We studied the timing of reproductive maturity of cherry fruit fly, Rhagoletis cingulata (Loew), a key pest of sweet and tart cherries in the eastern United States. To determine when cherry fruit fly females become reproductively mature in managed and natural habitats, we deployed traps in sweet and tart cherry orchards and nearby stands of the ancestral host tree, black cherry. Flies were removed from the traps and females were dissected to determine the presence of fully developed eggs. We found that capture of reproductively mature female flies occurred earlier in orchards that are not sprayed with insecticides than in sprayed orchards or in black cherry tree sites. In addition, the gap between the flights of immature and mature females in unmanaged sweet or tart cherry orchards was shorter than in managed orchards or black cherry tree sites. We also determined fruit color, size, and skin hardness to characterize the progression of fruit maturity. We found that fruit became mature earlier in sweet and tart cherry orchards than in black cherry tree sites. This study indicates that the timing of female reproductive maturity is plastic and varies among cherry fruit fly populations present in distinct habitats. Variation in the timing of reproductive maturity is related to the fruit maturity period of distinct host plant species and to orchard management.

It has been claimed that plant architecture can alter aphid reproductive rates, but the mechanism driving this effect has not been identified. We studied interactions between plant architecture, aphid density, environmental conditions, and nutrient availability on the reproduction of pea aphids [Acyrthosiphon pisum (Harris)] using four near-isogenic peas (Pisum sativum L.) that differ in morphology. Manipulations of aphid density (1, 5, and 10 adults per plant) allowed us to examine any effects of plant morphology on crowding and consequently reproduction. Pea morphology per se did not alter pea aphid crowding, as measured by mean nearest neighbor distance, and there was no effect on reproduction. In addition, reproduction increased with increasing adult density, indicating positive density dependence. In a separate experiment, peas were fertilized to determine whether differences between nutrient availability of the four different morphologies might drive any observed differences in aphid reproduction. Although plant nitrogen content was altered by fertilization treatments, this did not have an impact on aphid reproduction. Greenhouse experiments, however, suggested that pea morphology can interact with environmental conditions to reduce aphid reproduction under some conditions. We conclude that plant morphology only influences aphid reproduction when environmental conditions are less than optimal.

Larval development of insects introduced for biological control of invasive weeds may be constrained if the new climate is more extreme than in their native range. We surveyed larval development in Agapeta zoegana L. and Cyphocleonus achates (Fahraeus), two species of biological control insects introduced from eastern Europe against spotted knapweed in western North America. We dissected spotted knapweed roots collected from five sites in western Montana over 6 yr either in late fall or early spring and measured larval head capsule size to determine the overwintering instar stage. Development of A. zoegana was estimated equally well with late fall or early spring root collections, but C. achates rate of development may be underestimated using fall samples. The larvae of neither species entered diapause in as advanced an instar in western Montana as reported for their native range. Most A. zoegana larvae reached the third (26%) or fourth (20%) instar at diapause, with only 15% reaching sixth instars, as they typically do in their native Eurasia. Almost all (94%) C. achates overwintered as first instars, with most of the remaining (4%) being eggs, some of which were viable in the spring. Only a small number (2%) of C. achates larvae overwintered as second instars, the common overwintering stage in their native range. Slower development may explain, in part, why A. zoegana only has one generation per year in Montana compared with two to three generations per year in Europe.

In many Connecticut forests with an overabundance of white-tailed deer (Odocoileus virginianus Zimmermann), Japanese barberry (Berberis thunbergii DC) has become the dominant understory shrub, which may provide a habitat favorable to blacklegged tick (Ixodes scapularis Say) and white-footed mouse (Peromyscus leucopus Rafinesque) survival. To determine mouse and larval tick abundances at three replicate sites over 2 yr, mice were trapped in unmanipulated dense barberry infestations, areas where barberry was controlled, and areas where barberry was absent. The number of feeding larval ticks/mouse was recorded. Adult and nymphal ticks were sampled along 200-m draglines in each treatment, retained, and were tested for Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt, and Brenner) presence. Total first-captured mouse counts did not differ between treatments. Mean number of feeding larval ticks per mouse was highest on mice captured in dense barberry. Adult tick densities in dense barberry were higher than in both controlled barberry and no barberry areas. Ticks sampled from full barberry infestations and controlled barberry areas had similar infection prevalence with B. burgdorferi the first year. In areas where barberry was controlled, infection prevalence was reduced to equal that of no barberry areas the second year of the study. Results indicate that managing Japanese barberry will have a positive effect on public health by reducing the number of B. burgdorferi-infected blacklegged ticks that can develop into motile life stages that commonly feed on humans.

Changes in arthropod fauna assemblages after different goat grazing treatments (breeds and stocking rates) and responses to grazing cessation were studied in a heath-gorse shrubland located in northern Spain. Three treatments (low grazing pressure and high grazing pressure with Cashmere breed and high grazing pressure with local Celtiberic breed) with three replicates were randomly allocated to nine plots. Fauna data were collected three times per year during 3 grazing yr (2003, 2004, and 2005) and three times during 2007, i.e., 2 yr after grazing cessation. Arthropods were collected by 12 pitfall traps per plot, whereas vegetation cover and height were estimated by 100 random contacts per plot. Arthropod community composition was mostly affected by sampling year during the grazing period (between 2003 and 2005) but also between 2005 and 2007 (after cessation). Species composition differed between treatments, although the differences were not attributed to the stocking rates or to the goat breeds along those periods. Differences between treatments remained constant from 2003 to 2005 and between 2005 and 2007. Heather height explained most of the variance in arthropod species data during the last grazing year (2005), whereas heather cover was the most explanatory environmental variable 2 yr after grazing cessation (2007). Grazing effects still remained on both vegetation and fauna 2 yr after grazing cessation.

This study examined how variability in Neotyphodium endophyte-grass associations influences black cutworm Agrotis ipsilon Hufnagel performance and susceptibility to the entomopathogenic nematode Steinernema carpocapsae (Weiser). Second-instar cutworm larvae were confined to greenhouse pots containing four different tall fescue Schedonorus phoenix (Scop.) Holub cultivars. After 1 wk, larvae were recovered from the pots, weighed, and individually exposed to 20 infective juvenile nematodes. Nematode-induced mortality was monitored for 72 h after exposure. Endophyte infection levels and ergot alkaloid concentrations varied between escue cultivars, but endophyte infection level was not a significant predictor of ergot alkaloid concentrations in aboveground plant tissue. Larval survival also varied between cultivars, but neither endophyte infection level nor ergot alkaloid concentration was a significant covariate. Larval susceptibility to the entomopathogenic nematode varied between cultivars at 48 and 72 h after exposure. In all but one cultivar (Plantation), cumulative mortality at 72 h decreased significantly as ergot alkaloid concentrations increased. Neither larval biomass nor endophyte infection levels in tall fescue were significant predictors of larval susceptibility to the nematode. Results show that variation in endophyte-plant associations can influence black cutworm performance and susceptibility to entomopathogenic nematodes and that susceptibility to the nematode H. bacteriophora may be partially tied to ergot alkaloid levels in the insects' food. Findings further support the assertion that black cutworm may use certain endophyte-mediated toxins, particularly ergot alkaloids, as a form of acquired chemical defense against nematode-induced septicaemia.

