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The Weevil-Watermilfoil Interaction at Different Spatial Scales: What We Know and What We Need To Know


Authors: Robert P. Creed, Jr.

Author Affiliation: Department of Biology, Appalachian State University, Boone, NC 28608.

Journal: J. Aquatic. Plant Manage. 38: 2000.

Abstract: The North American weevil (Euhrychiopsis lecontei (Dietz)) is being considered as a biological control agent for Eurasian watermilfoil (Myriophyllum spicatum L.). This native insect damages watermilfoil plants and is frequently associated with declining watermilfoil populations. Weevils and watermilfoil interact over at least four different spatial scales—1) the level of the individual plant, 2) the level of beds within lakes, 3) lakes within geographic regions and 4) geographic regions—and we still have much to learn about the interaction at these different scales. For example, at the level of the individual plant, we have a good idea of how weevil herbivory influences plant growth but we still need to determine whether or not weevils can cause plant death. At the level of beds, we do not know how long it takes a weevil population to reach a density that will result in a significant reduction in watermilfoil biomass. Finally, at the level of lakes within geographic regions, we do not know if differences in lake productivity influence the weevil-watermilfoil interaction. It is my hope that addressing these questions and filling in the gaps in our knowledge will lead to a better understanding of the interactions between these two species and to more efficient use of the insect in watermilfoil control projects.