Showing papers in "Environmental Entomology in 2016"

Landscape and Local Correlates of Bee Abundance and Species Richness in Urban Gardens.

Abstract: Urban gardens may preserve biodiversity as urban population densities increase, but this strongly depends on the characteristics of the gardens and the landscapes in which they are embedded. We investigated whether local and landscape characteristics are important correlates of bee (Hymenoptera: Apiformes) abundance and species richness in urban community gardens. We worked in 19 gardens in the California central coast and sampled bees with aerial nets and pan traps. We measured local characteristics (i.e., vegetation and ground cover) and used the USGS National Land Cover Database to classify the landscape surrounding our garden study sites at 2 km scales. We classified bees according to nesting type (i.e., cavity, ground) and body size and determined which local and landscape characteristics correlate with bee community characteristics. We found 55 bee species. One landscape and several local factors correlated with differences in bee abundance and richness for all bees, cavity-nesting bees, ground-nesting bees, and different sized bees. Generally, bees were more abundant and species rich in bigger gardens, in gardens with higher floral abundance, less mulch cover, more bare ground, and with more grass. Medium bees were less abundant in sites surrounded by more medium intensity developed land within 2 km. The fact that local factors were generally more important drivers of bee abundance and richness indicates a potential for gardeners to promote bee conservation by altering local management practices. In particular, increasing floral abundance, decreasing use of mulch, and providing bare ground may promote bees in urban gardens.

Cold Tolerance of Halyomorpha halys (Hemiptera: Pentatomidae) Across Geographic and Temporal Scales.

Abstract: The brown marmorated stink bug, Halyomorpha halys (Stal), is native to eastern Asia and is presently invading North America. Little is known about the exposure to and effects of winter temperatures in newly invaded regions on H. halys The overwintering habitats that this species utilizes vary greatly in their thermal buffering capacity. They naturally overwinter in aggregations beneath loose bark on trees and in cliff outcroppings, but will also commonly aggregate in buildings. Effects of cold temperatures such as mortality and freezing have yet to be quantified in the invading population. We report that H. halys is chill intolerant (i.e., dies before reaching its freezing point), and that the degree of cold tolerance of populations in North America differs by season, sex, and acclimation location. The mean winter supercooling point (± SEM) of individuals acclimated in Minnesota was -17.06 °C ± 0.13 and in Virginia was -13.90 °C ± 0.09. By using laboratory assays of lower lethal temperatures and ambient air temperature records, we accurately forecasted mortality for field experiments in Minnesota and Virginia. Temperature refugia provided by human-built structures are likely crucial for overwintering survival during atypically cold winters and possibly contribute to the northern geographic range expansion of this economically damaging insect in the temperate climates of North America.

Developmental Acclimation of Drosophila suzukii (Diptera: Drosophilidae) and Its Effect on Diapause and Winter Stress Tolerance.

Abstract: We investigated the influence of developmental conditions on adult morphology, reproductive arrest, and winter stress tolerance of the invasive pest of small fruit, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). Cooler rearing temperatures (15 °C) resulted in larger, darker "winter morph" (WM) adults than "summer morph" flies reared at optimal temperatures (25 °C). Abdominal pigmentation scores and body size measurements of laboratory-reared WMs were similar to those of D. suzukii females captured in late autumn in Geneva, NY. We evaluated reproductive diapause and cold hardiness in live-captured D. suzukii WMs as well as WMs reared in the laboratory from egg to adult under four developmental conditions: static cool temperatures (SWM; 15 °C, 12:12 h L:D), fluctuating temperatures (FWM; 20 °C L: 10 °C D, 12:12 h L:D), and static cool temperatures (15 °C, 12:12 h L:D) followed by posteclosion chilling (CWM; 10 °C) under short-day (SD; 12:12 h L:D) or long-day photoperiods (LD; 16:8 h L:D). Live-captured D. suzukii WMs and CWMs had longer preoviposition times than newly eclosed summer morph adults, indicating a reproductive diapause that was not observed in SWMs or FWMs. Additionally, recovery after acute freeze stress was not different between CWM-SD females and live captured WM females. More 7-d-old CWMs survived 0, -1, or - 3 °C freeze stress than summer morph adults, and more CWM-SD adults survived -3 °C freeze stress than CWM-LD adults. Survival after -3 °C freeze stress was significantly higher in diapausing, CWMs than nondiapausing SWMs and FWMs.

Essential Amino Acid Supplementation by Gut Microbes of a Wood-Feeding Cerambycid.

Abstract: Insects are unable to synthesize essential amino acids (EAAs) de novo, thus rely on dietary or symbiotic sources for them. Wood is a poor resource of nitrogen in general, and EAAs in particular. In this study, we investigated whether gut microbiota of the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), a cerambycid that feeds in the heartwood of healthy host trees, serve as sources of EAAs to their host under different dietary conditions. δ(13)C-stable isotope analyses revealed significant δ(13)C-enrichment (3.4 ± 0.1‰; mean ± SEM) across five EAAs in wood-fed larvae relative to their woody diet. δ(13)C values for the consumers greater than 1‰ indicate significant contributions from non-dietary EAA sources (symbionts in this case). In contrast, δ(13)C-enrichment of artificial diet-fed larvae (controls) relative to their food source was markedly less (1.7 ± 0.1‰) than was observed in wood-fed larvae, yet still exceeded the threshold of 1‰. A predictive model based on δ(13)CEAA signatures of five EAAs from representative bacterial, fungal, and plant samples identified symbiotic bacteria and fungi as the likely supplementary sources of EAA in wood-fed larvae. Using the same model, but with an artificial diet as the dietary source, we identified minor supplementary bacterial sources of EAA in artificial diet-fed larvae. This study highlights how microbes associated with A. glabripennis can serve as a source of EAAs when fed on nutrient-limited diets, potentially circumventing the dietary limitations of feeding on woody substrates.

