Monday, December 11, 2006

Ecology of invasive weevils in a northern hardwood forest

David R. Coyle, dcoyle@entomology.wisc.edu1, Alexander L. Friend2, William J. Mattson, wmattson@fs.fed.us3, and Kenneth F. Raffa, Raffa@entomology.wisc.edu1. (1) University of Wisconsin, Department of Entomology, 1630 Linden Drive, 345 Russell Labs, Madison, WI, (2) USDA Forest Service, North-Central Research Station, 410 MacInnes Drive, Houghton, MI, (3) USDA Forest Service, North Central Research Station, 5985 Highway K, Rhinelander, WI

A complex of invasive weevils has recently undergone a population eruption in the upper Great Lakes region. Adult and larval ecology is being examined in the Ottawa National Forest, near Watersmeet, in the Upper Peninsula of Michigan. Adult weevils are folivores, feeding primarily on the leaf margins of sugar maple, ironwood, and raspberry. Weekly adult censuses in 2006 indicated the presence of four species: Phyllobius oblongus, Polydrusus sericeus, Sciaphilis asperatus, and Barypeithes pellucidus. Phyllobius oblongus were the most common; weekly sweep net samples captured from 0 to 79 adults. Polydrusus sericeus was less common than P. oblongus, but still nearly twice as abundant as S. asperatus or B. pellucidus. Adult weevil populations peaked in mid-June, and nearly all adults were gone by late July. Larvae are rhizophagous, and feed primarily on fine (i.e., <1 mm diameter) roots. Monthly larval sampling via soil cores indicated high early mortality rates, which tapered off as fall approaches. Studies are underway to determine the effects of larval and adult feeding on seedling growth, and fine root dynamics, in this northern hardwood ecosystem.

Species 1: Coleoptera Curculionidae Phyllobius oblongus
Species 2: Coleoptera Curculionidae Polydrusus sericeus
Species 3: Coleoptera Curculionidae Sciaphilis asperatus