Mortality data from the literature on the southwestern corn borer, Diatraea grandiosella Dyar, were analyzed to determine which factors have the most impact on populations of this insect. Adult mortality, presumed to occur primarily as a result of dispersal, appears to have been the largest source of mortality, as well as the key factor in the annual variance of mortality. Nonpredation mortality during diapause was also an important factor. Of the density-dependent mortality factors, predation by the flicker, Colaptes aruaus (L.) appears to be the factor that limits the size of overwintering populations in the southeastern United States, while cannibalism among prediapausing larvae limits the size of overwintering populations in the western Great Plains. Based on the analysis of mortality rates and historical field data, the annual finite capacity for increase (multiplication rate) was estimated to be ≈10 in the central United States. This analysis suggests that to comprehend more clearly the factors that influence population variation in D. grandiosella, future research efforts should be focused on understanding adult dispersal, and the interaction between flicker predation and nonpredation mortality in the diapausing larvae stage.

Optimal sample size methodology, which has been used by plant and marine ecologists for decades, is applied in this study to whole-community invertebrate data in the form of a case study. Wiegert’s method, based on maximizing the precision of biomass or catch data for the least cost in sampling or processing time, was conducted on guilds, habitat associations, and entire communities of tropical rice invertebrates at three crop stages (vegetative, reproductive, ripening) using five circular quadrats (35, 45, 55, 65, 80 cm in diameter) and a petrol-driven suction apparatus. Analysis of invertebrate samples and comparisons of different quadrat sizes showed that: (1) invertebrate abundance was a better predictor of processing time than was either species richness or species evenness for two of three crop stages; (2) average processing time per sample increased with crop age; and (3) size recommendations for one crop stage did not correspond to another for the same invertebrate group; however, after averaging over crop stages, one optimal quadrat size emerged for three out of six faunal groups. Unexpectedly, the optimal (and most practical) quadrat size determined for rice-invertebrate communities (35 cm diameter) was smaller than the majority (90%) of published studies have previously used, leading us to conclude that the majority of researchers (including the present authors) have used larger quadrats than were needed to obtain the same precision. Results of this case study underscore the need for researchers to conduct efficiency tests of their sampling program before starting large field trials and to resist the temptation of using published quadrat sizes whose optimality characteristics have not been field tested.

Harmonia axyridis Pallas is a highly polymorphic coccinellid with a wide geographic distribution. Genetic polymorphism seems to be the strategy adopted for facing different habitats at different times. Many modifications, such as body shape, body size, and elytral patterns, may be adaptive through imparting increased tolerance to adverse conditions. Previous studies evaluating differences in the light-colored aulica and dark colored nigra phenotypes found differences in biological performances at 20°C. However, whether the predatory activity of the different phenotypes changes under different temperatures remains unknown. Relative consumption rate and predation activity of fourth instars and adults of aulica and nigra phenotypes were compared at 10, 15, 20, 25, and 30°C. Our results showed that temperature is a limiting factor to larval and adult relative consumption rate. The thermal optimum of nigra adults was 3.7°C lower than that of aulica. Both larvae and adults of nigra were more stenothermic than aulica. Close to the upper limit of tolerance (30°C), predation activity of nigra adults was more affected than aulica. In larvae body size and shape could explain the differences observed, because aulica is significantly bigger than nigra and thus aulica presumably can better control heat exchange.

Reproductive diapause in the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was studied by dissection of field collected adults or adults reared from field collected nymphs in 1999–2001 in Washington County near Stoneville, MS. The critical photoperiod for diapause induction was 12.5:11.5 (L:D) h, or ≈12 September. This photoperiod was also near the day-length at which new generation adults produced in late winter and early spring became reproductive. Overwintering adults collected from winter host plants in December 1999 and 2001 began breaking diapause in the second and third weeks of December at a day-length near 10:14 (L:D) h. Most of the overwintering females collected on winter host plants had mature eggs by the end of December in both winters, and new generation adults were produced on winter hosts by the second or third week in March. Overwintering adults also were collected in January 2002 from plant debris not associated with any winter host plant. Most of the females overwintering in plant debris had mature eggs at the end of January, approximately 1 month later than overwintering females collected from winter hosts. This indicated than the adults from plant debris were in a different state of diapause, because they did not overwinter on a food source and matured reproductively at a later date. The winters of 1998–1999 and 1999–2000 were mild, whereas in the winter of 2000–2001, winter host plants were killed or stunted by cold weather. Diapause in plant debris in the winter of 2000–2001 was probably favored, because these adults would be more likely to survive until suitable host plants were available.

Phloridzin, a plant-derived compound toxic to Rhagoletis pomonella (Walsh), the apple maggot fly, was degraded and detoxified by the bacterium Enterobacter agglomerans. Spectrophotometric and thin-layer chromatography data showed that E. agglomerans begins to use the glycoside in aqueous solution after 6 h of incubation at 24°C. All apple maggot flies that fed on three different concentrations of sterilized phloridzin solutions died within 24 h. Incubation of E. agglomerans in 0.001 and 0.01 M aqueous phloridzin for 3 d eliminated toxicity for apple maggot flies but most died after being fed a 1 M solution. Plant leachate containing phenolic compounds extracted from McIntosh apple leaves also was used by E. agglomerans. Enterobacter agglomerans entered logarithmic growth more quickly in leachate samples than in solutions of commercially-purified phloridzin. Protein, amino acid, and reducing sugar content of the leachate increased after incubation with E. agglomerans for 12 h. Reducing sugar content decreased, however, after 24 h of incubation, whereas protein and amino acid content continued to increase. Scanning electron micrographs of leachate intact on apple leaf surfaces revealed the presence of healthy rod-shaped bacteria and yeast aggregating about it. These images suggest that phylloplane microorganisms use leachate as a source of nutrients and this activity may affect the potency of plant defensive chemicals. The potential benefits afforded by the catabolic activities of phylloplane and/or gut microorganisms on plant compounds to apple maggot flies are discussed.

We tested the hypothesis that nonhost conifers contain compounds that repel coniferophagous bark beetles (Coleoptera: Scolytidae) during host selection in four experiments (n = 10) involving paired trees baited with aggregation pheromones. Mountain pine beetles, Dendroctonus ponderosae Hopkins, and Douglas-fir beetles, Dendroctonus pseudotsugae Hopkins, were tested for discrimination between their respective hosts, lodgepole pine and Douglas-fir, and spruce beetles, Dendroctonus rufipennis Kirby, and western balsam bark beetles, Dryocoetes confusus Swaine, for discrimination between interior spruce and interior fir. Both host and nonhost conifers in a pair were baited with the same aggregation pheromone. Most baited host trees were successfully attacked and contained galleries with eggs or young larvae. Neither D. rufipennis nor D. confusus attempted to establish galleries on nonhosts. A few attacks were initiated on nonhosts by D. pseudotsugae and D. ponderosae, but most did not reach the phloem tissue, and in no case were they numerous enough to have produced a significant source of aggregation pheromone. Thus employing pheromone-baited nonhost trap trees would not be an effective management tactic. Higher trap catches in unbaited multiple funnel traps within 1 m of nonhost trees than in control traps 12.5 m away also indicated that there was no strong long range repellence caused by nonhost volatiles. Although this study was not designed to evaluate primary attraction to host trees, the lack of strong repellence from nonhost conifers partly supports the hypothesis of random landing followed by close range olfactory or gustatory rejection of nonhosts.