Host Plant Effects on Halyomorpha halys (Hemiptera: Pentatomidae) Nymphal Development and Survivorship

Abstract: Halyomorpha halys (Stal) (Hemiptera: Pentatomidae) is a highly polyphagous invasive species and an important pest of orchard crops in the United States. In the Mid-Atlantic region, wild hosts of H. halys are common in woodlands that often border orchards, and H. halys movement from them into orchards poses ongoing management issues. To improve our understanding of host plant effects on H. halys populations at the orchard-woodland interface, nymphal survivorship, developmental duration, and adult fitness (size and fresh weight) on apple (Malus domestica Borkh.), peach (Prunus persica (L.) Batsch), Tree of Heaven (Ailanthus altissima (Mill.) Swingle), and northern catalpa (Catalpa speciosa (Warder)) were examined in laboratory studies. Specifically, we investigated nymphal performance on the foliage and fruiting structures of those hosts and on single- versus mixed-host diets, as well as the effects of host phenology on their suitability. Nymphal performance was poor on a diet of foliage alone, regardless of host. When fruiting structures were combined with foliage, peach was highly suitable for nymphal development and survivorship, whereas apple, Tree of Heaven, and catalpa were less so, although nymphal survival on Tree of Heaven was much greater later in the season than earlier. Mixed-host diets yielded increased nymphal survivorship and decreased developmental duration compared with diets of suboptimal single hosts. Adult size and weight were generally greater when they developed from nymphs reared on mixed diets. The implications of our results to the dispersal behavior, establishment, and management of H. halys are discussed.

On-Plant Larval Movement and Feeding Behavior of Fall Armyworm (Lepidoptera: Noctuidae) on Reproductive Corn Stages.

Abstract: Spodoptera frugiperda J.E. Smith (fall armyworm) is considered one of the most destructive pests of corn throughout the Americas. Although this pest has been extensively studied, little is known about its larval movement and feeding behavior on reproductive compared to vegetative corn stages. Thus, we conducted studies with two corn stages (R1 and R3) and four corn plant zones (tassel, above ear, ear zone, and below ear) in the field at Concord, NE (USA), and in the field and greenhouse at Botucatu, SP (Brazil), to investigate on-plant larval movement. The effects of different corn tissues (opened tassel, closed tassel, silk, kernel, and leaf), two feeding sequence scenarios (closed tassel-leaf-silk-kernel and leaf-silk-kernel), and artificial diet (positive control) on larval survival and development were also evaluated in the laboratory. Ear zone has a strong effect on feeding choice and survival of fall armyworm larvae regardless of reproductive corn stage. Feeding site choice is made by first-instar. Corn leaves of reproductive plants were not suitable for early instar development, but silk and kernel tissues had a positive effect on survival and development of fall armyworm larvae on reproductive stage corn.

Paradigms in Eastern Spruce Budworm (Lepidoptera: Tortricidae) Population Ecology: A Century of Debate.

Abstract: Three main hypotheses have been postulated over the past century to explain the outbreaking population dynamics of eastern spruce budworm, Choristoneura fumiferana (Clemens). The Silviculture Hypothesis first arose in the 1920s, with the idea that outbreaks were driven by forestry practices favoring susceptible softwood species. In the 1960s, it was proposed that populations were governed by Multiple Equilibria, with warm weather conditions releasing low-density populations from the regulatory control of natural enemies. Dispersal from outbreak foci, or “epicenters,” was seen as causing widespread outbreaks that eventually collapsed following resource depletion. However, in the 1980s, following the re-analysis of data from the 1940s outbreak in New Brunswick, this interpretation was challenged. The alternative Oscillatory Hypothesis proposed that budworm population dynamics were governed by a second-order density-dependent process, with oscillations being driven by natural enemy–victim interactions. Under this hypothesis, weather and resource availability contribute to secondary fluctuations around the main oscillation, and weather and moth dispersal serve to synchronize population cycles regionally. Intensive, independent population studies during the peak and declining phases of the 1980s outbreak supported the principal tenet of the Oscillatory Hypothesis, but concluded that host plant quality played a more important role than this hypothesis proposed. More recent research on the early phase of spruce budworm cycles suggests that mate-finding and natural-enemy-driven Allee effects in low-density populations might be overcome by immigration of moths, which can facilitate the onset of outbreaks. Even more recent research has supported components of all three hypotheses attempting to explain spruce budworm dynamics. In the midst of a new rising outbreak (2006-present), we discuss the evolution of debates surrounding these hypotheses from a historic perspective, examine gaps in current knowledge, and suggest avenues for future research (e.g., intensive studies on low-density populations) to better understand and manage spruce budworm populations.

Alightment of Spotted Wing Drosophila (Diptera: Drosophilidae) on Odorless Disks Varying in Color.