Large-scale experimental manipulations of dead wood are needed to better understand its importance to animal communities in managed forests. In this experiment, we compared the abundance, species richness, diversity, and composition of arthropods in 9.3-ha plots in which either (1) all coarse woody debris was removed, (2) a large number of logs were added, (3) a large number of snags were added, or (4) no coarse woody debris was added or removed. The target taxa were ground-dwelling arthropods, sampled by pitfall traps, and saproxylic beetles (i.e., dependent on dead wood), sampled by flight intercept traps and emergence traps. There were no differences in total ground-dwelling arthropod abundance, richness, diversity, or composition among treatments. Only the results for ground beetles (Carabidae), which were more species rich and diverse in log input plots, supported our prediction that ground-dwelling arthropods would benefit from additions of dead wood. There were also no differences in saproxylic beetle abundance, richness, diversity, or composition among treatments. The findings from this study are encouraging in that arthropods seem less sensitive than expected to manipulations of dead wood in managed pine forests of the southeastern United States. Based on our results, we cannot recommend inputting large amounts of dead wood for conservation purposes, given the expense of such measures. However, the persistence of saproxylic beetles requires that an adequate amount of dead wood is available in the landscape, and we recommend that dead wood be retained whenever possible in managed pine forests.

Understanding the contributions of environmental variation and density feedbacks to changes in vector populations is essential for designing effective vector control. We analyzed monitoring datasets describing larval densities over 7 yr of the two dominant mosquito species, Aedes vigilax (Skuse) and Culex annulirostris (Skuse), of the greater Darwin area (Northern Territory, Australia). Using generalized linear and linear mixed-effects models, we tested hypotheses regarding the environmental determinants of spatio-temporal patterns in relative larval abundance in both species. The most important spatial drivers of Ae. vigilax and Cx. annulirostris larval densities were elevation and water presence. Ae. vigilax density correlates negatively with elevation, whereas there was a positive relationship between Cx. annulirostris density and elevation. These results show how larval habitats used by the saltwater-influenced breeder Ae. vigilax and the obligate freshwater breeder Cx. annulirostris are separated in a tidally influenced swamp. The models examining temporal drivers of larval density also identified this discrimination between freshwater and saltwater habitats. Ae. vigilax larval densities were positively related to maximum tide height and high tide frequency, whereas Cx. annulirostris larval densities were positively related to elevation and rainfall. Adult abundance in the previous month was the most important temporal driver of larval densities in both species, providing a clear dynamical link between the two main life phases in mosquito development. This study shows the importance of considering both spatial and temporal drivers, and intrinsic population dynamics, when planning vector control strategies to reduce larval density, adult population density, and disease transmission effectively.

Relationships between macroinvertebrates and microorganisms in aquatic environments are only poorly understood despite the fact that many aquatic macroinvertebrates feed on microbial biofilms during some life stage. Better understanding of trophic interactions between microbial biofilms, macroinvertebrates, and fish may also help control fish diseases and loss of natural resources. It has also been suggested that pollution, habitat fragmentation, and poor water quality may contribute to increased pathogenesis and mortality in fish. Increased disease incidence is difficult to assess, however, in part because of the complexity of pathogen transmission dynamics. Several environmental pathogens exist whose reservoir (s) and means of transmission remain poorly understood, highlighting the need to study pathogen ecology and interactions with organisms other than susceptible hosts. Aeromonas salmonicida is rarely isolated from freshwater sediments. However, stonefly nymphs were found to frequently harbor A. salmonicida and were shown to preferentially feed on the bacterium. Rainbow trout juveniles were presented with different feeding regimes to determine the transmission capacity of nymphs, and all fish fed stoneflies harboring A. salmonicida expressed symptoms of disease. Although current rates of furunculosis in freshwater ecosystems are unknown, trout primarily feed on stoneflies when water oxygen levels are high and temperatures are low (winter months), which is presumed to correspond to high resistance to the pathogen. Given that furunculosis is associated with physiological stress and higher water temperatures, its natural incidence may change in response to global or regional climatological effects.

The interface between cultivated fields and wildlands has become a central focus for conservation biology, particularly as previously uncultivated lands worldwide are converted to agriculture at an escalating pace. Although research in some parts of the world has highlighted the potential value of agricultural lands for managing and preserving native animals, we know comparatively little about native animals spanning the cultivated/wildlands interface in North America. The study reported here investigated insect communities at three sets of paired sites (cultivated alfalfa fields and native, sagebrush areas) on the western edge of the Great Basin. Two hundred ninety-nine morphospecies were sorted from a collection of >9,000 insects: 221 morphospecies were found in cultivated fields, and 143 were found in the native areas. Insect communities in alfalfa fields were higher in species richness and abundance than communities in adjacent, native fields. However, communities in the cultivated habitat were relatively more homogenous: species composition was more similar among cultivated fields than among native fields. Considering the number of individual insects and morphospecies found in the cultivated habitat, and the relatively small number of species that overlap the two habitat types, the potential ecological consequences of the widespread, anthropogenic habitat are discussed.

In the southeast United States, a field of peanuts, Arachis hypogaea L., is often closely associated with a field of cotton, Gossypium hirsutum L. The objective of this 4-yr on-farm study was to examine and compare the spatiotemporal patterns and dispersal of the southern green stink bug, Nezara viridula L., and the brown stink bug, Euschistus servus (Say), in six of these peanut-cotton farmscapes. GS Version 9 was used to generate interpolated estimates of stink bug density by inverse distance weighting. Interpolated stink bug population raster maps were constructed using ArcMap Version 9.2. This technique was used to show any change in distribution of stink bugs in the farmscape over time. SADIE (spatial analysis by distance indices) methodology was used to examine spatial aggregation of individual stink bug species and spatial association of the two stink bug species in the individual crops. Altogether, the spatiotemporal analyses for the farmscapes showed that some N. viridula and E. servus nymphs and adults that develop in peanuts disperse into cotton. When these stink bugs disperse from peanuts into cotton, they aggregate in cotton at the interface, or common boundary, of the two crops while feeding on cotton bolls. Therefore, there is a pronounced edge effect observed in the distribution of stink bugs as they colonize the new crop, cotton. The driving force for the spatiotemporal distribution and dispersal of both stink bug species in peanut-cotton farmscapes seems to be availability of food in time and space mitigated by landscape structure. Thus, an understanding of farmscape ecology of stink bugs and their natural enemies is necessary to strategically place, in time and space, biologically based management strategies that control stink bug populations while conserving natural enemies and the environment and reducing off-farm inputs.

