Anderson, Jennifer
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
Abstract
In 2023, the large-scale leaf drop or death of Nymphoides peltata (sjögull, fringed water lily), an invasive species detrimental to freshwater ecosystems, was observed in parts of Sweden. While initial investigations suggested fungal or fungus-like infections as a possible cause, the link could not be made at that time due to a lack of comprehensive knowledge regarding the diversity of N. peltata pathogens in Sweden and information about the status or changes in status of the plants before the putative plant deaths. This project was designed to fill these knowledge gaps through the: i) collection of observations from 2023 to produce a timeline of events; ii) coordination of observations and samples for 2024; iii) review of knowledge onpathogens of N. peltata; iv) survey of N. peltata-associated fungi in Sweden. The work was undertaken through a combination of public engagement, collaboration with public authorities and interest groups, and scientific investigation at the Swedish University of Agricultural Sciences. We find that similar plant death or leaf drop events have been previously reported from Asia but not observed in western Europe. Reports submitted by the public and public authorities suggest the presence of N. peltata pathogens are widespread in Sweden, with lesions observed on affected plants in most reports. However, it remains unclear whether the plants are being killed, dropping their leaves in response to infection, and/or weakened by infection. Through the identification of fungi and fungus like-organisms (e.g., protists) from infected plant samples, fifteen potential plant pathogens were identified. Notably, Septoria villarsiae, a pathogen linked to severe N. peltata devastation elsewhere (e.g., South Korea), was documented for the first time in Sweden. Causation between infection, leaf loss, reduced plant condition, or plant death for any pathogen of N. peltata has not yet been reported in the scientific literature and requires additional investigation before the impacts of infection can be understood. It remains unknown if the S. villarsiae strain present in Sweden is particularly virulent, or if all clones of N. peltata in the region are susceptible to it. However, observations from 2024 in Lake Mälaren, for example, suggest that some N. peltata clones may be less affected. This raises concerns about the potential for a resistant plant genotype to spread more widely. Further, important uncertainties in our knowledge of Septoria fungi exist, including whether they can infect species important in Swedish freshwater or terrestrial ecosystems. These question, among others, must addressed to inform effective control of this invasive plant and before any fungus can be considered as a potential biocontrol agent for N. peltata in Sweden. Regardless, the presence of naturally occurring pathogens that may diminish the condition of the plant can synergistically benefit efforts towards eradication.
Keywords
Nymphoides peltata; Septoria; Invasive species; Freshwater; Freshwater ecosystem; Pathogen; Fungi
Published in
Publisher: Zenodo
SLU Authors
Wang, Ziming
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
UKÄ Subject classification
Ecology
Publication identifier
- DOI: https://doi.org/10.5281/zenodo.16538285
Permanent link to this page (URI)
https://res.slu.se/id/publ/143424