Bt maize can provide non-chemical pest control and enhance food safety in China.

China is the world's second-largest maize producer and consumer. In recent years, the invasive fall armyworm Spodoptera frugiperda (J.E. Smith) has adversely affected maize productivity and compromised food security. To mitigate pest-inflicted food shortages, China's Government issued biosafety certificates for two genetically modified (GM) Bt maize hybrids, Bt-Cry1Ab DBN9936 and Bt-Cry1Ab/Cry2Aj Ruifeng 125, in 2019. Here, we quantitatively assess the impact of both Bt maize hybrids on pest feeding damage, crop yield and food safety throughout China's maize belt. Without a need to resort to synthetic insecticides, Bt maize could mitigate lepidopteran pest pressure by 61.9-97.3%, avoid yield loss by 16.4-21.3% (range -11.9-99.2%) and lower mycotoxin contamination by 85.5-95.5% as compared to the prevailing non-Bt hybrids. Yield loss avoidance varied considerably between experimental sites and years, as mediated by on-site infestation pressure and pest identity. For either seed mixtures or block refuge arrangements, pest pressure was kept below established thresholds at 90% Bt maize coverage in Yunnan (where S. frugiperda was the dominant species) and 70% Bt maize coverage in other sites dominated by Helicoverpa armigera (Hübner) and Ostrinia furnacalis (Guenée). Drawing on experiences from other crop/pest systems, Bt maize in se can provide area-wide pest management and thus, contribute to a progressive phase-down of chemical pesticide use. Hence, when consciously paired with agroecological and biodiversity-based measures, GM insecticidal crops can ensure food and nutrition security, contribute to the sustainable intensification of China's agriculture and reduce food systems' environmental footprint.

Effects of cadmium stress at different concentrations on the reproductive behaviors of beet armyworm Spodoptera exigua (Hübner).

Insects are exposed to cadmium stress since cadmium pollution has increasingly become a serious global environmental issue. However, until now few studies have paid attention to the effect of heavy metals on insect reproductive behaviors. In our study, the courtship behaviors, mating behaviors and fecundity of beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae) exposed to different concentrations of cadmium in artificial diets at larval stage were studied. The results showed that cadmium stress changed the courtship rhythm by significantly advancing or delaying the courtship starting time. Low dose of cadmium (0.2 mg/kg) increased the courtship frequency in the first two scotophases, but in the fourth phase, the two cadmium treatments reduced the frequency. The total courtship duration was significantly shortened in the first six scotophases except high dose of cadmium treatment (51.2 mg/kg) in the sixth dark phase. Paired adults did not mate after the seventh scotophase under low cadmium exposure, while high cadmium stress made the paired adults just copulate in the first four scotophases. The daily mating rate and total mating rate decreased with the increase in cadmium concentration. The number of eggs of low cadmium treatment was higher than that of control, but the difference was not significant; the number of eggs in high cadmium treatment was lower than that of control and low cadmium treatment. Our results indicate that cadmium exposure can disrupt the courtship rhythm for females and has negative influences on copulation behavior and high cadmium stress can reduce fecundity. Hence, the insect population increase will be affected by heavy metal pollution. Our study will provide scientific reference for environmental risk assessment of heavy metal pollution.

Perception of and Behavioral Responses to Host Plant Volatiles for Three Adelphocoris Species.

In China, the genus Adelphocoris (Hemiptera: Miridae) includes three dominant pest species (A. suturalis, A. lineolatus and A. fasciaticollis), which cause great damage to cotton, alfalfa and other crops. In this study, we examined the role of the major volatile organic compounds from plants in host location by these three insects. Gas chromatography-electroantennography and gas chromatography/mass spectrometry analyses identified seven electroantennogram (EAG)-active compounds from 11 host plants. Although the insects responded to all of these compounds in EAG trials, some compounds did not elicit behavioral responses in Y-tube olfactometer bioassays. Adelphocoris suturalis adults showed behavioral responses to four EAG-active compounds, n-butyl ether, butyl acrylate, butyl propionate and butyl butyrate. These four compounds, in addition to p-xylene, were also attractive to A. lineolatus adults. However, A. fasciaticollis adults were attracted only by butyl acrylate, butyl propionate and butyl butyrate. In field trials, A. suturalis and A. fasciaticollis were each attracted to five individual compounds (m-xylene, n-butyl ether, butyl acrylate, butyl butyrate and butyl propionate for A. suturalis and m-xylene, butyl acrylate, butyl butyrate, butyl propionate, and 1,8-cineole for A. fasciaticollis). By contrast, A. lineolatus aduts were attracted to six individual compounds, m-xylene, p-xylene, n-butyl ether, butyl acrylate, butyl butyrate, and butyl propionate. These compounds may be important in host plant location by the Adelphocoris species, and may be useful for developing attractants for adults of these species.