In the current study, we tested the effect of peanut, Arachis hypogaea L. (Leguminoseae), stem infection by the white mold fungus, Sclerotium rolfsii Saccodes (Basidiomycetes), on the oviposition preference of beet armyworms (BAW), Spodoptera exigua Hübner (Lepidoptera: Noctuidae) and on the host-searching behavior by a BAW larval parasitoid Cotesia marginiventris. We found that, in choice tests, adult BAW oviposited more on white mold-infected plants than on healthy plants. We also found evidence that this preference is mediated by plant volatiles and other biochemical changes in plant chemistry caused by fungal infection. When plants were exposed to BAW feeding, the parasitoid C. marginiventris landed more frequently on infected than on healthy plants. We conducted wind tunnel choice experiments to determine whether the more frequent landing by the wasps was mediated by the volatiles emitted by healthy and white mold-infected plants in response to BAW damage. In these wind tunnel experiments, wasps were more responsive to volatiles from plants infected with the white mold compared with healthy ones, when both types of plants were exposed to damaged by BAW caterpillars. Thus, white mold-infected peanut plants were preferred by BAW for oviposition, but, when damaged by BAW larvae, infected plants were also more attractive to one of the BAW natural enemies. To our knowledge, this is the first time that the effect of pathogen-induced biochemical changes in plants on parasitoid behavior has been evaluated.

Evidence for field attraction by beneficial insects to synthetic herbivore-induced plant volatiles (HIPVs) is presented. Three synthetic HIPVs (methyl salicylate, (Z)-3-hexenyl acetate, (E)-4,8-dimethyl-1,3,7-nonatriene) were evaluated in a Washington state hop yard during April–October 2002 for attractiveness to beneficial insects. The predatory mirid, Deraeocoris brevis (Uhler), and the anthocorid, Orius tristicolor (White), were attracted to sticky cards baited with (E)-3-hexenyl acetate, while the geocorid, Geocoris pallens Stal., and hover flies (Syrphidae) were attracted to methyl salicylate-baited cards. The coccinellid, Stethorus punctum picipes (Casey), was attracted to both HIPVs in July and September. The (E)-4,8-dimethyl-1,3,7-nonatriene did not attract any beneficial insects. Lygus hesperus Knight, Leptothrips mali (Fitch), Anagrus spp., other Miridae, Coccinellidae, and parasitic Hymenoptera were not attracted to the three HIPVs tested. The possible exploitation of HIPVs in enhancing spring populations of beneficial insects and conservation biological control in cropping systems is discussed.

The work presented examines the effects of soil moisture on the virulence of selected entomopathogenic nematode isolates in the laboratory and has broad implications for managing soil-dwelling insects in all production systems. Two species of entomopathogenic nematodes, Heterorhabditis bacteriophora (Oswego and Tuscarora strains) and Steinernema glaseri (NC1 strain), were applied to sandy loam soils ranging from below the permanent wilting point of plants to near saturation. Fluctuations in soil moisture were created by simulating a rainfall or irrigation event (i.e., rehydration), or by allowing soil to dry. Nematode virulence was evaluated by measuring insect mortality in Galleria mellonella larvae bioassays. Soils prepared at four moisture contents were inoculated with nematodes and subsequently bioassayed at their original moisture contents and after rehydration, over an 18-mo period. Insect mortality increased with soil moisture content for both H. bacteriophora isolates but was highest in relatively low moisture soils (≈−15 bar) for S. glaseri. Insect mortality was generally low in low-moisture soils before rehydration but rebounded to high levels posthydration. Both isolates of H. bacteriophora nematodes were reactivated to cause high insect mortality (≥ 98%) as long as 18 mo after infective juveniles were inoculated into very low moisture soils (≈−30 bar). The posthydration insect mortality levels in the S. glaseri treatments were significantly lower than in the H. bacteriophora treatments. For all nematode treatments, the cumulative insect mortality of prehydration and posthydration bioassays was higher in lower moisture soils compared with higher moisture soils. In an additional experiment, moisture thresholds for activation of nematodes in dry soil were determined.

A behavioral change in some western corn rootworm (Diabrotica virgifera virgifera LeConte) populations is threatening the effectiveness of crop rotation, a successful management strategy for controlling this pest. We created a set of simple meteorologic and behavioral models that can be used to predict the spread of the beetle infesting soybean (Glycine max (L.)) throughout the midwestern United States. We used data collected in Illinois, IN, MI, and Ohio to create maps of observations to evaluate the model. We displayed data on the maps using detection thresholds for western corn rootworm in soybean fields of 10 or 20 beetles per 100 sweeps and one or two beetles per yellow sticky trap per day. Counts greater than a detection threshold represent populations with a lack of fidelity to corn (Zea mays L.) and adapted to circumvent corn-soybean rotation. Some of the models invoked a landscape-diversity function that included the proportion of noncorn, nonrotated soybean vegetation on farmland in each county (i.e., extra vegetation). The best model for the period from 1997 to 2001 is based on heavy-storm data, with distance that beetles spread each year reduced by the proportion of extra vegetation in a county. This version is superior to a previously published model and to two new models that do not consider landscape diversity. Most of the models predicted spread at too high a rate between 1997 and 2001, compared with observations, but a few new models with rates of spread reduced by a landscape-diversity function matched the observations relatively well. Results suggest that the conclusions based on a linear model using proportion of extra vegetation as the key parameter are likely to be robust. Thus, we hypothesize that as the landscape diversity represented by the proportion of noncorn and nonrotated soybean vegetation in a geographic region increases, the rate of regional spread of the rotation-resistant western corn rootworm decreases over several years.

Our objective was to examine the pattern of agonistic behavior observed among 11 colonies of the Formosan subterranean termite, Coptotermes formosanus Shiraki, collected from two locations in New Orleans, LA. In 24-h petri dish tests, 13 of the 40 colony pairs displayed agonism in at least one replicate. In 14-d tests conducted in sand-filled foraging arenas, seven of the nine colony pairs tested showed agonism, including three that had showed agonism in the 24-h test and four that had not shown any agonism in the 24-h test. In tests in which individual behavior was observed for 1 h, there was variation in the prevalence of aggressive behavior shown by individual workers. This study shows that interactions between colonies of C. formosanus from the same geographic area are complex and that these interactions could influence strategies for termite control.

