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.

Brain Organization of Apolygus lucorum: A Hemipteran Species With Prominent Antennal Lobes

The anatomical organization of distinct regions in the insect brain often reflects their functions. In the present study, the brain structure of Apolygus lucorum was examined by using immunolabeling and three-dimensional reconstruction. The results revealed the location and volume of prominent neuropils, such as the antennal lobes (AL), optic lobes (OL), anterior optic tubercles (AOTU), central body (CB), lateral accessory lobes (LAL), mushroom lobes, and distinct tritocerebral neuropils. As expected, this brain is similar to that of other insects. One exception, however, is that the antennal lobes were found to be the most prominent neuropils. Their size relative to the entire brain is the largest among all insect species studied so far. In contrast, the calyx, a region getting direct input from the antennal lobe, has a smaller size relative to the brain than that of other species. These findings may suggest that olfaction plays an essential role for A. lucorum.

Mouthparts enriched odorant binding protein AfasOBP11 plays a role in the gustatory perception of Adelphocoris fasciaticollis

Insect odorant binding proteins (OBPs), one of the most important groups of odor carriers, are believed to play essential roles in chemoreception. In the present study, we focused on AfasOBP11 in Adelphocoris fasciaticollis. Expression profiles showed that AfasOBP11 was mainly expressed in the mouthparts of A. fasciaticollis. Additionally, two types of sensilla, sensilla trichodeum and sensilla basiconicum, were found on the mouthparts of bugs. Moreover, anti-AfasOBP11 antiserum strongly labeled the sensilla basiconica. In fluorescence binding assays, recombinant AfasOBP11 displayed much stronger binding abilities to non-volatile secondary metabolite compounds than to volatile odors, suggesting a role of AfasOBP11 in taste sensing. To further investigate the biological functions of AfasOBP11, the feeding behavior of wild-type, dsGFP-injected and dsAfasOBP11-injected bugs was evaluated by performing electrical penetration graph (EPG) tests. After RNA interference of target AfasOBP11, A. fasciaticollis bugs spent a longer time and pierced more frequently on the artificial diet containing 2.0% gossypol, indicating that RNAi treated bugs reduced sensitivity to gossypol. Our findings suggest that AfasOBP11 may play a vital role in chemoreception of A. fasciaticollis, especially in gustatory perception.

Cry2A rice did not affect the interspecific interactions between two rice planthoppers, Nilaparvata lugens, and Sogatella furcifera

Interspecific interactions are complex in agro-ecosystems and could be affected by agricultural technologies including transgenic crop planting. Few studies focused on the effects of Bt crops on the interspecific interactions of non-target organisms. Here we assessed the effects of transgenic cry2A rice (Cry2A rice) on the interspecific interaction between two rice planthoppers, namely, Nilaparvata lugens (the brown planthopper, BPH) and Sogatella furcifera (the white-backed planthopper, WBPH). Cry2A rice showed no significant effects on most biological parameters of these two rice planthoppers, except for wet weight of BPH female adults and development duration of WBPH female nymphs. In contrast, interspecific interactions between BPH and WBPH showed significant impacts on their biological parameters, no matter on Cry2A rice or non-transgenic control. In two-factor analysis combing rice line and interspecific interaction together, the interaction between these two factors did not affect most biological parameters of neither planthopper species, except for development duration of BPH female nymphs and WBPH nymphs (both male and female). Additionally, the egg distributions of BPH and WBPH had no significant differences between Cry2A and non-Cry2A treatments. Results of field experiments showed that Cry2A rice did not affect their population densities at most sampling dates in a five-year survey, and the interaction between BPH and WBPH showed no significant differences in both Cry2A and non-Cry2A rice paddies. In conclusion, our tested Cry2A rice would not affect the interspecific interactions between BPH and WBPH based both laboratory and field results.

Genome Analysis of Cytochrome in Dinotefuran-Treated Apolygus lucorum (Meyer-Dür)

In this study, two CYP genes, CYP395G1 and CYP4EY1, were analyzed in Apolygus lucorum (Hemiptera: Miridae). The expression pattern in different developmental stages of both CYP395G1 and CYP4EY1 revealed that first instar nymphs possessed the highest gene-transcript levels. After 12 h of dinotefuran treatments, the expression levels of CYP395G1 increased by 1.92-fold, while the CYP4EY1 expression decreased. It was observed that the sensitivities of dinotefuran to laboratory strains from F₀ to F₉ and the mRNA expression levels of CYP395G1 in the F₉ dinotefuran selected strain were higher when compared to the control strain. The results suggest that CYP395G1 was possibly a candidate P450 that was involved in dinotefuran detoxification. The dinotefuran resistant strain of A. lucorum was difficult to increase, due to its special molecular structure of dinotefuran compared with other neonicotinoids.

Occurrence and Distribution of Apolygus lucorum on Weed Hosts and Tea Plants in Tea Plantation Ecosystems

The mirid bugs are one of the most important piercing–sucking insect pests in tea plantations, which severely reduce the quality and economic benefits of tea. In this study, the mirid bug species in the three tea-producing areas in Shandong Province of China were investigated. The distribution and occurrence of dominant species of mirid bugs on four weed host plants and tea plants Camellia sinensis (L.) O. Kuntze (Theaceae) were also studied in the tea agro-ecosystems. The results showed that Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae) was the dominant mirid bug species in the tea growing areas. Apolygus lucorum densities on Humulus scandens (Lour.) (Moraceae) and Artemisia lavandulaefolia DC. (Asteraceae) were relatively higher than those on Conyza canadensis (Linn) Cronq (Asteraceae), Artemisia annua Linn (Asteraceae), and C. sinensis. Host plant switching of A. lucorum in the tea agro-ecosystem was: A. lucorum scattered on and seriously infested tea plants in June and July; A. lucorum largely migrated to and gathered on H. scandens, A. lavandulaefolia, C. canadensis, and A. annua at the flowering stage, and population densities of A. lucorum on these flowering hosts peaked in late September; in October, A. lucorum gradually moved back to flowering tea plants. These results could provide a reference for selecting host plants, such as Artemisia plants, as trap plants for sustainable control of mirid bugs in tea plantations.

Predation pressure in maize across Europe and in Argentina: an intercontinental comparison

Humankind draws important benefits from large-scale ecological processes termed ecosystem services, yet the status of several of them is declining. Reliable monitoring methods are essential for tracking the status of ecosystem services. Predation is the mainstay of natural pest control, a key ecosystem service. We used green plasticine caterpillars to monitor predation pressure, and to obtain baseline data on predator activity in transgenic Bt versus non-Bt maize fields in Old and New World countries. Predation pressure was measured at ground and canopy levels using an identical, small-plot experimental design in four European countries (Denmark, Slovakia, Romania and Italy) and Argentina. Total predation rate in maize was 11.7%d^-1 (min. 7.2%d^-1 in Argentina, max. 29.0%d^-1 in Romania). Artificial caterpillars were attacked both by invertebrates (mostly chewing insects with 42.0% of the attack marks, and ants with 7.1%, but also predatory and parasitoid wasps, spiders and slugs), and vertebrates (small mammals 25.5%, and birds 20.2%). Total predation at ground level (15.7%d^-1 ) was significantly higher than in maize canopies (6.0%d^-1 ) in all countries, except Argentina. We found no significant differences between predator pressure in Bt versus non-Bt maize plots. The artificial caterpillar method provided comparable, quantitative data on predation intensity, and proved to be suitable for monitoring natural pest control. This method usefully expands the existing toolkit by directly measuring ecological function rather than structure.

