Identification of the Population Structure of Myzus persicae (Hemiptera: Aphididae) on Peach Trees in China Using Microsatellites

In this study, we characterized the genetic structure of Myzus persicae (Sulzer) (Hemiptera: Aphididae) populations in China using microsatellites. We expected that these data will reveal the genetic relationships among various populations of M. persicae and will be of value in the development of better methods for pest control. Four hundred sixty individuals from 23 areas over 13 provinces were collected in the early spring of 2010, all from their primary host, Prunus persicae. The markers analyzed were highly polymorphic, as demonstrated by the expected heterozygosity value (H_e = 0.861) and the Polymorphism Information Content (PIC = 0.847), which indicated that M. persicae maintains a high level of genetic diversity. Analysis of molecular variance revealed an intermediate level of population differentiation among M. persicae populations (F_ST = 0.1215). Geographic isolation existed among these populations, and, consequently, the genetic structure of the populations was split into a southern group and a northern group divided by the Yangtse River.     

Virtual Screening of Plant Volatile Compounds Reveals a High Affinity of Hylamorpha elegans (Coleoptera: Scarabaeidae) Odorant-Binding Proteins for Sesquiterpenes From Its Native Host

Hylamorpha elegans (Burmeister) is a native Chilean scarab beetle considered to be a relevant agricultural pest to pasture and cereal and small fruit crops. Because of their cryptic habits, control with conventional methods is difficult; therefore, alternative and environmentally friendly control strategies are highly desirable. The study of proteins that participate in the recognition of odorants, such as odorant-binding proteins (OBPs), offers interesting opportunities to identify new compounds with the potential to modify pest behavior and computational screening of compounds, which is commonly used in drug discovery, may help to accelerate the discovery of new semiochemicals. Here, we report the discovery of four OBPs in H. elegans as well as six new volatiles released by its native host Nothofagus obliqua (Mirbel). Molecular docking performed between OBPs and new and previously reported volatiles from N. obliqua revealed the best binding energy values for sesquiterpenic compounds. Despite remarkable divergence at the amino acid level, three of the four OBPs evaluated exhibited the best interaction energy for the same ligands. Molecular dynamics investigation reinforced the importance of sesquiterpenes, showing that hydrophobic residues of the OBPs interacted most frequently with the tested ligands, and binding free energy calculations demonstrated van der Waals and hydrophobic interactions to be the most important. Altogether, the results suggest that sesquiterpenes are interesting candidates for in vitro and in vivo assays to assess their potential application in pest management strategies.     

Population Dynamics of Empoasca fabae (Hemiptera: Cicadellidae) in Central Iowa Alfalfa Fields

Adults and nymphs of Empoasca fabae Harris (Hemiptera: Cicadellidae) and adults of predatory species in the families Coccinellidae, Anthocoridae, Nabidae, Chrysopidae, and Hemerobiidae were sampled in Iowa alfalfa fields from June to September in 1999 and 2000. The relationship between each predatory taxa and E. fabae was examined using regression analysis. In 2000, all predators were found to be positively correlated with the presence of E. fabae during all periods sampled and most likely contributed to mortality. Orius insidiosus (Say) (Hemiptera: Anthoridae) was the most numerous insect predatory species; population numbers ranged from 0 to 1 and 0.1 to 3.7 adults per 0.25 m² in 1999 and 2000, respectively. Partial life tables were constructed for E. fabae nymphs for two alfalfa-growing periods. Nymphs were grouped into three age intervals: first and second, third and fourth, and fifth instars. For the first alfalfa growing period examined, E. fabae nymphal mortality was 70% in 1999 and 49% in 2000. During the last growing period of each season (August–September), total nymphal mortality was relatively low (<25%). Adult E. fabae density ranged from 5.4 to 25.6 and 1.4–9.2 per 0.25 m² in 1999 and 2000, respectively. E. fabae population peaks were similar for each age interval in all growing periods. This study provides further information on the population dynamics of E. fabae and its relationship with select predatory species in Iowa alfalfa fields.     

