Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is an omnivorous insect used for biological control. Augmentative release and conservation of N. tenuis have been used for pest control in tomato crops. Intracellular bacterial symbionts of arthropods are common in nature and have diverse effects on their hosts; in some cases they can dramatically affect biological control. Fingerprinting methods showed that the symbiotic complex associated with N. tenuis includes Wolbachia and Rickettsia. Rickettsia of N. tenuis was further characterized by sequencing the 16S rRNA and gltA bacterial genes, measuring its amount in different developmental stages of the insect by real-time polymerase chain reaction, and localizing the bacteria in the insect's body by fluorescence in situ hybridization. The Rickettsia in N. tenuis exhibited 99 and 96% similarity of both sequenced genes to Rickettsia bellii and Rickettsia reported from Bemisia tabaci, respectively. The highest amount of Rickettsia was measured in the 5th instar and adult, and the symbionts could be detected in the host gut and ovaries. Although the role played by Rickettsia in the biology of N. tenuis is currently unknown, their high amount in the adults and localization in the gut suggest that they may have a nutritional role in this insect.

Aphid–plant interactions depend on genotypes of both organisms, which determine the two-way molecular exchange that leads to compatible or incompatible outcomes. The underlying genes are mostly unknown, making it difficult to predict likelihood of aphid success or host resistance, and hampering crop genetic improvement. Here we screened eight pea aphid clonal genotypes collected from diverse legume hosts, on a species-wide panel of Medicago truncatula (Mt) genotypes. Aphid virulence was measured by survival, fecundity and growth rate, together with scores for chlorosis and necrosis as host response indicators. Outcomes were highly dependent on the specific aphid–host genotype combinations. Only one Mt line was fully resistant against all clones. Aphid-induced host chlorosis and necrosis varied greatly, but correlated with resistance only in a few combinations. Bi-clustering analysis indicated that all aphid clones could be distinguished by their performance profiles across the host genotypes tested, with each clone being genetically differentiated and potentially representing a distinct biotype. Clones originating from Medicago sativa ranged from highly virulent to almost completely avirulent on both Medicago species, indicating that some were well adapted, whereas others were most likely migrants. Comparisons of closely related pairs of Australian Mt genotypes differing in aphid resistance revealed no enhanced resistance to European pea aphid clones. Based on the extensive variation in pea aphid adaptation even on unfamiliar hosts, most likely reflecting multiple biotype-specific gene-for-gene interactions, we conclude that robust defences require an arsenal of appropriate resistance genes.

Insect artificial diets are the foundation for mass production of insect predators. Whether there is an influence of long-term rearing with artificial diet on the control ability of predators should be considered. Here, we focused on the effect of nutritional history on the functional response of Geocoris pallidipennis to Myzus persicae. The influence of nutritional history (artificial diet versus natural prey, M. persicae) on the functional response of third to fifth instar nymphs and female G. pallidipennis was examined in the laboratory. The results showed that the functional response curve of both the nymphs and the adult female of G. pallidipennis to M. persicae reflected similar trends on both nutritional histories and confirmed the type II response. Adult female G. pallidipennis reared on either M. persicae or artificial diet produced a significantly better performance than the juvenile stages tested. We estimated that adult female G. pallidipennis can consume 141.6 (artificial diet) or 131.6 (M. persicae) aphids per day, respectively. This indicated that G. pallidipennis reared on both artificial diet and M. persicae displayed high rates of predation.

The common green lacewing Chrysoperla carnea is a key biological control agent employed in integrated pest management (IPM) programs for managing various insect pests. Spinosad is used for the management of pests in ornamental plants, fruit trees, vegetable and field crops all over the world, including Pakistan. A field-collected population of C. carnea was selected with spinosad and fitness costs and realized heritability were investigated. After selection for five generations, C. carnea developed 12.65- and 73.37-fold resistance to spinosad compared to the field and UNSEL populations. The resistant population had a relative fitness of 1.47, with substantially higher emergence rate of healthy adults, fecundity and hatchability and shorter larval duration, pupal duration, and development time as compared to a susceptible laboratory population. Mean relative growth rate of larvae, intrinsic rate of natural population increase and biotic potential was higher for the spinosad-selected population compared to the susceptible laboratory population. Chrysoperla species are known to show resistance to insecticides which makes the predator compatible with most IPM systems. The realized heritability (h2) value of spinosad resistance was 0.37 in spinosad-selected population of C. carnea.