Host-plant switching promotes the population growth of Apolygus lucorum: implications for laboratory rearing

The mirid bug Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae) is a major pest on cotton, fruit trees and other crops in China. A. lucorum adults often switch host plants in the agro-ecosystem, and such host-plant switching may promote more rapid population growth of A. lucorum. Here, we examined the population fitness of A. lucorum on different combinations of two plant foods [fresh maize kernels (Zea mays) and green bean pods (Phaseolus vulgaris)] in the laboratory when reared either individually or in groups. Our results suggested that, compared with A. lucorum nymphs reared on green bean alone, the survival rate, developmental rate, and adult weight significantly increased when they were fed fresh maize kernels for both rearing methods. Both two-plant combinations of foods (i.e., maize as nymphal food then green bean as adult food, and green bean as nymphal food then maize as adult food) generally prolonged adult longevity, improved female fecundity, and higher egg hatching rate compared with maize or green bean as food for both nymphs and adults. The combination of nymphs with maize and adults with green bean showed the highest population growth rate for both individual and group rearing of mirid bugs. Host food switching greatly promoted the population growth of A. lucorum, and suggests a new diet for laboratory rearing of A. lucorum.

Key Amino Residues Determining Binding Activities of the Odorant Binding Protein AlucOBP22 to Two Host Plant Terpenoids of Apolygus lucorum

Odorant binding proteins (OBPs) are considered to be highly expressed at antennae sensillum lymph and play crucial roles in detection of insect host plant volatiles. The polyphagous mirid bug Apolygus lucorum is one of a series of insect pests on many important agricultural crops that heavily rely on sophisticated olfaction to locate host plants. Previously, putative OBP genes and their tissue-related expression patterns in this pest species have been clarified. In this study, we characterized the ligand spectrum and the molecular binding mechanism of the antennae-biased AlucOBP22 to host plant volatiles of A. lucorum. Frist, the recombinant AlucOBP22 protein was constructed and purified, and its binding affinities to selected host plant volatiles were assessed. Two terpenoids, β-ionone and β-caryophyllene, could highly bind to AlucOBP22. Next, three-dimensional model prediction indicated that AlucOBP22 employed six α-helices to form a typical pocket for ligand accommodation. Molecular docking analysis suggested that both β-ionone and β-caryophyllene were located at the AlucOBP22 pocket with some hydrophobic amino acid residues close to the two chemicals, suggesting that hydrophobic interactions might be crucial for ligand-specific binding. Finally, site-directed mutagenesis combined with fluorescence binding assays revealed that mutants of five hydrophobic residues Leu5, Ile40, Met41, Val44, and Met45 displayed significantly decreased or completely abolished binding affinities to the two ligands. Our findings showed the specific binding characteristic of AlucOBP22 and suggested that hydrophobic residues and their hydrophobic interactions were involved in AlucOBP22 binding to terpenoids, which provided new insights into the molecular interaction mechanisms of hemipteran insect OBPs to host plant odors.

Plant Response and Economic Injury Levels for a Boll-Feeding Sucking Bug Complex on Cotton

Whole-plant cage field experiments were conducted in 2014, 2015, and 2016 to characterize cotton injury from a species complex of boll-feeding sucking bugs represented by the verde plant bug, Creontiades signatus (Distant) (Hemiptera: Miridae), brown stink bug, Euschistus servus (Say), green stink bug, Acrosternum hilare (Say), and redbanded stink bug, Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae). Field-collected adult bugs were used to infest cotton plants previously maintained free of insect injury. Plants caged in groups of four were infested at mid-bloom and late-bloom for 7 d with four insect densities: 0 (control), 0.25 bugs per plant, 1 bug per plant, and 2 bugs per plant. Species and water stress conditions varied across years, allowing selective within-year comparisons. Response to feeding resulted in boll injury in the form of lint deterioration and cotton boll rot at mid- and late-bloom stages, and in water limiting and non-water limiting conditions. Although plant injury was apparent across a wide range of conditions, subsequent yield decline attributed to insect feeding was seen primarily under water limiting conditions when plants were infested at mid-bloom. For these conditions, significant yield-insect density relationships were used to calculate economic injury levels (EILs) for each species. EILs expressed as bugs per plant from lowest to highest were the brown stink bug (0.29-0.31 bugs per plant), redbanded stink bug (0.33), verde plant bug (0.49), and green stink bug (0.50). Given the variability observed among species, species-specific EILs may be used where the injurious species is known and combined for stink bugs (a common EIL of 0.34 bugs per plant) where multiple species occur. Verde plant bug was less damaging and can be considered separately, but its EIL was generally within a range of values for the boll-feeders encountered.

How low can you go? Estimating impacts of reduced pesticide use

Recent research has suggested that a high proportion of farms can dramatically reduce pesticide applications without reducing crop yields or farm profits. Yet this research has made estimation choices that may systematically bias downwards estimates of the productivity and profitability of pesticides. Fifty years of agricultural economics research provides lessons about how to avoid pitfalls in estimating pesticide productivity. Carefully executed econometric studies have found evidence of overuse, underuse, and near-optimal use of pesticides in different cropping systems. There are now standard methods to test and correct for sources of biases (either upward or downward) in estimates of pesticide productivity. Ignoring these lessons and methods can seriously bias estimates of the potential for reducing pesticide use at little or no economic cost. © 2018 Society of Chemical Industry.

Transgenic Cry1Ac cotton does not affect the development and fecundity of Chrysoperla carnea

The development and fecundity of the predator Chrysoperla carnea Stephens (Neuroptera: Chrysopidae) were assessed by feeding Aphis gossypii Glover (Hemiptera: Aphididae) that had been reared on transgenic Bacillus thuringiensis (Bt) cotton SGK321 and a non-Bt cotton control (SY321) for two successive generations. We found no significant differences in the developmental stage duration, stage survival, or egg hatch rate between C. carnea fed A. gossypii reared on the Bt and non-Bt cotton. The fecundity per female over a 25-day observation period was very similar between treatments; for C. carnea fed A. gossypii reared on SGK321 vs. SY321, the amount of eggs laid was not significantly different in both generations. Furthermore, a population dynamics of A. gossypii and lacewing (mainly C. carnea) were highly similar in the SGK321 and SY321 treatments during 2016–2017. These results suggest that Bt cotton does not have a significantly negative or positive effect on C. carnea in terms of development, survival, fecundity, or population dynamics.

Recent progress on the interaction between insects and Bacillus thuringiensis crops

Extensive use of chemical pesticides poses a great threat to the environment and food safety. The discovery of Bacillus thuringiensis (Bt) toxins with effective insecticidal activity against pests and the development of transgenic technology of plants opened a new era of pest control. Transgenic Bt crops, including maize, cotton and soya bean, have now been produced and commercialized to protect against about 30 major coleopteran and lepidopteran pests, greatly benefiting the environment and the economy. However, with the long-term cultivation of Bt crops, some target pests have gradually developed resistance. Numerous studies have indicated that mutations in genes for toxins activation, toxin-binding and insect immunization are important sources in Bt resistance. An in-depth exploration of the corresponding Bt-resistance mechanisms will aid in the design of new strategies to prevent and control pests. Future research will focus on Bt crops expressing new genes and multiple genes to control a broader range of pests as part of an integrated pest management programme. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.

First transgenic trait for control of plant bugs and thrips in cotton

BACKGROUND

Plant bugs (Lygus spp.) and thrips (Thrips spp.) are two of the most economically important insect pest groups impacting cotton production in the USA today, but are not controlled by current transgenic cotton varieties. Thus, seed or foliar-applied chemical insecticides are typically required to protect cotton from these pest groups. Currently, these pests are resistant to several insecticides, resulting in fewer options for economically viable management. Previous publications documented the efficacy of transgenic cotton event MON 88702 against plant bugs and thrips in limited laboratory and field studies. Here, we report results from multi-location and multi-year field studies demonstrating efficacy provided by MON 88702 against various levels of these pests.

RESULTS

MON 88702 provided a significant reduction in numbers of Lygus nymphs and subsequent yield advantage. MON 88702 also had fewer thrips and minimal injury. The level of control demonstrated by this transgenic trait was significantly better compared with its non-transgenic near-isoline, DP393, receiving insecticides at current commercial rates.

