LAUSR

Nuisance growths of aquatic plants in Canadian surface waters continue to be problematic. Only diquat, a contact herbicide that is used to control many free-floating plants (but is less effective at controlling emergent plants), is registered in Canada for general aquatic use. Other herbicides are currently only permitted under “emergency registration.” Recent emergency registrations have been granted to glyphosate and imazapyr, and these two herbicides are likely candidates to be proposed for full registration for direct application to water in Canada in the foreseeable future. These herbicides have been extensively studied in laboratory conditions and have provided a benchmark for ecotoxicity for a variety of aquatic organisms, yet the inherent toxicity of these herbicides derived from tests does not always translate into their environmental toxicity in natural aquatic ecosystems as the fate (e.g., removal from the water body via binding to sediments and suspended solids, degradation, volatization, etc....