Better cold tolerance of Bt-resistant Spodoptera exigua strain and the corresponding cold-tolerant mechanism.

Spodoptera exigua is a secondary target pest of Bt cotton commercialized in China. With the continuous adoption of Bt cotton, populations of S. exigua have gradually increased. However, the cold tolerance ability of Bt-resistant S. exigua and the effect of continuous Bt diet on anti-cold materials are unknown. In our study, it was found that Bt-resistant S. exigua (Bt10) developed better with shorter larval and pupal duration and higher pupation rate compared to CK at the suboptimal low temperature. The supercooling points and freezing points of the Bt-resistant S. exigua strain were determined, and body water content and anti-cold materials such as total sugar, trehalose and glycogen, glycerol and fat were examined to explore the effect of Bt toxin on overwintering and on population increase. The results showed that the supercooling point and the freezing point of the Bt-resistant S. exigua pupae were both significantly lower than that of the Bt-susceptible strain. No difference was found in the body water content of pupae and adults between the two strains. Total sugar content of the Bt-resistant strain at both the pupal and adult stages was higher than that of the susceptible strain at the corresponding stages, and glycogen content of the Bt-resistant strain at the larval stage was higher than that of the susceptible larval S. exigua. Fat content of the Bt-resistant larvae, pupae and adults was for each higher than that of the susceptible strain, but the difference was not significant except for that of the 3rd instar larvae. Glycerol content of the Bt-resistant strain at larval, pupal and adult stages was for each higher than that of the corresponding life stages of the susceptible strain. It can be seen that more glycerol was accumulated in Bt-resistant S. exigua. The results indicate that Bt-resistant S. exigua has better cold tolerance. The contents of the anti-freeze substances of progeny, especially glycerol, were increased after previous generations were continuously fed on Bt protein, which means that the Bt-resistant secondary target pests could more easily overcome the overwinter season and become a source of crop damage the following year.

Accumulation and excretion of cadmium in three successive generations of Spodoptera exigua (Lepidoptera: Noctuidae) and impact on the population increase.

Nowadays, heavy metal pollution has become more and more serious. Cadmium is one of the heavy metals that have caused serious pollution. Spodoptera exigua Hübner (Lepidoptera: Noctuidae), one of important agricultural pests, has broken out more frequently in recent years. In this study, accumulation at different developmental stages and excretion of Cd were detected, and effect of cadmium (Cd concentrations were 0.2, 0.8, 3.2, 12.8, and 51.2 mg/kg, respectively) on three successive generations of beet armyworm was also studied using life table in the laboratory. Results showed that Cd2+ contents were significantly different when S. exigua was reared under different Cd2+ concentrations in the same generation in a significant dose-dependent manner. The concentration of Cd2+ increased with extension of stress time. Cd2+ concentration at different developmental stages was different, that is, larvae > pupa > adult. After emergence, Cd2+ concentration in both females and males decreased gradually, but that in paired adults decreased to a greater extent than that in unpaired ones. Beet armyworm could excrete heavy metals by means of faeces, prepupa exuviate, and puparium. Life table of the laboratory population was constructed, which showed that low doses of cadmium promoted the increase of population, whereas high doses inhibited the increase, meanwhile, with the extension of exposure length, the index of population trend (I) declined more rapidly. The study might provide references for the long-term and objective assessment of heavy metal pollution and its effect on the populations of important agricultural pests.

Iron accumulation induced by hepcidin1 knockout accelerates the progression of aging osteoporosis.