CONCLUSION

The level of efficacy demonstrated here suggests that MON 88702, when incorporated into existing IPM programs, could become a valuable additional tool for management of Lygus and thrips in cotton agroecosystems experiencing challenges of resistance to existing chemical control strategies. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Reduced caterpillar damage can benefit plant bugs in Bt cotton

Bt cotton was genetically modified to produce insecticidal proteins targeting Lepidopteran pests and is therefore only minimally affected by caterpillar damage. This could lead to reduced levels of inherent, systemically inducible defensive compounds in Bt cotton which might benefit other important cotton herbivores such as plant bugs. We studied the effects of plant defense induction on the performance of the plant bug Lygus hesperus by caging nymphs on different food sources (bolls/squares) of Bt and non-Bt cotton which were either undamaged, damaged by Bt tolerant caterpillars, or treated with jasmonic acid (JA). Terpenoid induction patterns of JA-treated and L. hesperus-damaged plants were characterized for different plant structures and artificial diet assays using purified terpenoids (gossypol/heliocide H1/4) were conducted. Nymphs were negatively affected if kept on plants damaged by caterpillars or sprayed with JA. Performance of nymphs was increased if they fed on squares and by the Bt-trait which had a positive effect on boll quality as food. In general, JA-sprayed plants (but not L. hesperus infested plants) showed increased levels of terpenoids in the plant structures analyzed, which was especially pronounced in Bt cotton. Nymphs were not negatively affected by terpenoids in artificial diet assays indicating that other inducible cotton responses are responsible for the found negative effects on L. hesperus. Overall, genetically engineered plant defenses can benefit plant bugs by releasing them from plant-mediated indirect competition with lepidopterans which might contribute to increasing numbers of hemipterans in Bt cotton.

Genetically Engineered Crops: Importance of Diversified Integrated Pest Management for Agricultural Sustainability

As the global population continues to expand, utilizing an integrated approach to pest management will be critically important for food security, agricultural sustainability, and environmental protection. Genetically engineered (GE) crops that provide protection against insects and diseases, or tolerance to herbicides are important tools that complement a diversified integrated pest management (IPM) plan. However, despite the advantages that GE crops may bring for simplifying the approach and improving efficiency of pest and weed control, there are also challenges for successful implementation and sustainable use. This paper considers how several GE traits, including those that confer protection against insects by expression of proteins from Bacillus thuringiensis (Bt), traits that confer tolerance to herbicides, and RNAi-based traits that confer resistance to viral pathogens, can be key elements of a diversified IPM plan for several different crops in both developed and developing countries. Additionally, we highlight the importance of community engagement and extension, strong partnership between industry, regulators and farmers, and education and training programs, for achieving long-term success. By leveraging the experiences gained with these GE crops, understanding the limitations of the technology, and considering the successes and failures of GE traits in IPM plans for different crops and regions, we can improve the sustainability and versatility of IPM plans that incorporate these and future technologies.

Duplication and expression of horizontally transferred polygalacturonase genes is associated with host range expansion of mirid bugs

BACKGROUD

Horizontal gene transfer and gene duplication are two major mechanisms contributing to the evolutionary adaptation of organisms. Previously, polygalacturonase genes (PGs) were independently horizontally transferred and underwent multiple duplications in insects (e.g., mirid bugs and beetles). Here, we chose three phytozoophagous mirid bugs (Adelphocoris suturalis, A. fasciaticollis, A. lineolatus) and one zoophytophagous mirid bug (Nesidiocoris tenuis) to detect whether the duplication, molecular evolution, and expression levels of PGs were related to host range expansion in mirid bugs.

RESULTS

By RNA-seq, we reported 30, 20, 19 and 8 PGs in A. suturalis, A. fasciaticollis, A. lineolatus and N. tenuis, respectively. Interestingly, the number of PGs was significantly positive correlation to the number of host plants (P = 0.0339) in mirid bugs. Most PGs (> 17) were highly expressed in the three phytozoophagous mirid bugs, while only one PG was relatively highly expressed in the zoophytophagous mirid bug. Natural selection analysis clearly showed that a significant relaxation of selection pressure acted on the PGs in zoophytophagous mirid bugs (K = 0.546, P = 0.0158) rather than in phytozoophagous mirid bugs (K = 1, P = 0.92), suggesting a function constraint of PGs in phytozoophagous mirid bugs.

CONCLUSION

Taken together with gene duplication, molecular evolution, and expression levels, our results suggest that PGs are more strictly required by phytozoophagous than by zoophytophagous mirid bugs and that the duplication of PGs is associated with the expansion of host plant ranges in mirid bugs.

Impacts of soil salinity on Bt protein concentration in square of transgenic Bt cotton

Insect-resistance of transgenic Bacillus thuringiensis (Bt) cotton varies among plants organs and with different environmental conditions. The objective of this study was to examine the influence of soil salinity on Bt protein concentration in cotton squares and to elucidate the potential mechanism of Bt efficacy reduction. Two cotton cultivars (NuCOTN 33B and CCRI 07, salt-sensitive and salt-tolerant) were subjected to salinity stress under four natural saline levels in field conditions in 2015 and 2016 and seven regimes of soil salinity ranged from 0.5 to 18.8 dS m-1 in greenhouse conditions in 2017. Results of field studies revealed that Bt protein content was not significantly changed at 7.13 dS m-1 salinity, but exhibited a significant drop at the 10.41 and 14.16 dS m-1 salinity. The greenhouse experiments further showed similar trends that significant declines of the insecticidal protein contents in squares were detected when soil salinity exceeded 9.1 dS m-1. Meanwhile, high salinity resulted in significant reduction in contents of soluble protein and total nitrogen, activities of nitrate reductase (NR), glutamine synthetase (GS) and glutamic-pyruvic transaminase (GPT), but increased amino acid content, activities of protease and peptidase in cotton squares. High salinity also decreased root vigor (RV), root total absorption area (RTA) and root active absorption area (RAA). The extent of decrease of Bt protein content was more pronounced in NuCOTN 33B than CCRI 07, and CCRI07 exhibited stronger enzymes activities involved in square protein synthesis and higher levels of RV, RTA and RAA. Therefore, the results of our present study indicated that insecticidal protein expression in cotton squares were significantly affected by higher salinity (equal to or higher than 9.1 dS m-1), reduced protein synthesis and increased protein degradation in squares and reduced metabolic activities in roots might lead to the decrease of Bt protein content in squares.

Expression patterns and ligand binding characterization of Plus-C odorant-binding protein 14 from Adelphocoris lineolatus (Goeze)

Odorant-binding proteins (OBPs) can bind and transport hydrophobic odorants across the sensillum lymph to the olfactory receptors (ORs) and play crucial roles in insect chemosensory systems. Although the ligand spectra of classical OBPs have been extensively characterized, little is known about OBPs in the Plus-C subgroup. Here, we focus on AlinOBP14, a Plus-C OBP from the hemipteran mirid bug pest Adelphocoris lineolatus (Goeze). Quantitative real-time PCR experiments suggest that AlinOBP14 is ubiquitously expressed at different developmental stages but is highly expressed in the adult head, the non-chemosensory organ. Fluorescence-based competitive binding assays show that β-ionone, nerolidol, farnesol and insect juvenile hormone III (JHIII) strongly bind to AlinOBP14. No significant internal binding pocket is predicted by homology modeling. Instead, the long N-terminal and C-terminal regions and parts of several α-helixes form a cupped cavity to accommodate ligands. Molecular docking reveals that the four potential ligands have distinct binding orientations, implying different roles of the N-terminal extension in ligand recognition. This hypothesis is further confirmed via a ligand binding assay in which the recombinant N-terminal mutant AlinOBP14 displays comparable binding affinities for β-ionone and trans, trans-farnesol but decreased binding affinities for nerolidol and JHIII. Thus, our current study is the first to characterize the ligand binding spectra of a Plus-C OBP in hemipteran insect species and reveals that N-terminal extensions could be required for its recognition of putative ligands.

