by Carolyn Bernhardt
March 10, 2025
Across 1,500 acres of Minnesota’s small fruit farms, raspberries, blueberries, and strawberries are under siege by the invasive spotted wing drosophila (SWD), causing crop losses of up to 50%. While farmers rely on frequent insecticide sprays, nearby plants may serve as SWD hosts and enable its spread. What role do these plants play in pest management, and how can understanding this dynamic help develop more effective, layered strategies for controlling both invasive pests and plants statewide?
Researchers have identified invasive honeysuckle as one such culprit. On the bright side, that means managing one invasive can help berry farmers manage the other.
A sweet-smelling invasive
Non-native honeysuckles became invasive in Minnesota through a combination of intentional breeding and unintentional spread. Species like Tatarian (Lonicera tatarica) and Morrow’s (L. morrowii) honeysuckle were initially introduced as ornamental plants for their hardiness, vigor, and qualities like producing flowers, berries, and scent. Later, horticulturalists hybridized honeysuckle to enhance traits like flower color and form. These desirable characteristics also allowed the plant to escape cultivation, naturalize, and thrive in various conditions. Honeysuckle is one of Minnesota's most problematic invasive plants.
Non-native honeysuckles are among the most frequently reported invasive plants in Minnesota, but most reports remain unidentified to species, complicating management and regulation. “Part of the problem with the honeysuckle group is that, morphologically, they're so similar,” says David Tork, MS, a researcher in the Department of Horticultural Science. "It’s not as bad as buckthorn, but remains a significant issue. There's a lot of places where honeysuckle and buckthorn are growing together, and almost nothing else exists in the understory." Further, a limited knowledge of honeysuckle seed production and germination requirements hinders risk assessments for spread.
Trailblazing research to define species, spread, host capabilities, and ecological risks
A research project funded by the Minnesota Invasive Terrestrial Pests and Plants Center is tackling this issue. Researchers at the University of Minnesota’s Department of Horticultural Science are using genetic and morphological analyses to refine honeysuckle species identification and inform regulatory management. Their findings aim to determine species composition and enhance both honeysuckle and SWD management strategies. This project is led by Alan Smith, PhD, a professor in the Department of Horticultural Sciences, and includes co-principal investigators Neil Anderson, PhD, Mary Rogers, PhD, David Tork, MS, Brandon Miller, PhD; researcher Kevin Kamau, MS; and many undergraduate research assistants.
Currently, there is no method to distinguish whether a successful treatment is specific to a particular honeysuckle species. By combining genetic analysis, field surveys, and collaboration with key stakeholders, the team will work to define the geographic distribution of native and non-native honeysuckle species in Minnesota and how often they hybridize.
The scientists have turned to whole genome sequencing and genetic structure analysis—a method used commonly in genetics research, but not yet widely applied to invasive species research—to identify honeysuckle species. A previous MITPPC-funded project they did on reed canarygrass inspired this approach in its aim to address the gap in information on the genetic identity and distribution of species.
As part of their investigation into mechanisms of spread, they are studying honeysuckle seed germination requirements. Led by undergraduate researcher Anna Worden, the team has developed seed viability protocols through a blend of literature review and hands-on work, including seed staining and dissection.
They are also evaluating native and non-native honeysuckles’ suitability as a host for SWD, and analyzing their role in SWD-related crop damage. The experts will leverage their statewide collection of native and non-native honeysuckles to measure whether SWD prefers particular species or hybrids, and if SWD is impacting the state’s native honeysuckles.
To assess the ecological risks of non-native honeysuckle, particularly its potential as a host for SWD, the researchers have engaged in close collaboration with both regulatory agencies and agricultural stakeholders to locate plants near berry farms to evaluate potential impacts. "If you're a berry grower and you've planted non-native honeysuckle, or it's naturalized, or your neighbor has it, I think a conversation has already started that says, ‘Hey, I might want to be putting some time and effort into controlling the non-native honeysuckle that's on my property,’" says Smith, principal investigator.
Early findings describe extent of invasion
Researchers on the project say that findings could lead to better control methods for non-native honeysuckle and SWD, and inform regulation, risk assessments, and policies. At the same time, this work raises awareness that non-native honeysuckle is a complex of species, potentially requiring species-specific management strategies that protect our native honeysuckles.
Although the project is in progress, preliminary findings are already bringing the larger picture into focus. For example, populations of the European fly honeysuckle (L. xylosteum), an unregulated species that has not previously been recognized as an invasive threat, were found to be naturalizing in Minnesota. While European fly honeysuckle and non-native honeysuckle can be morphologically distinguished, they may form hybrids that would complicate identification.
The team has also confirmed the presence of Amur honeysuckle (L. maackii) in southern Minnesota—an aggressive species that has caused significant ecological damage in the lower midwest. They also found that cultivated honeyberry (L. caerulea) can be heavily infested with SWD.
A dual-ended focus with manifold outcomes
The team visits both farms and natural areas, conducts sampling, and provides insights into the severity of nearby infestations, with Minnesota berry growers eager to tackle the persistent threat of SWD.
"Minnesota berry growers are very aware of SWD, so it's been easy to get them interested in the project," says Tork. By working directly with farmers, the team is advancing their study while offering valuable insights to help manage ongoing agricultural challenges.
Smith says collaborations with the Minnesota Department of Agriculture, the Department of Natural Resources, and academic institutions like the University of Saskatchewan, have strengthened the study. They have helped to align objectives with regulatory and ecological priorities. "Farmers are appreciative of information from field research that helps them manage losses from SWD," he says.
More information
- Informing management of invasive Lonicera (honeysuckle) and spotted wing drosophila, research project
- Overwintering, migration and development of cost-effective practical management strategies for the invasive spotted wing drosophila in MN, research project
- Non-native bush honeysuckles information, MN Department of Natural Resources
- Spotted wing drosophila information, US Department of Agriculture
- Spotted wing drosophila, MN Department of Agriculture
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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