Aphicidal Activity of an Ageraphorone Extract From Eupatorium adenophorum Against Pseudoregma bambucicola (Homoptera: Aphididae,Takahashi)

The bamboo aphid, Pseudoregma bambucicola, is an important insect pest of bamboo that affects normal bamboo growth and induces sooty molds. The control of P. bambucicola involves the application of chemicals, such as imidacloprid, to which many species are resistant. In this study, we isolate a novel botanical pesticide (9-oxo-10,11-dehydro-ageraphorone) from an Eupatorium adenophorum(Asteraceae: Compositae) petroleum ether extract and test the aphicidal activity of this compound against P. bambucicola in laboratory bioassay and field-based experiments. This ageraphorone compound at a concentration of 2 mg/ml caused 73.33% mortality (corrected mortality [Subtracted the mortality of the negative control]: 70%) of P. bambucicola by laboratory bioassay within 6 h. Even at lower concentrations, this compound caused greater 33% mortality (corrected mortality: 30%) of aphids. Field experiments with naturally infested bamboo plants showed that two applications of 2 mg/ml ageraphorone to infested plants completely cleared infestations within 30 d. These effects were similar to those of the positive control (imidacloprid). These results reveal that 9-oxo-10,11-dehydro-ageraphorone exhibits significant aphicidal activity against bamboo aphids. We suggest that future research be directed at developing this ageraphorone compound from E. adenophorum as an aphicidal agent for biocontrol.     

Analysis of Inter-Individual Bacterial Variation in Gut of Cicada Meimuna mongolica (Hemiptera: Cicadidae)

Intestinal bacterial community plays a crucial role in the nutrition, development, survival, and reproduction of insects. When compared with other insects with piercing-sucking mouthparts, the habitats of cicada nymphs and adults are totally different. However, little is known about the differences in the gut bacterial communities in the nymphs and adults within any cicada species. The diversity of bacteria in the gut of nymphs and adults of both genders of Meimuna mongolica (Distant) was studied using the denaturing gradient gel electrophoresis (DGGE) method. Few inter-individual variations among gut microbiota were observed, suggesting that M. mongolica typically harbors a limited and consistent suite of bacterial species. Bacteria in the genera Pseudomonas and Enterobacter were the predominant components of the gut microflora of M. mongolica at all life stages. Bacteria of Pantoea, Streptococcus, and Uruburuella were also widespread in the cicada samples but at relatively lower concentrations. The relative stability and similarity of the PCR-DGGE patterns indicate that all individuals of this cicada species harbor a characteristic bacterial community which is independent from developmental stages and genders. Related endosymbionts that could be harbored in bacteromes of cicadas were not detected in any gut samples, which could be related to the cicada species and the distribution of these endosymbionts in the cicada cavity, or due to some of the possible limitations of PCR-DGGE community profiling. It is worthwhile to further address if related cicada endosymbiont clades distribute in the alimentary canals and other internal organs through diagnostic PCR using group-specific primer sets.     

Analysis of Differential Proteins in Two Wing-Type Females of Sogatella furcifera (Hemiptera: Delphacidae)

Sogatella furcifera (Horvath) is an important rice pest with the wing dimorphism, including macropterous and brachypterous morphs. The protein expression profiles in two wing-type adults and two wing-type disc fifth-instar nymphs were analyzed using two-dimensional gel protein electrophoresis and mass spectrometry. In adults and fifth-instar nymphs, 127 and 162 protein spots were detected, respectively. Fifty-five differentially expressed protein spots were identified between the long-winged adults and the short-winged adults, and 62 differentially expressed protein spots were found between the long-winged disc fifth-instar nymphs and short-winged disc fifth-instar nymphs. In long-winged and short-winged adults, six and seven specific protein spots were identified, respectively, with five and seven protein spots having more than threefold increased level, respectively. In long-winged and short-winged disc morph nymphs, 8 and 12 specific protein spots were identified, respectively, with 11 and 17 spots containing more than threefold increased level, respectively. Among the 16 identified proteins, five proteins are associated with muscle function, suggesting that muscle is a main tissue where the genes were differentially expressed between the two wing types. In addition, the content of a peptidase with an insulinase domain was higher (by 3.02 ± 0.59 fold) in the short-winged fifth-instar nymphs than in the long-winged fifth-instar nymphs, which suggests that this peptidase may be involved in wing differentiation by regulating insulin receptors. The results of this study provide some genetic clues for the wing differential development in S. furcifera and provide more references for future studies.     