Insect cytochrome P450 monooxygenases (P450s) play an important role in catalysis of many reactions leading to insecticides resistance. Our previous studies on transcriptome analysis of chlorantraniliprole-resistant development in the diamondback moth, Plutella xylostella revealed that up-regulation of cytochrome P450s are one of the main factors leading to the development of chlorantraniliprole resistance. Here, we report for the first time a novel cytochrome P450 gene CYP321E1, which belongs to the cytochrome P450 gene family CYP321. Real-time quantitative PCR (RT–qPCR) analyses indicated that CYP321E1 was expressed at all developmental stages of P. xylostella but was highest in the fourth-instar larvae; furthermore, the relatively high expression was observed in the midgut of the fourth-instar larvae, followed by fat bodies and epidermis. The expression of CYP321E1 in P. xylostella was differentially affected by three representative insecticides, including alphamethrin, abamectin and chlorantraniliprole. Among them, the exposure to chlorantraniliprole resulted in the largest transcript level of this cytochrome P450 gene. The findings suggested potential involvement of CYP321E1 in chlorantraniliprole resistance of P. xylostella. To assess the functional link of CYP321E1 to chlorantraniliprole resistance, RNA interference (RNAi)-mediated gene silencing by double stranded RNA (dsRNA) injecting was used. Results revealed that injection delivery of dsRNA can greatly reduce gene expression after 24 h. As a consequence of RNAi, a significant increment in mortality of larvae injected CYP321E1 dsRNA was observed after 24 h of exposure to chlorantraniliprole. These results strongly support our notion that this novel cytochrome P450 gene plays an important role in chlorantraniliprole detoxification in the diamondback moth and is partly responsible for its resistance.

Genetically modified crops with insect resistance genes from Bacillus thuringiensis Berliner (Bt-plants) are increasingly being cultivated worldwide. Therefore, it is critical to improve our knowledge of their direct or indirect impact not only on target pests but also on non-target arthropods. Hence, this study evaluates comparative leaf consumption and performance of Spodoptera eridania (Cramer), a species that is tolerant of the Cry1Ac protein, fed with Bt soybean, MON 87701×MON 89788 or its non-Bt isoline. We also assessed the comparative performance of the egg parasitoid Telenomus remus Nixon on eggs of S. eridania produced from individuals that fed on these two soybean isolines as larvae. Results showed that Bt soybean reduced by 2 days larval development and increased by 3 days adult male longevity. Therefore, we conclude that the effect of Bt soybean MON 87701×MON 89788 on S. eridania development and reproduction is small, and favorable to pest development. These differences are less likely to directly result from the toxin presence but indirectly from unintended changes in plant characteristics caused by the insertion of the transgene. Our results should be viewed as an alert that S. eridania populations may increase in Bt soybeans, but on the other hand, no adverse effects of this technology were observed for the egg parasitoid T. remus which can help to prevent S. eridania outbreaks on these crops.

The summer and autumn migrations of the brown planthopper (Nilaparvata lugens) were observed in Southern China with a millimetric scanning entomological radar and a searchlight trap supplemented with capture in field cages, field surveys, and dissections of females. Nilaparvata lugens took off at dusk and dawn in summer, but in autumn there was sometimes only a dusk take-off. The variation of the area density of the radar targets indicated that flight durations were about 9–10 h. In summer, planthopper-size targets generally flew below 1800 m above ground level (AGL), although some insects reached 2000 m AGL; in autumn, they flew lower, generally below 1100 m although some insects reached 1700 m AGL. Multiple layer concentrations were seen every night in both summer and autumn. The depths of these layers in autumn were less than in summer. Nilaparvata lugens flew in strong winds; wind shear may be the main factor causing them to accumulate and form dense layers at certain heights. Nilaparvata lugens emigrating in summer from the vicinity of the radar site in the Northeastern Guangxi Zhuang Autonomous Region, and carried by the prevailing southwesterly wind, would have travelled northeastwards and reached Northern Hunan Province. In autumn, with the prevailing northeasterly wind, emigrants would have reached overwintering areas (south of 21°N).

