Temporal and spatial changes in milfoil distribution and biomass associated with weevils in Fish Lake, WI

Jester, Laura L. and Bozek, Michael A. and Helsel, Daniel R. and Sheldon, Sallie P. (2000) Temporal and spatial changes in milfoil distribution and biomass associated with weevils in Fish Lake, WI. Journal of Aquatic Plant Management, 38, pp. 98-104.

Preview

PDF - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader Download (180Kb) | Preview

Abstract

During the course of an eight year monitoring effort, the Wisconsin Department of Natural Resources documented a significant decline in milfoil biomass and distribution in Fish Lake, Wisconsin. Average milfoil biomass declined by 40- 50% from 374-524 g dw m -2 during 1991-93 to 265 g dw m -2 during both 1994 and 1995. Milfoil recovered fully in 1996- 98 to 446- 564 g dw m -2 . The size of the milfoil bed, as discerned from aerial photographs, shrank from a maximum coverage of 40 ha in 1991 to less than 20 ha during 1995. During the “crash” of 1994-95, milfoil plants exhibited typical signs of weevil-induced damage, including darkened, brittle, hollowed-out growing tips, and the arching and collapse of stems associated with loss of buoyancy. Monitoring of weevils and stem damage during 1995-98 showed highest densities and heaviest damage occurred near shore and subsequently fanned out into deeper water from core infestation sites each spring. The extent of milfoil stem damage was positively correlated with weevil densities (monthly sampling). However, weevil densities and stem damage were lower during 1995 (when milfoil biomass was in decline) than during 1996-98 (when milfoil biomass was fully recovered).

Actions (login required)