Edge effects resulting from logging on the distribution of carabid beetles (Coleoptera: Carabidae) were studied across ecotones between regenerating and mature forests established after harvesting of old-growth forests 20 yr prior to this study in southwestern China. Using pitfall traps, beetles were collected along five ecotone transects using nine samples with a distance interval of 25 m each. Although no significant differences were found in species richness and abundance of carabids among all three habitats, i.e., mature forest, young regenerating stand, and edge habitat, rarefaction estimates of species richness indicated that traps in young regenerating stands accumulated species faster than those on mature forest interiors and forest edges. Carabid species composition of the forest edges was more similar to those of the mature forest interiors than to those of the young regenerating stands. Variability in species composition was significantly reduced in young stands, suggesting that the carabid community from young stands is more homogeneous than the one from mature forests. Although most species occurred in all habitats, some species were significantly more abundant in mature forests and/or edges than in young stands. Results indicated that edge effects on forest carabids may persist for at least 20 yr after disturbance.

The Russian wheat aphid, Diuraphis noxia (Kurdjumov), is a significant pest of small grains in the United States and worldwide. There is an increasing need for quality population dynamic models to aid in development of integrated pest management strategies. Unfortunately, there exists high variability in published data regarding basic life history traits that frequently direct model parameterization. Metadata were analyzed to develop relationships between temperature and reproductive and developmental traits of D. noxia. Specifically, functions were developed between temperature and the following traits: lifespan, fecundity, fecundity rate, pre-nymphipositional period, reproductive period, and intrinsic rate of increase. Lower and upper temperature reproductive thresholds were calculated as 0.6 and 36.9°C, respectively. The lower temperature developmental threshold was calculated as -0.69°C. Modeled longevity reached its maximum at ≈80 d. Meta-analysis indicates maximum fecundity at ≈18.5°C, with a maximum fecundity rate of ≈2.1 nymphs per day over the nymphipositional period. The calculated maximum total fecundity was ≈55 nymphs per female. The maximum reproductive period was calculated to be 29.9 d. Compared with other aphid species, as temperature increased, the intrinsic rate of increase of D. noxia increased more slowly relative to Schizaphis graminum (Rondani) and Bhopalosiphum padi L., but at a similar rate to Sitobian avenae (F.).

Bacterial populations in Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) collected in diverse California environments consisted of two bacterial symbionts: BFo-1 and BFo-2 (B = bacteria, Fo = Frankliniella occidentalisi numbers reflect different types). Dual infections of BFo-1 and BFo-2 were found in 50% of the thrips, 18% had neither bacterium, and 24 and 8% were infected solely with BFo-1 and BFo-2, respectively. No other bacteria consistently infected F. occidentalis. Dual infections occurred more often in male thrips and in thrips of both sexes from southern mountain and valley sites. As average collection year or month minimum temperature decreased, infections of BFo-1, alone or in dual infections, increased significantly. As yearly precipitation increased, infection with BFo-1 alone also increased. F. occidentalis color morphology did not affect bacterial infection. BFo-1 created weak biofilms at 25 and 32°C; BFo-2 made strong biofilms at 25°C and no biofilms at 32°C. When the bacteria were grown in culture together, weak biofilms formed at both temperatures studied, although there was no way to determine what each bacterium contributed to the biofilm. BFo-1 and BFo-2 grew at similar rates at 25 and 30°C. Our data show BFo-1 and BFo-2 occur in natural populations of F. occidentalis and support the hypothesis BFo have a symbiotic relationship with F. occidentalis. Regional differences in bacterial prevalence suggest bacterial infection is associated with environmental conditions, and altitude, temperature, and precipitation may be important factors.

The characterization and identification of proteolytic bacteria from the gut of the velvetbean caterpillar (Anticarsia gemmatalis) were the objectives of this study. Twelve aerobic and anaerobic isolates of proteolytic bacteria were obtained from the caterpillar gut in calcium caseinate agar. The number of colony forming units (CFUs) of proteolytic bacteria was higher when the bacteria were extracted from caterpillars reared on artificial diet rather than on soybean leaves (1.73 ± 0.35 × 10³ and 0.55 ± 0.22 × 10³ CFU/mg gut, respectively). The isolated bacteria were divided into five distinct groups, according to their polymerase chain reaction-restriction fragment-length polymorphism profiles. After molecular analysis, biochemical tests and fatty acid profile determination, the bacteria were identified as Bacillus subtilis, Bacillus cereus, Enterococcus gallinarum, Enterococcus mundtii, and Staphylococcus xylosus. Bacterial proteolytic activity was assessed through in vitro colorimetric assays for (general) proteases, serine proteases, and cysteine proteases. The isolated bacteria were able of hydrolyzing all tested substrates, except Staphylococcus xylosus, which did not exhibit serine protease activity. This study provides support for the hypothesis that gut proteases from velvetbean caterpillar are not exclusively secreted by the insect cells but also by their symbiotic gut bacteria. The proteolytic activity from gut symbionts of the velvetbean caterpillar is suggestive of their potential role minimizing the potentially harmful consequences of protease inhibitors from some of this insect host plants, such as soybean, with implications for the management of this insect pest species.

Understanding factors that affect the context dependency of species interactions has been identified as a critical research area in ecology. The presence of symbionts in host plants can be an important factor influencing the outcome of plant-insect interactions. Similarly, herbivore identity can alter the outcome of plant-symbiont interactions. Symbiotic foliar fungal endophytes confer resistance to herbivores in economically important agronomic grasses, in part through the production of alkaloids. Although endophytes are common in nature, relatively little is known about their effects on herbivores of native, wild grass species, and a recent meta-analysis suggested that endophytes are only beneficial in agronomic settings. In this study, we performed choice trials for five insect species and a greenhouse experiment with one species to assess effects of the fungal endophyte Neotyphodium sp. on herbivores of the wild grass Festuca subverticillata. In feeding trials, endophyte presence altered the preference of all five insect species tested. However, the magnitude and direction of preference varied among species, with Pterophylla camellifolia (F.), Spodoptera frugiperda (J. E. Smith), and Rhopalosiphum padi L. preferring endophyte-disinfected plants and Encoptolophus costalis (Scudder) and Romalea guttata (Houttuyn) preferring endophyte-symbiotic plants. Despite reducing insect preference, the endophyte had no significant effect on S. frugiperda performance in a no-choice greenhouse experiment and did not increase plant growth in response to this herbivore. Our results show that endophyte-mediated resistance to herbivory depends strongly on herbivore identity and suggest that the fitness consequences of endophyte symbiosis for host plants will be context dependent on the local composition of insect herbivores.

