Stink bugs' natural enemy may help BC’s invasive species problem

Samurai wasps may just be the hero we all need to help with the stink bug problem BC is facing.

By now, you’ve probably noticed the smelly brown marmorated stink bugs (BMSB).

While these bugs are not dangerous to humans, the Invasive Species Council of BC recently warned that BMSB targets fruit trees, berries, grapes, vegetables, and ornamental plants. 

These insects look for warm places in the colder months, like inside people’s homes or sheds.

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However, Paul Abram, a research scientist with Agriculture and Agri-food Canada, explains that these invasive insects, which came from China, Korea, and Japan, also brought along their natural enemy — the samurai wasps. 

“These wasps are not the wasps you would normally think of,” Abram says. “These [parasitic] wasps are extremely specialized … All they do for their entire life is look for stink bug eggs to lay their eggs inside so their offspring develops inside of it. Then instead of a stink bug coming out of the egg, a wasp develops and comes out of the egg and looks for more stink bug eggs to parasites.”

Pros and cons of the natural enemy

However, this comes with some risk to the 60 to 70 species of native stink bugs. 

“So there’s a potential good side to the samurai wasp and that it may help dampen populations of the invasive insect, but it may also be able to attack our native stink bugs and may affect them negatively.”

This dilemma is what Abram and his team are working on understanding, along with the potential adverse environmental impacts of the invasive species and its natural enemies that follow.

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Abram says that earlier this year, he and his team started a “dry run” of a community science project, hoping they could track the spread of samurai wasp in particular. 

British Columbians were asked to send in collect stink bug eggs hidden away and send them to researchers to see so they can see if the wasps had parasitized them.

Stink bugs normally lay eggs between June, July, and August. The project has since wrapped up but Abram says it will return in late June next year.

Abram adds it’s difficult to measure how much impact the Samurai wasps have on stink bugs, so the research will take a few years. 

“We can’t just do it in one place in one year and call that the final word. We have to measure … long-term trends to know whether the wasps are really having a significant impact on the stink bug populations.”

The major public awareness about the bug has prompted many people in the Lower Mainland, Kelowna and Okanagan in particular to report the invasive species. 

However, Abram says this has caused overwhelming submissions from these areas. 

Abram is encouraging people outside the Lower Mainland like Vancouver Island or Northern or Eastern BC to send in their information instead. 

For those British Columbians that are tired of seeing these bugs, the good news is in November and December you will see fewer stink bugs, Abram says. 

However, they will come out from their overwintering places again around March, April or May, depending on how warm the spring is. 

With files from Amir Ali