OBJECTIVE: Iron accumulation is associated with osteoporosis. This study aims to explore the effect of chronic iron accumulation induced by hepcidin1 deficiency on aging osteoporosis. METHODS: Iron accumulation in hepcidin1 knockout aging mice was assessed by atomic absorption spectroscopy and Perl's staining. Bone microarchitecture was observed using Micro-CT. Hepcidin, ferritin, oxidative stress, and markers of bone turnover in serum were detected by enzyme-linked immunosorbent assay. Bone formation and resorption markers were measured by real-time quantitative PCR. Cell aging was induced by D-galactose treatment. CCK-8, flow cytometry, EdU assays, and Alizarin red staining were performed to reveal the role of hepcidin1 knockout in cell model. Iron Colorimetric Assay Kit and western blot were applied to detect iron and ferritin levels in cells, respectively. RESULTS: In hepcidin1-knockout mice, the ferritin and iron contents in liver and tibia were significantly increased. Iron accumulation induced by hepcidin1 knockout caused a phenotype of low bone mass and deteriorated bone microarchitecture. Osteogenic marker was decreased and osteoclast marker was increased in mice, accompanied by increased oxidative stress level. The mRNA expression levels of osteoclast differentiation markers (RANKL, Mmp9, OPG, Trap, and CTSK) were up-regulated, while bone formation markers (OCN, ALP, Runx2, SP7, and Col-1) were down-regulated in model group, compared to wild type mice. In vitro, hepcidin1 knockdown inhibited proliferation and osteogenic differentiation, while promoted apoptosis, with increased levels of iron and ferritin. CONCLUSION: Iron accumulation induced by hepcidin1 deficiency aggravates the progression of aging osteoporosis via inhibiting osteogenesis and promoting osteoclast genesis.

Systemicity of chlorantraniliprole in velvetleaf (Abutilon theophrasti).

The systemicity of chlorantraniliprole was investigated and evidence was collected for formulating strategies in controlling vegetable or rice pests. Systemicity of chlorantraniliprole was investigated through chlorantraniliprole application on velvetleaf (Abutilon theophrasti) leaves as well as through hydroponic experiments. The roots of velvetleaf were incubated in chlorantraniliprole solution with a concentration of 50 microg/mL; the concentrations of chlorantraniliprole in xylem above the solution parts were 3.14, 5.67, and 6.89 microg/g at 24, 48, and 72 h after treatment. When the roots were incubated in chlorantraniliprole solution with a concentration of 200 microg/mL, the concentrations of chlorantraniliprole in xylem above the solution reached 6.48, 8.76, and 10.55 microg/g at 24, 48, and 72 h after treatment. Chlorantraniliprole was not detected in the phloem above the solution after these two treatments. When chlorantraniliprole solution with a concentration of 100 microg/mL was applied on mature leaves, chlorantraniliprole was found in xylem above the mature leaves at concentrations of 0.55, 0.74, and 0.92 microg/g at 24, 48, and 72 h after the treatment. No chlorantraniliprole was detected in the leaves below the mature leaves or the phloem above them. When chlorantraniliprole solution with a concentration of 100 microg/mL was applied on apical leaves, no chlorantraniliprole was detected in the xylem or phloem below them. These results indicated that chlorantraniliprole can be transported through xylem only upward, but chlorantraniliprole has no phloem mobility in velvetleaf.

Bottom-Up Effects of Drought-Stressed Cotton Plants on Performance and Feeding Behavior of Aphis gossypii.

Drought, a major stress for crop plants, is expected to increase in frequency due to climate change. Drought can alter crop growth and levels of secondary plant metabolites, which in turn can affect herbivores, but this latter point is still controversial. This study used three different polyethylene glycol (PEG-6000) levels (0%, 1%, and 3%) to simulate drought stress and evaluated their effects on cotton plants and the impacts on the performance of the cotton aphid Aphis gossypii. Cotton plants under drought stress showed decreased water content, above-ground biomass, and nitrogen content and increased soluble protein, soluble sugar, and tannin contents. Based on analysis of the developmental time and fecundity data from individuals and at the population level, a significantly lower fecundity and population abundance of A. gossypii were detected on cotton plants with drought stress, which supports the "plant vigor hypothesis". The poor development of A. gossypii is possibly related to lower xylem sap and phloem ingestion under drought stress. In addition, the increased tannin content of cotton plants induced by drought and lower detoxification enzyme activities of A. gossypii may have affected the responses of aphids to drought-stressed plants. Overall, the results showed that drought stress altered the physiological characteristics of the cotton plants, resulting in adverse bottom-up effects on cotton aphid performances. This implies that the adoption of drip irrigation under plastic film that can help alleviate drought stress may favor the population growth of cotton aphids.

