Temperature-dependent toxicity of molluscicides to zebra mussels

Project manager: James Luoma

Funded by: Clean Water Fund

Description: This project will create water-temperature dependent treatment protocols to eradicate localized zebra mussel infestations in a rapid response scenario. New infestations of zebra mussels are more likely to be found in late summer or autumn, when the dropping water temperatures can impact treatment options.

These protocols will provide resource managers with a critical support tool for:

  1. Selecting the correct molluscicide
  2. Determining the treatment concentration
  3. Determining the treatment duration

The project will also help determine the probability of treatment success and estimate the treatment costs. Four molluscicides will be evaluated – Zequanox, Earthtec QZ, potassium chloride, and niclosamide – to determine the dose and duration required to kill zebra mussels at various water temperatures.

This project will have an immediate impact for managers who are implementing a rapid response treatment to eradicate a new, localized zebra mussel infestation.

Project start date: 2016

Project end date: 2018

Findings:

This project evaluted four molluscicides in order to inform the selection of an effective molluscicide and the proper dose that will induce 100% zebra mussel mortality at different temperatures. Findings are presented in brief below, please read this white paper for details.

  • EarthTecQZ: The data suggests that effective control of zebra mussels in a rapid response action could be obtained at or below the current the maximum label concentration of EarthTec QZ using exposures ≥ 336 h in duration when water temperatures are 7 to 12°C and with exposures ≥ 96 h in duration when water temperatures are ≥ 17°C
  • Niclosamide: The data suggests that 96 h of exposure to 0.10 mg/L of niclosamide at water temperatures ≥ 12°C would induce a complete zebra mussel kill
  • Potassium chloride: The data suggests that KCl is not an effective molluscicide for zebra mussel eradication when water temperatures are < 12°C and that KCl is an effective molluscicide for zebra mussel eradication when water temperatures are ≥ 12°C and exposures are ≥ 336 h in duration. When water temperatures are ≥ 22°C then KCl exposures ≥ 96 h in duration are also effective.
  • Zequanox: Previous research demonstrates that Zequanox may be a reasonable tool for zebra mussel management, however, the inability of Zequanox to consistently achieve a complete mortality of zebra mussels preclude its use for eradication efforts

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