize its impact." At least a decade of delay before the borer was discovered in North America has had tragic implications for control, but hopefully this can be avoided elsewhere.
The team are working on a warning system that will alert ranges when a borer has been caught in a trap, rather than having to rely on regular checking. By creating lures that only interest the emerald ash borers, the forest service will not have to sort through other species caught in the traps.
The researchers hope to extend the work to other species, but this may depend on the mechanisms that other species use to recognize each other. "Small bumps and spines on the outer surface of their wings and heads that aren't visible to the human eye scatter light in a distinctive pattern. Beetles appear to be able to recognize this feature of the decoys and are strongly attracted to it,” says Domingue.
Wang et al. He thinks she's got great skin, but the truth could be shocking.