Buckwheat Flower Volatiles Attract Peristenus spretus and Enhance Its Field-Level Parasitism of Apolygus lucorum.

Volatile compounds play indispensable roles in the interactions among host plants, herbivores and natural enemies. Previous studies showed that the addition of buckwheat strips in cotton fields could attract Peristenus spretus, the dominant parasitoid of Apolygus lucorum, and enhance its parasitic activity. Through the combined analysis of Y-tube olfactometer, solid-phase microextraction (SPME), gas chromatography-mass spectrometer (GC-MS) and electroantennography (EAG), we found that male and female P. spretus responded to compounds present in buckwheat flowers. The five major components of buckwheat flowers, cis-3-hexenyl acetate (Z3HA), 4-methylanisole, 4-oxoisophorone, p-methylphenol and 2-ethylhexyl salicylate, all had a significant attraction to P. spretus adults and led to positive electroantennogram responses, especially for 10 mg/mL 4-oxoisophorone, indicating the components played a key role in the selection behavior of P. spretus to buckwheat flowers. Additionally, field trials showed that the five volatiles could significantly increase the parasitism by P. spretus. Our study screened the key active components of buckwheat flower volatiles that have an attractive effect on P. spretus, revealing its behavioral selection mechanism and emphasizing the important role of plant volatiles on host selection and parasitism of parasitic wasps, providing a theoretical basis for the development of attractants for P. spretus and the reduction of pesticides in the field to promote conservation biological control (CBC) of A. lucorum.

Determination of residual flubendiamide in the cabbage by QuEChERS-liquid chromatography-tandem mass spectrometry.

Flubendiamide, which belongs to the new chemical class of phthalic acid diamides, is widely used against lepidopteron pests in a variety of vegetable and rice pests. It provides superior plant protection against a broad range of economically important lepidopterous pests, including Spodoptera exigua and Plutella xylostella. A determination method of flubendiamide in the cabbage was established in this paper. Flubendiamide in the cabbage was extracted with acetonitrile and ultrasonic extraction, and was purified by QuEChERS and analyzed by LC-MS/MS (liquid chromatography-tandem mass spectrometry). The results indicated that the average recovery of flubendiamide in the cabbage was 81.27%-91.45%, the coefficient of variation was 1.79%-4.81%, and the lowest detection concentration was 0.3 µg/kg. The extraction of flubendiamide from the cabbage and its analysis was in accordance with the pesticide residue criterion, i.e., simple, rapid, accurate, reproducible, stable, separatory, and convenient. It identifies and quantifies trace-level flubendiamide residues in the cabbage extracts using LC-MS/MS in the ESI negative mode coupled with the QuEChERS method.

Transcriptomic and Metabolomic Responses in Cotton Plant to Apolygus lucorum Infestation.

With the wide-scale adoption of transgenic Bacillus thuringiensis (Bt) cotton, Apolygus lucorum (Meyer-Dür) has become the most serious pest and has caused extensive yield loss in cotton production. However, little is known about the defense responses of cotton at the seedling stage to A. lucorum feeding. In this study, to elucidate the cotton defense mechanism, cotton leaves were damaged by A. lucorum for 0, 4, 12 and 24 h. The transcriptomic results showed that A. lucorum feeding elicits a rapid and strong defense response in gene expression during the whole infestation process in cotton plants. Further analysis revealed that at each assessment time, more differentially expressed genes were up-regulated than down-regulated. The integrated analysis of transcriptomic and metabolic data showed that most of the genes involved in jasmonic acid (JA) biosynthesis were initially up-regulated, and this trend continued during an infestation. Meanwhile, the content levels of JA and its intermediate products were also significantly increased throughout the whole infestation process. The similar trend was displayed in condensed tannins biosynthesis. This research proved that, after plants are damaged by A. lucorum, the JA pathway mediates the defense mechanisms in cotton plants by promoting the accumulation of condensed tannins as a defense mechanism against A. lucorum. These results will help us to discover unknown defensive genes and improve the integrated pest management of A. lucorum.

Impact of Heat Stress on the Predatory Ladybugs Hippodamia variegata and Propylaea quatuordecimpunctata.

