Operational control of Eurasian watermilfoil (Myriophyllum spicatum) and impacts to the native submersed aquatic macrophyte community in Lake Pend Oreille, Idaho

Published source details Madsen J.D., Wersal R.M. & Woolf T.E. (2015) Operational control of Eurasian watermilfoil (Myriophyllum spicatum) and impacts to the native submersed aquatic macrophyte community in Lake Pend Oreille, Idaho. Invasive Plant Science and Management, 8, 219-232.
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Summary

Action: Use herbicide to control problematic plants

A controlled study in 2007–2008 in a lake invaded by Eurasian watermilfoil Myriphyllum spicatum in Idaho, USA (Madsen et al. 2015) found that applying herbicide reduced the overall richness of submerged macrophytes and affected the abundance of some individual species. After 1–14 months, areas treated with herbicide had lower overall submerged macrophyte richness (1.7 species/point) than untreated areas (2.0 species/point). However, there was no significant difference in the richness of native submerged macrophytes (treated: 1.3; untreated: 1.3 species/point). Of 17 macrophyte species in the lake, 12 occurred at a statistically similar frequency in treated and untreated areas (see original paper for full data). One species, leafy pondweed Potamogeton foliosus, was more common in treated areas (present at 25% of survey points) than untreated areas (14%). Four species were less common in treated areas, including Eurasian watermilfoil (treated: 23%; untreated: 53%) and coontail Ceratophyllum demersum (treated: 11%; untreated 18%). Methods: In autumn 2008, submerged macrophytes were surveyed in the littoral zone (<15 m water depth) of Lake Pend Orielle. Some survey points (precise number unclear) were in milfoil-invaded areas that had been treated with herbicide in summer 2007 and/or 2008. A range of herbicide treatments were used (e.g. 2,4-D, diquat, fluridone, triclopyr as liquids or granules; see original paper for details). Other survey points were in milfoil-invaded areas that had not been treated with herbicide.