Samurai Wasps Could Be Our Secret Weapon Against Invasive Stink Bugs

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Invasive stink bugs are damaging crops, but a newly arrived wasp might keep them in check. KQED Science

The brown marmorated stink bug looks harmless, even cute. But this little speckled insect has a dark side. Native to Asia and introduced to the U.S. in the 1990s, the stink bug is simply trying to make a go of living in this new environment. Unfortunately, it's incredibly successful at it.

The prolific species is responsible for millions of dollars of crop loss since its arrival, as it feasts on fruits, vegetables and ornamental crops. It also can invade homes and businesses in huge numbers while seeking shelter in the winter, which is a problem considering it smells like old socks when squished.

Examples of the damage stink bugs do to food crops.
Examples of the damage stink bugs do to food crops. KQED Science

Pesticides are one option, but chemicals target everything including our native bees and other pollinators. In the search for a more targeted solution, researchers have turned to another introduced species: the samurai wasp. This stinger-less insect is about the size of a sesame seed.

"Also native to Asia, this parasitic wasp keeps the stink bug population in check there. How? By colonizing its rivals' eggs," reports KQED. "A female wasp will lay its own egg inside of a stink bug’s egg. About two weeks later, an adult samurai wasp will emerge. Between 60 to 90 percent of stink bug eggs in Asia are destroyed this way."

A samurai wasp emerges from a stinkbug egg, feasting on the shell.
Once the brown marmorated stink bug eggs have been parasitized, the samurai wasp chews its way out, leaving a jagged hole. Chris Hedstrom, Oregon Department of Agriculture, Oregon State University/Flickr CC BY-SA 2.0

It's always a hair-raising option to introduce a species to deal with an introduced species. The situation is rife with unintended consequences, as past mistakes have illustrated in all-too-alarming detail, like introducing mongooses to Hawaii, cane toads to Australia, and stoats to New Zealand. You never know what a predator will go after in a new environment, when easier or tastier options than its intended target prey are suddenly available.

But the samurai wasp is already here in the States, having arrived accidentally sometime before 2014. Researchers from Oregon State University are studying the wasp as a possible solution to the stink bug's damaging effect on Oregon's hazelnut and berry crops. Meanwhile, California is studying both introduced species as a way of getting ready should the invasion hit the Golden State's huge and economically essential agricultural industry.

KQED's Deep Look has created this great mini-documentary explaining the stink bug's life and how the samurai wasp has turned the tables.