Abstract: Methods for trapping spotted wing drosophila, Drosophila suzukii (Matsmura) (Diptera: Drosophilidae), have not yet been optimized for detecting this devastating pest of soft-skinned fruits. Here, we report outcomes of choice and no-choice laboratory bioassays quantifying the rates of spotted wing drosophila alightment on 5-cm-diameter sticky disks of various colors, but no fruit odors. Red, purple, and black disks captured the most spotted wing drosophila when presented against a white background. Male and female spotted wing drosophila responded identically in these tests. Significantly more D. suzukii were captured on the red and yellow disks than those presenting the corresponding grayscale for that color, proving that D. suzukii perceives colors and not just the level of target brightness. Fluorescent red is the best candidate for trap color, while clear and white are the least desirable. However, when the background was switched to black, all nonfluorescent colors were equally acceptable to spotted wing drosophila, suggesting that background must be specified when reporting spotted wing drosophila color preference. Additional spotted wing drosophila research is justified on the effects of target color against natural backgrounds.

Generalist Behavior Describes Pollen Foraging for Perceived Oligolectic and Polylectic Bees.

Abstract: Native bees provide essential pollination services to cultivated and wild plants worldwide. Despite the need to conserve pollinators, the foraging patterns of native bees are poorly understood. Classic concepts of resource use have typically categorized bee species as specialists or generalists based on floral visitation patterns. While intraspecific variation in bee foraging likely depends on local land use, sex, and phenological period, among other factors, these potential drivers of floral visitation are rarely explicitly investigated. In this study, we explore the potential for inter- and intra-specific variation in floral visitation by investigating the pollen loads of two solitary, similarly sized, ground-nesting native bee species within the Apinae, Melissodes tepaneca (Cresson) and Diadasia rinconis (Cockerell), categorized as generalist and specialist based on past floral visitation studies, respectively. Our analyses reveal generalist foraging and indicate that natural habitat availability significantly drives pollen load composition for both species. The putative specialist, D. rinconis, exhibited significant differences in pollen load composition between males and females, between pan and net collection methods, and between the different phenological periods. The putative generalist, M. tepaneca, exhibited significant differences in pollen load composition between the sexes, but only in the late season. Both species exhibited significant preference levels for multiple native plant species across the study region. Given that pollen collection is essential for native bee population persistence across natural and human-dominated habitats, our findings suggest consideration of both pollen collection and floral visitation patterns to holistically describe floral usage and develop pollinator conservation strategies.

Fungal Associates of the Xylosandrus compactus (Coleoptera: Curculionidae, Scolytinae) Are Spatially Segregated on the Insect Body.

Abstract: Studies of symbioses have traditionally focused on explaining one-to-one interactions between organisms. In reality, symbioses are often much more dynamic. They can involve many interacting members, and change depending on context. In studies of the ambrosia symbiosis-the mutualism between wood borer beetles and fungi-two variables have introduced uncertainty when explaining interactions: imprecise symbiont identification, and disregard for anatomical complexity of the insects. The black twig borer, Xylosandrus compactus Eichhoff, is a globally invasive ambrosia beetle that infests >200 plant species. Despite many studies on this beetle, reports of its primary symbionts are conflicting. We sampled adult X. compactus and infested plant material in central Florida to characterize the fungal symbiont community using dilution series, beetle partitioning, and DNA-based identification. X. compactus was consistently associated with two fungal taxa, Fusarium spp. and Ambrosiella xylebori Multivariate analyses revealed that A. xylebori was strongly associated with the beetle mycangium while Fusarium spp. were associated with the abdomen and external surfaces. The Fusarium spp. carried by X. compactus are not members of the Ambrosia Fusarium Clade, and are probably not mutualists. Fungal community composition of the mycangium was less variable than external body surfaces, thus providing a more consistent fungal inoculum. This is the first report of spatial partitioning as a mechanism for maintenance of a multimember ambrosia fungus community. Our results provide an explanation for discrepancies among previous reports, and suggest that conflicting results are not due to differences in symbiont communities, but due to inconsistent and incomplete sampling.

Lethal and Sublethal Effects of Essential Oils From Artemisia khorassanica and Vitex pseudo-negundo Against Plodia interpunctella (Lepidoptera: Pyralidae)

Abstract: Plodia interpunctella (Hubner, 1813) is a polyphagous and key pest of different stored products worldwide. The lethal and sublethal effects of essential oils of Artemisia khorassanica Podl. and Vitex pseudo-negundo (Hausskn) were studied on P. interpunctella The chemical constituents of the essential oils were also assessed using gas chromatography-mass spectrometry. Assays showed that the fumigant toxicity of A. khorassanica (LC50: 9.60 µl/liter air) was higher than V. pseudo-negundo (LC50: 23.05 µl/liter air). Moreover, the speed of mortality caused by A. khorassanica oil (LT50: 2.07 h) was higher than V. pseudo-negundo (LT50: 3.11 h). To assess the sublethal effects of the essential oils, adult moths were exposed to the LC30 of each essential oil, and life table parameters and energy contents of the surviving P. interpunctella were studied. Exposure to sublethal concentration of A. khorassanica negatively affected the life table of P. interpunctella, and also the protein, lipid, and glycogen contents of the larvae that came from treated adults. Vitex pseudo-negundo also affected lipid, protein, and glycogen contents of P. interpunctella The intrinsic rate of increase (rm), finite rate of increase ([Formula: see text]), and doubling time (DT) were not significantly different between control and V. pseudo-negundo treatment. According with these results, both tested essential oils, especially one extracted from A. khorassanica, have potential applications for the integrated management of P. interpunctella.