Risk of exposure to Borrelia burgdorferi sensu lato (s.l.) spirochetes, which include the causative agents of Lyme disease, is, in part, determined by the density of questing infected vector ticks. We sought to clarify the temporal patterns of nymphal activity, and the extent of variation in peak and cumulative densities of B. burgdorferi s.l.-infected Ixodes pacificus Cooley & Kohls nymphs, at 12 sites within the ecologically diverse Mendocino County in northwestern California. Also, we assessed the impact of various environmental characteristics (e.g., climatologic variables, habitat type, deer usage) on the aforementioned tick-related traits. The average durations of total and peak (nymphal density > 75% of absolute peak) questing activity were 31% and 82% longer, respectively, in areas with conifers present than in oak woodlands, which represented the warmest and driest habitat type examined. Peak and cumulative densities of infected nymphs varied > 400-fold between sites. Both traits were positively associated with the presence of Quercus spp. oaks or deer, and lower in redwood/tanoak versus oak and oak/Douglas fir habitats. However, a prolonged duration of nymphal activity in redwood habitats, relative to oak woodlands, resulted in a shift from peak nymphal densities occurring in oak woodlands in spring to redwood/tanoak habitats in summer. In conclusion, our data clearly show significant variability in seasonal as well as spatial risk of exposure to Lyme disease spirochetes within a small but ecologically, diverse geographic area. Hence, temporally dynamic and spatially explicit models are needed to assess the risk of exposure to tick-borne pathogens at spatial scales encompassing diverse climatologic or ecological conditions.

Parasitism rates of the nonnative tachinid fly, Compsilura concinnata (Meigen), on experimental populations of native luna moth caterpillars (Actias luna (L.)) were determined in central Virginia, where both C. concinnata and the gypsy moth, its biocontrol target, have become established in the past few decades. In a forest that has not yet had gypsy moth damage, we placed cohorts of second through fifth instar Actias luna caterpillars on understory hickory trees. At the end of each instar, surviving caterpillars were collected and reared. Four parasitoid species and two hyperparasitoid species emerged from the caterpillars and pupae. C. concinnata was the most common parasitoid, attacking 0% to 62% of the caterpillars recovered in each instar. Hyperparasitism of C. concinnata by trigonalid wasps was high: 47% and 16% in the two generations. UV light census data indicate that current saturniid populations in this area of central Virginia are robust, but the long-term effects of C. concinnata introductions on populations of these and other native macrolepidoptera should be monitored.

Anoplophora glabripennis (Motschulsky) is an invasive wood-boring cerambycid beetle that kills hardwood trees. The host range of this species is unusually broad but is not well defined in the available literature and may include tree species that have not been reported as hosts because they have not previously been exposed to the beetle. We evaluated oviposition by A. glabripennis offered a choice of four common eastern North American forest and landscape hardwood tree species, and performance of the resulting larvae, under greenhouse conditions. Significantly greater numbers of oviposition sites were found on sugar maple, Acer saccharum Marshall, than on red maple, Acer rubrum L., green ash, Fraxinus pennsylvanica Marshall, or red oak, Quercus rubra L., with no significant differences among the other three tree species. Similarly, significantly greater numbers of living larvae were found in sugar maple than in the other tree species; however, more were found in red oak and fewer in green ash than expected, considering relative numbers of oviposition sites. After 90 d, mean mass of living larvae did not differ significantly among tree species. These results suggest that all four tree species may be suitable hosts for A. glabripennis. Most importantly, although larval establishment was poor in green ash and larval growth may have been retarded in red oak, larvae did survive and grow in both species. We recommend that these tree species be considered potential hosts when surveys are conducted to detect infested trees or when replanting infested areas.

We evaluated the within-plant distribution of Frankliniella spp. and the predator Orius insidiosus (Say) in pepper (Capsicum anuum L.), over a range of field conditions, and we conducted behavioral experiments to examine the time budgets of F. occidentalis (Pergande) and F. tritici (Fitch) females on pepper plant parts. In the field experiments Frankliniella species composition varied by season and location. Still, all populations of thrips and O. insidiosus in untreated and insecticide-treated pepper were highly concentrated in the flowers, with 82–99% of individuals of each taxa found in flowers. This preference for flowers was corroborated by laboratory-choice experiments. Adult females of F. occidentalis and F. tritici showed a strong preference for pepper flowers over leaves and buds. In laboratory observations, females of F. occidentalis spent 3.6× as much time on flowers as on all other plant parts, and females of F. tritici spent over 6.3× as much time on flowers as on all other plant parts. Therefore, the concentration of these thrips in flowers appears to be behaviorally based and not an artifact of insecticide applications or sampling. Using estimates of populations from flowers of field pepper is sufficient for understanding the local dynamics of Frankliniella spp. and the predator O. insidiosus, and for estimating the benefits of biological control in scouting programs based on predator to prey ratios.

Endocrine disruptors have well-known effects on vertebrate population sex ratios, but a variety of chemicals can also affect sex ratios of invertebrates. We tested whether sex ratios of fleas (Ceratophyllus idius Jordan and Rothschild) living in the nests of tree swallows (Tachycineta bicolor Vieillot) were affected by exposure to environments containing different chemicals. Fleas were collected from nests adjacent to sewage lagoons that received unknown chemical inputs, from nests fumigated with insecticidal vegetation (yarrow, Achillea millefolium L.), from nests treated with both commercial flea powder and diatomaceous earth, and from control nests. The proportion of males was lower in nests treated with both commercial flea powder and diatomaceous earth than it was in nests around the sewage lagoon or in nests to which yarrow had been added. These results suggest potentially novel effects of chemicals on invertebrate populations that would not be revealed by, for example, LD₅₀s.

The main effects and interactions between temperature and host instar on development and survival of Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae), a parasitoid of many pyralid (Lepidotera: Pyralidae) larvae, were studied under laboratory conditions. The duration of development in Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) larvae of second, third, fourth and fifth instar and at seven constant temperatures (15, 17.5, 20, 25, 30, 31, and 32°C) was measured. Development time decreased significantly with increasing temperature within the range 15–30°C. When parasitism took place on second instar hosts the parasitoid development took significantly longer compared with other instars. Differences among third, fourth and fifth instar proved to be insignificant. Thermal requirements of development (developmental thresholds, thermal constant, optimum temperature) of V. canescens in each host instar were estimated with application of a linear and one nonlinear model (Logan I). Upper and lower developmental thresholds ranged between 36.01–36.41 and 10.86–11.37°C, respectively. Optimum temperature for development was estimated at between 30.59–30.81°C. All above-mentioned parameters did not vary significantly with host instar. The thermal constant decreased with host instar at parasitism and ranged between 370.4 and 555.6 d-degrees. Immatures’ survival peaked at 30°C and was higher in older instars (third-fifth).

The current study investigated the interaction among density, feeding impact, and dispersal of western flower thrips, Frankliniella occidentalis (Pergande), on potted flowering chrysanthemum plants. In cage experiments using chrysanthemum plants infested with either 0, 400, 800, or 1,200 thrips, the proportion of senescent inflorescences increased with time and with the number of thrips released on chrysanthemum plants. Positive correlations between the proportion of senescent inflorescences and the density of thrips per inflorescence for different time periods indicate that the feeding activity of thrips causes a premature senescence of inflorescences. On plants infested with 0 or 400 thrips, population density slightly increased for 10–14 d and then leveled off; on plants infested with 800 or 1,200 thrips, in contrast, population density remained high for 7–10 d and then steadily declined to very low levels. A high proportion of senescent inflorescences was positively correlated with the proportion of females that dispersed on blue sticky cards for different time periods, whereas the rate of dispersal by males was not consistently impacted by the quality of inflorescences. Releasing adult thrips marked with fluorescent powder in greenhouses indicated that the quality of inflorescences meditates the dispersal behavior of adult thrips up to a distance of 4 m: females are more likely to disperse from senescent than healthy inflorescences and preferentially colonize healthy inflorescences over senescent inflorescences. The dispersal behavior of adult thrips has important implications in terms of sex-specific optimal reproductive strategies, sampling procedures, and population dynamics.

