Phyllobius oblongus (Linnaeus), Polydrusus sericeus (Schaller) and Sciaphilus asperatus (Bondsdorf) comprise a complex of invasive root feeding weevils affecting northern hardwood forests in Wisconsin and Michigan. The relative abundance, seasonal distribution and host range of this complex were investigated during a two-year field and laboratory study. Phyllobius oblongus was predominant, representing >60% of the sample in 8 of 10 sites. Polydrusus sericeus and S. asperatus were predominant in one site each, where each represented >80%. Phyllobius oblongus and S. asperatus, but not P. sericeus, were predominant in sites characterized by a sugar maple understory. Adult P. oblongus and P. sericeus did not coincide. Over 70% of each was collected during 4-week intervals in mid June and mid July respectively. Conversely, S. asperatus had a more evenly distributed population that overlapped with both P. oblongus and P. sericeus and was present from June 6- August 27. No-choice feeding assays indicated P. sericeus is polyphagous, feeding on all 11 tree species tested. Polydrusus sericeus fed significantly more on alder, yellow birch, white birch and ironwood than mountain maple, red maple, sugar maple or quaking aspen. Host diet affected ovipositonal patterns. Polydrusus sericeus that consumed only sugar maple produced 90% fewer eggs than those consuming yellow birch. Future research will focus on how root herbivory by this invasive weevil complex affects seedling regeneration in hardwood forests.
Species 1: Coleoptera Curculionidae Phyllobius oblongus
Species 2: Coleoptera Curculionidae Polydrusus sericeus
Species 3: Coleoptera Curculionidae Sciaphilus asperatus
Keywords: invasive species, life history
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