Development of Temporal Modeling for Forecasting and Prediction of the Incidence of Lychee,Tessaratoma papillosa (Hemiptera: Tessaratomidae), Using Time-Series (ARIMA) Analysis

The most destructive enemy of the lychee, Litchi chinensis Sonn. (Sapindales: Sapindaceae), in India is a stink bug, Tessaratoma papillosa (Drury) (Hemiptera: Tessaratomidae). The population of T. papillosa on lychee trees varied from 1.43 ± 0.501 to 9.85 ± 3.924 insects per branch in this study. An increase in the temperature and a decrease in the relative humidity during summer months (April to July) favor the population buildup of T. papillosa. A forecasting model to predict T. papillosa incidences in lychee orchards was developed using the autoregressive integrated moving average (ARIMA) model of time-series analysis. The best-fit model for the T. papillosa incidence was ARIMA (1,1), where the P-value was significant at 0.01. The highest T. papillosa incidences were predicted for April in 2010, January in 2011, May in 2012, and February in 2013. A model based on time series offers longer-term forecasting. The forecasting model, ARIMA (1,1), developed in this study will predict T. papillosa incidences in advance, thus providing functional guidelines for effective planning of timely prevention and control measures.     

Characterization of 12 Novel Microsatellite Markers of Sogatella furcifera (Hemiptera: Delphacidae) Identified From Next-Generation Sequence Data

The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), is a major pest of rice and has long-range migratory behavior in Asia. Microsatellite markers (simple sequence repeats) have been widely used to determine the origins and genetic diversity of insect pests. We identified novel microsatellite loci for S. furcifera samples collected from Laos, Vietnam, and three localities in Bangladesh from next-generation Roche 454 pyrosequencing data. Size polymorphism at 12 microsatellite loci was verified for 40 adult individuals collected from Shinan, South Korea. The average number of alleles per locus was 7.92. The mean values of observed (H_o) and expected heterozygosities (H_E) were 0.615 and 0.757, respectively. These new microsatellite markers will be a resource for future ecological genetic studies of S. furcifera samples across more broad geographic regions in Asia and may assist in estimations of genetic differentiation and gene flow among populations for implementation of more effective management strategies to control this serious rice pest.     

Intraspecific Variation of Eysarcoris guttigerus (Hemiptera: Pentatomidae) in Japanese Southwest Population Based on Mitochondrial DNA

The white-spotted globular bug Eysarcoris guttigerus (Thunberg) (Hemiptera: Pentatomidae) is widely distributed in East Asia and the Pacific region. In Japan, the species is found in grassy or composite weeds in the western area of the main islands and Ryukyu Islands of Japan. One notable characteristic of the Eysarcoris genus is the two white spots on the scutellum. This is not the case with the Ishigaki Island population, however, which sports red spots instead of white, suggesting that intraspecific variation exists in the species. Therefore, we investigated intraspecific variation in E. guttigerus using mitochondrial NADH dehydrogenase subunit 2 (ND2), cytochrome oxidase subunit 1 (CO1), cytochrome b (Cytb), tRNA-Serine (tRNA^ser), NADH dehydrogenase subunit 1 (ND1), and 16S ribosomal RNA (16SrRNA) genes from 13 populations of Japan. The obtained maximum likelihood phylogenetic tree was divided into three groups—Group 1: Mainland, Group 2: Central Ryukyu Islands (Okinawa-Amamioshima Islands), and Group 3: South Ryukyu Islands (Ishigaki Island). The Ishigaki population was significantly separated from the other populations with consistent differences in spot color. The estimated period of divergence between the Ishigaki population and the other populations was consistent with the period of formation of the Kerama Gap in the Ryukyu arc. Thus, the process of formation of the Kerama Gap may have influenced the intraspecific variation of E. guttigerus.     