Insects of forest canopies are poorly known, especially in temperate forests of eastern North America. From June to August 2001, we sampled Cerambycidae using paired canopy and understorey flight-interception traps in nine pine and nine maple sites in south-central Ontario. Canopy traps were set using a simple ground-based bow-and-arrow method, and averaged 24.5 m in height at pine sites and 20.5 m at maple sites. In total, 297 individuals from 28 species were collected during 6 wk of sampling. Clytus ruricola (Olivier) accounted for 37% of all individuals. Pine sites had more species and higher expected richness than maple sites but significantly fewer individuals. Ten species were unique to pine, six to maple, and 12 occurred in both forest types. The two trap heights had similar observed richness, but expected richness was higher for canopy than understorey traps. Understorey traps accumulated significantly higher abundances than canopy traps. Eleven species were unique to canopy traps, 11 to understorey traps, and six occurred at both heights. Species accumulation was much faster when both heights were sampled compared with either alone. Anthophylax attenuatus (Newman), which has been rarely caught in other studies, was collected only in the canopy and was relatively abundant. Top collecting bottles on traps yielded similar observed richness as bottom bottles but had higher expected richness. Several species showed strong associations with either top or bottom collecting bottles. Species accumulation rates appeared to be higher than in other studies. Our results emphasize the necessity of including the canopy fauna in diversity studies.

In 2001 and 2002, we pit trapped arthropods at eight riparian forest sites along the middle Rio Grande, four characterized by flooding in some years (flood sites) and four others where periodic flooding no longer occurs (nonflood sites). All flood sites flooded in 2001 but not in 2002, while nonflood sites never flooded. Arthropod counts and hierarchical cluster analyses of the sites indicated (1) significantly greater abundance of carabid beetles and the isopod Porcellio laevis in 2001 than in 2002; (2) significantly greater carabid beetle abundance at flood sites during each year of the study, with the relative abundance of one carabid species, Calathus opaculus, significantly higher at nonflood sites in 2002; (3) marginally significantly higher (2001) or significantly higher (2002) carabid species richness at flood sites; (4) no obvious response of the other taxa examined (isopods, tenebrionid beetles, and the cricket Gryllus alogus) to flooding regime, although differences in isopod abundance between flood and nonflood sites approached significance in 2001; (5) successful classification of all nonflood sites and three flood sites using the Bray–Curtis Similarity Index and carabid abundance. Overall, our results suggest that carabid beetles are fairly sensitive indicators of hydrologic connectivity between the Rio Grande and its riparian forest, while the other taxa examined are not. With the number of ongoing or planned restoration efforts increasing along the middle Rio Grande, carabids may represent an important tool for monitoring the response of riparian areas to managed flooding.

Ground cover is used in some vineyards to improve soil structure and help manage insect pests; previous studies have shown lower leafhopper (Erythroneura spp.) densities on vines grown with ground cover. We undertook a 2-yr study to determine why ground cover is associated with reduced leafhopper densities. Ground cover consisted of a fall-planted cover crop of purple vetch (Vicia benghalensis) and barley (Hordeum vulgare), which senesced in May and was replaced by a complex of resident vegetation comprised primarily of the grasses Echinochloa spp., Digitaria sanguinalis, and Setaria spp., as well as common knotweed (Polygonum aviculare). We compared three treatments during the growing season: Cover, No Cover, and Cover/Exclusion. Cover/Exclusion was similar to Cover treatment but with barriers to impede arthropod movement between ground cover and vines. We measured leafhopper density and egg parasitism, spider density and diversity, and grapevine vigor, and found that mid- and late-season leafhopper densities were significantly lower in Cover versus No Cover. Neither leafhopper egg parasitism nor spider density on the vines or ground cover could explain these differences; however, grapevine vigor was significantly lower in Cover than No Cover, and provides the best correlation to leafhopper density. Late-season leafhopper density was highest in the Exclusion treatment but cannot be explained by changes in grapevine vigor. Individual spider species composition and density on the grapevine canopy varied significantly among treatments: Trachelas pacificus (Chamberlin and Ivie) was higher in the Cover treatment, Hololena nedra Chamberlin and Ivie, Cheiracanthium inclusum (Hentz), and Neoscona oaxacensis (Keyserling) were lower in the Exclusion treatment, and Oxyopes spp. was higher in the Exclusion treatment. We suggest the lower densities of leafhoppers in the Cover treatment resulted from poorer host plant quality because of the competition between ground cover and grapevines. The higher late-season leafhopper densities in the Exclusion treatment may be due to changes in spider species composition, and subsequently, differences in rates of predation on leafhopper nymphs.

This study examined insect diversity in two native grassland ecosystems undergoing burning and grazing by bison and cattle, the Niobrara Valley Preserve (Nebraska) and the Tallgrass Prairie Preserve (Oklahoma). Sweep-sampling for insects was conducted during July 1994 and 1995 along transects in management units that were grazed by bison and partially burned, grazed by cattle and either burned (Tallgrass) or unburned (Niobrara), or ungrazed and unburned. At both sites, species richness (S) and diversity (log series α) were higher and similarity (Sorensen’s index) lower for bison than for cattle or ungrazed management units. High bison management unit diversity was associated with significantly higher S and α in burned (Tallgrass) and unburned (Niobrara) portions of bison units compared with their respective cattle units, suggesting that habitat heterogeneity in terms of plant productivity, composition, and structure were higher in bison versus cattle and ungrazed management units. Replicated factorial experiments and sampling of additional taxa and time points are needed to verify how fire and grazing management impacts insect diversity in these grasslands.

We conducted investigations on seasonal population fluctuations of Serangium parcesetosum Sicard and citrus whitefly, Dialeurodes citri (Ashmead), in the East Mediterranean citrus orchards in Turkey from 1992 to 1995. Serangium parcesetosum and D. citri were sampled in two mandarin orchards at 2- to 3-wk intervals. Sooty-mold growth on honeydew excreted by the citrus whitefly on sampled trees also was evaluated as an indirect measure of the predator’s success. Serangium parcesetosum controlled D. citri populations effectively and prevented them from causing sooty-mold growth in the citrus groves in all 4 yr. It also fed and reproduced on brown soft scale, Coccus hesperidum L., another citrus pest, as an alternate host when D. citri populations were lower, and contributed to biological control, along with two other predators of coccoids, Chilocorus bipustulatus (L.) and Exochomus quadripustulatus L.

