Research on Non-native Phragmites Control

Scientists are working to find species-specific means of controlling the population densities of Phragmites.

Biological Control

Could introduction of a new insect species impact non-native Phragmites?

Phragmites internode filled with black mycelium and larvae of Lasioptera hungarica. Photo courtesy of Bernd Blossey

Non-native plant species are often successful in new environments due to reduced effect from wildlife and pathogens. In some instances, scientists are able to identify natural predators of the invasive species and intentionally release them in hopes that they will decrease the population of the invasive species. Introducing a non-native species is a complicated issue and requires rigorous testing and evaluation before such a release is approved. In terms of Phragmites, finding a biological control agent means looking for insects from Europe that would target non-native Phragmites and releasing them in North America. Other examples of biological control include the introduction of beetles to control purple loosestrife and the introduction of salmon into the Great Lakes to control alewives.

In recent years, scientists at Cornell University have been studying insects that prey on Phragmites. The researchers are evaluating the host-specificity of each insect species in preparation for wide-spread releases of insects that may help control Phragmites populations. It is important to find insects that will specifically target non-native Phragmites because introducing a new insect to North America that is not specific to Phragmites could cause even more damage to these fragile ecosystems.

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Microbial Control

Could manipulation of endophytes reduce the competitive advantage of non-native Phragmites?

Beneficial endophytes (microbes living in plants) have been shown to enhance Phragmites performance compared to those grown without (Ernst et al. 2003).

All plants host a diverse suite of microbes, such as fungi and bacteria, throughout all stages of the plant’s life cycle. Some of these microbes form relationships that are mutually beneficial, or symbiotic, and are thought to confer many benefits to plants including tolerance to certain stressors, accelerated seedling development, and increased overall growth (Fig 1). As a result, symbiotic relationships with microbes can improve the competitive ability of some plants.

Some microbes (known as endophytes) live entirely within the plant’s leaves, stems, roots, and rhizomes.  Researchers at the USGS Great Lakes Science Center (GLSC), Indiana University, and Rutgers University are interested in examining the role of endophytes in both the success of invasive Phragmites and as a potential mechanism for restoring native plant assemblages. Scientists believe that studying microbial symbiosis may be integral to understanding non-native plant invasions.

If invasive Phragmites strengthens its competitive advantage due in part to positive interactions with the microbial community, then control efforts focused on disrupting these interactions may decrease Phragmites’ competitiveness. Scientists are seeking to better understand the microbes associated with invasive Phragmites and the benefits they confer to their host (Fig 2). The ultimate goal of this research is to identify new control methods based on microbial symbiosis that give land managers another tool in their toolbox for managing this invasive species. The ability to combat Phragmites from multiple fronts in an integrated manner will lead to improved success over traditional control methods.

Fig 2: Phragmites rhizomes (top left) and seeds (bottom left) and the fungal endophytes cultured from each plant part (right). Plants were collected by researchers at the GLSC and cultures performed by Indiana University. IU researchers will later inoculate Phragmites plants with individual endophyte species to assess the roles played by each type.

To maximize the collective impact of research efforts, the GLSC is using a collaborative approach by assembling a team of scientists with expertise in microbial ecology to focus on Phragmites microbiome. This group of scientists, known as the Collaborative for Microbial Symbiosis and Phragmites Management (i.e. the Phragmites Symbiosis Collaborative), was formed to coordinate research efforts to explore mutualisms between microbes an

d Phragmites. The Great Lakes Commission facilitated the development of the collaborative and continues to provide critical support. The members outlined a scientific agenda (Fig 3) to guide their research activities going forward, with each researcher bringing his/her own expertise to collaborative research projects that are focused on developing a comprehensive microbe-based Phragmites control approach (Kowalski et al. 2015). The group meets regularly to discuss progress towards the agenda’s goal as well as the current state of symbiosis science.

Fig 3: Major steps of the Phragmites Symbiosis Collaborative science agenda (Kowalski et al. 2015).

The structure of the Phragmites Symbiosis Collaborative lends support for individual research projects targeting a specific component of the science, and integrates these projects to foster progress towards a broader overall goal of effective and efficient Phragmites control. For example, the GLSC is currently working with researchers at Indiana University and Rutgers University to identify fungal and bacterial endophytes present in Phragmites and to identify their roles in the plant.

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Gene Silencing

What if land managers could treat Phragmites without fear of affecting other plant species or the environment? What if this treatment specifically targeted the traits that make Phragmites most problematic?

That’s what scientists at Wayne State University and the U.S. Geological Survey are working towards, and their approach starts with a basic understanding of where these traits originate: within a plant’s genes.

gene silencing pic

Maize plant with silenced genes coding for photosynthesis (right) compared to a plant of the same age without gene silencing (left).

Genes give instructions used in plant development and function. For example, genes dictate the design, color and emergence of flowers on a plant. Genes also regulate key plant processes like photosynthesis and seed production. Genes drive plant processes by coding for the formation of specific proteins that ultimately result in the expression of various traits. Scientists have known for some time that protein formation can be disrupted by preventing these genetic messengers from reaching their destination. If the genes cannot send their code, the proteins are not formed and the trait is not expressed. This process is known as “gene silencing.” Using a transcriptome (i.e., road map of genetic material in specific parts of a plant), scientists can target specific traits and silence the genes that code for them.

Researchers at Wayne State University and the U.S. Geological Survey – Great Lakes Science Center think this technology could be used to develop new forms of Phragmites control. Phragmites gains a competitive advantage over other species through its ability to grow rapidly and shade out other species, produce a large number of seeds, and expand its underground root network over a large area. Wayne State and USGS scientists are working on ways to silence important genes in Phragmites (e.g., those for flowering, seed set, and photosynthesis) in an effort to reduce its competitive advantage. Analysis of the transcriptome for Phragmites is currently underway and this year, scientists will begin to test gene silencing of photosynthesis in Phragmites. The next step will be to test the technology in the field and develop an application method that will be feasible over a large scale.

Gene silencing in Phragmites is a promising strategy because it has the potential to be superior to existing control methods. For instance, because this technology targets a specific genetic message, it is thought to be entirely species specific. Additionally, the silencing effects are transient in that they cannot spread within the plant or be transferred to offspring.  Unlike the process to genetically modify crops, this process does not alter the genome (i.e., ‘hard-wired’ genetic material). That means that land managers may be able to treat rapidly expanding or well established stands of Phragmites without having detrimental effects on other plant or animal species. Gene silencing may offer land managers an additional tool to add to their arsenal against this aggressive invader, and one that may even prove more effective over the long term.

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For more information contact

  • Dr. Kurt Kowalski – US Geological Survey (kkowalski@usgs.gov)
  • Dr. Edward Golenberg – Wayne State University (egolenb@biology.biosci.wayne.edu)
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