Effects of Alligatorweed Control in Seasonal Wetlands Managed for Waterfowl

Wildlife managers commonly use herbicides to control invasive plant species and maintain early-successional vegetation communities in seasonally flooded moist-soil wetlands. However, there is limited information on how herbicides influence plant and animal communities following application. Thus, we investigated the response of vegetation, food density, and the abundance and activities of dabbling ducks (Anatini) to application of imazapyr herbicide in moist-soil wetlands in Tennessee to control invasive alligatorweed (Alternanthera philoxeroides). Imazapyr was applied topi- cally at Tennessee National Wildlife Refuge during July 2011 following an early water drawdown and dry weather conditions. Food density and use and activities of dabbling ducks were similar between treatment and control plots during the year of application and in the subsequent year. Dabbling duck use was negatively related to increasing water depth during winter, independent of treatment type. Imazapyr treatments reduced canopy cover of alliga- torweed in the year of and one-year post-treatment in most plots, but repeated herbicide applications and a more integrated approach are likely needed for long-term control in moist-soil wetlands where alligatorweed is established. Using an integrated pest management approach to control invasive species in moist-soil wetlands is important for National Wildlife Refuges to meet their waterfowl energy objectives in support of the North American Waterfowl Management Plan.

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