Bt rice could provide ecological resistance against nontarget planthoppers

Genetically engineered (GE) rice lines expressing Lepidoptera-active insecticidal cry genes from the bacterium Bacillus thuringiensis (Bt) have been developed in China. Field surveys indicated that Bt rice harbours fewer rice planthoppers than non-Bt rice although planthoppers are not sensitive to the produced Bt Cry proteins. The mechanisms underlying this phenomenon remain unknown. Here, we show that the low numbers of planthoppers on Bt rice are associated with reduced caterpillar damage. In laboratory and field-cage experiments, the rice planthopper Nilapavata lugens had no feeding preference for undamaged Bt or non-Bt plants but exhibited a strong preference for caterpillar-damaged plants whether Bt or non-Bt. Under open-field conditions, rice planthoppers were more abundant on caterpillar-damaged non-Bt rice than on neighbouring healthy Bt rice. GC-MS analyses showed that caterpillar damage induced the release of rice plant volatiles known to be attractive to planthoppers, and metabolome analyses revealed increased amino acid contents and reduced sterol contents known to benefit planthopper development. That Lepidoptera-resistant Bt rice is less attractive to this important nontarget pest in the field is therefore a first example of ecological resistance of Bt plants to nontarget pests. Our findings suggest that non-Bt rice refuges established for delaying the development of Bt resistance may also act as a trap crop for N. lugens and possibly other planthoppers.

Evaluating Action Thresholds for Amrasca devastans (Hemiptera: Cicadellidae) Management on Transgenic and Conventional Cotton Across Multiple Planting Dates

An action threshold (AT) based on the specific pest-crop relationship is an important element of integrated pest management (IPM) programs. We evaluated planting time-based ATs to manage a sucking pest, cotton leafhopper (Amrasca devastans; Hemiptera: Cicadellidae) in conventional (CIM-554) and transgenic (Bt.CIM-599) cotton cultivars under field conditions. Cultivars were planted on 15 March, April, and May during 2011 and 2012. Only two ATs (0.1 and 1.0 A. devastans per leaf) and an untreated control could be tested on 15 March planted cotton, as the populations of A. devastans never reached a density of two per leaf. Cotton planted on 15 March had the highest seed cotton yield, highest net and marginal rate of returns (MRRs) than other planting times. At this planting time, only one insecticidal application was needed at an AT of 1.0 A. devastans per leaf, with no significant yield loss. Four ATs (0.1, 1.0, 2.0, and 3.0 A. devastans per leaf) and an untreated control were tested for cotton planted on 15 April and 15 May. For the 15 April planting, 2.0 AT led to 3 applications as compared with 10 applications needed with 0.1 AT; without any significant yield loss, generating the highest net return and MRR for this planting date. The 15 May planting was more vulnerable to A. devastans damage and 1.0 AT generated the highest net return and MRR with four applications as compared with all other ATs. These results suggest that the use of planting time-based ATs can improve cotton yield through cost-effective applications of insecticides.

Long-Term Empirical and Observational Evidence of Practical Helicoverpa zea Resistance to Cotton With Pyramided Bt Toxins

Evidence of practical resistance of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) to Bt cotton in the United States is debatable, supported with occasional reports of boll damage in the field. Our objective was to provide both empirical and long-term observational evidence of practical resistance by linking both in-season and end-of-season measurements of H. zea damage to pyramided Bt cotton bolls and to provide Cry1Ac diet-based bioassay data in support of these damage estimates. In-season boll damage from H. zea was highly correlated to end-of-season damaged bolls. Across North Carolina, Bt cotton fields with end-of-season bolls damaged by H. zea increased during 2016 compared to previous years. Elevated damage was coupled with an increase in field sprays targeting H. zea during 2016, but not related to an increase in H. zea abundance. Bioassay data indicated that there was a range of Cry1Ac susceptibility across the southeastern United States. Given the range of susceptibility to Cry1Ac across the southeastern United States, it is probable that resistant populations are common. Since H. zea is resistant to cotton expressing pyramided Cry toxins, the adoption of new cotton varieties expressing Vip3Aa will be rapid. Efforts should be made to delay resistance of H. zea to the Vip3Aa toxin to avoid foliar insecticide use.

Defoliation of Soybean Expressing Cry1Ac by Lepidopteran Pests

Lepidoptera, stink bugs, and weevils are important pests in soybean. For lepidopteran control, insecticides and seed treatments are used. As an alternative, Bt soybean was developed to control primary pests of Lepidoptera such as Rachiplusia nu (Guenée) (Noctuidae), Chrysodeixisincludens (Walker) (Noctuidae), Anticarsia gemmatalis Hübner (Erebidae), Helicoverpa gelotopoeon (Dyar) (Noctuidae), and Crocidosema aporema (Walsingham) (Tortricidae). However, the use of transgenic plants, and the resulting reduction of insecticide against target pests, may allow other pest species to become more prevalent in agricultural environments. Soybean expressing Cry1Ac against different lepidopteran nontarget and target insect pests was evaluated, and its performance was compared with non-Bt soybean with seed treatment. The treatments were Bt soybean, non-Bt soybean with seed treatment (Fortenza® diamide insecticide, Syngenta, Buenos Aires, Argentina), and non-Bt soybean without seed treatment. Larvae of H. gelotopoeon, Spodoptera albula (Walker) (Noctuidae), Spodoptera cosmiodes (Walker) (Noctuidae), Spodoptera eridania (Stoll) (Noctuidae), and Spodoptera frugiperda (J. E. Smith) (Lep.: Noctuidae) were used. The plants of each treatment were infested with larvae of each species, and the percentage of leaf damage produced by each species was recorded. The results showed that Bt soybean provided control of H. gelotopoeon and had a suppressive effect on S. frugiperda and S. albula. However, S. eridania and S. cosmiodes were not susceptible to the Cry1Ac protein in MON 87701 × MON 89788 soybean when evaluated by greenhouse infestation. Considering the performance of each species using non-Bt soybean without seed treatment, S. eridania would represent a potential risk in soybean crops.

Multidecadal, county-level analysis of the effects of land use, Bt cotton, and weather on cotton pests in China

Changes in land use, climate, and agricultural technologies affect pest severity and management. We analyzed long-term longitudinal data (1991–2015) on three major cotton pests for 51 Chinese counties. Bacillus thuringiensis (Bt) insect-resistant cotton had pervasive effects on the whole pest complex and its management. Adoption resulted in major reductions in insecticide use against bollworm. The resulting restoration of aphid biocontrol decreased aphid severity. Mirid bug severity increased, aided by higher May temperatures and reduced insecticide sprays against bollworm. Landscape effects on pest severity varied between species. Farmers sprayed at nondamaging infestation levels. Findings support Bt-based plant resistance as a component of integrated pest management (IPM) but highlight the potential for unintended outcomes for the whole pest complex and the importance of climate change.

Long-term changes in land use, climate, and agricultural technologies may affect pest severity and management. The influences of these major drivers can only be identified by analyzing long-term data. This study examines panel data on land use, adoption of genetically modified Bacillus thuringiensis (Bt) insect-resistant cotton, weather, pest severity, and insecticide use on three major cotton pests for 51 counties in China during 1991–2015. Bt cotton had pervasive effects on the whole pest complex in cotton and its management. Adoption resulted in major reductions in insecticide use for bollworm control. The resulting restoration of aphid biological control decreased aphid severity. However, mirid bugs, which have few effective natural enemies in cotton, increased in severity with warming May and reduced insecticide spraying against bollworm. The effects of landscape on pest severity were pest specific. The severity of cotton aphid and mirid bugs decreased with higher land use diversity, but the severity of highly polyphagous cotton bollworm was unrelated to land use diversity. Shares of forest, water body, and unused land area were negatively associated with the severity of mirid bugs, whereas cotton bollworm responded positively to the shares of water body and unused land area. Farmers sprayed insecticides at mild infestation levels and responded aggressively to severe bollworm outbreaks. Findings support the usefulness of Bt-based plant resistance as a component of integrated pest management (IPM) but highlight the potential for unexpected outcomes resulting from agro-ecosystem feedback loops as well as the importance of climate.