Food Limitation Affects Parasite Load and Survival of Bombus impatiens (Hymenoptera: Apidae) Infected With Crithidia (Trypanosomatida: Trypanosomatidae).

Abstract: Bumble bees (genus Bombus) are globally important insect pollinators, and several species have experienced marked declines in recent years. Both nutritional limitation and pathogens may have contributed to these declines. While each of these factors may be individually important, there may also be synergisms where nutritional stress could decrease pathogen resistance. Understanding interactions between bumble bees, their parasites, and food availability may provide new insight into the causes of declines. In this study, we examined the combined impacts of pollen and nectar limitation on Crithidia, a common gut parasite in Bombus impatiens Cresson. Individual worker bees were inoculated with Crithidia and then assigned in a factorial design to two levels of pollen availability (pollen or no pollen) and two nectar sugar concentrations (high [30%] or low [15%] sucrose). We found that lack of pollen and low nectar sugar both reduced Crithidia cell counts, with the most dramatic effect from lack of pollen. Both pollen availability and nectar sugar concentration were also important for bee survival. The proportion of bees that died after seven days of infection was ∼25% lower in bees with access to pollen and high nectar sugar concentration than any other treatment. Thus, nectar and pollen availability are both important for bee survival, but may come at a cost of higher parasite loads. Our results illustrate the importance of understanding environmental context, such as resource availability, when examining a host-parasite interaction.

Behavioral Responses of Drosophila suzukii (Diptera: Drosophilidae) to Visual Stimuli Under Laboratory, Semifield, and Field Conditions.

Abstract: Drosophila suzukii Matsumura (Diptera: Drosophilidae) is an invasive pest in North America and Europe that attacks soft-skinned ripening fruit such as raspberries, blackberries, and blueberries. Little is known regarding the specific cues D. suzukii utilizes to locate and select host fruit, and inconsistencies in trap performance indicate the need for the development of improved monitoring and management techniques for this insect. Our studies focused on identifying attractive visual cues for adult D. suzukii and incorporating these cues into a potential attract-and-kill tactic for D. suzukii management. We evaluated D. suzukii response to color, shape, and size-specific stimuli. For color, we evaluated 10.2-cm-diameter spheres painted black, red, purple, orange, green, yellow, blue, or white. Shape stimuli (254 cm3 surface area) included sphere, cube, pyramid, inverted pyramid, vertical or horizontal cylinder and were painted red. Size stimuli included red 2.5-, 10.2-, 15.2-, and 25.4-cm-diameter spheres. Trials were conducted under laboratory, semifield, and field conditions. For color, adults preferred black and red spheres to all other colors evaluated. Among shapes, there was no significant preference. For size, larger spheres captured significantly more D. suzukii compared with a small 2.5-cm-diameter sphere. Determining D. suzukii visual preference will aid in trapping and behaviorally based management programs.

Local Plant Diversity Across Multiple Habitats Supports a Diverse Wild Bee Community in Pennsylvania Apple Orchards.

Abstract: Wild pollinators supply essential, historically undervalued pollination services to crops and other flowering plant communities with great potential to ensure agricultural production against the loss of heavily relied upon managed pollinators. Local plant communities provision wild bees with crucial floral and nesting resources, but the distribution of floristic diversity among habitat types in North American agricultural landscapes and its effect on pollinators are diverse and poorly understood, especially in orchard systems. We documented floristic diversity in typical mid-Atlantic commercial apple (Malus domestica Borkh.) orchards including the forest and orchard-forest edge ("edge") habitats surrounding orchards in a heterogeneous landscape in south-central Pennsylvania, USA. We also assessed the correlation between plant richness and orchard pollinator communities. In this apple production region, edge habitats are the most species rich, supporting 146 out of 202 plant species recorded in our survey. Plant species richness in the orchard and edge habitats were significant predictors of bee species richness and abundance in the orchard, as well as landscape area of the forest and edge habitats. Both the quantity and quality of forest and edges close to orchards play a significant role in provisioning a diverse wild bee community in this agroecosystem.

Parasitism and Predation on Sentinel Egg Masses of the Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) in Three Vegetable Crops: Importance of Dissections for Evaluating the Impact of Native Parasitoids on an Exotic Pest.

Abstract: We conducted a survey to examine parasitism, predation, and the species composition of native parasitoids attacking sentinel egg masses of the invasive pest, the brown marmorated stink bug, Halyomorpha halys (Stal), in bell pepper, squash, and tomato. A 2-yr survey was conducted for each crop. The species composition of parasitoids was determined for parasitoids that successfully emerged from eggs, parasitoids that were identified from dissections, and parasitoids that were found attending egg masses at the time of collection. The overall rate of brown marmorated stink bug nymphal emergence was 82.7% from laboratory-reared control egg masses compared with only 23.4% from sentinel egg masses due to a combination of predation, parasitism, and unknown mortality causes. Overall, 12.4% of sentinel eggs were parasitized. Parasitoids emerged successfully from only 2.3% of eggs, but they were dissected from an additional 10.1% of eggs. Telenomus podisi Ashmead was the predominant species identified from emerged parasitoids (57.4%), dissected parasitoids (90.2%), and parasitoids attending egg masses (77%). This study provides further evidence that the impact of native parasitoids on brown marmorated stink bug egg mortality may be greatly underestimated based solely on parasitoid emergence rates alone.

Defining the Insect Pollinator Community Found in Iowa Corn and Soybean Fields: Implications for Pollinator Conservation.

