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Phyllobius oblongus (L.), Polydrusus sericeus (Schaller), and Sciaphilus asperatus (Bonsdorff) comprise a complex of nonindigenous root-feeding weevils in northern hardwood forests of the Great Lakes region. Little is known about their detailed biology, seasonality, relative abundance, and distribution patterns. We studied 10 sites over a 2-yr period. Two sites were in northeastern Wisconsin, and eight were in the neighboring southern upper peninsula of Michigan. Larval abundance was estimated by soil sampling, and adult abundance was estimated by sweep netting, emergence trapping, and beating samples. Sweep netting collected the most weevils overall (71.0%), whereas beating and emergence traps collected 22.1 and 6.9%, respectively. P. sericeus were the predominant larvae, representing 34.3% of total Curculionidae, whereas P. oblongus were the predominant adults, representing 66.4% of Curculionidae. Few S. asperatus and Trachyphloeus aristatus (Gyllenhal) larvae and adults were collected, with the latter being a new record for Wisconsin. Two additional species, Barypeithes pellucidus (Boheman) and an undetermined Polydrusus sp., were collected only as larvae. Six species of curculionids were collected overall, with at least five being confirmed as nonindigenous species. P. oblongus and P. sericeus adults were the most abundant. These did not coincide temporally. Over 63% of P. oblongus and P. sericeus were collected during single 4-wk intervals in mid-June and mid-July, respectively. Conversely, S. asperatus adults overlapped with both other species, occurring sparingly from 4 June through 28 August. One species was predominant at each site and generally accounted for ≥80% of the total weevil population. P. oblongus larvae and adults predominated in five and eight sites, respectively, whereas P. sericeus and S. asperatus larvae and adults predominated in one site each. Adult and larval populations were generally clustered. We evaluated vertical stratification of P. sericeus larvae in the soil, and most were located within the top 10 cm. [ABSTRACT FROM AUTHOR]

Polydrusus sericeus (Schaller) and Phyllobius oblongus (L.) are nonindigenous rootfeeding weevils in northern hardwood forests of Wisconsin and Michigan. Detailed studies of adult host range, tree species preferences, and effects of food source on fecundity and longevity have not been conducted in North America. P. sericeus and P. oblongus adults fed on leaves of all 11 deciduous tree species offered in no-choice assays, but amount of consumption varied among species. P. sericeus consumed more yellow birch (Betula allegbaniensis Britton), basswood (Tilia americana L.), and ironwood [Ostrya virginiana (Miller) K. Koch] than maple (Acer spp.). Conversely, P. oblongus consumed more ironwood than poplar (Populus spp.) and yellow birch, with maple being intermediate. Females ate 2.5 times as much as males. Mean frass production by P. sericeus was strongly correlated with foliage consumption among host tree species. In feeding choice assays, P. sericeus preferred yellow birch over ironwood, basswood, and aspen (Populus tremuloides Michaux). P. sericeus produced 29.93 ± 1.43 eggs/d when feeding on yellow birch compared with 2.04 ± 0.36 eggs/d on sugar maple (Acer saccharum Marshall). P. oblongus produced 4.32 ± 1.45 eggs/d when feeding on sugar maple compared with just 0.2 ± 0.1 eggs/d on yellow birch. Overall, total egg production for P. sericeus and P. oblongus averaged 830.1 ± 154.8 and 23.8 ± 11.8 eggs, respectively, when feeding on their optimal host plants. P. sericeus survived approximately five times longer in assays than P. oblongus, and it oviposited a total of 25.8 ± 4.0 d, whereas P. oblongus oviposited 1.9 ± 0.9 d. Egg size among P. sericeus and P. oblongus was 0.53 ± 0.008 by 0.32 ± 0.003 and 0.56 ± 0.005 by 0.29 ± 0.004 mm, respectively. In laboratory rearing of P. sericeus on yellow birch seedlings, 18% of the initial 500 larvae completed development to adults. [ABSTRACT FROM AUTHOR]