The efficacy and subsurface application of Zequanox®, a commercially prepared spray-dried powder formulation of Pseudomonas fluorescens (strain CL145A), were evaluated for controlling zebra mussels (Dreissena polymorpha) within 27-m2 enclosures in Lake Minnetonka (Deephaven, Minnesota). Five treatments consisting of (1) two whole water column Zequanox applications, (2) two subsurface Zequanox applications, and (3) an untreated control were completed on each of three independent treatment days during September 2014. The two types of samplers used in the study were (1) custom built multi-plate samplers (type 1 samplers), with wood, perforated aluminum, and tile substrates that were placed into Robinson’s Bay in June of 2013 to allow for natural colonization by zebra mussels, and (2) samplers that were designed to contain zebra mussels (type 2 samplers) which consisted of zebra mussels adhering to perforated aluminum trays that were placed into mesh containment bags. One day prior to treatment, three individual samplers of each type were distributed to test enclosures and exposed to a randomly assigned treatment. Sampling to determine the living zebra mussel biomass adhering to type 1 samplers and the survival assessments for zebra mussels contained in type 2 samplers were completed ~40 days after exposure. The living zebra mussel biomass adhering to type 1 samplers and the survival of zebra mussels contained in type 2 samplers were significantly less in groups treated with the highest Zequanox concentrations and in groups that received whole water column applications compared to groups treated with lower Zequanox concentrations and subsurface applications. However, standardization biomass and survival results to the amount of Zequanox applied showed that the lower Zequanox concentrations and subsurface applications were more efficient at reducing zebra mussel biomass and inducing zebra mussel mortality. Although more efficient, biological significance and management goals should be evaluated prior to selecting subsurface application methods and lower treatment concentrations for Zequanox applications. Development and refinement of additional application techniques may improve the utility of the subsurface Zequanox applications.

Zebra mussels (Dreissena polymorpha) have continued their spread within inland lakes and rivers in North America despite diligent containment and decontamination efforts by natural resource agencies and other stakeholders. Identification of newly infested waterways with early detection surveillance programs allows for rapid response zebra mussel eradication treatments in some situations. Previous eradication treatments have been conducted during times of variable water temperatures and temperature has been shown to influence the efficacy of molluscicides. Natural resource managers would benefit from knowledge regarding the impacts of water temperature and exposure duration on toxicity of molluscicides to zebra mussels. In particular, temperature specific data are needed to inform the selection of an effective molluscicide and the proper dose that will induce 100% zebra mussel mortality. We evaluated the influences of temperature and exposure duration on the toxicity of two EPA-registered (EarthTec QZ and Zequanox) and two nonregistered (niclosamide and potassium chloride) molluscicides to zebra mussels at water temperatures of 7, 12, 17, and 22 °C. Our results indicate that treatment options for the eradication of zebra mussels in waters ≤ 12 °C include 336 h or longer treatments with EarthTec QZ and KCl and treatments with niclosamide ≥ 24 h in duration. In waters ≥ 17 °C, multiple toxicant and exposure duration combinations would be effective for zebra mussel eradication treatments. However, site specific variables should be considered prior to treatment including: the extent of the infestation, water chemistry, aquatic vegetation, substrate, and the presence of nontarget organisms. The use of on-site or in situ zebra mussel bioassays would also be a useful tool for the evaluation of treatment efficacy. The dataset includes: Water Quality, Chemical Concentrations, Mortality, and Zebra Mussel Condition Data

