An operational study of repeated diquat treatments to control submersed flowering rush

摘要

Flowering rush (Butomus umbellatus L.) was first introduced to eastern North America from its native Eurasia over 100 yr ago (Core 1941). Additional introductions of unique genetic strains, likely as garden ornamentals that escaped to natural areas, led to its establishment in the western United States (J. Gaskin, unpub. data). The first flowering rush record in western North America was from the Snake River, Idaho in 1949 (Anderson et al. 1974).Flowering rush is able to exploit a wide range of habitats, making it an impressive invasive plant. In the northwestern United States, it grows as an emergent along shorelines, graduating out to water depths of more than 6 m where it can grow completelysubmersed. It can grow in all conditions, ranging from still water with muddy substrate to flowing water with rocky substrate. Flowering rush thrives in areas with fluctuating water levels, but also persists and spreads in stable water conditions (Hroudova 1989, Hroudova et al. 1996). It invades and dominates native plant beds (Madsen et al. 2012) and can also colonize habitats previously barren of plant growth (Parkinson et al. 2010). Flowering rush has been termed an ecosystem engineer for its abilityto alter habitat by sediment accretion (Gunderson et al. 2016). These characteristics, along with the rapidly expanding population, have raised concern about potential impacts on habitat and irrigation water delivery if flowering rush becomes well-established in northwestern North America.