Euhrychiopsis lecontei distribution, abundance, and experimental augmentations for Eurasian watermilfoil control in Wisconsin lakes

The specialist aquatic herbivore Euhrychiopsis lecontei (Dietz) is currentl y being researched as a potential biological control agent for Eurasian wat ermilfoil (Myriophyllum spicatum L.), Our research in Wisconsin focused on 1) determining milfoil weevil distribution across lakes, 2) assessing limno logical characteristics associated with their abundance, and 3) evaluating milfoil weevil augmentation as a practical management tool for controlling Eurasian watermilfoil, The geographic distribution of the milfoil weevil is widespread with 49 new records of the weevil among Wisconsin lakes contain ing Eurasian watermilfoil. Among 31 of the Wisconsin lakes that contained t he milfoil weevil, their abundance varied from non-detectable to 2.5 weevil s per stem of Eurasian watermilfoil. No whole-lake characteristics and only some milfoil bed characteristics such as the percentage of natural shoreli ne, the depth and distance of the Eurasian watermilfoil bed from shore, the number of apical tips and the percentage of broken epical tips per stem of Eurasian watermilfoil, were significantly correlated with milfoil weevil a bundance. Twelve Wisconsin lakes augmented with one of three different trea tment levels of weevils (1, 2 or 1 weevils per Eurasian watermilfoil stem) showed some significant damage to the Eurasian watermilfoil in small study plots at the end of the first treatment season, Additional sampling to asse ss longterm effects of this augmentation is ongoing.