Host Breadth and Ovipositional Behavior of AdultPolydrusus sericeusandPhyllobius oblongus(Coleoptera: Curculionidae), Nonindigenous Inhabitants of Northern Hardwood Forests

Abstract

Polydrusus sericeus (Schaller) and Phyllobius oblongus (L.) are nonindigenous root-feeding 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 alleghaniensis 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.