In cotton-growing regions of northwestern China, Hippodamia variegata (Goeze) and Propylaea quatuordecimpunctata (Linnaeus) (Coleoptera: Coccinellidae) are key natural enemies of hemipteran pests. As only H. variegata can be encountered in hot, arid production areas, the thermal responses and climatic adaptability of both species likely differ substantially. In this study, we assessed the survival, longevity, fecundity, prey consumption rate, and antioxidant capacity of both species under laboratory conditions at 32-38 °C. The (negative) impacts of elevated temperatures (i.e., 35 and 38 °C) on adult survival and reproduction were more pronounced for P. quatuordecimpunctata than for H. variegata. Similarly, high temperatures exhibited the strongest negative impacts on the prey consumption rates of P. quatuordecimpunctata. At elevated temperatures, superoxide dismutase and catalase activity increased, while glutathione-S-transferases activity decreased for both species. However, for P. quatuordecimpunctata, peroxidase activity and total antioxidant capacity progressively declined. Antioxidant responses thus constitute a key physiological adaptation of ladybugs to heat stress, reflecting a superior thermal tolerance of H. variegata. Our work emphasizes how laboratory assays can explain spatiotemporal distribution patterns of individual ladybugs and inform strategies to bolster their ensuing biological control under conditions of global warming or extreme weather events.

Behavioral Responses of Bemisia tabaci Mediterranean Cryptic Species to Three Host Plants and Their Volatiles.

Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a worldwide pest that damages over 900 host plant species. The volatile organic compounds (volatiles) of contrasting plants, as well as their growth stage, influence this pest's infestation behavior. The chemical contents of volatiles isolated from three plants (Gossypium hirsutum, Abutilon theophrasti, and Ricinus communis) during various growth phases (pre-flowering, fluorescence, and fruiting) were examined, as well as their influence on the behavior of adult B. tabaci. The olfactometer studies demonstrated that growth periods of the three plants affected the preference of B. tabaci. Volatiles of piemarker and cotton plants had dissimilar levels of attraction to adults during all stages. Volatile substances released by the castor at the stage of flowering had repellent effect on B. tabaci. In the plant versus plant combination, piemarker volatiles before and during anthesis were most preferred by adults, followed by cotton and then castor. A total of 24, 24, and 20 compounds were detected from volatiles of piemarker, cotton, and castor, respectively, and proportions among the compounds changed during different stages of plant development. The olfactory responses of B. tabaci to volatile compounds presented that linalool and high concentration of (Z)-3-hexenyl acetate had a strong trapping effect on this pest, while nonanal had a significant repellent effect at high concentration. This study indicates that distinct plants and their growth stage affect their attractiveness or repellency to B.tabaci adults, which are mediated by changing plant volatiles. These compounds obtained by analysis screening can be adopted as potential attractants or repellents to control Mediterranean (MED) B. tabaci.

Reproduction Evaluation and Transcription Analysis of Aphis gossypii under Various Photoperiods.

Aphis gossypii Glover (Hemiptera, Aphidoidae) is a polyphagous pest, whose complex phenotypic form, combined with its high fecundity and short reproductive cycle, has caused serious economic losses to agriculture worldwide. Photoperiod plays an important role in the reproduction of aphids. However, the molecular mechanisms underlying its response to seasonal photoperiodic changes are not known. In this study, the effects of different photoperiod treatments (8 L:16 D, 10 L:14 D, 12 L:12 D and 14 L:10 D) on A. gossypii reproduction in the first, third, and fifth generations at low temperatures were investigated. Then, transcriptome sequencing analysis was performed after the fifth generation of A. gossypii, exposed to different photoperiods (8 L:16 D and 12 L:12 D), using high-throughput sequencing technology. The results showed that (I) the effect of photoperiod on aphids was gradually evident with increasing exposure generations. In general, daylight extension help the A. gossypii to reproduce with the optimum photoperiod of L:D 12:12. (II) The transcriptome analysis results showed that 170 differentially expressed genes (DEGs) (123 downregulated and 47 upregulated genes) were identified between aphids under 8 h daylight and 12 h daylight. (III) Gene Ontology (GO) enrichment analysis showed that the DEGs involved in "proteolysis", "metabolic process", "peptidase activity" and "structural molecule activity" were significantly enriched; Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that there were more DEGs in "Longevity regulating pathway-multiple species", "Lysosome", "Endocytosis", "Spliceosome" and "Protein processing in endoplasmic reticulum". (IV) Ten related genes were chosen for validation of statistical analysis based on RNA-Seq by the reverse transcription quantitative (RT-qPCR). The comparison was consistent with the expression pattern and supported the accuracy and reliability of RNA-Seq. In summary, the genes involved in these pathways play an important role in the reproduction of A. gossypii under photoperiodical changes. These will contribute to the sustainable management of cotton aphids through the disruption of their reproduction by the method of RNA interference in the future.