Coexistence of Bacillus thuringiensis (Bt)-transgenic and conventional rice affects insect abundance and plant fitness in fields

BACKGROUND

As genetically modified (GM) crops are cultivated worldwide, concerns are emerging about the ecological consequences of the coexistence of transgenic and non-transgenic crops in fields. We first conducted field experiments using insect-resistant transgenic rice expressing Bacillus thuringiensis (Bt-transgenic rice) and its counterpart conventional rice (Oryza sativa L.) with or without insecticide spraying in 2013 and 2014. In 2015 and 2016, Bt-transgenic and conventional rice plants were employed in pure and mixed cages, with an infestation of the target insect (Chilo suppressalis) and with insecticide spraying as the control treatment to prevent target insect infestation.

RESULTS

The presence of Bt-transgenic rice decreased the abundance of target insects but did not affect non-target insects and predators in fields. Compared with conventional rice, Bt-transgenic rice showed more empty seeds but comparable seed production in cages. The infestation of target insects significantly decreased the plant fitness of conventional rice in pure cages, but did not affect its fitness when conventional rice coexisted with Bt-transgenic rice. In mixed cages, the presence of Bt-transgenic rice decreased the abundance of target insects and the percentage of dead sheaths in conventional rice.

CONCLUSION

The presence of Bt-transgenic rice benefits the growth and reproduction of non-transgenic rice in fields because of a decreased abundance of target insects. © 2018 Society of Chemical Industry.

Overexpression of cytochrome P450s in a lambda-cyhalothrin resistant population of Apolygus lucorum (Meyer-Dür)

The mirid bug, Apolygus lucorum Meyer-Dür, has been an important pest of cotton crop in China, and is primarily controlled with insecticides, such as pyrethroids. To elucidate the potential resistant mechanisms of A. lucorum to lambda-cyhalothrin, a series of biological, biochemical, and molecular assays were conducted in the reference (AL-S) and lambda-cyhalothrin-resistant (AL-R) populations. Comparison of the molecular target of pyrethroid insecticides, voltage-gated sodium channel, revealed that there were no mutation sites in the resistant population, indicating target insensitivity is not responsible for increased resistance of AL-R to lambda-cyhalothrin. Furthermore, the synergism assays and the activities of detoxification enzymes were performed to determine detoxification mechanism conferring the lambda-cyhalothrin resistance. In the tested synergists, the piperonyl butoxide had the highest synergism ratio against lambda-cyhalothrin, which was up to five-fold in both populations. In addition, the result also showed that only cytochrome P450 had significantly higher O-deethylase activity with 7-ethoxycoumarin (1.78-fold) in AL-R population compared with AL-S population. Seven cytochrome P450 genes were found to be significantly overexpressed in the resistant AL-R population compared with AL-S population. Taken together, these results demonstrate that multiple over-transcribed cytochrome P450 genes would be involved in the development of lambda-cyhalothrin resistance in AL-R population.

Evaluation of the Impact of Genetically Modified Cotton After 20 Years of Cultivation in Mexico

For more than 20 years cotton has been the most widely sown genetically modified (GM) crop in Mexico. Its cultivation has fulfilled all requirements and has gone through the different regulatory stages. During the last 20 years, both research-institutions and biotech-companies have generated scientific and technical information regarding GM cotton cultivation in Mexico. In this work, we collected data in order to analyze the environmental and agronomic effects of the use of GM cotton in Mexico. In 1996, the introduction of Bt cotton made it possible to reactivate this crop, which in previous years was greatly reduced due to pest problems, production costs and environmental concerns. Bt cotton is a widely accepted tool for cotton producers and has proven to be efficient for the control of lepidopteran pests. The economic benefits of its use are variable, and depend on factors such as the international cotton-prices and other costs associated with its inputs. So far, the management strategies used to prevent development of insect resistance to GM cotton has been successful, and there are no reports of insect resistance development to Bt cotton in Mexico. In addition, no effects have been observed on non-target organisms. For herbicide tolerant cotton, the prevention of herbicide resistance has also been successful since unlike other countries, the onset of resistance weeds is still slow, apparently due to cultural practices and rotation of different herbicides. Environmental benefits have been achieved with a reduction in chemical insecticide applications and the subsequent decrease in primary pest populations, so that the inclusion of other technologies—e.g., use of non-Bt cotton- can be explored. Nevertheless, control measures need to be implemented during transport of the bolls and fiber to prevent dispersal of volunteer plants and subsequent gene flow to wild relatives distributed outside the GM cotton growing areas. It is still necessary to implement national research programs, so that biotechnology and plant breeding advances can be used in the development of cotton varieties adapted to the Mexican particular environmental conditions and to control insect pests of regional importance.

Establishment of a dietary exposure assay for evaluating the toxicity of insecticidal compounds to Apolygus lucorum (Hemiptera: Miridae)

With the commercialization of transgenic cotton that expresses Bt (Bacillus thuringiensis) insecticidal proteins, mirid bugs have become key pests in cotton and maize fields in China. Genetically engineered (GE) crops for controlling mirids are unavailable owing to a lack of suitable insecticidal genes. In this study, we developed and validated a dietary exposure assay for screening insecticidal compounds and for assessing the potential effects of insecticidal proteins produced by GE plants on Apolygus lucorum, one of the main mirid pests of Bt cotton and Bt maize. Diets containing potassium arsenate (PA) or the cysteine protease inhibitor E-64 were used as positive controls for validating the efficacy of the dietary exposure assay. The results showed that with increasing concentrations of PA or E-64, A. lucorum larval development time was prolonged and adult weight and fecundity were decreased, suggesting that the dietary exposure assay was useful for detecting the toxicity of insecticidal compounds to A. lucorum. This assay was then used to assess the toxicity of Cry1Ab, Cry1Ac, Cry1F, Cry2Aa, and Cry2Ab proteins, which have been transformed into several crops, against A. lucorum. The results showed that A. lucorum did not show a negative effect by feeding on an artificial diet containing any of the purified Cry proteins. No significant changes in the activities of digestive, detoxifying, or antioxidant enzymes were detected in A. lucorum that fed on a diet containing Cry proteins, but A. lucorum fitness was reduced when the insect fed on a diet containing E-64 or PA. These results demonstrate that A. lucorum is not sensitive to the tested Cry proteins and that the dietary exposure assay is useful for evaluating the toxicity of insecticidal compounds to this species.

Potential dermal and inhalation exposure to imidacloprid and risk assessment among applicators during treatment in cotton field in China

Quantifying operator exposure to pesticides is a key component of the decision-making procedure for risk assessment. China is the largest cotton-planting country in the world. Dense cotton planting patterns and pesticide overuse potentially place Chinese cotton farmers at high levels of exposure risk. Using whole-body dosimetry during backpack spraying application in cotton filed, the present study monitored potential dermal and inhalation exposure to the insecticide imidacloprid. For forward spraying (when the operators walked forward), the total potential dermal and inhalation exposure was 2059mg/kg of active ingredient (ai), corresponding to 0.21% of the applied quantity of the insecticide. However, the total exposure of backward walking (188mg/kg of ai) was approximately 11 times lower than that of forward walking. The upper body parts (head, chest, back and arms) were the most exposed. The potential inhalation exposure contributed to <0.1% of the total exposure. The exposure risk to imidacloprid inherent in these agricultural procedures was evaluated by margin of exposure values and was found to be safe under the present cotton treatment scenarios. In general, similar body exposure and distribution between Allura Red and imidacloprid verify Allura Red's feasibility as an environmentally friendly pesticide surrogate for exposure assessment.