Zebra mussels (Dreissena polymorpha) have continued their spread within inland lakes and rivers in North America despite diligent containment and decontamination efforts by natural resource agencies and other stakeholders. Identification of newly infested waterways with early detection surveillance programs allows for rapid response zebra mussel eradication treatments in some situations. Previous eradication treatments have been conducted during times of variable water temperatures and temperature has been shown to influence the efficacy of molluscicides. Natural resource managers would benefit from knowledge regarding the impacts of water temperature and exposure duration on toxicity of molluscicides to zebra mussels. In particular, temperature specific data are needed to inform the selection of an effective molluscicide and the proper dose that will induce 100% zebra mussel mortality. We evaluated the influences of temperature and exposure duration on the toxicity of two EPA-registered (EarthTec QZ and Zequanox) and two nonregistered (niclosamide and potassium chloride) molluscicides to zebra mussels at water temperatures of 7, 12, 17, and 22 °C. Our results indicate that treatment options for the eradication of zebra mussels in waters ≤ 12 °C include 336 h or longer treatments with EarthTec QZ and KCl and treatments with niclosamide ≥ 24 h in duration. In waters ≥ 17 °C, multiple toxicant and exposure duration combinations would be effective for zebra mussel eradication treatments. However, site specific variables should be considered prior to treatment including: the extent of the infestation, water chemistry, aquatic vegetation, substrate, and the presence of nontarget organisms. The use of on-site or in situ zebra mussel bioassays would also be a useful tool for the evaluation of treatment efficacy. The dataset includes: Water Quality, Chemical Concentrations, Mortality, and Zebra Mussel Condition Data

Quagga (Dreissena rostriformis bugensis) and Zebra (Dreissena polymorpha) mussels are highly invasive and easily transported from one waterybody to another. California has an extensive program designed to prevent the spread of these mussels. This program is coordinated by the California Department of Fish and Wildlife (CDFW) Invasive Species Program, within the Habitat Conservation Planning Branch. This data set summarizes the locations of Quagga and Zebra mussel findings within California waterbodies, using data from the U.S. Geological Surveys NAS (Nonindigenous Aquatic Species) database.

We applied Zequanox using a custom-engineered, boat mounted application system to replicated 0.30 Hectare plots within a small inland lake. The objectives of these applications were to determine if uncontained, open-water Zequanox applications could effectively control zebra mussel populations and protect native unionid mussel populations within zebra mussel infested systems. The datasets included are as follows: Exposure Water Chemistry Hardness and Alkalinity Native Mussel Sonde Water Chemistry Zebra Mussel Density Zebra Mussel Length Zebra Mussel Mortality Zequanox Concentration ShapeFiles: PLOTS, UNIONID, ZEQUANOX CONCENTRATION, ZM_DENSITY, ZM_MORTALITY

The environmental fate, persistence, and point-source discharge of traditional molluscicidal compounds led to the development of an alternative biomolluscicide, Zequanox. Previous studies evaluated the efficacy and non-target animal safety of Zequanox in laboratory, mesocosm, and field enclosure studies. One study indicated sensitivity of salmonid species and lake sturgeon (Acipenser fulvescens Rafinesque 1817) following exposure to Zequanox, however, the exposures were not conducted in a manner consistent with the product label. This laboratory study evaluated sublethal and lethal impacts of Zequanox on lake sturgeon and lake trout (Salvelinus namaycush Walbaum in Artedi, 1792) following exposures that were conducted consistent with a Zequanox open-water label application. Fish were exposed to 50 and 100 mg Zequanox active ingredient/L for 8 h and then held for an additional 33-d for post-exposure observation. No acute mortality was observed in either species, however, significant latent mortality (46.2%) was observed in lake trout that were exposed to 100 mg of Zequanox active ingredient/L for 8 h. At the termination of the 33d holding period, biologically minimal, yet statistically significant, differences were observed in the terminal weight of surviving lake sturgeon (range 20.17 to 21.49 g) and biologically, as well as, statistically significant differences were observed in the terminal weight of surviving lake trout (range 6.19 to 9.55 g). Histological evaluation of lake trout gastrointestinal tracts suggest that a different mode of action is responsible for the Zequanox exposure-related impacts to lake trout than the mode of action that induces zebra and quagga mussel mortality. Further research is required to determine if Zequanox sensitivity is limited to lake trout or if all salmonid species are vulnerable to exposure and to determine if native fish will avoid Zequanox exposure.