Abstract: Although corn (Zea mays L.) and soybeans (Glycine max L.) do not require pollination, they offer floral resources used by insect pollinators. We asked if a similar community of insect pollinators visits these crops in central Iowa, a landscape dominated by corn and soybean production. We used modified pan traps (i.e., bee bowls) in both corn and soybean fields during anthesis and used nonmetric multidimensional scaling (NMS) to compare the communities found in the two crops. Summed across both crops, 6,704 individual insects were captured representing at least 60 species, morphospecies, or higher-level taxa. Thirty-four species were collected in both crops, 19 collected only in corn and seven were collected only in soybean. The most abundant taxa were Lasioglossum [Dialictus] spp., Agapostemon virescens Cresson, Melissodes bimaculata (Lepeletier), and Toxomerus marginatus (Say), which accounted for 65% of the insect pollinators collected from both crops. Although social bees (Apis mellifera L. and Bombus spp.) were found in both crops, they accounted for only 0.5% of all insects captured. The NMS analysis revealed a shared community of pollinators composed of mostly solitary, ground nesting bees. Many of these species have been found in other crop fields throughout North America. Although corn and soybean are grown in landscapes that are often highly disturbed, these data suggest that a community of pollinators can persist within them. We suggest approaches to conserving this community based on partnering with activities that aim to lessen the environmental impact of annual crop production.

Effects of Temperature and Photoperiod on the Reproductive Biology and Diapause of Oobius agrili (Hymenoptera: Encyrtidae), an Egg Parasitoid of Emerald Ash Borer (Coleoptera: Buprestidae).

Abstract: Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) is a solitary egg parasitoid of the invasive emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), and has been introduced to the United States for classical biological control. We characterized the weekly survivorship, fecundity, and diapause patterns of both diapaused and nondiapaused populations of O. agrili under four different temperature–photophase combinations: 30°C (warm) and 20°C (cold) temperatures with both long-day (16 h) and short-day (8 h) photophase. Results of this study showed that regardless of the length of photophase, parental parasitoids of both diapaused and nondiapaused O. agrili survived significantly longer at 20°C than at 30°C. Both populations also laid their eggs faster at 30°C compared with those at 20°C. Higher proportions of the progeny produced by both populations of O. agrili were induced into diapause by short-day (8 h) photophase, regardless of rearing temperature. In addition, the diapaused parasitoids in the short-day photophase treatment at both warm and cold temperatures produced increasing proportions of diapaused progeny over time, whereas no significant differences were observed in the proportions of diapaused progeny by the nondiapaused parasitoids over different sampling times. These findings suggest that O. agrili should be continuously reared under warm temperature and long-day photoperiod (to avoid diapause for increased reproduction). In addition, we recommend that diapaused adults be used for field releases in early summer when temperatures are still relatively low (∼20°C) and host eggs are available so that they can produce multiple generations prior to overwintering.

Manipulation of Frankliniella occidentalis (Thysanoptera: Thripidae) by Tomato Spotted Wilt Virus (Tospovirus) Via the Host Plant Nutrients to Enhance Its Transmission and Spread.

Abstract: Earlier studies have shown that Tomato spotted wilt virus (TSWV) influences the biology, performance, and behavioral patterns of its vector Frankliniella occidentalis Pergande. In this study, using Capsicum annuum L. as the host plant, we aimed to determine the manipulation of F. occidentalis by TSWV through switching of the diet (+ or −TSWV) during vector’s development. Behavioral patterns, fitness, as well as vector performance were evaluated. The specific parameters investigated included longevity/survival, fecundity, development time, feeding, and preferential behavior. F. occidentalis were reared on either TSWV-infected (exposed) or healthy leaves (non-exposed) throughout their larval stages. The emerging adults were then individually transferred to either healthy or TSWV-infected leaf disks. This resulted into four treatments, consisting of exposed or non-exposed thrips reared on either infected or healthy leaf disks as adults. All F. occidentalis exposed to TSWV in their larval stages had shorter development time regardless of the adults’ diet. Whereas, the ones that were later reared on healthy leaf disks as adults recorded the highest longevity and reproduction rate. Furthermore, adults of F. occidentalis that were exposed to TSWV in their larval stages showed preference toward healthy leaf disks (−TSWV), whereas the non-exposed significantly preferred the infected leaf disks (+TSWV). These are further indications that TSWV modifies the nutritional content of its host plants, which influences vector’s biology and preferential behavior, in favor of its multiplication and dispersal. The findings offer additional explanation to the often aggressive spread of the virus in crop stands.

The Effects of Crop Intensification on the Diversity of Native Pollinator Communities.

Abstract: Increases in agricultural conversion are leading to declines in native grasslands and natural resources critical for beneficial insects. However, little is known regarding how these changes affect pollinator diversity. Land use types were categorized within 300 m and 3 km radii of pollinator sampling locations in Brookings County, SD. Pollinator abundance and species richness were regressed on the proportion of the landscape dedicated to row crops, grass and pasture, forage crops, small grains, and aquatic habitats using variance components modeling. Row crops had a negative effect on bee abundance at 300 m, after fixed effects modeling accounted for outliers skewing this relationship. At 3 km, corn positively affected bee abundance and richness, while soybean acreage decreased species richness. The landscape matrix of outlying sites consisted of large monocultured areas with few alternative habitat types available, leading to inflated populations of Melissodes and Halictidae. Syrphids had a positive parabolic relationship between diversity and row crops, indicating potential for competitive exclusion from intermediate landscapes. Unlike other studies, landscape diversity within 300 m was not found to significantly benefit pollinator diversity. Within especially agriculturally developed areas of the region, high abundances of pollinators suggest selection for a few dominant species. There was no effect of forage crops or aquatic habitats on pollinator diversity, indicating that less highly managed areas still represent degraded habitat within the landscape. Incorporating pollinator-friendly crops at the farm level throughout the region is likely to enhance pollinator diversity by lessening the negative effects of large monocultures.

