Effects of repeated, early season, herbicide treatments of curlyleaf pondweed on native macrophyte assemblages in Minnesota lakes

  • Published source details Jones A.R., Johnson J.A. & Newman R.M. (2012) Effects of repeated, early season, herbicide treatments of curlyleaf pondweed on native macrophyte assemblages in Minnesota lakes. Lake and Reservoir Management, 28, 364-374.


Action: Use herbicide to control problematic plants

A replicated, controlled study in 2005–2009 of 11 lakes invaded by curly-leaf pondweed Potamogeton crispus in Minnesota, USA (Jones et al. 2012) reported that low-dose, spring herbicide treatments had no clear effect on the richness and abundance of native macrophytes over 1–4 growing seasons. Results summarized for this study are not based on assessments of statistical significance. Total richness (4–37 species/lake; 0.1–3.8 species/survey point), frequency (presence at 7–100% of survey points) and biomass (1–794 g/m2) of native macrophytes all fluctuated between years within lakes, with no clear and consistent differences in these fluctuations between treated and untreated lakes. The same was true for several individual taxa (see original paper for data). However, substantial increases in total biomass (>100% change from one year to next) were more common in treated lakes (5 of 15 comparisons) than in untreated lakes (1 of 8 comparisons). Methods: Between 2005 and 2009, endothall herbicide was added (in May) to eight invaded lakes (0.75–1.00 mg active ingredient/L in treated areas). Each lake received herbicide in at least three consecutive years. Three additional lakes were left untreated. Macrophytes (submerged, floating and emergent) were surveyed at 101–408 points/lake/year in August 2006–2009, i.e. 1–4 growing seasons after treatment began. All survey points were in water ≤4.6 m deep.

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