Fungus cultivation by ambrosia beetles is one of the four independently evolved cases of agriculture known in animals. Such cultivation is most advanced in the highly social subtribe Xyleborina (Scolytinae), which is characterized by haplodiploidy and extreme levels of inbreeding. Despite their ubiquity in forests worldwide, the behavior of these beetles remains poorly understood. This may be in part because of their cryptic life habits within the wood of trees. Here we present data obtained by varying a laboratory breeding technique based on artificial medium inside glass tubes, which enables behavioral observations. We studied species of the three most widespread genera of Xyleborina in the temperate zone: Xyleborus, Xyleborinus, and Xylosandrus. We raised several generations of each species with good breeding success in two types of media. The proportion of females of Xyleborinus saxesenii Ratzeburg producing offspring within 40 d depended significantly on founder female origin, which shows a transgenerational effect. Labor-intensive microbial sterilization techniques did not increase females' breeding success relative to a group of females shortly treated with ethanol. Gallery productivity measured as the mean number of mature offspring produced after 40 d varied between species and was weakly affected by the type of medium used and foundress origin (field or laboratory) in X. saxesenii, whereas different preparation and sterilization techniques of the beetles had no effect. Behavioral observations showed the time course of different reproductive stages and enabled to obtain detailed behavioral information in all species studied. We propose that the laboratory techniques we describe here are suited for extensive studies of sociality and modes of agriculture in the xyleborine ambrosia beetles, which may yield important insights into the evolution of fungal agriculture and advanced social organization.

The predatory beetle assemblage of Ontario carrot and sweet potato fields was described and assessed to identify species of interest to the control of the emerging pest millipede Cylindroiulus caeruleocinctus (Wood) (Diplopoda: Julidae). Pterostichus melanarius (Coleoptera: Carabidae) was identified as a dominant species, and seven other carabid species [Pterostichus melanarius (Illiger), Harpalus pensylvanicus (DeGeer), Ophonus puncticeps (Stephens), H. erraticus Say, Bembidion quadrimaculatum oppositum Say, Poecilus chalcites (Say), Scarites subterraneus Fabricius, and Pterostichus permundus (Say)] were identified as common species on the basis of activity density. Common species became more abundant as the growing season progressed. In laboratory bioassays, P. melanarius preyed on millipedes regardless of prey size, whereas H. erraticus never selected millipedes as prey. A significant positive spatiotemporal relationship was found between P. melanarius and C. caeruleocinctus in sweet potato fields. P. melanarius was found to be a natural enemy of C. caeruleocinctus, and other common carabid species warrant future study. The role of Staphylinidae in millipede control could not be elucidated, likely because of low trapping efficiency. Tachinus corticinus Gravenhorst, an introduced staphylinid from Europe, was newly recorded in Ontario, extending its North American range considerably westward from the province of Quebec. The results of this study are an important foundational step toward developing a successful integrated pest management strategy for controlling millipede damage in crops.

Field observation, field cages, and laboratory arenas were compared as methods to estimate daily per capita consumption for larvae of Harmonia axyndis Pallas (Coleoptera: Coccinellidae) and Chrysopa nigricornis Burmeister (Neuroptera: Chrysopidae), the two most abundant predators of Hyalopterus pruni Geoffroy (Hemiptera: Aphididae) in prune orchards in California's Central Valley. Daily per capita consumption increased with larval size, and the highest estimates were obtained from the field observation method and the lowest from the laboratory arena method for both predator species. Possible explanations for differences between estimates for each method are explored in detail, the most important of which is the need to measure both biomass killed and biomass consumed, because H. axyridis consumed nearly all of each prey item, whereas C. nigricornis always killed more biomass than they consumed. This study suggests that the laboratory arena method can lead to underestimation of daily consumption and that field cages may be more appropriate for quantifying daily consumption when prey are colonial and predators are relatively immobile. For highly mobile predators or predators of dispersed prey, the field observation method, combined with observations of both the duration and pattern of feeding activity throughout the day, is the best option for quantifying daily per capita consumption.

The plum curculio (Conotrachelus nenuphar Herbst) is a key pest of pome and stone fruit in eastern North America. We tested the efficacy of five pathogens over the course of three seasons in 10 Michigan apple and cherry orchards, with introductions of larvae to caged pots containing pathogen-treated soil. The nematode Steinernema riobrave was the most effective pathogen in the 2 yr it was tested, but only in soils with the highest sand content (81–88%) and when it was applied 1 h or 5 d after last instars of plum curculio. S. carpocapsae in an organic formulation was less effective, but significantly reduced plum curculio emergence in 1 yr of the study when applied 3 d before C. nenuphar larvae were introduced. Beauveria bassiana was effective in only 1 of the 3 yr it was tested, only in soils with lower sand content, and only when it was introduced within 1 h of plum curculio larvae. Metarhizium anisopliae and Heterorhabditis bacteriophora were ineffective. Michigan orchards may require sprinkler irrigation coupled with precise timing recommendations and oviposition monitoring to enhance entomopathogen application efficacy against soil-dwelling last instars.

Native to China, Chinese tallow, Triadica sebifera L. Small (Euphorbiaceae), is an invasive plant in the southeastern United States. The leaf-rolling weevil, Heterapoderopsis bicallosicollis Voss, is a common herbivore attacking this plant in China. To evaluate its potential as a biological control agent of T. sebifera, biology and host specificity of this weevil were studied in China. H. bicallosicollis occurs over a wide, native, geographic range and its immatures successfully develop at 15–35°C, indicating its physiological potential to establish and persist throughout the range of climatic conditions where the target plant grows in the United States. Adults make feeding holes on leaves. Before oviposition, the female makes a sealed leaf roll called a nidus and then lays one to two eggs inside. Eggs, larvae, and pupae develop within nidi, and larvae survive only when they develop inside the nidi. This requirement makes the weevil highly host specific to T. sebifera, In laboratory no-choice tests of 54 species from eight families, adults fed on only 3 plant species, T. sebifera, Sapium chihsinianum S. K. Lee, and Phyllanthus urinaria L. and only oviposited on T. sebifera. These results were confirmed where, in multiple-choice tests, adults only oviposited on T. sebifera. Given that T. sebifera is the only species in the genus Triadica in the United States, the results of this study suggest that H. bicallosicollis is a potential biological control agent of T. sebifera and should be considered to be imported into quarantine in the United States for further tests on native North American species.

The invasive tree Melaleuca quinquenervia (Cav.) Blake is widely distributed throughout peninsular Florida and poses a significant threat to species diversity in the wetland systems of the Everglades. Mitigation of this threat includes the areawide release campaign of the biological control agents Oxyops vitiosa Pascoe and Boreioglycaspis melaleucae Moore. We summarize the results of this release effort and quantify the resulting geographic distribution of the herbivores as well as their regional impact on the target weed. A combined total of 3.3 million individual Melaleuca biological control agents have been redistributed to 407 locations and among 15 Florida counties. Surveys of the invaded a the geogO. vitiosa encompasses 71% of the Melaleuca infestation. Although released 5 yr later, the distribution of B. melaleuca is slightly greater than its predecessor, with a range including 78% of the sampled Melaleuca stands. Melaleuca stands outside both biological control agents' distributions occurred primarily in the northern extremes of the tree's range. Strong positive association between herbivore species was observed, with the same density of both species occurring in 162 stands and no evidence of interspecific competition. Soil type also influenced the incidence of biological control agents and the distribution of their impacts. The odds of encountering O. vitiosa or B. melaleucae in cells dominated by sandy soils were 2.2 and 2.9 times more likely than those predominated by organically rich soils. As a result, a greater level of damage from both herbivores was observed for stands growing on sandy versus organic-rich soils.