Many natural enemies of bark beetles are attracted to bark beetle pheromones, and substantial numbers of them are removed along with the target pests in mass trap-out programs. Thus, additional information on bark beetle and predator behavior is needed to maximize trap-out of target pests while decreasing trapping of beneficial insects. Ips pini (Say) is the most widespread bark beetle associated with pine trees in the United States and Canada. Geographically distant populations vary considerably in their production of, and response to, different stereoisomers of their principal pheromone component, ipsdienol, and an additional pheromone component, lanierone. California populations of I. pini are attracted to 99.9%(–)-ipsdienol, and the presence of lanierone has no effect on attraction. We simulated trap-outs by conducting no-choice assays using three different ratios of ( )/(−) enantiomers of ipsdienol with or without lanierone in the field. Experiments were performed in mixed pine forests in northern California in 1997 and 1998. Experiments were performed twice each year to sample the two major flight periods of I. pini. Ips pini and its predators showed temporal and behavioral differences in their attraction to lures. Lures that are preferred by I. pini, 3( )/97(−) ipsdienol with or without lanierone, selectively removed up to 5–7 times more pests than predators during early summer. Moreover, the ratios of pest to predators were much higher in the late than early summer, and pest numbers were as much as 282 times higher than predators. In contrast, lures most attractive to predators removed as much as 10 predators for each I. pini trapped. These results suggest that timely applications of carefully selected synthetic lures, in combination with other complementary forest management practices, can greatly improve trap-out programs for bark beetles and natural enemy conservation. In addition, behavioral differences in attraction suggest the potential for augmentation of natural enemies.

The extent to which encapsulation of eggs of Bathyplectes curculionis (Thomson) reduces the effectiveness of this parasitoid as a control agent for the alfalfa weevil, Hypera postica (Gyllenhal), was evaluated in two studies over the period from 1973 to 2000. Collections of alfalfa weevil larvae were made annually from research areas in Grady and Payne Counties (Study I) and in statewide surveys (Study II) across Oklahoma to estimate the prevalence of encapsulation of eggs of both first and second generations of B. curculionis. Subsamples of 100 weevil larvae were dissected for each sampling date to determine the numbers and condition (healthy versus encapsulated) of parasitoids in each host larva. Probabilities for encapsulation of solitary eggs ranged from 0.20 to 0.29 for the first generation and from 0.07 to 0.08 for the second generation of B. curculionis. Although probabilities for encapsulation of at least one egg in superparasitized larvae ranged from 0.48 to 0.55 for the first generation, the probabilities of supernumerary eggs being encapsulated were much lower, ranging from 0.03 to 0.19. Regression analyses indicated highly significant relationships between effective (hosts containing healthy parasitoids) and actual (all hosts containing parasitoids) parasitism for both studies across all values (1–100%) for actual parasitism. Regression of efficiency of encapsulation (percentage of reduction in effective parasitism caused by encapsulation) on years indicates that the value of encapsulation as a defense for H. postica against B. curculionis may have diminished over the 28 yr that these studies were conducted. The reduction in efficiency of encapsulation does not appear to have resulted from greater prevalence of superparasitism, as the occurrence of supernumerary parasitoids in larvae of H. postica also decreased during these studies.

Generalist predators are common in most agricultural cropping systems. However, pest control from these predators is often overlooked as a component of integrated pest management (IPM) because the extent of predation is generally unknown and difficult to assess. In western New York sweet corn (Zea mays L.), the primary predators are Orius insidiosus (Say), Coleomegilla maculata (DeGeer), and Harmonia axyridis (Pallas). European corn borer [Ostrinia nubilalis (Hübner)] is the primary insect pest. The objectives of this study were to compare O. nubilalis egg predation rates for these three species and to understand how egg predation by these predators is affected by the availability of alternative food. Laboratory data indicate that all three predators feed on O. nubilalis eggs. C. maculata consumed more eggs than H. axyridis or O. insidiosus. Immatures of C. maculata and O. insidiosus readily completed development on a diet of O. nubilalis eggs, but H. axyridis larvae could not complete development on this diet. The presence of corn leaf aphids [Rhopalosiphum maidis (Fitch)] and corn pollen reduced egg predation per insect for some stage of all species. The reduction in O. nubilalis egg predation associated with the presence of aphids was confirmed in field cage studies and was similar among the coccinellid populations tested. Field studies comparing aphids, predator populations, and O. nubilalis egg predation show that reduced egg predation per insect more than offsets the higher populations encountered when aphids and pollen are numerous, resulting in less biological control of O. nubilalis when alternative foods are available.

The effects of an undetermined species of Nosema on fitness of the muscoid fly parasitoid Tachinaephagus zealandicus were examined in the laboratory. Infected female parasitoids that were given honey and water lived about one-half as long as uninfected parasitoids under these feeding conditions. Effects of infection on longevity were strongest at 30°C; infected and uninfected females lived 2.8 and 8.7 d, respectively. Infected and uninfected parasitoids that were given only water had similar longevities, but water-only–fed parasitoids had much shorter lifespans than honey-fed parasitoids at all temperatures. Infection did not result in significant lengthening of development times of immature stages, with male and female parasitoids completing development from egg to adult in ≈23, 33, and 60 d at 25, 20, and 15°C, respectively. Overall emergence of uninfected parasitoid adults was 16 times greater than infected parasitoids at 15°C. Emergence of uninfected parasitoids was 11 and 3 times greater than infected parasitoids at 20 and 25°C, respectively, and sex ratios of emerged adults were significantly more male-biased in infected parasitoids at these temperatures than among uninfected parasitoids. Dissections of uneclosed puparia revealed that many infected parasitoids completed development to the adult stage but did not successfully emerge from host puparia. Infected and uninfected females killed similar numbers of hosts (70–75 house fly or Sarcophaga bullata larvae killed per group of five females in 24 h). Uninfected females parasitized significantly more house fly larvae (59.7) and produced more than twice as many adult progeny (311.1) as infected females (34.1 hosts parasitized, 138.3 progeny produced). Infected females parasitized about as many S. bullata hosts as uninfected females and produced slightly fewer adult progeny (588.2 and 460.1 progeny per group of five uninfected and infected females, respectively). In tests with individual females given house fly hosts daily throughout life, uninfected and infected parasitoids had similar longevities (3.9 and 3.7 d, respectively), but uninfected parasitoids produced 2–5 times as many adult progeny.

Several methods were investigated for managing Nosema disease in the parasitoid Muscidifurax raptor Girault and Sanders. Treatment of parasitoid eggs or pupae within host puparia with gamma radiation from a cesium-137 source were either lethal to the parasitoids at all dosages tested (eggs) or failed to reduce infection rates (pupae). Exposure of parasitoid eggs within host puparia to heat was effective at several temperatures and exposure times. Optimal results for disease reduction were achieved with a 5-h exposure to 45°C, which resulted in no infection in the resulting adult parasitoids. Continuous rearing at elevated temperatures (30 and 32°C) for three generations resulted in decreased spore loads in infected parasitoids but did not reduce infection rates. Incorporation of the drugs albendazole and rifampicin into rearing media of the parasitoid’s host (house fly immatures) resulted in pupae that were of poor quality and did not reduce infection rates in parasitoids that developed in flies reared on drug-treated media. Treatment of adult parasitoids with 3% albendazole and/or rifampicin resulted in decreased rates of transovarial transmission of the disease. Transmission blockage required 3–7 d of exposure to the drug before substantial treatment effects were manifest. Parasitoids that fed for 7 d on rifampicin-treated honey transmitted the disease to 57.7% of their progeny compared with a 99.1% transmission rate among untreated parasitoids. An uninfected colony of M. raptor was established by pooling cured parasitoids from heat shock and drug treatment experiments. Parasitoids from the uninfected colony lived longer and produced over twice as many female progeny (201.2) as infected parasitoids (85.2).

