by Carolyn Bernhardt
January 13, 2025
As an entomologist, Sabrina Celis is focused on finding sustainable pest control solutions. Celis is a PhD candidate in the Department of Entomology at the University of Minnesota, dedicating her time to investigating how parasitoid wasps, particularly the samurai wasp (Trissolcus japonicus), could work as a natural enemy to help manage the invasive brown marmorated stink bug (Halyomorpha halys). In addition, Celis and her team study the broader impacts of stink bugs on native plants and insects, considering the complex relationships between pests, their parasitoids, and the ecosystem.
A lifelong journey
From an early age, Celis was drawn to insects. “I was one of those kids who spent recess digging up worms and chasing butterflies. I never wanted to stop,” she says. This fascination with the natural world led her to study entomology at Cornell University, where she had a wealth of hands-on experiences. “I spent a semester identifying insects for a graduate student in an agroecology lab. I also worked in a spider behavior lab with Dr. Linda Rayor, caring for spiders and tarantulas.”
Her interest in biological control grew during her time at the New York State Hemlock Initiative, where she worked with predators targeting the invasive hemlock woolly adelgid, a pest threatening eastern hemlock forests. “I got to do my undergraduate thesis on parasitoid wasps attacking our biological control agents. That’s where my interest in parasitic wasps really took off,” she says.
After earning her degree, she applied to work with George Heimpel, PhD, a Distinguished McKnight Professor in the Department of Entomology in the College of Food, Agricultural and Natural Resource Sciences, and a leading expert in biological control. Celis’ project on the brown marmorated stink bug began when the Minnesota Department of Agriculture (MDA) contacted Heimpel after discovering the samurai wasp in the state for the first time.
One species of stink bug, many problems
The brown marmorated stink bug is a challenging pest to manage due to its wide range of host plants, including orchard fruits, vegetables, and field crops. Unlike pests that can be controlled through crop rotation or sanitation, the stink bug prefers to overwinter in forest settings or human structures, making it difficult for growers to prevent infestations year to year. Effective management relies on monitoring populations and treating them with pesticides when necessary.
The pest could pose a threat to native species, as it is known to feed on many plants native to Minnesota. Increased pesticide use to control stink bug populations could also inadvertently harm native insects. While Minnesota hasn't yet seen significant economic impacts, Celis notes past outbreaks on the East Coast, where the pest caused $37 million in losses to apple growers alone. It highlights the potential for increased pesticide use if stink bug populations continue to rise.
"It is really fascinating how this one insect can have so many impacts on other species, whether it's insects or plants or different groups of people,” Celis says. “So, it's kind of fun to be at the intersection of all of that and examining all those different relationships."
In order to most effectively examine that nexus, though, Celis says collaboration is a must.
Partnering for progress
"This entire research project is born of a collaboration between our lab and the MDA,” Celis says. “The MDA has been really helpful for figuring out what orchards seem most likely to have Trissolcus japonicus, and then coordinating with apple growers to help us find good sites for our surveys.”
Celis also says the growers have been great to work with. “It's been useful getting their perspective on brown marmorated stink bugs showing up in their orchards, and hearing their concerns about when they should start worrying about managing this pest.” They’ve also shared pesticide data with Celis and her team, indicating when they spray and how much, which can help inform the research on pesticide use against the brown marmorated stink bug.
Meanwhile, to get a better understanding of how the brown marmorated stink bug impacts native plants in Minnesota, Celis is learning from experts from the Fond du Lac Band of Lake Superior Chippewa and the North American Traditional Indigenous Food Systems. “We’ve been talking to tribal representatives to ask about the cultural importance of some of the native plants that brown marmorated stink bugs have been found on,” she says. “I had a great conversation with ethnobotanist Linda Black Elk, who is an educator with North American Traditional Indigenous Food Systems. I was hoping that she could highlight a couple of plants as ones that would be important to look at, but instead, she gave me multiple uses for every single plant I had in a list of over 40 species native to Minnesota."
The complexities of biocontrol
Still, biological control remains a somewhat contested methodology. The samurai wasp has been found to attack native stink bugs in other states, although currently reported parasitism rates are low. “It’s still too early to say if the samurai wasp will have population-level impacts on native stink bugs here,” Celis says.
The Heimpel lab has published a 2024 paper that offers a framework for assessing the risks and benefits of introducing biological control agents based on their impact on native species. “It helps us decide if the benefits outweigh the risks of releasing something into the environment,” she explains.
Celis’s excitement about the samurai wasp is palpable. “In our first year of sampling, we found thousands of wasps in the genus Trissolcus and other stink bug parasitoids, but only one was the samurai wasp. It was found about an hour away from the Twin Cities,” she says. The samurai wasp had only been previously detected in St. Paul.
Buzzing past challenges
“It would be great if the samurai wasp can successfully control BMSB. It could help prevent high pest populations that would lead to increased pesticide use,” she adds. “A biological control agent will almost never eradicate the pest. And that's not the goal. The goal is to bring populations back to sub-economic levels, if we're talking about agricultural commodities, but also bringing balance back into the ecosystem."
Celis’s research is still in its early stages, with BMSB only first discovered in Minnesota in 2010 and the samurai wasp not found until 2022. This makes field sampling difficult. “It’s hard to catch them, especially the wasp. They are still in the early stages of establishment here,” Celis says. However, she says data from other states has been useful in guiding her approach to sampling and predictions.
Celis believes that this project will provide valuable insights into whether the samurai wasp will be beneficial or harmful to Minnesota’s ecosystem. Other states have already started redistributing the samurai wasp to accelerate its spread and improve control of the brown marmorated stink bug. Says Celis, "Once we have completed the research, groups like the MDA can make decisions on whether redistribution is a good idea and if that's something they should do."
Celis is also passionate about the future of biological control as a long-term solution for managing pests, recognizing the ongoing challenge posed by global trade and the movement of species. She believes that biological control will be a crucial tool in addressing these challenges. "I would like to see biological control continue to grow as a practice for controlling invasive species in the long term, because with how global our society has become, trade is never going to stop. Invasive species are never going to stop."
Looking ahead, Celis aims to continue her work in this field, whether through research or in a teaching role. "I would love to continue being someone helping to control invasive species in a sustainable way, whether it's as a researcher or as a professor at the head of my own lab,” she says. “If I end up in a position that's more teaching-focused, rather than research-focused, I hope to aid future students interested in biological control and be able to inform them from my own experiences."
More information
- Assessing samurai wasp biocontrol for brown marmorated stink bug, research project
- Brown marmorated stink bug factsheet, Minnesota Department of Agriculture
- Brown marmorated stink bug information, UMN Extension
- EDDMapS distribution map for brown marmorated stink bug
- Early detection and management for brown marmorated stink bug, completed research project
Research from the Minnesota Invasive Terrestrial Plants and Pests Center is supported by the Environment and Natural Resources Trust Fund, as recommended by the Legislative-Citizen Commission on Minnesota Resources.
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