Crapemyrtle aphids, Sarucallis kahawaluokalani (Kirkaldy), are a common pest of crapemyrtle (Lagerstroemia spp.) throughout the southeastern United States. Breeding programs have produced >100 crapemyrtle cultivars that vary in floral color, plant height, and disease resistance, but these programs did not evaluate insect resistance as part of the selection process. In this study, the host suitability of crapemyrtle cultivars and host preference of the crapemyrtle aphid were tested using the following seven crapemyrtle cultivars: ‘Carolina Beauty’, ‘Byers Wonderful White’, ‘Apalachee’, ‘Lipan’, ‘Tuscarora’, ‘Sioux’, and ‘Natchez’. Host suitability or aphid preference may be affected by cultivar attributes of plant parentage, source of Lagerstroemia fauriei Koehne germplasm, and mature plant height. Host suitability was evaluated by measuring daily and total fecundity under no-choice conditions. Host preference of the crapemyrtle aphid was tested in a choice experiment that used eight crapemyrtle cultivars; the seven used in the no-choice experiment plus Lagerstroemia speciosa L. In the no-choice experiment, aphid daily fecundity was not different among the crapemyrtle cultivars, but aphid total fecundity was different for the factors cultivar, plant parentage, source of germplasm, and mature plant height. Crapemyrtle aphid host preference in the choice experiment indicated that there were differences among cultivar, parentage, source of germplasm, and mature plant height. Results from this study are useful for plant breeding programs that have the objective of producing aphid resistant cultivars.

Elevational gradients provide natural experiments for examining how variation in abiotic forces such as nutrient mineralization rates, risk of photodamge, temperature, and precipitation influence plant—insect interactions. At the Coweeta LTER site in the Southern Appalachian Mountains, we examined spatial and temporal variation in striped maple, Acer pensylvanicum, foliar quality and associated patterns in the arthropod community. Variation in herbivore densities was associated more strongly with seasonal variation in plant quality than with spatial variation in quality among three sampling sites. Leaf chewer, but not phloem feeder or arthropod predator, densities increased with elevation. Foliar quality, by our measures, decreased throughout the growing season, with decreases in nitrogen concentrations and increases in lignin concentrations. Foliar quality varied among the three sites but not systematically along the elevational gradient. We conclude that, in this system, temporal heterogeneity in plant quality is likely to be more important to insect herbivores than is spatial heterogeneity and that other factors, such as the abiotic environment and natural enemies, likely have substantial effects on herbivore density.

Nezara viridula L. (Hemiptera: Pentatomidae) is a serious pest of macadamia nuts, Macadamia integrifolia, in Hawaii. Using ruthenium red dye to stain stink bug feeding probes, feeding activity was determined for nuts of various maturity levels harvested from the tree and off the ground throughout the growing season in five commercial cultivars. Damage occurred in the tree and on the ground during all nut growth stages. Damage on the ground was often higher than in the tree. Cultivar 246 was more susceptible to attack than cultivars 333 and 800. It was previously thought that cultivar susceptibility was related to husk and shell thickness, but cultivar 246 showed higher damage than other cultivars even during early nut development when the nuts are small and before the shell has formed. This suggests that shell and husk thickness may play a secondary role in susceptibility to feeding by N. viridula. Monitoring N. viridula feeding activity during early nut development may help alert growers to potential problems later in the season, but early-season probing activity in immature nuts was not a good predictor of damage levels in mature nuts later in the season in our study.

Rice, Oryza sativa, is the most important staple food for a significant portion of the world's population. Despite the importance of rice, however, induced resistance to insects has not been thoroughly studied in rice; in fact, to our knowledge, direct induced resistance after injury by chewing insects has not been shown in rice. We conducted a series of experiments designed to characterize direct induced resistance in rice after feeding by larvae of the fall armyworm (Spodoptera frugiperda J. E. Smith) and application of jasmonic acid. Weight gains and relative growth rates of fall armyworm larvae were lower when fed leaves from plants previously damaged by armyworms than when fed leaves from undamaged plants. This response was stronger at a systemic spatial scale; that is, the induced resistance was stronger in newly emerged leaves not present at the time plants were damaged than in damaged leaves themselves. Armyworm growth rates were also reduced on foliage from plants treated with jasmonic acid, a hormone known to mediate plant responses to wounding. The response to injury by armyworm larvae and to exogenous jasmonic acid was stronger in transgenic rice plants in which levels of salicylic acid (a signaling molecule that inhibits jasmonic acid) were suppressed. These results show the existence of a direct induced resistance response in rice and suggest that this response to injury by a chewing insect may be mediated by jasmonic acid.

The Asiatic rice borer Chilo suppressalis (Walker) occurs mainly on rice Oryza sativa L. and water-oat Zizania latifolia (Turcz). Certain ecological and physiological differentiations between rice and water-oat populations have been shown. To determine whether there is host-associated differentiation in supercooling capacity, seasonal changes in supercooling points, glycerol content, and other physiological parameters of naturally occurring C. suppressalis larvae overwintering in rice and water-oat plants were compared over the winter. Supercooling points were low in the winter (November and December), significantly higher in March, and significantly lower in the water-oat population than in the rice population in the winter. Larvae from the water-oat population experienced a significant weight loss from December to March and were heavier than those from the rice population in the winter. Body water content (percentage of fresh weight) was low in the winter and increased significantly in March; no population differences were detected. Hemolymph glycerol content was high in the winter and dropped significantly in March; interpopulation differences were significant in December. Hemolymph trehalose content increased in the winter, and no population differences were detected. Whole body glucose and lipid content varied differently between the rice and the water-oat populations over the winter. It was found that variations in hemolymph glycerol content were responsible for the host-associated seasonal changes in supercooling capacity of overwintering larvae of the Asiatic rice borer.