The environmental fate, persistence, and point-source discharge of traditional molluscicidal compounds led to the development of an alternative biomolluscicide, Zequanox. Previous studies evaluated the efficacy and non-target animal safety of Zequanox in laboratory, mesocosm, and field enclosure studies. One study indicated sensitivity of salmonid species and lake sturgeon (Acipenser fulvescens Rafinesque 1817) following exposure to Zequanox, however, the exposures were not conducted in a manner consistent with the product label. This laboratory study evaluated sublethal and lethal impacts of Zequanox on lake sturgeon and lake trout (Salvelinus namaycush Walbaum in Artedi, 1792) following exposures that were conducted consistent with a Zequanox open-water label application. Fish were exposed to 50 and 100 mg Zequanox active ingredient/L for 8 h and then held for an additional 33-d for post-exposure observation. No acute mortality was observed in either species, however, significant latent mortality (46.2%) was observed in lake trout that were exposed to 100 mg of Zequanox active ingredient/L for 8 h. At the termination of the 33d holding period, biologically minimal, yet statistically significant, differences were observed in the terminal weight of surviving lake sturgeon (range 20.17 to 21.49 g) and biologically, as well as, statistically significant differences were observed in the terminal weight of surviving lake trout (range 6.19 to 9.55 g). Histological evaluation of lake trout gastrointestinal tracts suggest that a different mode of action is responsible for the Zequanox exposure-related impacts to lake trout than the mode of action that induces zebra and quagga mussel mortality. Further research is required to determine if Zequanox sensitivity is limited to lake trout or if all salmonid species are vulnerable to exposure and to determine if native fish will avoid Zequanox exposure.

Zequanox® is a commercial formulation of the killed bacterium, Pseudomonas fluorescens (strain CL145A) that has USEPA approval for use in open water to kill dreissenid mussels. Previous nontarget studies demonstrated the safety and selectivity of the product, but the database is limited for macroinvertebrate taxa and exposure conditions. We evaluated the safety of the product to two high value macroinvertebrates, the amphipod Gammarus lacustris lacutris, and nymphs of the burrowing mayfly, Hexagenia spp., at the maximum approved concentration (100 mg/L A.I.) and exposure duration (8 h). Survival of animals was measured at the end of 8 h exposure and at 24 h post-exposure and 96 h post-exposure. Additionally, histological changes in the digestive tract of both species were compared with controls at 96 h post-exposure. The results showed no effect of Zequanox on survival of either species. Survival of G. lacustris exceeded 85% in all concentrations at all three sampling time points. Survival of Hexagenia spp. ranged from 71% (control) to 91% (50 mg/L) at 8 h, 89-93% at 24 h post-exposure and 70-73% at 96 post-exposure h across all treatments. We also saw no evidence of pathology in the visceral organs of treated animals. Our results indicate that application of Zequanox at the maximum approved concentration and exposure duration does not cause acute mortality or pathology to G. lacustris and Hexagenia spp.

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Zebra mussels (Dreissena polymorpha Pallas 1771) are a tenacious aquatic invasive species in the United States and new infestations can rapidly expand into dense colonies. Zebra mussels were first reported in Marion Lake (Dakota County, Minnesota) in September 2017 and surveys indicated the infestation was likely isolated near the public boat access. A 2.4-hectare area, containing the known zebra mussel infestation, was enclosed and treated for nine days with EarthTec QZ®, a copper-based molluscicide, in an attempt to eradicate the zebra mussels. We conducted an on-site bioassay to confirm treatment efficacy. The bioassay was conducted in mobile assay trailer that received a continuous flow of treated lake water and zebra mussels test animals that were collected from White Bear Lake (Ramsey County, MN). Zebra mussel mortality in the treated bioassay tanks achieved 99 percent mortality (95-percent Confidence Interval: 98 – 100 percent) and a predictive model indicates in-lake mortality as low as 85 percent may have occurred; therefore, our results indicate that the Marion Lake treatment may not have induced complete zebra mussel mortality. Post-treatment assessments and surveys are recommended to further verify treatment success and monitor lake conditions in regards to zebra mussel infestation.