Rhynchophorus ferrugineus (Coleoptera, Curculionidae) is the most destructive pest of palm trees worldwide containing it invasive areas, such as the southern part of China. It is always emphasized to develop integrated pest management based on biological agents, but their success is not very exciting. Presently, the immune defenses of this pest against biological agents attract scarce attention. It is still unclear whether immune priming also generally occurs in insect pests and in response to different pathogens. Our results indicated that previous challenge of bacteria pathogen enhanced the magnitude of phenoloxidase activity and antibacterial activity in R. ferrugineus larvae against the secondary infection. Furthermore, trans-generational immune priming was also determined in this pest, and only challenged R. ferrugineus mothers transferred the immune protection to their offspring which suggested males and females of this pest might have evolved different strategies on the investment of delivering immune protection to their offspring. Importantly, our data provide the evidence to suggest that different kinds of biological control agents might be used alternatively or in combination to fight against R. ferrugineus because of the existence of immune priming with low species-specific level. On the other hand, for this invasive pest, the immune priming may also facilitate its adaptation and dispersal in the new regions.

Laboratory studies were conducted to assess the effect of temperature on the survival, development, longevity and fecundity of Helicoverpa armigera (Lepidoptera: Noctuidae) at eight different fluctuating temperatures with an amplitude ±9 °C under constant photoperiodic conditions of 16:8 h (L:D). H. armigera achieved complete development from egg to adult emergence between mean 17.5 and 32.5 °C. At mean 35 °C, all newly hatched larvae died and at mean 15 °C entered diapause at pupal stage. The lower developmental thresholds of the immature stages were estimated by a linear model and ranged from 4.63 °C (pupal stage) to 7.69 °C (egg stage). The developmental thresholds estimated by a nonlinear model were slightly higher than those estimated by the linear model. Adult longevity and fecundity were reduced at mean fluctuating temperatures 17.5 and 32.5 °C, but tended to be independent of the pattern of temperature change at moderate temperatures. The maximum reproductive performance, 1130 eggs per female, was observed at mean 25 °C. The intrinsic rates of increase were positive, meaning that H. armigera could be expected to persist or increase in number between mean 17.5 and 32.5 °C, with the maximum value at mean 27.5 °C. H. armigera survives, develops and reproduces within a wide range of fluctuating temperatures, while it completes the above functions with different levels of success at different mean temperatures of diurnal variation. Comparison of our results with similar data from the literature involving constant conditions is discussed. This information will provide a better understanding of H. armigera phenology and population dynamics under natural conditions and is essential to understanding the ecological and evolutionary consequences of climate change on this important species.

For a better understanding of the population structure and dispersal rates of Sogatella furcifera, we developed 21 novel polymorphic expressed sequence tags (EST) derived microsatellites, which were successfully amplified in four multiplex polymerase chain reaction sets. These new microsatellites were firstly assessed in 20 individuals sampled from Wenshan in China. The results showed that all 21 loci were highly polymorphic; the number of alleles ranged from 3 to 9, with an average of 4.8 alleles per locus. The observed and expected heterozygosity ranged from 0.200 to 0.900 and from 0.184 to 0.799, respectively. Nineteen of the 21 microsatellites without null allele, were subsequently used for population genetic structure analyses of five S. furcifera populations sampled in south region of China (sites up to 1314 kilometers apart). The observed and expected heterozygosity for each population ranged from 0.436 to 0.494 and from 0.454 to 0.482, respectively. The level of population differentiation was very low, with an average pairwise FST of 0.002. Bayesian cluster analysis result suggested that the five S. furcifera populations formed one genetic cluster. Discriminant analysis of principle components detected three genetic clusters. The spread of the three clusters across the five populations explained the lack of population differentiation and the Bayesian cluster result. All the results indicated that long-distance migration of this pest allowed genetic mixing between populations from remote geographical origins. These new microsatellites will be powerful tools for population genetics studies of S. furcifera.