The spatial influences of host and nonhost trees and shrubs on the colonization patterns of white pine weevil Pissodes strobi (Peck) were studied within a stand of planted interior hybrid spruce [Picea glauca (Moench) Voss × Picea engelmannii (Parry) ex Engelm.]. Planted spruce accounted for one third of all trees within the stand, whereas the remaining two thirds were comprised of early-successional nonhost vegetation, such as alder (Alnus spp.), paper birch (Betula papyrifera Marsh.), black cottonwood [Populus balsamifera ssp. trichocarpa (T. Ng.) Brayshaw], lodgepole pine [Pinus contorta (Dougl.) ex Loud.], trembling aspen (Populus tremuloides Michx), willow (Solix: spp.), and Canadian buffaloberry [Shepherdia canadensis (L.) Nutt.]. Unlike the spruce trees, nonhost vegetation in the stand was not uniformly distributed. Spatial point process models showed that Canadian buffaloberry, paper birch, black cottonwoood, and trembling aspen had negative associations with damage caused by the weevil, even though the density of the insects' hosts in these areas did not change. Moreover, knowing the locations of these nonhost trees provided as much, or more, inference about the locations of weevil-attacked trees as knowing the locations of suitable or preferred host trees (i.e., those larger in size). Nonhost volatiles, the alteration of soil composition, and overstory shade are discussed as potential explanatory factors for the patterns observed. New research avenues are suggested to determine whether nonhost vegetation in early successional stands might be an additional tool in the management of these insects in commercially important forests.

Pine seedlings and saplings are seldom attacked by bark beetles of the genus Dendroctonus. However, Dendroctonus rhizophagus (Coleoptera: Curculionidae: Scolytinae) Thomas and Bright specifically attacks pine seedlings and causes conspicuous mortality in naturally regenerated stands in the Sierra Madre Occidental, northern Mexico. We evaluated the host preference and attack of D. rhizophagus under field conditions. We tried to establish any relationship between tree growth or host size and the number of attacking beetles. Generally, only one pair of beetles attacked each of the seedlings regardless of host size; however, a significant positive linear relationship between host size and adult brood size was observed. We found that this species preferred the best growing seedlings in our study sites.

Thrips cause damage to seedling cotton, and they are associated with the spread of Fusarium hardlock, a serious disease affecting cotton bolls that reduces lint yield in the southern United States. The population dynamics and within-plant distribution of Frankliniella spp. thrips in cotton were determined in 2005, 2006, and 2007 in Quincy and in 2006 and 2007 in Marianna, FL. Frankliniella tritici (Fitch) was >98% of the adult thrips collected. The adults of F. bispinosa (Morgan), F. occidentalis (Pergande), and F. fusca (Hinds) also were collected. Populations of F. fusca inhabited the cotton leaves of vegetative-stage cotton. The other species were highly anthophilic, primarily inhabiting cotton during its reproductive growth stages. Densities of these species peaked during mid-season, which also coincided with peak bloom. The adult F. tritici and the thrips larvae were aggregated in the flowers over the other plant parts, with more collected in the upper than the lower canopies. These patterns of aggregation were observed at each location each year, and the numerical differences usually were significant (P < 0.05). Densities of adult F. tritici were low on the leaves, squares, and bolls. The population dynamics and with-plant distribution of individual thrips species has not previously been determined for cotton in the southern United States.

Our primary objective in this study was to determine the plant level and environmental factors that affect oviposition choice and subsequent offspring survival in Megathymus yuccae (Boisduval and Leconte) on its host plant, Yucca filamentosa L. A preliminary survey suggested that the frequency of pupal eclosion tent presence increased only with host plant height. In an expanded survey conducted during the adult flight period the following spring, we found that plant height increased the probability of oviposition, whereas the density of herbaceous stems and fire damage decreased the probability of egg presence. Similarly, the number of eggs on occupied plants increased with plant height and decreased with fire damage. When we surveyed the plants from the spring 2008 sampling the following winter to determine presence of late-instar larvae or pupae, we found that the probability that at least one larva survived on previously occupied plants decreased with the density of herbaceous stems. These results collectively suggest that larger, unburned Y. filamentosa individuals and those in relatively open areas are more attractive as host plants for oviposition and that larval performance is generally, but not exclusively, consistent with female preference in this system.

The postmating behavior of female dogwood borer, Synanthedon scitula (Harris) (Lepidoptera: Sesiidae), was examined in a young apple orchard planted on size-controlling rootstock in Virginia. All female dogwood borers captured while exhibiting casting flight near the base of trees were mated, based on the presence of a spermatophore. Surveys of female activity within orchards were conducted at regular intervals throughout the daylight hours, showing a diel periodicity that peaked between 1700 and 1900 hours, with most females located below the graft union of trees. A transition matrix based on 1,108 behavioral sequences exhibited by 66 females was used to produce a first-order Markov chain of behavioral events that occurred significantly more often than expected by chance. Casting flight, probing with ovipositor, and oviposition were the most frequent behaviors observed, representing 31.7, 30.0, and 18.1% of all behaviors recorded, respectively. Our observations showed that 88, 99, and 99% of casting flight, probing with the ovipositor, and oviposition, respectively, occurred below the graft union. Observed behaviors considered not directly related to oviposition site selection or oviposition included antennal grooming, noncasting flight, and resting, representing 1.3, 8.3, and 10.6% of all behaviors recorded, respectively. Mated females spent significantly more time resting than in other behaviors and significantly more time in that state within the apple tree canopy than on other parts of the tree. Results are discussed in relation to the influence of insect—host plant interactions on oviposition site selection by female dogwood borer.

The early detection of populations of a forest pest is important to begin initial control efforts, minimizing the risk of further spread and impact. Emerald ash borer (Agrilus planipennis Fairmaire) is an introduced pestiferous insect of ash (Fraxinus spp. L.) in North America. The effectiveness of trapping techniques, including girdled trap trees with sticky bands and purple prism traps, was tested in areas with low- and high-density populations of emerald ash borer. At both densities, large girdled trap trees (>30 cm diameter at breast height [dbh], 1.37 m in height) captured a higher rate of adult beetles per day than smaller trees. However, the odds of detecting emerald ash borer increased as the dbh of the tree increased by 1 cm for trap trees 15–25 cm dbh. Ash species used for the traps differed in the number of larvae per cubic centimeter of phloem. Emerald ash borer larvae were more likely to be detected below, compared with above, the crown base of the trap tree. While larval densities within a trap tree were related to the species of ash, adult capture rates were not. These results provide support for focusing state and regional detection programs on the detection of emerald ash borer adults. If bark peeling for larvae is incorporated into these programs, peeling efforts focused below the crown base may increase likelihood of identifying new infestations while reducing labor costs. Associating traps with larger trees (≈25 cm dbh) may increase the odds of detecting low-density populations of emerald ash borer, possibly reducing the time between infestation establishment and implementing management strategies.

Beech scale, Cryptococcus fagisuga Lindinger, is a non-native invasive insect associated with beech bark disease. A quantitative method of measuring viable scale density at the levels of the individual tree and localized bark patches was developed. Bark patches (10 cm²) were removed at 0, 1, and 2 m above the ground and at the four cardinal directions from 13 trees in northern New York and 12 trees in northern Michigan. Digital photographs of each patch were made, and the wax mass area was measured from two random 1-cm² subsamples on each bark patch using image analysis software. Viable scale insects were counted after removing the wax under a dissecting microscope. Separate regression analyses at the whole tree level for the New York and Michigan sites each showed a strong positive relationship of wax mass area with the number of underlying viable scale insects. The relationships for the New York and Michigan data were not significantly different from each other, and when pooling data from the two sites, there was still a significant positive relationship between wax mass area and the number of scale insects. The relationships between viable scale insects and wax mass area were different at the 0-, 1-, and 2-m sampling heights but do not seem to affect the relationship. This method does not disrupt the insect or its interactions with the host tree.