Identifying a Potential Trap Crop for a Novel Insect Pest, Halyomorpha halys (Hemiptera: Pentatomidae), in Organic Farms

Abstract: The invasive brown marmorated stink bug, Halyomorpha halys, poses significant risk to organic farming systems because they rely on biological control, nonsynthetic inputs, and cultural tactics for pest management. This study evaluated the potential of five crop plants (sorghum, admiral pea, millet, okra, and sunflower) to be used as trap crops under organic production in four mid-Atlantic states. Stink bug (H. halys and endemic species) densities and host plant phenologies were recorded weekly (mid-June through September). Sorghum attracted significantly more H. halys than the other crops evaluated, followed by sunflower and okra. Seasonal average H. halys density was 1.5-4× higher on sorghum than the other crops (P < 0.05), depending on site. Endemic stink bugs were equally attracted to all crops except admiral pea. A significant effect of time was detected (P < 0.0001), with H. halys densities initially higher on sunflower; as the sunflower senesced, sorghum supported significantly higher average H. halys densities. While sunflower and sorghum phenologies differed, these crops together provided a 5-wk attraction period coinciding with peak H. halys activity. The efficacies of pheromone-baited traps, flaming, applying OMRI-approved insecticides (Azera and Venerate), and vacuuming to removing stink bugs were evaluated as a management tactic. Flaming was the most effective treatment against H. halys and endemic stink bugs. Our results suggest that a trap crop composed of sorghum and sunflower may be an effective management tool for the mid-Atlantic stink bug complex, including H. halys. Future research should address the appropriate size and placement of trap crop within the farm.

Pheromone lure and trap color affects bycatch in agricultural landscapes of Utah

Abstract: Aerial traps, using combinations of color and attractive lures, are a critical tool for detecting and managing insect pest populations. Yet, despite improvements in trap efficacy, collection of nontarget species ("bycatch") plagues many insect pest surveys. Bycatch can influence survey effectiveness by reducing the available space for target species and increasing trap screening time, especially in areas where thousands of insects are captured as bycatch in a given season. Additionally, bycatch may negatively impact local nontarget insect populations, including beneficial predators and pollinators. Here, we tested the effect of pheromone lures on bycatch rates of Coccinellidae (Coleoptera), Apoidea (Hymenoptera), and nontarget Lepidoptera. Multicolored (primarily yellow and white) bucket traps containing a pheromone lure for capturing one of three survey target species, Spodoptera litura (F.), S. littoralis (Boisduval), or Helicoverpa armigera (Hubner), were placed in alfalfa and corn fields, and compared to multicolored traps without a pheromone lure. All-green traps with and without H. armigera lures were employed in a parallel study investigating the effect of lure and trap color on bycatch. Over 2,600 Coccinellidae representing seven species, nearly 6,400 bees in 57 species, and >9,000 nontarget moths in 17 genera were captured across 180 traps and seven temporal sampling events. Significant effects of lure and color were observed for multiple taxa. In general, nontarget insects were attracted to the H. armigera lure and multicolored trap, but further studies of trap color and pheromone lure specificity are needed to better understand these interactions and to minimize nontarget captures.

Native Bee Diversity and Pollen Foraging Specificity in Cultivated Highbush Blueberry (Ericaceae: Vaccinium corymbosum) in Rhode Island.

Abstract: We identified 41 species of native bees from a total of 1,083 specimens collected at cultivated highbush blueberry plantings throughout Rhode Island in 2014 and 2015. Andrena spp., Bombus spp., and Xylocopa virginica (L.) were collected most often. Bombus griseocollis (DeGeer), B. impatiens Cresson, B. bimaculatus Cresson, B. perplexus Cresson, and Andrena vicina Smith collected the largest mean numbers of blueberry pollen tetrads. The largest mean percent blueberry pollen loads were carried by the miner bees Andrena bradleyi Viereck (91%), A. carolina Viereck (90%), and Colletes validus Cresson (87%). The largest mean total pollen grain loads were carried by B. griseocollis (549,844), B. impatiens (389,558), X. virginica (233,500), and B. bimaculatus (193,132). Xylocopa virginica was the fourth and fifth most commonly collected bee species in 2014 and 2015, respectively. They exhibit nectar robbing and females carried relatively low blueberry pollen loads (mean 33%). Overall, we found 10 species of bees to be the primary pollinators of blueberries in Rhode Island.

Influence of CO2 and Temperature on Metabolism and Development of Helicoverpa armigera (Noctuidae: Lepidoptera).

