THE EFFECT OF FEEDING BY A NORTH-AMERICAN WEEVIL, EUHRYCHIOPSIS-LECONTEI, ON EURASIAN WATERMILFOIL (MYRIOPHYLLUM-SPICATUM)

The North American weevil, Euhrychiopsis lecontei (Dietz), has been found associated with a declining population of Eurasian watermilfoil, Myriophyllum spicatum L., in Brownington Pond, Vermont, USA. Feeding experiments revealed that adult weevils can reduce watermilfoil growth, and that they concentrate their feeding activity on the stem and leaves at the tops of plants. When presented with both M. spicatum and a native milfoil, Myriophyllum sibiricum Komarov (=Myriophyllum exalbescens Fernald), adult weevils fed primarily on M. spicatum. Surveys in Brownington Pond and other lakes have shown that all life stages of this weevil are associated with M. spicatum. These results suggest that E. lecontei has either expanded its diet to include M. spicatum or undergone a host shift from a native, North American macrophyte to M. spicatum.