Evaluation of large-scale low-concentration 2,4-D treatments for Eurasian and hybrid watermilfoil control across multiple Wisconsin lakes

Effects of Low, Subchronic Exposure of 2,4‐Dichlorophenoxyacetic Acid (2,4‐d) and Commercial 2,4‐d Formulations on Early Life Stages of Fathead Minnows (Pimephales promelas)

“…Environmental Toxicology and Chemistry, 2019;38:1382-1385 (Nault et al 2014;. These studies illustrate that even with a low concentration application and without reapplication, initial whole-lake treatments can result in a prolonged presence of 2,4-D in the water column (Nault et al 2018). Hence, 2,4-D exposure to lake biota may often exceed 21 d during permitted applications, which encompasses the observed 2,4-D critical window of exposure leading to decreased survival in fathead minnow larvae (Dehnert et al 2018).…”

“…Granted, in a laboratory setting and under highly aerobic conditions, 2,4-D undergoes rapid degradation (half-life of 15 d) and is also susceptible to aqueous photolysis (half-life of 12.9 d; US Environmental Protection Agency 2005); however, this is not representative of ecological scenarios in which 2,4-D is used. The USEPA reregistration eligibility decision (US Environmental Protection Agency 2005) states that the measured range of 2,4-D degradation in water is 14 to 333 d. The degradation of 2,4-D in water is highly variable, depending on microbial presence, light, oxygen saturation, nutrient levels, temperature, and pH, and whether the water had been previously contaminated with 2,4-D or other phenoxyacetic acids (Sinton et al 1986;Howard 1991;US Environmental Protection Agency 2005;Sandoval-Carrasco et al 2013;Nault et al 2014Nault et al , 2018. Even considering the most optimistic degradation of 2,4-D (13-d half-life), native fish species in treated waters could still be exposed to 2,4-D long enough to experience deleterious impacts on larval survival after 14 d of exposure, as indicated in Figures 1a, 3b Note that our highest treatment encompasses the 2.00-ppm range.…”

Factors Influencing the Distribution of Invasive Hybrid (Myriophyllum Spicatum x M. Sibiricum) Watermilfoil and Parental Taxa in Minnesota

“…[3] and concern has arisen that hybrid watermilfoil may respond differently to management or be more invasive than pure Eurasian [18,19]. Several studies indicate that some hybrid watermilfoil genotypes are less affected by certain commonly-used herbicides than Eurasian, including auxinic herbicides such as triclopyr and 2,4-D (2,4-dichlorophenoxy acetic acid) [18,[20][21][22] as well as fluridone [23][24][25][26]. Parks et al [21] found a greater reduction in Eurasian watermilfoil in comparison to hybrid, following treatment with auxinic herbicides, and similar results were found by Nault et al [20] following treatment with 2,4-D. Fluridone-resistant populations of hybrid watermilfoil have been confirmed in several studies [23,26,27].…”

“…Its occurrence has been documented in Minnesota since 2002 [3] and four lakes since 2007 [6], although we do not know how common or widespread infestations in Minnesota are. Hybrid watermilfoil is widespread in Michigan [30] and~150 hybrid watermilfoil infestations have been identified in Wisconsin [20]. Although hybrid watermilfoil populations have long been documented, the spatial distribution in Minnesota and habitat characteristics associated with hybrid presence have yet to be investigated.…”

Constraining invader dominance: Effects of repeated herbicidal management and environmental factors on curlyleaf pondweed dynamics in 50 Minnesota lakes

“…how to best design a control plan for multi‐year reductions, or how winter conditions will mediate control effectiveness), arise at least partly due to research on CLP biology and management having mainly comprised small‐scale and case studies. Integration and analysis of larger datasets across greater spatial and temporal scales would allow more robust inferences and generalisations to be made (Frater et al, ; Kujawa et al, ; Nault et al, ). Even if implementing treatments based on existing science, managers face challenges such as variable outcomes (Kujawa et al, ), uncertainty regarding best practices (Hussner et al, ), and a lack of coordination and sharing of accumulated data and knowledge (c.f.…”