A ground penetrating radar (GPR) technique was used to detect Formosan subterranean termite (Coptotermes formosanus) and red imported fire ant (Solenopsis invicta) hazards and risks (targets) in a soil levee at the London Avenue Canal in New Orleans, LA. To make this assessment, GPR signal scans were examined for features produced by termite or ant activities and potential sources of food and shelter such as nests, tree roots, and voids (tunnels). The total scanned length of the soil levee was 4,125 m. The average velocity and effective depth of the radar penetration was 0.080 m/ns and 0.61 m, respectively. Four hundred twenty-seven targets were identified. Tree roots (38), voids (31), fire ant nests (209), and metal objects (149) were detected, but no Formosan termite carton nests were identified. The lack of identified termite nests may be related to drowning events at the time to the flood. Based on the target density (TD), the two new floodwall and levee sections that were rebuilt or reinforced after they were destroyed by Hurricane Katrina in 2005 were determined to be at low potential risk from termites and ants. A merging target density (MTD) method indicated a high potential risk near one of the breached sections still remains. Foraging and nesting activity of Formosan subterranean termites and red imported fire ants may be a contributory factor to the levee failure at the London Avenue Canal.

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is an important pest of citrus. It is an efficient vector of three bacterial pathogens that are the presumptive causal agents of huanglongbing (HLB) or citrus greening disease. The movement patterns and dispersal capabilities of D. citri require study to better understand the spread of HLB and to improve management strategies for D. citri. A recently developed immunomarking technique that uses crude food proteins (chicken egg albumin, bovine casein, and soy protein) was evaluated for marking and tracking movement of D. citri in Florida citrus groves. In general, both egg and milk protein markers exhibited longer residual activity (35 d) than the soy protein marker (20 d) when applied to citrus leaves with a residual activity order of egg > milk > soy protein. However, residues of all three protein markers decreased with a simulated rain; this was more pronounced for soy protein than for egg and milk proteins. Temperature did not significantly affect acquisition of markers by adult D. citri. Egg, milk, and soy protein markers were detected on >90% of adult D. citri for up to 10, 10, and 5 d, respectively, after field application. Addition of tetrasodium ethylenediamine tetraacetic acid (water softener) and/or Silwet L-77 (wetting agent) to marker solutions did not affect longevity of detection. Each of the protein markers was detected on ≥80% of exposed D. citri for up to 30 d after direct application to adults. A field study was conducted to measure movement of D. citri between replicated pairs of 0.4 ha managed and unmanaged citrus plots separated by 60–100 m. Approximately 70% of captured D. citri were found marked 3 d after application of proteins in the field. Using two marker proteins, it was determined that D. citri moved bi-directionally between managed and unmanaged (abandoned) groves within 3 d with a greater number of D. citri adults moving from unmanaged into managed plots than from managed into unmanaged plots (net movement). These data indicate frequent movement by adult D. citri between groves and suggest that unmanaged groves may act as refuge sites for D citri, leading to reinfestation of nearby managed groves.

At present, the most effective synthetic lures for pest Anastrepha fruit flies are multicomponent blends that include ammonia and the diamine synergist putrescine (1,4-diaminobutane). Both chemicals generally have been regarded as protein cues that result in female-biased attraction. Using electroantennography (EAG) and flight tunnel bioassays, this study evaluated response of the Caribbean fruit fly, Anastrepha suspensa (Loew) to vapors released from commercial lure formulations of ammonium bicarbonate and putrescine. Over a range of doses tested, EAG response to ammonium bicarbonate was equivalent for both sexes, but female response was significantly greater than male response to putrescine and to a 1:1 mixture of ammonium bicarbonate and putrescine. Amplitude of EAG response to the mixture was approximately equal to the summation of responses to the individual substrates. Using a fixed dose of substrate, EAG measurements from females 1–14 d old indicated that antennal sensitivity to both lures varied according to physiological state of the fly. Peak response to ammonium bicarbonate was recorded from immature females, peak response to putrescine from sexually mature females. In bioassays, more females were captured with ammonium bicarbonate plus putrescine than with ammonium bicarbonate alone. This difference was not observed in males, resulting in a higher female to male ratio in captures with ammonium bicarbonate plus putreseine (3:1) versus ammonium bicarbonate alone (1:1). Results suggest that separate olfactory receptors are involved in detection of the two semiochemicals, and that the putrescine component is primarily responsible for the female-biased attraction.

Adult male and female Callidiellum rufipenne (Motschulsky) (Coleoptera: Cerambycidae) aggregate on severely stressed or fallen trees and cut logs of cypress species (Cupressaceae) that are the hosts of their larvae. Our studies showed that male C. rufipenne actively search for females on these trees and only respond to females after contacting them with their antennae. Removing cuticular hydrocarbons from fresh carcasses of females with solvent rendered the carcasses unattractive to males, but activity was restored when the solvent extract was reapplied. These findings suggest that contact pheromones mediate mate recognition in this species. Bioassays of fractions of the extracts determined that the branched chain hydrocarbon fraction was primarily responsible for activity. 5,17-Dimethylnonacosane was a key sex-specific component in extracts of females, and synthetic 5,17-dimethylnonacosane elicited a strong mating response from males. We conclude that this compound is an important component of the contact sex pheromone of C. rufipenne if not the sole component. Solvent extracts of both sexes also contained 9-pentacosyne and 9-heptacosyne. To our knowledge, this is only the second report of alkynes in the cuticular lipids of insects.

This study focused on a 75-d microplot experiment to access lead (Pb) entrance into the terrestrial ecosystem using Morus alba (mulberry) and Bombyx mori (silkworm) as pollution indicator sources. The Pb(II) mobility in different systems was in the following order: synthetic effluents > soil > plant > larva > larva—fecal. The Pb (II) mobility from an inorganic source to different life forms was found to be highly dependent on soil pH and the concentration of Pb in synthetic effluents. At lower concentrations, Pb was less lethal to B. mori larvae. Fifth instars of B. mori were found to be more tolerant to toxicity caused by Pb compared with lower instars. M. alba was not a hyperaccumulator plant because Pb(II) concentration was <1,000 mg/kg at all soil pHs and Pb(II) concentrations in effluents. The maximum amount of Pb(II) detected in soil, mulberry leaves, silkworm larvae, and silkworm feces was 326.5 ± 0.04,42.78 ± 0.02,61.24 ± 0.02, and 22.3 ± 0.02 mg/kg, respectively.