Parasitic wasps are fascinating organisms that rely on a wide range of communication channels to locate their hosts. Associative learning for foraging kairomones has been demonstrated for various parasitic wasps, but little is known for parasitoids of Tephritidae flies. Psyttalia concolor (Hymenoptera: Braconidae) is a koinobiont parasitoid able to attack at least 14 tephritid pests. Females are innately attracted by some host-induced plant volatiles (HIPVs), whereas others of the same bouquet are unattractive. We hypothesize that females may detect unattractive HIPVs in association with key resources, such as food and hosts, learning to respond favourably to these cues in consecutive experiences. We evaluated associative learning for HIPVs in P. concolor females, testing if they are able to associate a food reward with the presence of different dosages of three HIPVs, thus developing a preference for an odour innately unattractive. Results demonstrated that P. concolor responded favourably to the learned cue in consecutive experiences. For all tested HIPVs (nonanoic acid, decanoic acid and geranyl acetone), regardless of dosage, trained females preferred the reward-associated odour, whereas naïve did not. Both HIPV-trained and naïve females did not show consistent differences in latencies when choosing HIPVs over blank. HIPV-trained and naïve wasps did not spend more time on HIPVs over blank. Odour learning is of adaptive importance for this generalist parasitoid, since it enhances host location efficiency by reducing the time wasted on the decision of where to search for hosts. From an applied perspective, these HIPVs could be used to train mass-reared P. concolor in pre-release, to potentially improve its efficacy in the field.

The egg parasitoid Telenomus podisi is a natural control agent of pentatomids, including Euschistus heros and Tibraca limbativentris, and success of parasitism is dependent upon the parasitoid finding the host. We tested the influence of host egg volatiles and the synthetic sex pheromone (zingiberenol) of T. limbativentris on chemotaxic behaviour of T. podisi, as well as, the impact of the original host on parasitoid selection. We used mated female T. podisi (48 h old) that emerged from the eggs of T. limbativentris or E. heros. The bioassays related to chemotaxy were performed in a Y-tube olfactometer and, to parasitism success, in laboratory and semi-field conditions. Telenomus podisi females that emerged from either the stink bug eggs, chose the pheromone more than control, or the pheromone plus eggs of E. heros in the semi-field bioassay, led to greater parasitism. Females that emerged from E. heros eggs chose egg volatiles from their original host rather than those from T. limbativentris, while females emerging from T. limbativentris, chose the egg volatiles of both hosts equally. When T. limbativentris was the original host, T. podisi females parasitized T. limbativentris over E. heros, while those emerging from E. heros exclusively parasitized E. heros eggs. These results demonstrated that T. podisi is more likely to parasitize the host in which it developed and that the original host can exert influence on the choice by those parasitoids. Understanding how the factors that mediate host–parasitoid communication are interrelated can help biological control programmes establish more effective and reliable tools with T. podisi.

Members of the family Cimicidae (Heteroptera: Cimicomorpha) are temporary bloodsuckers on birds and bats as primary hosts and humans as secondary hosts. Acanthocrios furnarii (2n=12=10+XY, male) and Psitticimex uritui (2n=31=28+X1X2Y, male) are two monotypic genera of the subfamily Haematosiphoninae, which have achiasmatic male meiosis of collochore type. Here, we examined chromatin organization and constitution of cimicid holokinetic chromosomes by determining the amount, composition and distribution of constitutive heterochromatin, and number and location of nucleolus organizer regions (NORs) in both species. Results showed that these two bloodsucker bugs possess high heterochromatin content and have an achiasmatic male meiosis, in which three regions can be differentiated in each autosomal bivalent: (i) terminal heterochromatic regions in repulsion; (ii) a central region, where the homologous chromosomes are located parallel but without contact between them; and (iii) small areas within the central region, where collochores are detected. Acanthocrios furnarii presented a single NOR on an autosomal pair, whereas P. uritui presented two NORs, one on an autosomal pair and the other on a sex chromosome. All NORs were found to be associated with CMA3 bright bands, indicating that the whole rDNA repeating unit is rich in G+C base pairs. Based on the variations in the diploid autosomal number, the presence of simple and multiple sex chromosome systems, and the number and location of 18S rDNA loci in the two Cimicidae species studied, we might infer that rDNA clusters and genome are highly dynamic among the representatives of this family.