Strategies for Enhanced Crop Resistance to Insect Pests

Insect pests are responsible for substantial crop losses worldwide through direct damage and transmission of plant diseases, and novel approaches that complement or replace broad-spectrum chemical insecticides will facilitate the sustainable intensification of food production in the coming decades. Multiple strategies for improved crop resistance to insect pests, especially strategies relating to plant secondary metabolism and immunity and microbiome science, are becoming available. Recent advances in metabolic engineering of plant secondary chemistry offer the promise of specific toxicity or deterrence to insect pests; improved understanding of plant immunity against insects provides routes to optimize plant defenses against insects; and the microbiomes of insect pests can be exploited, either as a target or as a vehicle for delivery of insecticidal agents. Implementation of these advances will be facilitated by ongoing advances in plant breeding and genetic technologies.

The nuclear hormone receptor E75A regulates vitellogenin gene (Al-Vg) expression in the mirid bug Apolygus lucorum

Apolygus lucorum is the predominant pest of Bacillus thuringiensis (Bt) cotton in China. 20-hydroxyecdysone (20E) plays a key role in the reproduction of this insect. To better understand the mechanism underlying 20E-regulated reproduction, the nuclear hormone receptor E75 isoform-A of Ap. lucorum (Al-E75A) was cloned and its expression analysed. A 2241-bp sequence of Al-E75A cDNA encoded an open reading frame of a polypeptide with a predicted molecular mass of 69.04 kDa. Al-E75A mRNA was detected in female adult stages of Ap. lucorum with peak expression in 7-day-old animals. Al-E75A was also expressed in several tissues, particularly in the fat body and ovary. A 3.2 kb Al-E75A mRNA was detected in all tissues by Northern blot. The fecundity and longevity were significantly decreased in female adults treated with Al-E75A small interfering RNA. The rates of egg incubation rates were considerably lower in the RNA interference-treated animals compared to the untreated controls. In order to investigate the molecular mechanism underlying the effects described above, vitellogenin (Al-Vg) was selected for further investigation. The expression pattern of Al-Vg was similar to that of Al-E75A and was up-regulated by 20E. After knockdown of Al-E75A, the expression profile of Al-Vg and the protein levels were down-regulated. These findings suggest that Al-E75A plays a crucial role in the regulation of Al-Vg expression in Ap. lucorum.

Characterization and Comparative Analysis of Olfactory Receptor Co-Receptor Orco Orthologs Among Five Mirid Bug Species

The phytophagous mirid bugs of Apolygus lucorum, Lygus pratensis as well as three Adelphocoris spp., including Adelphocoris lineolatus, A. suturalis, and A. fasciaticollis are major pests of multiple agricultural crops in China, which have distinct geographical distribution and occurrence ranges. Like many insect species, these bugs heavily rely on olfactory cues to search preferred host plants, thereby investigation on functional co-evolution and divergence of olfactory genes seems to be necessary and is of great interest. In the odorant detection pathway, olfactory receptor co-receptor (Orco) plays critical role in the perception of odors. In this study, we identified the full-length cDNA sequences encoding three putative Orcos (AsutOrco, AfasOrco, and LpraOrco) in bug species of A. suturalis, A. fasciaticollis, and L. pratensis based on homology cloning method. Next, sequence alignment, membrane topology and gene structure analysis showed that these three Orco orthologs together with previously reported AlinOrco and AlucOrco shared high amino acid identities and similar topology structure, but had different gene structure especially at the length and insertion sites of introns. Furthermore, the evolutional estimation on the ratios of non-synonymous to synonymous (Ka/Ks) revealed that Orco genes were under strong purifying selection, but the degrees of variation were significant different between genera. The results of quantitative real-time PCR experiments showed that these five Orco genes had a similar antennae-biased tissue expression pattern. Taking these data together, it is thought that Orco genes in the mirid species could share conserved olfaction roles but had different evolution rates. These findings would lay a foundation to further investigate the molecular mechanisms of evolutionary interactions between mirid bugs and their host plants, which might in turn contribute to the development of pest management strategy for mirid bugs.

Transgenic Bt cotton expressing Cry1Ac/Cry2Ab or Cry1Ac/EPSPS does not affect the plant bug Adelphocoris suturalis or the pollinating beetle Haptoncus luteolus

The widespread cultivation of transgenic Bt cotton makes assessing the potential effects of this recombinant crop on non-target organisms a priority. However, the effect of Bt cotton on many insects is currently virtually unknown. The plant bug Adelphocoris suturalis is now a major pest of cotton in southern China and the beetle Haptoncus luteolus is one of the most ancient cotton pollinators. We conducted laboratory experiments to evaluate the toxicity of the Bt cotton varieties ZMSJ, which expresses the toxins Cry1Ac and Cry2Ab, and ZMKCKC, which expresses Cry1Ac and EPSPS, on adult A. suturalis and H. luteolus. No significant increase in the mortality of either species was detected after feeding on Bt cotton leaves or pollen for 7 days. Trace amounts of Cry1Ac and Cry2Ab proteins could be detected in both species but in vitro binding experiments found no evidence of Cry1Ac and Cry2Ab binding proteins. These results demonstrate that feeding on the leaves or pollen of these two Bt cotton varieties has no toxic effects on adult A. suturalis or H. luteolus.

The Complete Mitochondrial Genome of the Plant Bug Lygus pratensis Linnaeus (Hemiptera: Miridae)

Lygus pratensis is a phytophagous pest responsible for yield losses in Bt alfalfa and other economic crops in Northwestern China. To better characterize Miridae at the genomic level, the complete mitochondrial (mt) genome of L. pratensis was sequenced and analyzed in this study. The mt genome was amplified via the polymerase chain reaction to generate overlapping fragments. These fragments were then sequenced, spliced, and analyzed to include the examination of nucleotide composition, codon usage, compositional biases, protein-coding genes (PCGs), and RNA secondary structures. Phylogenetic relationships between L. pratensis and other species in different Heteroptera families were also examined. The mt genome was found to be a typical circular genome with a length of 16,591 bp and a total AT content of 75.1%, encoded for 13 PCGs, 22 transfer RNAs (tRNAs), 2 ribosomal RNAs (lrRNA and srRNA), and a noncoding control region. The nucleotide composition of the entire mt genome was heavily biased toward A and T. All of the tRNAs were predicted to have classic clover leaf structures, but three of the tRNAs (tRNAAsn, tRNAHis, tRNAHis) were missing the TΨC loop. The control region (2,017 bp), which was found to be located between 12S and tRNAIle, contained three tandem repeat elements. Phylogenetic analyses showed that L. pratensis is closely related to the other three examined Lygus bugs, and that it is a sister group to Apolygus and Adelphocoris. This study confirms the usability of the mt genome in phylogenesis studies pertaining to the Lygus genus, within Miridae.

Yield Losses in Transgenic Cry1Ab and Non-Bt Corn as Assessed Using a Crop-Life-Table Approach

In this study, we constructed crop life tables for Bacillus thuringiensis Berliner (Bt) Cry1Ab and non-Bt corn hybrids, in which yield-loss factors and abundance of predaceous arthropods were recorded during 2 yr at two locations. Corn kernel/grain was the yield component that had the heaviest losses and that determined the overall yield loss in the corn hybrids across years and locations. Yield losses in both corn hybrids were primarily caused by kernel-destroying insects. Helicoverpa zea (Boddie) and Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) were the key loss factors at one location, while at the other, the key loss factor was the silk fly larvae, Euxesta spp. (Diptera: Ulidiidae). Although the realized yield of corn grains was not different (P > 0.05) between Cry1Ab and non-Bt corn hybrids, the Bt corn hybrid reduced (P < 0.05) the damage by H. zea and S. frugiperda in three of the four field trials, particularly at the location where Lepidoptera were the key loss factors. As expected, no reduction in the abundance of predaceous arthropods was observed in Cry1Ab corn fields. Various species of natural enemies were recorded, particularly the earwig Doru luteipes (Scudder) (Dermaptera: Forficulidae), which was the most abundant and frequent predaceous insect. These results indicate that integration of pest management practices should be pursued to effectively minimize losses by kernel-destroying insects during corn reproductive stages when growing non-Bt or certain low-dose Bt corn cultivars for fall armyworm and corn earworm, such as those producing Cry1Ab or other Cry toxins.