Monitoring for MACE resistance in the tobacco-adapted form of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) in the eastern United States

Organophosphate and carbamate insecticides exert their neurotoxic effects by inhibiting acetylcholinesterase (AChE), thereby, prolonging the action of acetylcholine at cholinergic synapses, resulting in neuronal hyperexcitation. Mutations at the AChE target site confer modified acetylcholinesterase (MACE) phenotypes. Target-site insensitivity of AChE was characterized in field-collected, tobacco-adapted forms of the green peach aphid, Myzus persicae (Sulzer), from nine different states in the eastern United States from 2004 to 2007. The specific activity of the AChE among the 65 aphid colonies screened by Ellman's assay ranged from 0.017–0.259 U/min/mg protein. Eight colonies, with a wide range of specific activities were chosen to study the inhibition of AChE in the presence of two carbamate insecticides, methomyl and pirimicarb. IC₅₀ values for methomyl ranged from 0.35 to 2.4 μM, while six out of eight colonies had lower values that ranged from 0.16 to 0.30 μM for pirimicarb. Two colonies that were inhibited by methomyl had very high IC₅₀ values for pirimicarb, 40.4 and 98.6 μM respectively. The target-site insensitivity in these two colonies that are resistant to pirimicarb could be due to an ace2 gene mutation. This is the first instance where MACE phenotypes in M. persicae from the United States were studied and confirmed. The results indicate that the possible insensitivity due to MACE resistance in some colonies may render selected carbamate insecticides ineffective. Concerns of MACE resistance in managing the tobacco-adapted form of the green peach aphid on tobacco in the United States are discussed.     

Demographic Parameters of Nezara viridula (Heteroptera: Pentatomidae) Reared on Two Diets Developed for Lygus spp.

Two artificial diets developed for rearing Lygus spp., a fresh yolk chicken egg based-diet (FYD) and a dry yolk chicken egg based-diet (DYD), were evaluated as an alternative food source for rearing the southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae). Survival to adult was 97.3 and 74.67%, respectively, on the fresh and dry yolk diets. Insects fed FYD had 100% survival of nymphs from first through fourth instars. Adult development was significantly shorter on FYD (30.37 ± SE 0.30 d) as compared with DYD (32.77 ± SE 0.16 d). Increased male and female longevity, higher fecundity, and larger egg mass sizes were also observed with N. viridula-fed FYD. However, fertility and hatchability was higher on DYD. A complete cohort life table was constructed to describe the development of N. viridula on both diets.     

Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) on winter wheat (Triticumaestivum L.)

Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall and winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather field conditions ranging from −13.3 to 28.9 °C from 2002 to 2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Percent control of greenbugs resulting from applications of dimethoate, chlorpyrifos and λ-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two days post-treatment. While percent control was unique for each insecticide, a combined regression of percent control against average daily temperature predicted that a 95% level of control would be achieved when post-treatment temperatures exceeded 13.6 °C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Insecticide persistence was extended under cooler temperatures, allowing acceptable control 14 days post-treatment if temperatures warmed. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug, but if treatment with an insecticide is warranted, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 °C within the following 14 days.     

