Comparison of generic and proprietary aquatic herbicides for control of invasive vegetation; part 3 : submersed plants

Herbicide selection is key to efficiently managing nuisance vegetation in our nation’s waterways. After selecting the active ingredient, there still remains multiple proprietary and generic products to choose from. Recent small-scale research has been conducted to compare the efficacy of these herbicides against floating and emergent species. Therefore, a series of mesocosm and growth chamber trials were conducted to evaluate subsurface applications of the following herbicides against submersed plants: diquat versus coontail (Ceratophyllum demersum L.), hydrilla (Hydrilla verticillata L.f. Royle), southern naiad (Najas guadalupensis (Sprengel) Magnus), and Eurasian watermilfoil (Myriophyllum spicatum L.); flumioxazin versus coontail, hydrilla, and Eurasian watermilfoil; and triclopyr against Eurasian watermilfoil. All active ingredients were applied at concentrations commonly used to manage these species in public waters. Visually, all herbicides within a particular active ingredient performed similarly with regard to the onset and severity of injury symptoms throughout the trials. All trials, except diquat versus Eurasian watermilfoil, resulted in no differences in efficacy among the 14 proprietary and generic herbicides tested, and all herbicides provided 43%–100% control, regardless of active ingredient and trial. Under mesocosm and growth chamber conditions, the majority of the generic and proprietary herbicides evaluated against submersed plants provided similar control.

Efficacy of florpyrauxifen-benzyl for eurasian watermilfoil control and nontarget Illinois pondweed, elodea, and coontail response

This research evaluated low concentrations and short exposure times of the recently registered aquatic herbicide florpyrauxifen-benzyl (4-amino-3-chloro-6-(4-chloro-2-fluoro-3-methoxyphenyl)-5-fluoro-pyridine-2-benzyl ester) on the target plant Eurasian watermilfoil (Myriophyllum spicatum L., hereafter referred to as EWM) as well as selectivity towards the nontarget submersed species Illinois pondweed (Potamogeton illinoensis Morong), elodea (Elodea canadensis Michx.), and coontail (Ceratophyllum demersum L.)

Absorption and Translocation of Florpyrauxifen-benzyl in Ten Aquatic Plant Species

Additional active ingredients are needed for use in aquatic systems in order to respond to new threats or treatment scenarios, enhance selectivity, reduce use rates, and to mitigate the risk of herbicide-resistance. Florpyrauxifen-benzyl is a new synthetic auxin developed for use as an aquatic herbicide. A study was conducted at North Carolina State University, in which 10 µg L−1 of 25% radiolabeled florpyrauxifen-benzyl was applied to the isolated shoot tissue of ten different aquatic plant species in order to elucidate absorption and translocation patterns in these species. Extremely high levels of shoot absorption were observed for all species and uptake was rapid. Highest shoot absorptions were observed for crested floatingheart [Nymphoides cristata (Roxb.) Kuntze] (A192 =20 µg g−1), dioecious hydrilla [Hydrilla verticillata (L.f.) Royle] (A192 =25.3 µg g−1), variable watermilfoil (Myriophyllum heterophylum Michx.) (A192 =40.1 µg g−1) and Eurasian watermilfoil (Myriophyllum spicatum L.) (A192 =25.3 µg g−1). Evidence of translocation was observed in all rooted species tested with the greatest translocation observed in N. cristata (1.28 µg g-1 at 192 HAT). The results of this study add to the growing body of knowledge surrounding the behavior of this newly registered herbicide within aquatic plants.

Predicting Eurasian Watermilfoil and Curly-leaf Pondweed Presence-Absence in Adirondack Lakes Using Geographically Weighted Logistic Regression

Aquatic invasive species, Eurasian Watermilfoil (EWM) and Curly-leaf Pondweed (CLP), have been dispersing across New York, USA and are threatening the ecosystem of Adirondack Park, a state park with a large forest preserve and heavily frequented by tourists. In this study, the prediction of EWM and CLP invasion across Adirondack Park lakes is modeled using logistic regression (LR) and geographically weighted logistic regression (GWLR) with lake, landscape, and climate variable predictors. EWM presence-absence is found to be best predicted by nearby invaded lakes, human presence, and elevation. The presence-absence of CLP models have similar findings, with the addition of game-fish abundance being important. GWLR increases model performance and prediction, with explained variation of EWM and CLP increasing by 23% and 16% and the percent correctly predicted increasing by 2.6% and 0.9%. The study shows that GWLR, a relatively novel methodology, works better than common LR models for predicting invasion of EWM and CLP across Adirondack Park, and corroborates anthropogenic influences on dispersal of aquatic invaders.

Predicting Eurasian Watermilfoil and Curly-leaf Pondweed Presence-Absence in Adirondack Lakes Using Geographically Weighted Logistic Regression

Aquatic invasive species, Eurasian Watermilfoil (EWM) and Curly-leaf Pondweed (CLP), have been dispersing across New York, USA and are threatening the ecosystem of Adirondack Park, a state park with a large forest preserve and heavily frequented by tourists. In this study, the prediction of EWM and CLP invasion across Adirondack Park lakes is modeled using logistic regression (LR) and geographically weighted logistic regression (GWLR) with lake, landscape, and climate variable predictors. EWM presence-absence is found to be best predicted by nearby invaded lakes, human presence, and elevation. The presence-absence of CLP models have similar findings, with the addition of game-fish abundance being important. GWLR increases model performance and prediction, with explained variation of EWM and CLP increasing by 23% and 16% and the percent correctly predicted increasing by 2.6% and 0.9%. The study shows that GWLR, a relatively novel methodology, works better than common LR models for predicting invasion of EWM and CLP across Adirondack Park, and corroborates anthropogenic influences on dispersal of aquatic invaders.

