Host Breadth and OvipositionaI Behavior of Adult Polydrmsus sericeus and Phyllobius oblongus (Coleoptera: Curculionidae) , Nonindigenous Inhabitants of Northern Hardwood Forests Environ. Entomol. 34(1): 148-157 (2005) ABSTRACT Polydm serice2Ls (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 alleghuniensis Britton), basswood (Tilia amaicanu L.), and ironwood [Ostrya virginianu (Miller) K. Koch] than maple (Acer spp.). Conversely, P. oblongus consumed more ironwood than poplar (Pgulw spp.) and yellow birch, with maple being interme- diate. Females ate 2.5 times as much as males. Mean frass production by P. saiceus was strongly correlated with foliage consumption among host tree species. In feeding choice assays, P. serim preferred yellow birch over ironwood, basswood, and aspen (Populustremuloides Michaux) .P. serim produced 29.93 + 1.43 eggsld when feeding on yellow birch compared with 2.04 + 0.36 eggsld on sugar maple (Am sacchrum Marshall). P. oblongus produced 4.32 2 1.45 eggsid when feeding on sugar maple compared with just 0.2 2 0.1 eggsid on yellow birch. Overall, total egg production for P. sericeus and P. obbngm averaged 830.1 rt 154.8 and 23.8 2 11.8 eggs, respectively, when feeding on their optimal host plants. P. saiceus 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 2 0.008 by 0.32 2 0.003 and 0.56 + 0.005 by 0.29 + 0.004 mm, respectively. In laboratory rearing of P, sericew on yellow birch seedlings, 18%of the initial 500 larvae completed development to adults. KEY WORDS host range, Phyllobius, Polydrusus, oviposition, rearing A COMPLEX OF NONINDIGENOUS root-feeding weevils has The adults of each species are typically found feed- become widely established throughout the northern ing on the foliage of just a few forest tree species in hardwood forests of the Great Lakes region. These Wisconsin and Michigan, including sugar maple (Acer European species include Phyllobius oblongus (L.) , saccharum Marshall), mountain maple (Acer spicatum Polydrusus saiceus (Schaller), and Sciaphilzis aspera- Lamark), American elm (Urnusamaicana L.), yellow tus (Bonsdorff), of which the first two are predomi- birch (Betula alleghniensis Britton), black cherry nant (Pinski et al. 2005). Adults are particularly abun- (Prunus serotinu Ehrhart), and speckled alder [Ahus dant on understory seedlings, where they have been rugosa Du Roi (Spreng) ] (Witter and Fields 1977). apparent in Michigan and Wisconsin since 1969 (Sim- However, they are described in the European litera- mons 1972). The life histories and seasonal phenolo- ture as polyphagous, feeding on a wide variety of tree gies of these univoltine weevils are reported in Voll- and shrub species (Henshaw 1888, Fryer 1919, Massee man (1954), Witter and Fields (1977), Levesque and 1941, Monis 1978, Jarfas et al. 1985, Casteels and De Levesque (1994), and Pinski et al. (2005). However, Clercq 1988, Helsen and Blommers 1988, Marko et d. the host range and species preferences are poorly 1995, Gharadjedaghi 1997, Czerniakowski 1998). De- understood. spite such generalist feeding habits, their food choice can be quite specific, because Rousi et al. (1997) found significant differences in the palatability of white Department of Entomology, University of Wisconsin-Madison, birch clones (Betuh penduh Roth and B. pubesm 345 Russell Laboratories, 1630 Linden h.,Madison, WI 53706. Ehrhart) to P. oblongus in Europe. Our understanding Corresponding author: Wisconsin Department of Natural Re- of the host range and feeding preferences of this non- sources, 3911 Fish Hatchery Rd., Fitchburg, WI 53711 (e-mail: [email protected]) . indigenous weevil complex is further complicated by WDAForest Service, Forestry Sciences Laboratory, 5985 High- field sampling data in the Great Lakes region, which way K, Rhinelander, WI 54501. have shown no consistent relationshipsbetween wee- 0046-225X105/0148-0157$04.M)/0B 2005 Entomological Society of America February 2005 PINSKI AL.: HOSTBREADTH OF NONINDIGENOUSWEEVILS 149 vil species and stand composition (Pinski 2004). Fur- netting understory plants of multiple species. They thermore, we have no information on how various were stored in a plastic box (30 by 20 by 10 cm) lined food sources can affect the longevity and fecundity of with damp filter paper and containing crumpled tissue these weevils, despite the pronounced effects host paper. Insects were starved for 24 h before assays. plants are known to have on species with similar life Initial leaf area was determined by digital scanning histories, such as the black vine weevil (Otiorhynchus (WinFolia 2001% Regent Instruments 2001). Whole sulcatus IF.] ) and the strawberry root weevil (Otio- leaves were used because these weevils feed at the rhynchus ovatus [L.]) (Penman and Scott 1976, perimeters and because