As adults, many predatory insects must adjust to a constantly changing prey environment while balancing between survival and reproduction. Two laboratory experiments were conducted to compare reproductive responses of females of two species of lady beetles, invasive Coccinella septempunctata L. and native C. transversoguttata richardsoni (Brown), in Utah alfalfa fields to varying availability of prey. When both lady beetles were placed immediately on experimental diets after being collected from the field (first experiment) and when they were provided excess prey for 14 d before being placed on experimental diets (second experiment), C. septempunctata produced more but individually smaller eggs than C. transversoguttata. Overall, however, in both experiments, C. septempunctata and C. transversoguttata responded similarly when they consumed pea aphids in varying amounts, by laying fewer and less viable eggs when fewer prey were consumed. In particular, the experiments provided no evidence that C. septempunctata converts pea aphids into eggs at a relatively higher rate than C. transversoguttata under limited prey availability. However, C. septempunctata had greater ability than C. transversoguttata to maintain body weight, even as they were producing eggs at low rates. This suggests that low aphid availability is less stressful for C. septempunctata, perhaps because it has more physiological ability than C. transversoguttata to assimilate pea aphid nutrients at low aphid availability. Such ability might contribute to the numerical dominance of the introduced C. septempunctata in alfalfa fields, which have supported low numbers of aphids in recent years.

The bottom-up effects of plant food quality and quantity and affect the growth, survival, and reproduction of herbivores. The larvae of solitary bee pollinators, consumers of nectar and pollen, are also herbivores. Although pollen quantity and quality are known to be important for larval growth, little is known about how nectar quality limits solitary bee performance. By adding different levels of nectar sugar directly to solitary bee provisions in the subalpine of Colorado, we tested the degree to which larval performance (development time, mass, and survival) was limited by nectar sugar. We found that larval growth increased with nectar sugar addition, with the highest larval mass in the high nectar-sugar addition treatment (50% honey solution). The shortest larval development time was observed in the low nectar-sugar addition treatment (25% honey solution). Neither low nor high nectar-sugar addition affected larval survival. This study suggests that, in addition to pollen, nectarsugar concentration can limit solitary bee larval growth and development, and nectar should be considered more explicitly as a currency governing foraging decisions related to producing optimally sized offspring. The availability and sugar content of nectar may scale up to affect bee fitness, population dynamics, and plant-pollinator mutualisms.

The soybean aphid (Aphis glycines Matsumura) is an invasive pest of cultivated soybean (Glycine max L.) in North America. After the initial invasion in 2000, the aphid has quickly spread across most of the United States and Canada, suggesting large-scale dispersal and rapid adaptation to new environments. Using microsatellite markers from closely related species, we compared the genetic diversity and the amount of genetic differentiation within and among 2 South Korean and 10 North American populations. Overall allelic polymorphism was low, never exceeding four alleles per locus. However, differences in genetic diversity were seen among South Korean and North American populations in terms of heterozygote excesses and genotypic richness. Within North America, two populations (Michigan and Ontario), had lower genetic diversities and exhibited high genetic differentiation compared with the remaining eight populations. The earlier collection time of Michigan and Ontario samples explained the genetic differences better than geographic subdivisions. These data indicate a pattern of small colonizing populations on soybeans, followed by rapid clonal amplification and subsequent large-scale dispersal across North America.

European corn borer, Ostrinia nubilalis (Hübner), adults were sampled at 13 sites along two perpendicular 720-km transects intersecting in central Iowa and for the following two generations at four of the same sites separated by 240 km in the cardinal directions. More than 50 moths from each sample location and time were genotyped at eight microsatellite loci. Spatial analyses indicated that there is no spatial genetic structuring between European corn borer populations sampled 720 km apart at the extremes of the transects and no pattern of genetic isolation by distance at that geographic scale. Although these results suggest high gene flow over the spatial scale tested, it is possible that populations have not had time to diverge since the central Corn Belt was invaded by this insect ≈60 yr ago. However, temporal analyses of genetic changes in single locations over time suggest that the rate of migration is indeed very high. The results of this study suggest that the geographic dimensions of European corn borer populations are quite large, indicating that monitoring for resistance to transgenic Bt corn at widely separated distances is justified, at least in the central Corn Belt. High gene flow further implies that resistance to Bt corn may be slow to evolve, but once it does develop, it may spread geographically with such speed that mitigation strategies will have to be implemented quickly to be effective.

We examined the genetic structure of populations of an ambrosia beetle, Xylosandrus brevis (Eichhoff) (Curculionidae: Scolytinae), to understand its colonization dynamics. We collected specimens from 20 sites in Japan and studied the genetic structure of these populations using portions of the mitochondrial cytochrome oxidase I gene (COI). A phylogenetic analysis showed three distinct lineages (clades A, B, and C) within X. brevis. Clade A had 65 haplotypes from all the populations, except for populations from Nagano (Chiisagata-gun) and the Ryukyu Islands (Ishigaki), whereas clade B had 14 haplotypes from nine populations (Yamagata, Saitama, Shimo-Minochi-gun, Chiisagatagun, Toyota, Watarai-gun, Wakayama, Tottori, and Kochi), and clade C had 6 haplotypes from the Ryukyu Islands (Ishigaki) population (and nowhere else). Nested clade phylogeographic analysis showed 65 clade A haplotypes and 14 clade B haplotypes geographically structured in two clades, respectively. A contact zone was identified in the Chubu and Tokai areas. Our results suggest that gene flow and individual movement of X. brevis between the Ryukyu Islands and the other three main islands of Japan has been rare, and X. brevis may be divided into two populations, eastern-central and northern-western, with little gene flow between the four areas of western Japan (Kinki, Chugoku, Shikoku, and Kyushu).

Helicoverpa armigera is an important lepidopteran pest of cotton in China. From 2002, the frequency of Bt resistance alleles and quantitative shifts in larval Cry1Ac tolerance of field H. armigera population were monitored using bioassays of F₁ and F₂ offspring of isofemale lines from Xiajin County of Shandong Province (an intensive Bt cotton planting area) and Anci County of Hebei Province (a multiple-crop system including corn, soybean, peanut, and Bt cotton) in northern China. During 2006–2008, a total of 2,306 isofemale lines from the Xiajin population and a total of 1,270 isofemale lines from the Anci population were successfully screened on Cry1Ac diets. For each year, it was estimated that the major resistance gene frequency in Xiajin population in 2006, 2007, and 2008 was 0, 0.00022, and 0.00033, respectively. No major alleles conferring resistance to Cry1Ac were found in the Anci population; the frequency of resistance alleles for Cry1Ac was 0. Based on the relative average development rates (RADRs) of H. armigera larvae in F₁ tests, no substantial increase in Cry1Ac tolerance was found in either location over the 3-yr period. There were also significantly positive correlations between RADR of lines in the F₁ generation and the RADR of their F₂ offspring, indicating genetic variation in response to toxin. The low frequency of resistance alleles found in this study and in our previous results from 2002 to 2005 suggest the frequency of resistance alleles has remained low and that natural refugia resistance management strategy maybe effective for delaying resistance evolution in H. armigera to Bt cotton in northern China.