Chromosome-level genome assemblies of two cotton-melon aphid Aphis gossypii biotypes unveil mechanisms of host adaption.

The cotton-melon aphid Aphis gossypii is a sap-sucking insect that is considered a serious global pest. The species is distributed over a large geographical range and uses a wide variety of hosts, with some populations being specialized to attack different plant species. Here, we provide de novo chromosome-level genome assemblies of a cotton specialist population (Hap1) and a cucurbit specialist population (Hap3). We achieved this by using a combination of third-generation sequencing platforms, namely Illumina and Hi-C sequencing technologies. We were able to anchor a total of 334.89 Mb (scaffold N50 of 89.13 Mb) and 359.95 Mb (scaffold N50 of 68.88 Mb) to four chromosomes for Hap1 and Hap3, respectively. Moreover, our results showed that the X-chromosome of Hap3 (113.01 Mb) was significantly longer than that of Hap1 (100.26 Mb), with a high level of sequence conservation between the aphid species. We also report variation in the number of protein-coding genes and repeat sequences between Hap1 and Hap3. In particular, olfactory and gustatory receptor genes underwent a high level of gene duplication and expansion events in A. gossypii, including between Hap1 and Hap3. Moreover, we identified two glutathione S-transferase genes which underwent single gene duplications in Hap3, and tandem duplication and inversion events affecting the cytochrome P450 monooxygenase between Hap1 and Hap3, all of which include the CYP3 family. Our results illustrate the variance in the genomic composition of two specialized A. gossypii populations and provide a helpful resource for the study of aphid population evolution, host adaption and insecticide resistance.

Life Table Construction under Different Temperatures and Insecticide Susceptibility Analysis of Uroleucon formosanum (Hemiptera: Aphididae).

Uroleucon formosanum is an important aphid pest of lettuce, but basic information on its biology is scarce. In this study, effects of three constant temperatures (17, 21, and 25 °C, simulating the mean temperature range in greenhouses) on the development and fecundity of U. formosanum were analyzed by constructing a life table. U. formosanum could develop and reproduce under all three temperatures, but the survival rate, development, and fecundity of U. formosanum were affected by temperature. The intrinsic rate of increase was lowest at 17 °C (0.17) and it was significantly less than at 21 °C (0.20) and 25 °C (0.23). Furthermore, U. formosanum had the lowest finite rate of increase (1.19) and the largest mean generation time (20.21) at 17 °C. These results mean that U. formosanum is less adapted to the lower temperatures (17 °C) among these three set temperatures. To screen insecticides for control, susceptibility of U. formosanum to six insecticides including chlorpyrifos, abamectin, beta-cypermethrin, imidacloprid, nitenpyram, and thiamethoxam was evaluated. U. formosanum was relatively sensitive to all six test insecticides. Chlorpyrifos had the highest toxicity to U. formosanum (LC50 = 3.08 mg/L). These data may help to develop integrated management strategies for better population control of U. formosanum.

The Effect of Mirid Density on Volatile-Mediated Foraging Behaviour of Apolygus lucorum and Peristenus spretus.

Plants would release herbivore-induced plant volatiles (HIPVs) to repel herbivores and attract natural enemies after being damaged by herbivores. In this study, after cotton plants were damaged by different densities of Apolygus lucorum, the behavioral responses of A. lucorum and Peristenus spretus to cotton plants volatiles were evaluated, and the quality and quantity of volatiles from cotton plants were analyzed. Only when cotton plants were damaged by four bugs did both A. lucorum and P. spretus show an obvious response to damaged cotton plants, which indicates that cotton defense is correlated with pest density. The collection and analysis of volatiles reveals that the increase in pest density results in the emission of new compounds and an increase in the total number of volatiles with an alteration in proportions among the compounds in the blend. These changes in volatile profiles might provide wasps and mirids with specific information on host habitat quality and thus could explain the behavioral responses of parasitoids and pests.