damaging tissue can poten- Nielsen and Dunlap 1981, Shanks et al. 1984). tially induce changes in leaf chemistry (Risch 1985, Detailed information of the host ranges and feeding Jones and Coleman 1988). Arenas consisted of 15-cm- preferences of larvae is likewise not available. Vollman diameter petri dishes lined with damp filter paper (1954) made general observations of larvae feeding in containing one leaf in a water tube and one weevil. the upper soil layers (5-25 cm deep) on roots of tree Weevils were randomly arranged across treatments species on which adults feed. The impacts of below- and replicates (n = 10). Assay units were randomly ground feeding by this complex are notknown. Below- positioned in growth chambers (1-35L; Percival, -ground herbivores can exert subtle effects that mav eo Boone, IA) at a 159-h (L:D) photoperiod and a 24: unnoticed for substantial periods, including rediczd 18°C (L:D) temperature regimen. Weevils were d- plant diversity, altered successional processes, altered lowed to feed for 72 h, and additional distilled water patterns of carbon and nitrogen allocation, increased was added to the filter paper at 36 h. susceptibility to other herbivores and pathogens, and After the assay, weevil sex (2003 only) and survi- reduced total vield (Swertsen and McCov 1985. vorship were recorded. Sex was determined based on Brown and ~&~e1991: 1992, Hunter 2001): ore: the anterior edge of the hind tibia, which has a brush over, detailed feeding and impact studies cannot be of long prominent, erect setae in males but is sparsely conducted until appropriate rearing and bioassay con- pilose in females, and the last abdominal sternite, ditions are established. which has an emarginate apical margin in males The purpose of this research is to (1) characterize (Fowler 1891, Sleeper 1957). The number of frass the host breadth of adult P. saiceus and P. oblongus in pellets was recorded, and a subsample was photo- the Great Lakes region, (2) determine the relative graphed with a Nikon digital camera (E995; Nikon, feeding preferences among suitable hosts of P. seri- Melville, NY). Leaves were removed from the assay ceus, (3) determine how adult feeding on various spe- unit, wiped clean, and rescanned to obtain postfeeding cies of suitable hosts affects fecundity, and (4) de- area and leaf area consumed. Foliage was dried at velop a rearing system for subsequent larval feeding 70°C, and dry mass consumed was calculated by mul- and impact assays. tiplying the post assay specific leaf mass (mglcm2) by the area consumed. Three different feeding measurements, leaf area, Materials and Methods dry mass, and frass pellet production, were analyzed, Host Breadth of Adult Weevils. Foliage was col- because each has limitations. Leaf area consumption lected 14 July 2002 and 17 July 2003 in the Ottawa does not account for differences in leaf thickness National Forest, Upper Peninsula, MI, from 11 north- among tree species, and can be dficult to measure for em hardwood tree species. Host tree selection fo- species such as alder, whose architecture resists com- cused on the species most commonly found in study plete leaf flattening for scanning. Dry mass accounts sites. These included sugar maple, red maple (Acer for leaf thickness, but includes veins, which comprise rubrum L.), mountain maple, yellow birch, paper a substantialproportion of aleaf's mass, are inedible by birch (Betula papyrifma Marshall), ironwood [Ostrya these weevils, and vary among tree species. Frass pro- uirginiana (Miller) K. Koch] , American basswood duction is an indirect measure of weevil consumption (Tilia a&ana L.), quaking aspen (Populus tremu- because it also reflects digestion, but it is a significant loides Michaux), hybrid poplar (Populus spp.), speck- predictor of both leaf area and mass consumed (see led alder, and northern red oak (Quercus rubra L.). Results). No-choice laboratory feeding assays were conducted The host breadth of P. obEongus was assayed using with P. sericeus in 2002 and 2003, with the only dif- similar methods. Weevils and foliage were field col- ference being that mountain maple was tested in 2002 lected 19 June 2003, and the same 11 tree species (n = onlv. 10) were tested. Because of equipment malfunction, 6ne leaf from each of 10 trees per species was some assays were repeated on 7 July 2003 (n = 7). Leaf removed at the petiole. All test leaves were fully ex- area, leaf mass, and weevil survival were recorded. panded, located within the first six positions from the The effects of tree species on leaf area consumed, branch tip inward, at least partially shaded from direct dry mass consumed, and frass production were ma- sunlight, and without any visible signs of insect her- lyzed by one-way analysis of variance (ANOVA; bivory or pathogens.