This study investigated the influence of different humidity levels on percentage of infection by Beauveria bassiana (Balsamo) Vuillemin (Hyphomycetes) (Botanigard Emulsifiable Suspension formulation) on greenhouse insect and mite pests, and their commercially available biological control agents. The target insect and mite species were sprayed with B. bassiana and evaluated in petri dish trials under controlled environment conditions, on cucumber leaves under greenhouse crop conditions, and under fully sprayed greenhouse conditions. Results of this study showed that in petri dish trials, a humidity of 97.5% RH resulted in significantly higher percentage of infection (60–88.8%), while at 75 and 80% RH only 15.3–43.9% of the pest insects were infected. On leaf surfaces, the differences in ambient humidity did not cause as great of variations in percentage of infection as in the petri dish trials. Increasing greenhouse humidity by 15% RH caused an increase of 17–25% in percentage of infection. Under high humidity conditions, whole greenhouse sprays with B. bassiana successfully suppressed populations of Frankliniella occidentalis (Pergande) and Trialeurodes vaporariorum (Westwood). Tetranychus urticae Koch was not infected by B. bassiana at significant levels in any of the trials. Predatory mites can be used with B. bassiana, while adult Orius insidiosus (Say), Aphidius colemani Viereck, and Dacnusa sibirica Telenga are not recommended to be introduced during the application of B. bassiana. Encarsia formosa Gahan, Eretmocerus eremicus (Rose and Zolnerowich), and Aphidoletes aphidimyza (Rondani) need to be used with caution when B. bassiana is applied.

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of corn in Kansas. Planting Bt corn hybrids resistant to this pest is being tested for control of the larval stage of corn rootworms. These hybrids express the Cry3Bb1 toxin and are expected to only directly impact chrysomelids and possibly related taxa. A 2-yr study was conducted to evaluate the effect of Bt corn expressing the Cry3Bb1 toxin on foliar and ground-dwelling nontarget arthropods in Kansas. Visual inspections of adult and immature Coleomegilla maculata (DeGeer), Orius insidiosus (Say), Hippodamia convergens Gurin-Meneville, and Scymnus spp. occurring in Bt corn and its isoline were made at eight locations in Kansas in 2000 and three locations in 2001. Pitfall traps were installed at three locations in 2000 and two locations in 2001 to collect ground-dwelling arthropods in Bt corn and its isoline. In general, no significant differences in numbers of C. maculata, O. insidiosus, H. convergens, and Scymnus spp. were detected between Bt corn and its non-Bt isoline. There were also no significant differences in number of insects collected in pitfall traps installed in plots of Bt corn and its isoline. Bt corn for corn rootworm control had no deleterious effects on beneficial and other nontarget arthropods sampled in this study.

The natural mechanism of intercolony transmission of Thelohania solenopsae, a pathogen of red imported fire ants, Solenopsis invicta, is unknown. However, T. solenopsae can be transmitted by introducing infected brood into an uninfected colony. We hypothesized that the transfer of brood among colonies during intercolony competition may be a mechanism for the horizontal transmission of T. solenopsae. Male and female reproductive caste alates, collected during the initiation of mating flights from infected colonies, had T. solenopsae infection rates of 93 and 75%, respectively. In addition, 47 field-collected, newly mated queens that were reared in the laboratory established T. solenopsae-infected colonies that contained egg, larvae, pupae, and adults. Because T. solenopsae is transovarially transmitted, this indicated that infected founding queens generated infected colonies. A life span of ≤52 wk was documented for 81% of the infected queens and 59% for uninfected queens. To determine whether imported fire ant colonies can become infected with T. solenopsae via colony raiding, seven pairs of S. invicta colonies consisting of large, uninfected and small, infected colonies were given access to each other in the laboratory. T. solenopsae infection was detected in four of seven of the large colonies. In the four large, infected colonies, brood levels declined an average of 64% after 22 wk in contrast to a 116% increase in the controls. Thus, there was evidence that incipient, T. solenopsae-infected colonies could provide a source of inocula for the horizontal transmission of T. solenopsae through the transfer of brood during colony raiding.

Four mark-release-recapture experiments were conducted from May to September 2000, to construct a 3D dispersal model for aster leafhopper (Macrosteles quadrilineatus Forbes). In the laboratory, flight mills and an optical sensor were used to measure the effects of fluorescent dust and rabbit protein marking on flight activity of aster leafhopper. No significant differences in proportion of leafhoppers flying, distance flown, average flight speed, or wing-beat frequencies were observed among marked leafhoppers versus unmarked controls. Leafhoppers were sampled in a grid pattern around a central release point of marked leafhoppers to estimate the patterns of leafhopper abundance and the distribution of dispersal distances. Geostatistical analysis of numbers of aster leafhopper adults captured by vacuum sampling in the grid pattern around a central release point was used to examine differences in dispersal pattern among crops. The spatial correlation range was ≈200 m for lettuce but only ≈35 m for endive. These differences in spatial pattern suggest leafhoppers disperse more slowly from lettuce plants, preserving aggregations over longer distances. The proportion of leafhoppers recaptured at various distances from a release point was modeled using a normal distribution for dispersal perpendicular to the wind and a Gumbel distribution for dispersal parallel with the wind. Goodness-of-fit tests indicated that both distributions fit field observations well. For all recaptured leafhoppers, the average distance from the release point was 53.6 m and the average distance for dispersal perpendicular to the wind was 17.6 m. The average distances moved parallel to the wind of those leafhoppers dispersing upwind and downwind were 12.1 and 43.9 m, respectively. The dispersal model will be used in spatially explicit simulation of aster yellows epidemiology.

The relative abundance of male grape berry moths, Endopiza viteana Clemens (Lepidoptera: Tortricidae), was studied within Michigan grape agroecosystems during 1999–2001. Distribution within and between habitats was determined using pheromone traps placed at different heights between the interior of deciduous woods and interior of adjacent vineyards. Comparisons of relative moth abundance across habitats using traps at the standard 1.5 m sampling height confirmed that moths are more abundant in the woods in spring and in the vineyard later in the season. Traps placed at 1.5, 3.0, 6.0, and 9.0 m above ground level in woods and vineyards revealed that moth relative abundance increases with height in woods, whereas 90.0% of moths caught in vineyards were at 1.5 m above ground level. Sampling inside the woods up to 15.2 m revealed that 76.1% of moths were found at or above 9.0 m. Relatively few moths were trapped in the interface between these habitats, where grapevines are not present. The results of vertical sampling suggests that moths are not moving from woods to vineyards, but instead are most abundant high in the woods canopy. These results show that the relative abundance of grape berry moth varies within and between habitats, and suggest that distribution of this specialist insect is associated with the distribution of its wild and cultivated host.