Abstract: Climate change will have a major bearing on survival and development of insects as a result of increase in CO2 and temperature. Therefore, we studied the direct effects of CO2 and temperature on larval development and metabolism in cotton bollworm, Helicoverpa armigera (Hubner). The larvae were reared under a range of CO2 (350, 550, and 750 ppm) and temperature (15, 25, 35, and 45°C) regimes on artificial diet. Elevated CO2 negatively affected the larval survival, larval weight, larval period, pupation, and adult emergence, but showed a positive effect on pupal weight, pupal period, and fecundity. Increase in temperature exhibited a negative effect on larval survival, larval period, pupal weights, and pupal period, but a positive effect on larval growth. Pupation and adult emergence were optimum at 25°C. Elevated CO2 and temperature increased food consumption and metabolism of larvae by enhancing the activity of midgut proteases, carbohydrases (amylase and cellulase), and mitochondrial enzymes and therefore may cause more damage to crop production. Elevated CO2 and global warming will affect insect growth and development, which will change the interactions between the insect pests and their crop hosts. Therefore, there is need to gain an understanding of these interactions to develop strategies for mitigating the effects of climate change.

Overwintering Survival of Drosophila suzukii (Diptera: Drosophilidae) and the Effect of Food on Adult Survival in California's San Joaquin Valley.

Abstract: The overwintering survival and development of Drosophila suzukii Matsumura were investigated in California’s San Joaquin Valley. Drosophila suzukii were exposed to overwintering conditions in cages hung in a citrus orchard, and the pupae were buried in the soil. Eggs exposed from late November to January did not survive; a low percentage (<3%) of larvae and pupae developed into adults. Survival of pupae was significantly higher when buried in the soil than on the citrus tree. From late January to March, all life stages developed into adults and overwintered adult female D. suzukii produced eggs when provided with 10% honey-water and sliced oranges. Adult survival varied among fruit juice provision treatments and overwintering exposure periods, ranging from 3.4 ± 0.9 d (water) to 44.1 ± 3.0 d (10% honey-water). Fruit juices of apple, cherry, grape, orange, and pomegranate were tested as adult food sources; results showed that adult female and male D. suzukii lived only 2 d with water only, whereas adults survived from 14.2 to 34.8 d with fruit juice treatments and the 10% honey-water control. An unexpected event was the oviposition and immature development of D. suzukii with the fruit juice. In a follow-up laboratory trial, when 10% honey-water or orange juice were provided along with an artificial diet for oviposition and immature development, female D. suzukii survived for 21.6 ± 2.4 or 21.6 ± 1.5 d, and produced 106.8 ± 14.1 or 98.5 ± 13.1 offspring, respectively. We discuss factors potentially influencing overwintering survival of D. suzukii.

Identification of a Pheromone Component and a Critical Synergist for the Invasive Beetle Callidiellum rufipenne (Coleoptera: Cerambycidae).

Abstract: The invasive Asian cerambycid beetle Callidiellum rufipenne (Motschulsky), informally known as the Japanese cedar longhorned beetle, was first detected in North America in North Carolina in 1997. The beetle has since been detected in neighboring states and is expected to further expand its range. However, delineating the current distribution of C. rufipenne has been hindered by the lack of efficient sampling methods. Here, we present the results of research on the chemistry of volatile pheromones of C. rufipenne. Analyses of headspace odors revealed that males produce (R)-3-hydroxyhexan-2-one, with lesser amounts of (S)-3-hydroxyhexan-2-one, and (R)- and (S)-2-hydroxyhexan-3-one. In field bioassays conducted over several years in Connecticut, where populations of the beetle were well established, no reconstructed blend of these compounds was significantly attractive to beetles of either sex. However, during field trials in Japan that targeted another species, we discovered that adult male and female C. rufipenne were attracted to a blend of racemic 3-hydroxyhexan-2-one and a novel natural product, 1-(1H-pyrrol-2-yl)-1,2-propanedione. Attraction to (R)-3-hydroxyhexan-2-one and the pyrrole subsequently was confirmed in field trials in Connecticut. Although it is unclear why the pyrrole acts as a synergist for a species that apparently does not produce it, the serendipitous discovery that adult C. rufipenne are attracted by the blend of ketone and pyrrole provides a badly needed method for monitoring its ongoing range expansion within North America, and for detecting new introductions in other parts of the world.

Imaginal Feeding for Progression of Diapause Phenotype in the Two-Spotted Spider Mite (Acari: Tetranychidae)

Abstract: Adult females of the two-spotted spider mite (Tetranychus urticae Koch) enter diapause under conditions of short-day length and low temperature. A conspicuous body color change, from greenish yellow to bright orange, accompanies diapause induction. This pigmentation is attributed to accumulation of keto-carotenoids produced internally from β-carotene, which is a precursor of vitamin A essential for inducing diapause. The quantity of β-carotene transferred from females to eggs has been considered sufficient to induce diapause. Moreover, carotenoid biosynthesis genes were recently found in this mite. Therefore, imaginal feeding is not likely to be necessary to progress to diapause. In contrast, diapause-induced adult females have been known to feed between the last molt and the time of body color changes. Consequently, the function of imaginal feeding in diapause-induced females was largely unknown. We aimed to clarify whether imaginal feeding was essential to enter diapause. First, we verified that body color change occurred in connection with the feeding behavior, and also verified the change in the composition of carotenoids in diapausing females. Subsequently, we tested the effects of restraints on feeding after molting on carotenoid composition and diapausing rates. Body color change required imaginal feeding. Fed, but not unfed, females accumulated astaxanthin. Moreover, starvation reduced diapausing rates. We concluded that imaginal feeding between the last molt and the time of body color change was necessary to progress to the diapausing phenotype and that starvation at the adult stage reduced the percentage of adults entering reproductive diapause.

