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Herbicide-Induced Fragmentation: Regenerative Ability of Cabomba Fragments After Exposure to Flumioxazin
1
School of Agriculture and Food Sustainability, The University of Queensland, Brisbane, QLD 4072, Australia
2
Invasive Plant Science, Department Agriculture and Fisheries, Brisbane, QLD 4001, Australia
*
Author to whom correspondence should be addressed.
Biology 2025, 14(8), 1023; https://doi.org/10.3390/biology14081023
Submission received: 2 July 2025
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Revised: 4 August 2025
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Accepted: 5 August 2025
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Published: 8 August 2025
Simple Summary
Cabomba is an invasive aquatic weed that threatens freshwater ecosystems in Australia by spreading rapidly through plant fragments. While herbicide flumioxazin has been approved for cabomba control, there is a concern that it might cause plant fragmentation and regrowth elsewhere. This study investigated whether cabomba fragments can regrow after being treated with different amounts of the herbicide in both summer and winter. The research found that flumioxazin prevents the regenerative ability of cabomba in a dose-dependent manner. In winter, the highest dose completely stopped regeneration. In summer, however, some regrowth still occurred, even at the strongest tested level. Notably, fragments in summer slowly regained their ability to grow over time, but this did not happen in winter. These results suggest that applying the herbicide during winter may be more effective in stopping the weed from coming back. This research helps improve weed control strategies, reduce the spread of cabomba, and protect water ecosystems while also helping managers use herbicides more effectively and responsibly.
Abstract
Cabomba caroliniana A. Gray (cabomba) is an invasive alien aquatic plant (IAAP) posing a significant threat to aquatic ecosystems in Australia. Its ongoing spread is primarily driven by its rapid growth rate and ability to readily regenerate from stem fragments. Flumioxazin, an effective herbicide for controlling cabomba, has been registered for use in Australia since 2021. However, exposing cabomba to flumioxazin can induce stem fragmentation, potentially facilitating further spread. This study aims to determine whether stem fragments of cabomba following treatment at different flumioxazin doses (i.e., 25, 50, 100, or 200 ppb a.i.) can regenerate new healthy shoots that could contribute to its future spread in a new environment, in either summer or winter. This study also aims to investigate how this regrowth potential changes over time after herbicide application. Results show that flumioxazin suppressed the regeneration of replanted stem fragments in a dose-dependent manner in both winter and summer. In winter, complete regeneration was suppressed at the highest concentration tested (200 ppb a.i.), while low concentrations (25 and 50 ppb a.i.) resulted in an average 45% lower regeneration rate and 93% lower regenerated biomass than the control. In summer, suppression of regeneration was lower; at 200 ppb a.i., partial regeneration (18%) occurred with a 97% biomass reduction. At lower concentrations (25 and 50 ppb a.i.), more stem fragments regenerated (66%) and biomass reduction was lower (69%) compared to winter. Furthermore, in summer, the plants gradually regained their ability to regenerate over time after herbicide exposure, regardless of flumioxazin concentration, while no such recovery occurred in winter at any concentration. The findings show that the highest tested dose (200 ppb a.i.) can effectively suppress cabomba regenerative ability, which will greatly reduce the risk of new infestations caused by dispersed fragments, particularly in winter, when cooler temperatures and lower light are suboptimal for cabomba growth. This suggests that winter may be a more effective season for flumioxazin application. However, since some regeneration still occurred in summer, even at the highest tested dose, the highest registered label rate (400 ppb a.i.) may be necessary to ensure effective suppression under warmer conditions. Further studies are needed to evaluate this higher dose and its long-term efficacy.