Symbiotic microbial studies in diverse populations of Aphis gossypii, existing on altered host plants in different localities during different times.

Complex interactions between symbiotic bacteria and insects ultimately result in equilibrium in all aspects of life in natural insect populations. In this study, abundance of principal symbiotic bacteria was estimated using qPCR in 1553 individuals of aphids, Aphis gossypii. Aphids were sampled from primary and secondary host plants-hibiscus and cotton. Hibiscus aphids were collected from 24 different locations in April, September, and November, whereas cotton aphids were collected between 2015 and 2017 from areas with wide variations in climatic conditions. About 30%-45% aphids were recorded with the most dominant symbiont, Arsenophonus. The other symbionts were in low frequency, and about 7% of aphids were noted with Hamiltonella, Acinetobacter, and Microbacterium, and 3% of aphids were verified with Serratia and Pseudomonas. Aphids infected with Hamiltonella, Arsenophonus, and Serratia can influence Buchnera densities. Hamiltonella has positive interaction with densities of Arsenophonus and Serratia. Almost 100% coinfection of Hamiltonella and Arsenophonus was detected in Xinxiang aphids and 50% coinfection was reported in aphids from North China, while no coinfection was detected in Hainan aphids. These findings describe the prevalence pattern and richness of core community of symbiotic bacteria in naturally occurring populations of A. gossypii and provide new insights for the study of symbiotic bacteria.

Transcriptome analysis of the ovary of beet armyworm Spodoptera exigua under different exposures of cadmium stress.

Heavy metal pollution is becoming an increasingly serious problem globally, and cadmium pollution ranks first in the world. Reproduction in insects is affected by cadmium stress in a dose-dependent manner. However, no previous studies have examined the molecular mechanisms underlying the influence of cadmium exposure on insect reproduction. In this study, RNA-Seq was used to investigate changes in ovary gene expression in newly emerged female beet army worms. The beet armyworms were reared under 4 cadmium concentrations: 0 mg/kg (control), low 0.2 mg/kg (L), medium 12.8 mg/kg (M) and high 51.2 mg/kg (H). Compared with the control (CK), a total of 3453 differentially expressed genes (DEGs) were identified in L cadmium stress, including 1791 up-regulated and 1662 down-regulated candidates; in L versus M groups, 982 up-regulated and 658 down-regulated DEGs; and in M versus H groups, 6508 up-regulated and 2000 down-regulated DEGs were identified and the expression patterns of ten genes were verified by q PCR. Many of the identified DEGs were relevant to juvenile hormone and molting hormone biosynthesis, insulin secretion, estrogen signaling, amino acid metabolism and lipid biosynthesis. These data will provide a molecular prospective to understand the ecological risk of heavy metal pollution and are a resource for selecting key genes as targets in gene-editing/silencing technologies for sustainable pest management.

Host plant use of a polyphagous mirid, Apolygus lucorum: Molecular evidence from migratory individuals.

While the host plant use of insect herbivores is important for understanding their interactions and coevolution, field evidence of these preferences is limited for generalist species. Molecular diet analysis provides an effective option for gaining such information, but data from field-sampled individuals are often greatly affected by the local composition of their host plants. The polyphagous mirid bug Apolygus lucorum (Meyer-Dür) seasonally migrates across the Bohai Sea, and molecular analysis of migrant bugs collected on crop-free islands can be used to estimate the host plant use of A. lucorum across the large area (northern China) from where these individuals come. In this study, the host plant use of A. lucorum adults was determined by identifying plant DNA using a three-locus DNA barcode (rbcL, trnH-psbA, and ITS) in the gut of migrant individuals collected on Beihuang Island. We successfully identified the host plant families of A. lucorum adults, and the results indicated that captured bugs fed on at least 17 plant families. In addition, gut analyses revealed that 35.9% of A. lucorum individuals fed on multiple host plants but that most individuals (64.1%) fed on only one plant species. Cotton, Gossypium hirsutum L., DNA was found in 35.8% of the A. lucorum bugs examined, which was much higher than the percentage of bugs in which other host plants were found. Our work provides a new understanding of multiple host plant use by A. lucorum under natural conditions, and these findings are available for developing effective management strategies against this polyphagous pest species.