Infection of the commercially important silkworm, Bombyx mori by a tachnid parasitoid, Exorista bombycis induced activation of genes and cellular responses associated with apoptosis in integumental epithelial cells. Composite cellular profile showed initial autophagy, intermediate endoplasmic reticulum degranulation and deformed nucleus as well as later DNA fragmentation indicating apoptosis. Two cell death-associated proteins, autophagy 5-like (Atg5L) and apoptosis-inducing factor (AIF), in addition to caspase, are identified from the infected integumental epithelium through mass spectrometric analysis. Genes encoding these proteins showed age-dependent activation after the infection as revealed by quantitative expression analysis. Atg5 showed early upregulation in association with signs of autophagy whereas AIF showed late upregulation in association with DNA condensation and fragmentation. Expression of AIF showed negative correlation with that of Atg5 after the infection. On the other hand, in control, caspase expression showed positive correlation with AIF expression indicative of regulated expression in normal larval epithelium, which was absent after infection. Activation of Atg5, AIF and caspase genes in close association with different cell death events revealed the synchronized differential expression of apoptosis-associated genes in response to the macroparasitism. Enhanced expression of Atg5, AIF and caspase genes coupled with the appearance of cell death symptoms indicate parasitism-induced activation of genetic machinery to modulate cell death events in the epithelium, which was hither to unknown in invertebrate systems.

Eukaryote transcription is controlled by regulatory DNA sequences and transcription factors, so transcriptional control of gene plays a pivotal role in gene expression. In this study, we identified the region of the CYP6B6 gene promoter of Helicoverpa armigera which responds to the plant secondary toxicant 2-tridecanone. Transient transfection assay results from five of stepwise deletion fragments linked to the luciferase reporter gene revealed that the promoter activity of each CYP6B6 fragment was significantly higher than that of their basal activity after the Sf9 cells were treated with 2-tridecanone. Among all, the fragment spanning −373 to +405 bp of the CYP6B6 promoter showed an obviously 2-tridecanone inducibility (P<0.0001), which might have the 2-tridecanone responsive element based on promoter activity. Electrophoretic mobility shift assays revealed that the nuclear protein extracted from midgut of the 6th instar larva of H. armigera, reared on 10 mg 2-tridecanone per gram artificial diet for 48 h, could specifically bind to the active region from −373 to 21 bp of the CYP6B6 promoter. The combination feature also appeared when using a shorter fragment from −292 to −154 bp of the CYP6B6 promoter. Taken together, we found a 2-tridecanone core responsive region between −292 and −154 bp of the CYP6B6 promoter. This may lead us to a better understanding of transcriptional mechanism of P450 gene and provide very useful information for the pest control.

Maize (Zea mays) is a major staple food in Africa. However, maize production is severely reduced by damage caused by feeding lepidopteran pests. In East and Southern Africa, Chilo partellus is one of the most damaging cereal stem borers mainly found in the warmer lowland areas. In this study, it was hypothesized that the future distribution and abundance of C. partellus may be affected greatly by the current global warming. The temperature-dependent population growth potential of C. partellus was studied on artificial diet under laboratory conditions at six constant temperatures (15, 18, 20, 25, 28, 30, 32 and 35 °C), relative humidity of 75±5% and a photoperiod of L12:L12 h. Several non-linear models were fitted to the data to model development time, mortality and reproduction of the insect species. Cohort updating algorithm and rate summation approach were stochastically used for simulating age and stage structure populations and generate life-table parameters. For spatial analysis of the pest risk, three generic risk indices (index of establishment, generation number and activity index) were visualized in the geographical information system component of the advanced Insect Life Cycle modeling (ILCYM) software. To predict the future distribution of C. partellus we used the climate change scenario A1B obtained from WorldClim and CCAFS databases. The maps were compared with available data on the current distribution of C. partellus in Kenya. The results show that the development times of the different stages decreased with increasing temperatures ranging from 18 to 35 °C; at the extreme temperatures, 15 and 38 °C, no egg could hatch and no larvae completed development. The study concludes that C. partellus may potentially expands its range into higher altitude areas, highland tropics and moist transitional regions, with the highest maize potential where the species has not been recorded yet. This has serious implication in terms of food security since these areas produce approximately 80% of the total maize in East Africa.