Field Trapping of Predaceous Insects With Synthetic Herbivore-Induced Plant Volatiles in Cotton Fields

Nine herbivore-induced plant volatiles (HIPVs) and one methyl jasmonate were field-tested for their attractiveness to the main predators in cotton fields of North China in 2 yr. The main predators including ladybird beetles (Propylaea japonica (Thunberg), Harmonia axyridis (Pallas)), green lacewings (Chrysoplera sinica (Tjeder), Chrysopa spp.), predatory bugs (Geocoris pallidipennis (Costa), Orius spp., Nabis spp.) and spiders (Misumenops tricuspidatus (Fabricius), Erigonidium graminicolum (Sundevall)) were investigated. Two-way ANOVA indicated that the volatile compound, year, and the volatile compound × year interaction affected the behavioral responses of predators. It was found that indole significantly attracted the ladybird beetle P. japonica, H. axyridis. Linalool could attract P. japonica. Green lacewing C. sinica was significantly attracted by α-pinene and β-pinene, whereas indole significantly attracted Chrysopa spp. Methyl jasmonate and α-pinene showed significant attraction to small-flower bug Orius spp. In addition, the attraction of α-humulene to C. sinica, attractiveness of β-pinene to Orius spp. and Chrysopa spp., were observed only in one of the two years. However, the big-eyed bug G. pallidipennis, damsel bug Nabis spp., spiders M. tricuspiata and E. graminicolum did not respond to any of the tested HIPVs. These results are discussed with respect to possible applications of a synthetic attractant for main predators in cotton fields.

Impact of transgenic soybean expressing Cry1Ac and Cry1F proteins on the non-target arthropod community associated with soybean in Brazil

Field-scale studies that examine the potential for adverse effects of Bt crop technology on non-target arthropods may supplement data from laboratory studies to support an environmental risk assessment. A three year field study was conducted in Brazil to evaluate potential for adverse effects of cultivating soybean event DAS-81419-2 that produces the Cry1Ac and Cry1F proteins. To do so, we examined the diversity and abundance of non-target arthropods (NTAs) in Bt soybean in comparison with its non-Bt near isoline, with and without conventional insecticide applications, in three Brazilian soybean producing regions. Non-target arthropod abundance was surveyed using Moericke traps (yellow pan) and pitfall trapping. Total abundance (N), richness (S), Shannon-Wiener (H'), Simpson's (D) and Pielou's evenness (J) values for arthropod samples were calculated for each treatment and sampling period (soybean growth stages). A faunistic analysis was used to select the most representative NTAs which were used to describe the NTA community structure associated with soybean, and to test for effects due to the treatments effects via application of the Principal Response Curve (PRC) method. Across all years and sites, a total of 254,054 individuals from 190 taxa were collected by Moericke traps, while 29,813 individuals from 100 taxa were collected using pitfall traps. Across sites and sampling dates, the abundance and diversity measurements of representative NTAs were not significantly affected by Bt soybean as compared with non-sprayed non-Bt soybean. Similarly, community analyses and repeated measures ANOVA, when applicable, indicated that neither Bt soybean nor insecticide sprays altered the structure of the NTA communities under study. These results support the conclusion that transgenic soybean event DAS-81419-2 producing Cry1Ac and Cry1F toxins does not adversely affect the NTA community associated with soybean.

Farmers willingness to grow GM food and cash crops: empirical evidence from Pakistan

Using data collected from 950 farmers in four provinces of Pakistan i.e. Punjab, Sindh, Khyber Pakhtunkhwa (KP) and Balochistan, the current paper analyzes the farmer's willingness to grow genetically modified (GM) food and cash crop. There exists a huge difference in farmers' perception about GM food and cash crops in Pakistan. In Pakistan, over 90 percent of the farmers were aware of the GM cash crop while only few farmers were aware of GM food crops and vegetables. Empirical results show that majority of the farmers were willing to grow GM cash crops but reluctant to grow the GM food crops and vegetables mainly due to the controversy surrounding the GM food crops. The econometric results illustrate the willingness to grow GM food and cash crop is higher among farm households with large land holdings, secured land rights, higher income levels and larger assets ownership. Result also reveals that farm household NGOs membership negatively affects the willingness of the farmers to grow GM food and cash crops. The access to credit and agricultural extension services do not affect farmer's willingness to grow GM food and cash crops in Pakistan.

Sublethal effects of sulfoxaflor on biological characteristics and vitellogenin gene (AlVg) expression in the mirid bug, Apolygus lucorum (Meyer-Dür)

The mirid bug, Apolygus lucorum (Meyer-Dür) has evolved the resistance towards some traditional insecticides, especially pyrethroids and organophosphates. Sulfoxaflor, as a novel insecticide, is used for control of sap-feeding insects, like A. lucorum. Therefore, it is necessary to determine the acute toxicity and the potential sublethal effects of sulfoxaflor in A. lucorum. Here, the LD₅₀ value of sulfoxaflor against A. lucorum was assayed as 3.347ng/adult at 48h via topical application. Besides, the effects of a sublethal dose (LD₁₅) of sulfoxaflor on biological characteristics of A. lucorum were estimated by comparison of the life table parameters. The longevities and fecundity of parent generation did not exhibited significant difference between both control and treatment groups after exposure to LD₁₅ dose of sulfoxaflor (0.568ng/adult) for 48-h. However, the parameters reflecting their progeny G1 generation population dynamics, including the intrinsic rate of increase (ri), the finite rate of increase (λ), the mean generation time (T), the net reproductive rate (R₀) and gross reproduction rate (GRR) significantly reduced in the treatment group compared to the control. Furthermore, the expression level of AlVg mRNA significantly decreased by 43.8% in the progeny whose parents were treated with LD₁₅ dose of sulfoxaflor in comparison with the control transgenerational female adults. These results suggested that sublethal dose of sulfoxaflor adversely affect the development and reproduction of transgenerational A. lucorum. The downregulation of AlVg might have negative impacts on the fecundity of A. lucorum.

Sterol content in the artificial diet of Mythimna separata affects the metabolomics of Arma chinensis (Fallou) as determined by proton nuclear magnetic resonance spectroscopy

Insects cannot synthesize sterols and must obtain them from plants. Therefore, reducing plant sterol content or changing sterol type might be an effective pest control strategy. However, the impacts of these changes on pests' natural predators remain unknown. Here, we fed artificial diets with reduced sterol content to Mythimna separata (Walker) (Lepidoptera: Noctuidae) and investigated the effects on its natural predator, Arma chinensis (Fallou) (Hemiptera: Pentatomidae). Reduced sterol content in M. separata (MS1, MS2, and MS5) was achieved by feeding them artificial diets prepared from a feed base subjected to one, two, or five cycles of sterol extractions, respectively. The content of most substances increased in A. chinensis (AC) groups feeding on MS2 and MS5. The content of eight substances (alanine, betaine, dimethylamine, fumarate, glutamine, glycine, methylamine, and sarcosine) differed significantly between the control (AC0) and treated (AC1, AC2, and AC5) groups. Metabolic profiling revealed that only AC5 was significantly distinct from AC0; the major substances contributing to this difference were maltose, glucose, tyrosine, proline, O-phosphocholine, glutamine, allantoin, lysine, valine, and glutamate. Furthermore, only two metabolic pathways, that is, nicotinate and nicotinamide metabolism and ubiquinone and other terpenoid-quinone biosynthesis, differed significantly between AC1 and AC5 and the control, albeit with an impact value of zero. Thus, the sterol content in the artificial diet fed to M. separata only minimally affected the metabolites and metabolic pathways of its predator A. chinensis, suggesting that A. chinensis has good metabolic self-regulation with high resistance to sterol content changes.