RÉSUMÉ L’abondance relative des mâles de la tordeuse de la vigne, Endopiza viteana Clemens (Lepidoptera: Tortricidae), a été étudiée dans l’écosystème agronomique des vignobles du Michigan aux états Unis, durant 1999–2001. La distribution relative intra- et inter-habitats (les bois adjacents et les vignobles) a été déterminée par l’utilization de pièges à phéromone placés à différentes hauteurs entre l’intérieur des bois et l’intérieur des vignobles contigus. Les comparaisons sur l’abondance relative de mâles en utilisant des pièges placés à la hauteur standard de 1.5 m, ont confirmé que les mâles sont plus abondants dans les bois au printemps et dans les vignobles plus tard dans la saison. Des pièges placés à des hauteurs de 1.5, 3.0, 6.0, et 9.0 m dans les bois et les vignobles adjacents ont montré que dans les bois, l’abondance relative augmente à mesure que la hauteur du piège augmente, pendant que dans les vignobles, le 90.0% des mâles capturés se trouvent à la hauteur de 1.5 m par-dessus le sol. En ayant des pièges placés jusqu’à une hauteur de 15.2 m dedans les bois, nous avons trouvé que le 76.1% des mâles se trouvaient à ou par-dessus le niveau de neuf mètres. Relativement peu de mâles furent capturés à l’interface entre ces deux habitats où les vignes sont absentes. Les résultats d’un échantillonnage vertical suggèrent que les mâles ne se déplacent pas des bois vers les vignobles, sinon qu’ils continuent tout le temps à être plus nombreux dans le haut des bois, les coupes des arbres. L’abondance relative de la tordeuse de la vigne varie non seulement intra- mais aussi inter-habitats, ce qui suggère que la distribution de cet insecte spécialiste soit associée avec la distribution de son hôte sauvage et cultivé.

Plant resistance to herbivores can be induced by application of elicitors such as jasmonic acid, which is a signal molecule that increases naturally in plants that have been damaged. The use of elicitors to induce resistance of crop plants against herbivores has been successful in small scale experiments but has not been developed in commercial agriculture. We tested jasmonic acid sprays as elicitors of resistance against leafminers and other pests on commercial celery fields in the central coast region of California. In two of three trials, significantly fewer leafminer adults emerged from the plants sprayed with jasmonic acid than the plants that were left untreated. In these two trials, aphid control was erratic, and thrips were not significantly reduced on the treated plants although thrips were not common during the trials. Leafminer parasitoid population densities tracked the number of available leafminer hosts regardless of treatment. The only effect found in the third trial was that conventionally grown celery had more leafminer oviposition stings than either the plants treated with jasmonic acid or untreated control plants. Treatment of plants with jasmonic acid seems to hold promise as an alternative pest management tool.

Field sampling plans are proposed for monitoring Helicoverpa armigera (Hübner) populations on cotton and for threshold insecticide treatment in sub-Saharan Africa. The geostatistical analysis of the spatial distribution of bollworms validates systematic sampling (along a diagonal for example); systematic sampling is easier to perform than random sampling. The same negative binomial distribution was observed in Burkina Faso and Cameroon under controlled conditions, with or without insecticide treatment. The low infestation levels prevented the use of the approximate methods of Iwao or Kuno. Hence, exact confidence intervals not available in the literature are presented in graph form. Sequential and fixed size sampling methods are presented.

Pseudaletia unipuncta (Haworth) is a pest in Azorean pastures that causes up to 8% yield loss mainly during summer and early autumn. The objective of this research was to develop robust sampling plans based on larval spatial distribution. The number of larvae in three 60-m² plots on S. Miguel Island (Azores) was determined. Plots of 0.25 m² were the most accurate unit for estimating the population size. The relationship between mean and variance fitted both Taylor’s power law and Iwao’s patchiness regression model. Relationships to determine optimum sample sizes for fixed levels of precision based on both models were developed, but demanded a heavy sampling cost for the usual precision values (0.1–0.25). To reduce sampling effort, two sequential sampling plans were developed and compared, one based on Taylor’s parameters and the other based on Iwao’s parameters. For a precision of 0.25, Taylor’s sequential sampling plan led to an average 76% reduction of the sampling effort compared with sample sizes estimated for fixed levels of precision. Simulations of Iwao’s sequential sampling plan applied to larval counts correctly predicted a “treat” or “not-treat” decision for 91% of the cases. However, this plan estimated field densities with a lower degree of precision than Taylor’s plan and required a considerable increase in sampling effort for larval densities close to the critical mean. Use of Taylor’s sequential sampling plan should provide effective management of P. unipuncta in grass pastures and minimize sampling time and cost.

Plant morphological complexity could provide a physical refuge to prey and/or could interfere with foraging activities of a natural enemy. Few studies have rigorously tested the hypothesis that plant structural complexity influences the behavior of natural enemies and thus predator-prey interactions. Thus, we tested the hypotheses that increased plant morphological complexity reduces the predation efficacy and new area search efficiency of Coccinella septempunctata L. as a predator of the pea aphid Acyrthosiphon pisum Harris. Essential to testing these hypotheses is the use of near-isogenic lines of the pea plant. The Normal, tl, and aftl near-isogenic lines used in experiments manifest distinct levels of morphological complexity ranging from low to high complexity. Further, the use of these genetic isolines allowed us to control, as much as possible, for non-morphological plant characters such as phytochemicals and surface waxes. Increased plant morphological complexity decreased the predator’s efficacy with most aphids surviving on the aftl plant. Observations on the predator foraging activity suggest that complexity in the form of increased leaf edge to leaf area ratio and increased number of junctions reduced the new area search efficiency of the predator. This study supports the notion that plant complexity can interfere with the foraging success of insect predators.

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most important insect pest in rice, Oryza sativa L., in the United States. Prior research indicates that rice water weevils feed primarily on monocotyledonous plants. Many monocot weeds occur in rice fields, but little is known about rice water weevil-weed interactions in rice. Host utilization of the rice water weevil was evaluated on rice, cultivar ‘Cocodrie’, and seven weeds commonly found in rice fields in preference and life cycle compatibility tests in the greenhouse. Barnyardgrass, Echinochloa crus-galli Beauv., yellow nutsedge, Cyperus esculentus L., broadleaf signalgrass, Brachiaria platyphylla Nash., and fall panicum, Panicum dichotomiflorum Michx., were more preferred for oviposition than rice. More neonate larvae eclosed on barnyardgrass and yellow nutsedge than eclosed on rice. Densities of late instars feeding on roots of yellow nutsedge and broadleaf signalgrass were significantly lower than densities on rice. Barnyardgrass was also more preferred for adult feeding than rice and all other weeds. Rice water weevils were able to complete their life cycle on all plants examined except hemp sesbania, Sesbania exaltata (Rafin.) Cory, the only dicotyledonous plant species tested in the greenhouse. Several new hosts can be added to an existing list of host plants for the rice water weevil. Field surveys confirmed larvae infested roots of all weed species sampled in the greenhouse, as well as several other weed species. Many of the plants infested with larvae were dicotyledonous plants, suggesting that the host range of rice water weevil is much broader than previously reported.