Laboratory Evaluation of Acute Toxicity of the Essential Oil of Allium tuberosum Leaves and Its Selected Major Constituents Against Apolygus lucorum (Hemiptera: Miridae)

The aim of this research was to evaluate acute toxicity of the essential oil of leaves of Chinese chives, Allium tuberosum Rottler ex Spreng (Asparagales: Alliaceae) and its major constituents against Apolygus lucorum Meyer-Dür (Hemiptera: Miridae). The essential oil of A. tuberosum leaves was obtained by hydrodistillation and analyzed by gas chromatography and gas chromatography-mass spectrometry. The major constituents of the oil were sulfur-containing compounds, including allyl methyl trisulfide (36.24%), diallyl disulfide (27.26%), diallyl trisulfide (18.68%), and dimethyl trisulfide (9.23%). The essential oil of A. tuberosum leaves exhibited acute toxicity against Ap. lucorum with an LD₅₀ value of 20.03 μg per adult. Among the main compounds, diallyl trisulfide (LD₅₀ = 10.13 μg per adult) showed stronger acute toxicity than allyl methyl trisulfide (LD₅₀ = 21.10 μg per adult) and dimethyl trisulfide (LD₅₀ = 21.65 μg per adult). The LD₅₀ value of diallyl disulfide against Ap. lucorum was 28.10 μg per adult. The results indicated that the essential oil of A. tuberosum and its major constituents may have a potential to be developed as botanical insecticides against Ap. lucorum.     

Relative Fitness of Helicoverpa armigera (Lepidoptera: Noctuidae) on Seven Host Plants: A Perspective for IPM in Brazil

The cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a widespread pest of many cultivated and wild plants in Europe, Africa, Asia, and Australia. In 2013, this species was reported in Brazil, attacking various host crops in the midwestern and northeastern regions of the country and is now found countrywide. Aiming to understand the effects of different host plants on the life cycle of H. armigera, we selected seven species of host plants that mature in different seasons and are commonly grown in these regions: cotton (Gossypium hirsutum, “FM993”), corn (Zea mays, “2B587”), soybean (Glycine max, “99R01”), rattlepods (Crotalaria spectabilis), millet (Pennisetum glaucum, “ADR300”), sorghum (Sorghum bicolor, “AGROMEN70G35”), and cowpea (Vigna unguiculata, “SEMPRE VERDE”). The development time of immatures, body weight, survivorship, and fecundity of H. armigera were evaluated on each host plant under laboratory conditions. The bollworms did not survive on corn, millet, or sorghum and showed very low survival rates on rattlepods. Survival rates were highest on soybean, followed by cotton and cowpea. The values for relative fitness found on soybean, cotton, cowpea, and rattlepods were 1, 0.5, 0.43, and 0.03, respectively. Survivorship, faster development time, and fecundity on soybean, cotton, and cowpea were positively correlated. Larger pupae and greater fecundity were found on soybean and cotton. The results indicated that soybean, cotton, and cowpea are the most suitable plants to support the reproduction of H. armigera in the field.     

Comparative overwintering host range of three Adelphocoris species (Hemiptera: Miridae) in northern China

In northern China, Adelphocoris suturalis, Adelphocoris lineolatus and Adelphocoris fasciaticollis (Hemiptera: Miridae) are common pests of cotton and several other crops. These species have vastly diverse geographic distribution, seasonal dynamics and abundance, the underlying causal factors of which are poorly understood. In this study, the importance of a broad range of plant species as overwintering hosts for each Adelphocoris sp. was compared. Nymphal emergence from a total of 126 plant species was monitored at two distinct locations. The eggs of A. suturalis successfully eclosed from un-plowed cotton field soil and 115 plant species, primarily pastures, weeds and agricultural crops. The eggs of A. lineolatus successfully eclosed from 40 plant species, mainly pastures and weeds. Finally, A. fasciaticollis overwintered on 35 plant species, primarily tree species, weeds and agricultural crops. In conclusion, the most common and widely distributed mirid species, A. suturalis, overwintered on a comparatively broader range of plants compared to the other two species. These observations help to understand the differences in geographical distribution and abundance of the three Adelphocoris species, and constitute the basis for forecasting and pest management protocols for Adelphocoris spp. in China.     