Antimicrobial activity of actinobacteria isolated from the guts of subterranean termites

Abstract: Subterranean termites need to minimize potentially pathogenic and competitive fungi in their environment in order to maintain colony health. We examined the ability of Actinobacteria isolated from termite guts in suppressing microorganisms commonly encountered in a subterranean environment. Guts from two subterranean termite species, Reticulitermes flavipes (Kollar) and Reticulitermes tibialis Banks, were extracted and plated on selective chitin media. A total of 38 Actinobacteria isolates were selected for in vitro growth inhibition assays. Target microbes included three strains of Serratia marcescens Bizio, two mold fungi (Trichoderma sp. and Metarhizium sp.), a yeast fungus (Candida albicans (C.P. Robin) Berkhout), and four basidiomycete fungi (Gloeophyllum trabeum (Persoon) Murrill, Tyromyces palustris (Berkeley & M.A. Curtis) Murrill, Irpex lacteus (Fries) Fries, and Trametes versicolor (L.) Lloyd). Results showed both broad and narrow ranges of antimicrobial activity against the mold fungi, yeast fungus, and S. marcescens isolates by the Actinobacteria selected. This suggests that termite gut-associated Actinobacteria produce secondary antimicrobial compounds that may be important for pathogen inhibition in termites. Basidiomycete fungi were strongly inhibited by the selected Actinobacteria isolates, with G. trabeum and T. versicolor being most inhibited, followed by I. lacteus and T. palustris The degree of inhibition was correlated with shifts in pH caused by the Actinobacteria. Nearly all Actinobacteria isolates raised pH of the growth medium to basic levels (i.e. pH ∼8.0-9.5). We summarize antimicrobial activity of these termite gut-associated Actinobacteria and examine the implications of these pH shifts.

Warming Accelerates Carbohydrate Consumption in the Diapausing Overwintering Peach Fruit Moth Carposina sasakii (Lepidoptera: Carposinidae)

Abstract: Climate warming provides a challenge for small insects persisting in cold seasons through diapause because they fail to accumulate and maintain adequate reserves to complete this stage successfully. One way of understanding this challenge is to follow physiological changes in these insects under higher temperatures, including the consumption and allocation of energy reserves during and after diapause. We simulated autumn and spring warming conditions to study carbohydrate consumption dynamics during diapause-post-diapause periods by monitoring shifts in carbohydrate levels in a facultative diapause species, the peach fruit moth Carposina sasakii Matsumura (Lepidoptera: Carposinidae). We found carbohydrates were rapidly consumed in the post-diapause phase, which might lead to a trade-off in the allocation of energy reserves between diapause maintenance and post-diapause development. This suggests that temperature increases in autumn and spring may alter diapause maintenance and post-diapause development through changing carbohydrate levels.

Contribution of Noncolonizing Aphids to Potato Virus Y Prevalence in Potato in Idaho.

Abstract: Potato virus Y (PVY) is a major concern for potato production in the United States given its impact on both crop quality and yield. Although green peach aphid, Myzus persicae (Sulzer), is the most efficient PVY vector, it may be less abundant in potato-growing areas of Idaho relative to non-potato-colonizing aphid vectors of PVY that may disperse from nearby cereal fields and other crops. A field study was conducted during 2012–2013 to examine if noncolonizing aphids disperse to nearby potato fields as cereal crops dry down before harvest. The aphid fauna was sampled weekly in four different potato fields in south-central and southeastern Idaho using yellow sticky traps and yellow pan traps. Potato fields were chosen with an adjacent cereal field such that the prevailing westerly wind would facilitate aphid dispersal from cereal fields to potato. Non-potato-colonizing aphids sampled included 10 cereal aphid species, the most abundant of which were Rhopalosiphum padi L. and Metopolophium dirhodum (Walker). More than 35 species from noncereal hosts also were found. Overall, green peach aphid abundance was relatively low, ranging from 0.5–2.5% of the total aphid capture between years and among fields. In both years and all locations, cereal aphid abundance peaked in mid- to late July (cereal ripening stage) and decreased thereafter as cereal crops dried. PVY prevalence in the potato fields increased following these increases in aphid abundance. This study suggests that cereal aphids and other noncolonizing aphids are important contributors to PVY prevalence in potato in southern Idaho.

The Effect of Conservation Tillage and Cover Crop Residue on Beneficial Arthropods and Weed Seed Predation in Acorn Squash.

Abstract: Conservation tillage combined with cover crops or mulching may enhance natural enemy activity in agroecosystems by reducing soil disturbance and increasing habitat structural complexity. In particular, weed seed predation can increase with vegetation cover and reduced tillage, indicating that mulches may improve the quality of the habitat for weed seed foraging. The purpose of this study was to quantify the effects of tillage and mulching for conservation biological control in cucurbit fields. The effects of mulch and reduced tillage on arthropods and rates of weed seed loss from arenas were examined in field trials on sandy soils in 2014 and 2015. Experimental factors included tillage and cover crop, each with two levels: strip-tillage or full-tillage, and cover crop mulch (rye residue) or no cover crop mulch (unmulched). Arthropod abundance on the crop foliage was not affected by tillage or cover crops. Contrary to expectations, epigeal natural enemies of insects and rates of weed seed removal either did not respond to treatments or were greater in full-tilled plots and plots without mulch. Our study demonstrates the potential importance of weed seed predators in reducing weed seedbanks in vegetable agroecosystems, and suggests that early-season tillage may not be detrimental to epigeal predator assemblages.