The effects of a black wood stain, caused by one or more fungi, on the natural resistance of Alaskan yellow cedar (AYC), Chamacyparis nootkatensis (D. Don) Spach, to the Formosan subterranean termite, Coptotermes formosanus Shiraki, were studied. Feeding and survival of groups of 300 C. formosanus feeding on unstained Alaskan yellow cedar heartwood and sapwood and fully and partially black-stained heartwood were compared with a control group feeding on loblolly pine, Pinus taeda L., wood. All termite groups feeding on unstained AYC died by the end of 14 wk. At the end of 32 wk, mortality of termite groups feeding on fully and partially black-stained AYC was significantly higher than that of groups feeding on pine. Termite mortality was significantly higher when feeding on partially than on fully black-stained AYC at the end of 32 wk. Wood consumption was significantly different among all treatment groups, with means of 4.07, 8.76, 19.81, and 29.77 mg/d in the unstained, partially, and fully black-stained AYC, and loblolly pine, respectively. This suggests that toxic and feeding deterrence properties of AYC heartwood were significantly reduced by black-staining fungus infection but were not totally lost. Chemical analysis of unstained and black-stained AYC wood showed approximately a 50% reduction in concentration of secondary chemicals in the black-stained wood. Carvacrol was totally absent in the black-stained wood. Concentrations of nootkatone in the black-stained wood were one-fourth of those observed in unstained AYC wood. Ecological implications are discussed.

We treated two citrus cultivars with a complete fertilizer diluted to 25, 100, 200, or 400 ppm N to test whether increasing fertilizer concentration alters root and leaf chemistry and decreases resistance of citrus to root-feeding larvae of Diaprepes abbreviatus L. Roots and leaves of better-nourished ‘sour orange’ (Citrus aurantium L.) had larger amounts of total proteins and increased activities of enzymes associated with resistance than did plants given 25 ppm N. The fertilizer effect was less consistent for ‘Swingle citrumelo’ (C. paradise Macf. × Poncirus trifoliate L.), which has greater resistance to D. abbreviatus. Herbivory increased root protein content and peroxidase but decreased activities of chitinase and β-1,3-glucanase, which are enzymes associated with resistance to microbial pathogens. When significant, the effect of root herbivory on enzyme activities in leaves was opposite the effects on roots. Fertilizer and herbivory rarely interacted, indicating enzyme induction was not a function of nutrient supply. Fertilizer did not affect total phenolics in roots of either citrus, but root herbivory increased levels in ‘sour orange’. Despite elevated levels of putative defense proteins, ‘sour orange’ given ≥100 ppm N produced 50% greater total larval mass per pot than did plants given 25 ppm N. Fertilizer concentration did not affect mass of larvae on ‘Swingle citrumelo’ roots and did not affect larval mortality for either citrus cultivar. Our results concerning a root herbivore are consistent with the body of studies of folivores that have demonstrated that increased fertilizer has no effect or increases herbivore performance.

The influence of garden symphylan (Scutigerella immaculata Newport) root feeding on crop health was measured in the laboratory and in the field. In the laboratory, the relative susceptibility of sweet corn (Zea mays L.), potato (Solanum tuberosum L.), spinach (Spinacia oleracea L.), and tomato (Lycopersicon esculentum L.) to S. immaculata feeding was investigated by subjecting each crop to three levels of pest pressure (0, 15, and 45 S. immaculata). As S. immaculata densities increased from 0 to 45, root length and dry weight of above-ground plant parts of 1-wk-old spinach and tomato seedlings were reduced from 85 to 98%, whereas corn root length was reduced by 34%. Potato and corn dry weight and potato root length were not reduced. The pest-host association was investigated in the field by examining the relationships between estimated S. immaculata densities and two vegetational parameters: (1) crop health measured by the normalized difference vegetation index (NDVI) and (2) post-tillage spring weed densities. S. immaculata densities were estimated using a baiting method. NDVI in corn and potato was only slightly reduced with increasing within-field S. immaculata densities after adjusting for spatial autocorrelation. Squash and broccoli showed sharp decreases in NDVI at densities from 1 to 10 S. immaculata. The nonlinear asymptotic form of the Bleasdale-Nelder curve was selected as the best curve to describe the damage/pest relationship for all crops using Akaike information criteria. The relative susceptibilities of direct seeded crop varieties to S. immaculata in western Oregon reported in 1937 by Morrison were reanalyzed to make comparisons with our data. In further analysis, seed size seemed to be linearly related with susceptibility of direct-seeded crops to S. immaculata. Stand count was predicted to increase by 0.24% for each 1-mg increase in seed size. These findings will be used to help develop action thresholds and sample size requirements and to help reduce S. immaculata damage by avoiding the planting of highly susceptible crops at sites with high S. immaculata populations.

The bark beetle, Ips confusus (LeConte), provides an opportunity to study the influence of past geologic events and host use on lineage diversification of a herbivorous insect. This beetle mainly feeds on two pinyon pine (Pinus) species, but it has been collected from other conifer species. Isolation by host may contribute to lineage diversity and population structure. Alternatively, the repeat fragmentation of pine and beetle populations during the Pleistocene may explain population structure. We performed cladistic and nested clade analyses of mitochondrial DNA cytochrome oxidase I (mtDNA COI) sequence data from 95 I. confusus individuals collected from two hosts, P. monophyllae and P. edulis, and an atypical host, spruce (Picea pungens), from 10 western United States populations. Thirty-one most-parsimonious trees of 15 COI haplotypes demonstrated little association between host species and monophyletic groups. Thus, host use does not appear to contribute to genetic structure among populations. Nested clade analysis revealed three main haplotype lineages, each associated with eastern, southwestern, and western geographic localities. Estimation of the time to the most recent common ancestor places the start of lineage divergence during the Pleistocene (≈836,000 yr ago). Past glaciation events better explain genetic population structure among I. confusus populations.

Colony and population genetic structure was determined for Reticulitermes flavipes (Kollar) and Reticulitermes virginicus (Banks) collected from Sentricon Termite Colony Elimination System monitoring stations at an apartment complex in Raleigh, NC. Once in each of 2000, 2001, and 2002, samples of termites were collected from monitoring stations just before the installation of bait tubes containing 0.5% hexaflumuron. Twenty workers from each sample were genotyped at five microsatellite loci. Comparison of worker genotypes among samples provided unambiguous colony associations. Analysis of worker genotypes within colonies coupled with estimates of F-statistics and nestmate relatedness showed that three fourths (30) of the 41 R. flavipes colonies and all three of the R. virginicus colonies were simple families headed by pairs of outbred monogamous reproductives. The remaining R. flavipes colonies were extended families, apparently headed by a few neotenic reproductives. Most colonies appeared to be localized, occupying only a single monitoring station. Termite pressure was initially heavy, with up to five colonies present around a single building simultaneously, but it progressively decreased over time. Of 35 R. flavipes colonies and 1 R. virginicus colony baited in 2000 or 2001, only a single R. flavipes colony was found again 1 yr later, but this colony was not detected the following year. These results suggest that although treatment with hexaflumuron bait successfully suppresses or eliminates Reticulitermes spp. colonies, new colonies can quickly move into areas vacated by treated colonies, but over time continuous baiting can reduce termite pressure and effectively protect structures.