Spatial analysis of two aquatic invaders in Adirondack Lakes: a modelling approach for environmental management

The global expansion of humans has stressed the natural world, removed boundaries between continents and habitats and exposed natural areas to invasive species. These cause billions of dollars of damage yet there are limited funds given for their management. Predictive tools can be used to develop pro-active strategies for managing invasive species and this study developed such a tool. Publicly available data were used to build predictive models for the presence of two invasive species, curly-leaf pondweed (Potamogeton crispus) and Eurasian watermilfoil (Myriophyllum spicatum) within the Adirondack Park (New York State). Predictors were identified through: bivariate analysis to test the variables; ordinary least squares regression to build predictive models and logistic regression to validate those models; geographically weighted logistic regression to evaluate local impacts. Models were ranked by Aikake information criterion minimization and evaluated with McFadden’s rho-squared, standard coefficients and variance inflation factors. The top five models for each invasive species established seven predictors for curly-leaf pondweed and nine predictors for Eurasian watermilfoil. Geographically weighted regression, a local analysis, was found to be a definite improvement over the global analysis for watermilfoil but not for pondweed. Two predictors (lake elevation and distance to Interstate-87) were significant in all the top models for both species. The identified predictors provided a group of characteristics that could be used to identify vulnerable lakes and prioritize management strategies. Even though these findings were specific to the Adirondack Park, this approach could be applied to other invasive species or other areas to help in the decision-making process for management.

Spatial analysis of two aquatic invaders in Adirondack Lakes: a modelling approach for environmental management

The global expansion of humans has stressed the natural world, removed boundaries between continents and habitats and exposed natural areas to invasive species. These cause billions of dollars of damage yet there are limited funds given for their management. Predictive tools can be used to develop pro-active strategies for managing invasive species and this study developed such a tool. Publicly available data were used to build predictive models for the presence of two invasive species, curly-leaf pondweed (Potamogeton crispus) and Eurasian watermilfoil (Myriophyllum spicatum) within the Adirondack Park (New York State). Predictors were identified through: bivariate analysis to test the variables; ordinary least squares regression to build predictive models and logistic regression to validate those models; geographically weighted logistic regression to evaluate local impacts. Models were ranked by Aikake information criterion minimization and evaluated with McFadden’s rho-squared, standard coefficients and variance inflation factors. The top five models for each invasive species established seven predictors for curly-leaf pondweed and nine predictors for Eurasian watermilfoil. Geographically weighted regression, a local analysis, was found to be a definite improvement over the global analysis for watermilfoil but not for pondweed. Two predictors (lake elevation and distance to Interstate-87) were significant in all the top models for both species. The identified predictors provided a group of characteristics that could be used to identify vulnerable lakes and prioritize management strategies. Even though these findings were specific to the Adirondack Park, this approach could be applied to other invasive species or other areas to help in the decision-making process for management.

Prioritizing Management of Non-Native Eurasian Watermilfoil Using Species Occurrence and Abundance Predictions

Prioritizing the prevention and control of non-native invasive species requires understanding where introductions are likely to occur and cause harm. We developed predictive models for Eurasian watermilfoil (EWM) (Myriophyllum spicatum L.) occurrence and abundance to produce a smart prioritization tool for EWM management. We used generalized linear models (GLMs) to predict species occurrence and extended beta regression models to predict abundance from data collected on 657 Wisconsin lakes. Species occurrence was positively related to the nearby density of vehicle roads, maximum air temperature, lake surface area, and maximum lake depth. Species occurrence was negatively related to near-surface lithological calcium oxide content, annual air temperature range, and average distance to all known source populations. EWM abundance was positively associated with conductivity, maximum air temperature, mean distance to source, and soil erodibility, and negatively related to % surface rock calcium oxide content and annual temperature range. We extended the models to generate occurrence and predictions for all lakes in Wisconsin greater than 1 ha (N = 9825), then prioritized prevention and management, placing highest priority on lakes likely to experience EWM introductions and support abundant populations. This modelling effort revealed that, although EWM has been present for several decades, many lakes are still vulnerable to introduction.

Mapping Rocky Mountain ridged mussel beds with preliminary identification of overlapping Eurasian watermilfoil within the Canadian range

The Rocky Mountain ridged mussel (Gonidea angulata) is a bivalve species whose Canadian range is limited to the Okanagan Valley, British Columbia. In 2019, conflicts between habitat protection for the mussel and potential habitat alteration to control the invasive Eurasian watermilfoil (Myriophyllum spicatum) (milfoil), led to a decision to maintain the status of the mussels as Special Concern under Canada’s Species at Risk Act (SARA) rather than classify it as Endangered. Milfoil control can cause direct mortality and/or burial of the mussels, but there had been no systematic study of the impacts of milfoil control on mussel beds. The purpose of this study was to address knowledge gaps by delineating known mussel beds and potential overlap with milfoil to provide information for management decisions that balance the needs of native species protection and invasive species control. Rocky Mountain ridged mussels in three reference locations were enumerated using snorkel surveys. The presence and distribution of milfoil was documented in relation to five sites within these three locations. Milfoil was encroaching on one site, causing some changes to the substrate. At other sites, the differences in the depth and distribution of the mussel and the milfoil could allow milfoil control without damaging the mussel beds. It is recommended that, before milfoil removal near known mussel beds be undertaken, a detailed site evaluation be conducted to determine potential impacts. This study suggests presumed impediments to co-managing the mussels and controlling an invasive species should not preclude classifying the mussels as Endangered and affording protections under SARA.