Efficacy, selectivity, and herbicide concentrations following a whole-lake 2,4-D application targeting Eurasian watermilfoil in two adjacent northern Wisconsin lakes

Abstract

(2014) Efficacy, selectivity, and herbicide concentrations following a whole-lake 2,4-D application targeting Eurasian watermilfoil in two adjacent northern Wisconsin lakes, Lake and Reservoir Management, 30:1, 1-10,

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)

“…These impacts on fishes are most likely realized when herbicide application coincides with the breeding cycles and recruitment periods. However, given previous studies illustrating a potentially long latency period (i.e., up to 93 d; Nault et al ) of 2,4‐D in the water column, risk periods to fish may range from 21 d to months after application dates (US Environmental Protection Agency ). Furthermore, exposure of the germ cells in adults potentially makes the larvae more susceptible to a broader range of concentrations (0.05–2.00 ppm; DeQuattro and Karasov ).…”

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).…”

“…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.…”

Lessons from a decade of lake management: effects of herbicides on Eurasian watermilfoil and native plant communities

“…McNemar's tests of individual treatments suggest a slightly more nuanced but still compelling narrative: About a third of herbicide treatments (23 of 61) coincided with statistically significant decreases in M. spicatum at the whole-lake scale (Table 1). These results suggest that herbicide treatment can be an effective tool for adaptive management of M. spicatum (Parsons et al 2001, Wersal et al 2010, Nault et al 2014.…”

“…This variability, particularly in response to small-scale spot treatment, echoes previous conclusions on the uncertainty of treatment outcomes (Nault et al 2015). All five treatments of >50% of a lake's surface resulted in a significant decrease in M. spicatum abundance, suggesting that large-scale treatments may be particularly effective at M. spicatum control (Nault et al 2012(Nault et al , 2014.…”