Overwintering hosts of Apolygus lucorum (Hemiptera: Miridae) in northern China

During the past decade, Apolygus lucorum Meyer-Dür (Heteroptera: Miridae) has become a key pest of cotton in northern China, due to widespread planting of Bt cotton and an associated drop in the use of broad-spectrum insecticides. Because of a lack of management alternatives, A. lucorum outbreaks are presently exclusively controlled with insecticides. In this study, we determined A. lucorum overwintering locations and host plants during the 2006–2009 winter seasons. A total of 126 plant species were screened and nymphal emergence of A. lucorum was monitored over time. Eggs of A. lucorum successfully overwintered in cotton field soils and on 86 plant species, including weeds, fruit trees, pastures and agricultural crops. More specifically, Vitis vinifera L., Ricinus communis L., Momordica charantia L., Artemisia argyi Levl. et Vant., Artemisia annua L., Artemisia lavandulaefolia DC., Isatis indigotica Fort., Artemisia scoparia Waldst. et Kit., Vigna radiate (L.) Wilczek, Ziziphus jujuba Mill., Vigna angularis (Willd.) Ohwi et, Ocimum basilicum L., Onobrychi viciifolia Scop., Pyrus bretschneideri Rehd., Malus domestica Borkh. and Brassica juncea (L.) Czern. et Coss proved optimal overwintering hosts of A. lucorum. Based upon plant species occurrence and distribution in Chinese cotton-growing regions, several weeds and fruit trees, such as V. vinifera, Z. jujuba, P. bretschneideri and M. domestica can be termed key overwintering hosts of A. lucorum. Our findings can form the basis for future formulation of targeted management actions to lower A. lucorum overwintering populations in cotton-growing landscapes of northern China.     

Variation in C:N:S Stoichiometry and Nutrient Storage Related to Body Size in a Holometabolous Insect (Curculio davidi) (Coleoptera: Curculionidae) Larva

Body size can be an important factor controlling consumer stoichiometry. In holometabolous insects, body size is typically associated with nutrient storage. Consumer stoichiometry is known to vary within species across a range of body sizes; however, the contribution of nutrient storage to this variation is not well understood. We used the fifth-instar larvae of the oak weevil (Coleoptera: Curculio davidi Fairmaire), which is characterized by a high capacity for nutrient storage, to investigate the effect of shifts in nutrient storage with body mass on variations in larva stoichiometry. Our results showed that weevil larvae with larger body mass had a lower carbon (C) content, reflecting decreases in the sequestration rate of C-rich lipids. Larger larvae had elevated concentrations of nitrogen (N), sulfur (S), and protein. The similar patterns of variation in elemental composition and macromolecule storage with body weight indicate that the shift in nutrient storage is the main factor causing the variation in larval stoichiometry with body weight. This finding was further supported by the low variation in residual larval biomass C, N, and S concentrations after lipid extraction. These results help decipher the physiological mechanism of stoichiometric regulation in growing organisms.     

Efficacy of Plectranthus glandulosus (Lamiaceae) and Callistemon rigidus (Myrtaceae) Leaf Extract Fractions to Callosobruchus maculatus (Coleoptera: Bruchidae)

As part of on-going efforts to use eco-friendly alternatives to chemical pesticides, methanol crude extracts of Plectranthus glandulosus and Callistemon rigidus leaves were sequentially fractionated in hexane, chloroform, ethyl acetate, and methanol to establish the most active fraction(s) against Callosobruchus maculatus in cowpea. Cowpea seeds (25 g) were treated with 0.5, 1, 2, and 4 g/kg of extract to evaluate the contact toxicity and F₁ progeny production of the beetles in the laboratory. Mortality was recorded 1, 3, and 7 d postexposure. P. glandulosus hexane fraction was more toxic than the other fractions recording 100% mortality at 4 g/kg, within 7 d with LC₅₀ of 0.39 g/kg. Hexane fraction of C. rigidus showed superior toxicity, causing 100% mortality at 4 g/kg within only 1 d of exposure with LC₅₀ of 1.02 g/kg. All the fractions greatly reduced progeny emergence, with C. rigidus hexane fraction being the best progeny inhibitor. Fractions of P. glandulosus and C. rigidus leaves had sufficient efficacy to be a component of storage pest management package for C. maculatus.