Use of a Native Insect as a Biological Control for an Introduced Weed

Abstract

We have evaluated the potential of a North American aquatic weevil, Euhrychiopsis lecontei, to serve as an agent of biological control for an exotic weed, Eurasian watermilfoil (Myriophyllum spicatum), which is currently found throughout much of the United States and in some southern provinces of Canada. We have found this weevil on M. spicatum in lakes where populations of the exotic weed have declined. We introduced weevils into enclosures in two lakes dominated by M. spicatum. In both lakes there was 50% less M. spicatum biomass in enclosures with weevils than in enclosures without weevils. Also, in control enclosures, M. spicatum formed a canopy on the water surface as it did outside the enclosures, while there was no plant canopy in any of the weevil enclosures. In laboratory feeding trials we quantified the effects of weevils on ten native aquatic plants including a native watermilfoil, Myriophyllum sibiricum. Weevils did not have a significant effect on the increase in plant length or final dry mass of any native plant, however the weevils did feed on the native watermilfoil. All native plants added new leaves, leaf whorls, or side branches under all weevil densities. The results from these studies suggest that a North American insect may be a suitable control agent for this introduced aquatic weed. Native biological control agents, when they can be found, offer potential advantages over classical biological control agents; they may have little impact on non‐target native species that have coexisted with the control agent, and may save the time and expense of foreign research and quarantine procedures.

How Interactions Between Ecology and Evolution Influence Contemporary Invasion Dynamics

“…In less than 11 years, however, a native weevil (Euhrychiopsis lecontei) has formed incipient host races on M. spicatum (Sheldon and Jones 2001). High abundances of the weevil have been associated with large declines of M. spicatum within lakes, and laboratory tests have shown that the weevil can have a significant impact on the growth of M. spicatum although, interestingly, not M. sibiricum (Sheldon and Creed 1995).…”

Native Cuscuta campestris restrains exotic Mikania micrantha and enhances soil resources beneficial to natives in the invaded communities

“…Previous studies have shown that native parasites can limit exotic invaders escaping from their natural enemies and have fewer negative effects on nontarget species (Sheldon and Creed 1995;Torchin and Mitchell 2004;Krakau et al 2006;Lian et al 2006;Mitchell et al 2006). Research has been dominated by laboratory studies.…”

Variation in hostplant preference and performance by the milfoil weevil, Euhrychiopsis lecontei Dietz, exposed to native and exotic watermilfoils

“…Little is known about freshwater host choice (Newman 1991) and our work with the weevil Euhrychiopsis lecontei Dietz (=Eubrychiopsis lecontei), which has expanded its host range to include Eurasian watermilfoil Myriophyllum spicatum L. (e.g., Sheldon and Creed 1995;Solarz and Newman 1996;Newman et al 1997), suggests that freshwater specialist herbivores may respond to hostplants in ways similar to terrestrial insects. Determining the response to an exotic plant by this specialist herbivore will contribute to our understanding of herbivory in aquatic systems and to how specialist herbivores in both terrestrial and aquatic systems may respond to the introduction of exotic plant species.…”

“…The life history and basic ecology of the weevil have been described (Sheldon and Creed 1995;Newman et al 1996;Sheldon and O'Bryan 1996). All life stages are associated with the submersed plant, indicating that the weevil is fully aquatic.…”