Diversifying Food Systems in the Pursuit of Sustainable Food Production and Healthy Diets

Increasing demand for nutritious, safe, and healthy food because of a growing population, and the pledge to maintain biodiversity and other resources, pose a major challenge to agriculture that is already threatened by a changing climate. Diverse and healthy diets, largely based on plant-derived food, may reduce diet-related illnesses. Investments in plant sciences will be necessary to design diverse cropping systems balancing productivity, sustainability, and nutritional quality. Cultivar diversity and nutritional quality are crucial. We call for better cooperation between food and medical scientists, food sector industries, breeders, and farmers to develop diversified and nutritious cultivars that reduce soil degradation and dependence on external inputs, such as fertilizers and pesticides, and to increase adaptation to climate change and resistance to emerging pests.

Silencing of odorant binding protein gene AlinOBP4 by RNAi induces declining electrophysiological responses of Adelphocoris lineolatus to six semiochemicals

Odorant binding proteins (OBPs) are believed to be important for transporting semiochemicals through the aqueous sensillar lymph to the olfactory receptor cells within the insect antennal sensilla. Here, we injected AlinOBP4-siRNA into the conjunctivum between prothorax and mesothorax of the lucerne plant bug, Adelphocoris lineolatus and evaluated the silencing of AlinOBP4 by reverse transcription polymerase chain reaction (RT-PCR) analysis, quantitative real-time PCR (qPCR) test and electroantennogram (EAG) assay. The combination of RT-PCR and qPCR analyses revealed that the levels of messenger RNA transcript were significantly reduced ∼95% in AlinOBP4-siRNA-treated A. lineolatus males and ∼75% in RNAi-treated females within 48 hours. It was found that there are different EAG responses between male and female bugs when the AlinOBP4 gene was silenced by RNAi. The EAGs of A. lineolatus to two plant volatiles, tridecanal and hexyl alcohol, were reduced 9.09% and 79.45% in RNAi-treated males, 62.08% and 62.08% in RNAi-treated females compared to the controls, separately. Antennae of RNAi-treated bugs showed significantly lower electrophysiological responses to four sex pheromone analogs, butyl butanoate, 1-hexyl butyrate, (E)-2-hexenyl butyrate and hexyl hexanoate. The EAG recordings were reduced 35.43%, 35.24%, 39.96% and 78.47% in RNAi-treated males and 64.52%, 18.13%, 36.88% and 49.52% in RNAi-treated females, respectively. The results suggested that AlinOBP4 might play dual-roles in the identification of plant volatiles and sex pheromones. It was suspected that AlinOBP4 may have different functions in odor perception between male and female A. lineolatus.

Identification and Characterization of Odorant Binding Proteins in the Forelegs of Adelphocoris lineolatus (Goeze)

The chemosensory system is essential for insects to detect exogenous compounds, and odorant binding proteins (OBPs) play crucial roles in odorant binding and transduction. In the alfalfa plant bug Adelphocoris lineolatus, an important pest of multiple crops, our understanding of the physiological roles of antenna-biased OBPs has increased dramatically, whereas OBPs related to gustation have remained mostly unexplored. In this study, we employed RNA sequencing and RACE PCR methods to identify putative OBPs from the adult forelegs of both sexes. Eight candidate OBPs were identified, and three OBPs (AlinOBP15, 16, and 17) were novel. Full-length sequence alignment and phylogenetic analyses suggested that these three candidate OBPs had characteristics typical of the insect OBP family. AlinOBP16 and 17 displayed six highly conserved cysteines, placing them in the classic OBP subfamily, whereas AlinOBP15 resembled AlinOBP14 and clustered with the Plus-C clade. Quantitative real-time PCR (qRT-PCR) revealed distinct and significant tissue- and sex-biased expression patterns. AlinOBP15 was highly expressed in female heads, and AlinOBP16 and 17 were strongly expressed in female antennae. In particular, AlinOBP11, the most abundant OBP gene in our foreleg transcriptome dataset, was predominately expressed in adult legs. Furthermore, four types of sensilla hairs were observed on the forelegs of adult A. lineolatus, including sensilla trichodea, setae, and two types of sensilla chaetica (Sch1 and Sch2). Anti-AlinOBP11 antiserum strongly labeled the outer sensillum lymph of Sch2, implying that it has important gustatory functions in A. lineolatus. Our current findings provide evidence that OBPs can be functionally expressed in the tarsal gustatory sensilla of hemipteran mirid species, broadening our understanding of OBP chemosensory function in insects and facilitating the discovery of new functional targets for the regulation of insect host-searching behaviors.

Seed Treatment Combined with a Spot Application of Clothianidin Granules Prolongs the Efficacy of Controlling Piercing-Sucking Insect Pests in Cotton Fields

Seed treatments can directly protect cotton from early season piercing-sucking insect Aphis gossypii Glover but hardly provide long-term protection against Apolygus lucorum (Meyer-Dür). Therefore, the efficacy of clothianidin seed treatments combined with spot applications of clothianidin granules at the bud stage of cotton was evaluated to control piercing-sucking pests during the entire cotton growing season. Clothianidin seed treatments (at the rate of 4 g ai/kg seed) combined with a clothianidin granular treatment (even at low rate of 0.9 kg ai/ha) at the bud stage can effectively suppress A. gossypii and A. lucorum infestations throughout the seedling and blooming stages after planting and can improve cotton yield. The spot application of clothianidin granules also reduced the population densities of Bemisia tabaci (Gennadius). The dynamic changes of clothianidin residues demonstrated that the control efficacy of clothianidin against A. gossypii and A. lucorum might be related to the residues of this neonicotinoid in cotton leaves. This pest management practice provided long-term protection against cotton piercing-sucking pests for the entire growing season of cotton plants and could supplement the short-term control efficiency of clothianidin used as a seed treatment.

Methyl jasmonate induction of cotton: a field test of the 'attract and reward' strategy of conservation biological control

Natural or synthetic elicitors can affect plant physiology by stimulating direct and indirect defence responses to herbivores. For example, increased production of plant secondary metabolites, a direct response, can negatively affect herbivore survival, development and fecundity. Indirect responses include increased emission of plant volatiles that influence herbivore and natural enemy behaviour, and production of extrafloral nectar that serves as a food source for natural enemies after their arrival on induced plants. Therefore, the use of elicitors has potential for the study of basic aspects of tritrophic interactions, as well as application in biorational pest control, i.e. an 'attract and reward' strategy. We conducted a field study to investigate the effects of methyl jasmonate, an elicitor of plant defence responses, on three trophic levels: the plant, herbivores and natural enemies. We made exogenous applications of methyl jasmonate to transgenic cotton and measured volatile emission, extrafloral nectar production and plant performance (yield). We also assessed insect abundance, insect performance, and parasitism and predation of brown stink bug, Euschistus servus, eggs in methyl jasmonate-treated and untreated control plots. Application of methyl jasmonate increased emission of volatiles, in particular, (+)-limonene and (3E)-4,8-dimethyl-1,3,7-nonatriene, and production of extrafloral nectar, but not yield, compared with the control treatment. Despite increased volatile and extrafloral nectar production, methyl jasmonate application did not affect plant bug performance, or mortality of E. servus egg masses, and only marginally influenced insect abundance. Mortality of E. servus eggs varied over the course of the study. Overall, methyl jasmonate treatment affected cotton plant-induced responses, but not the insects that inhabit the plants. Our results were probably influenced by reduced natural enemy colonization of cotton from adjacent non-crop habitats, and subsequent low within-field population recruitment. Much remains to be learned about the effects of exogenous application of plant-produced 'enhancers' on the behaviour of natural enemies before crop physiology can be manipulated to enhance pest control.