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Tyrosine kinase inhibitor (TKI) is a standard treatment for patients with NSCLC harboring constitutively active epidermal growth factor receptor (EGFR) mutations. However, most rare EGFR mutations lack treatment regimens except for the well-studied ones. We constructed two EGFR variant libraries containing substitutions, deletions, or insertions using the saturation mutagenesis method. All the variants were located in the EGFR mutation hotspot (exons 18-21). The sensitivity of these variants to afatinib, erlotinib, gefitinib, icotinib, and osimertinib was systematically studied by determining their enrichment in massively parallel cytotoxicity assays using an endogenous EGFR-depleted cell line. A total of 3914 and 70,475 variants were detected in the constructed EGFR Substitution-Deletion (Sub-Del) and exon 20 Insertion (Ins) libraries. Of the 3914 Sub-Del variants, 221 proliferated fast in the control assay and were sensitive to EGFR-TKIs. For the 70,475 Ins variants, insertions at amino acid positions 770-774 were highly enriched in all 5 TKI cytotoxicity assays. Moreover, the top 5% of the enriched insertion variants included a glycine or serine insertion at high frequency. We present a comprehensive reference for the sensitivity of EGFR variants to five commonly used TKIs. The approach used here should be applicable to other genes and targeted drugs. BACKGROUND: Tyrosine kinase inhibitors (TKIs) therapy is a standard treatment for patients with advanced non-small-cell lung carcinoma (NSCLC) when activating epidermal growth factor receptor (EGFR) mutations are detected. However, except for the well-studied EGFR mutations, most EGFR mutations lack treatment regimens. TRANSLATIONAL SIGNIFICANCE: The results demonstrated that patients with rare EGFR mutations were most likely to benefit from osimertinib therapy compared to afatinib, erlotinib, gefitinib, or icotinib therapy. This study provides a case of deep mutational scanning that simultaneously assayed substitution, deletion, and insertion variants. This approach is applicable for other oncogenes and targeted drugs.

Summary DACH1 abundance is reduced in human malignancies, including breast cancer. Herein DACH1 was detected among multipotent fetal mammary stem cells in the embryo, among mixed lineage precursors, and in adult basal cells and (ERα+) luminal progenitors. Dach1 gene deletion at 6 weeks in transgenic mice reduced ductal branching, reduced the proportion of mammary basal cells (Lin− CD24med CD29high) and reduced abundance of basal cytokeratin 5, whereas DACH1 overexpression induced ductal branching, increased Gata3 and Notch1, and expanded mammosphere formation in LA-7 breast cells. Mammary gland-transforming growth factor β (TGF-β) activity, known to reduce ductal branching and to reduce the basal cell population, increased upon Dach1 deletion, associated with increased SMAD phosphorylation. Association of the scaffold protein Smad anchor for receptor activation with Smad2/3, which facilitates TGF-β activation, was reduced by endogenous DACH1. DACH1 increases basal cells, enhances ductal formation and restrains TGF-β activity in vivo., Highlights • Dach1 is expressed in mammary gland fetal stem cells and adult luminal cells • Dach1 expands mammary gland basal/myoepithelial cells • Dach1 induces post-natal mammary gland ductal formation • Dach1 retrains TGF-β activity in the mammary gland in vivo, DACH1 abundance, is reduced in human malignancies, including breast cancer. In this article, Dr. Pestell and his colleagues showed that DACH1 is expressed in multipotent mammary gland fetal stem cells and both the adult basal and ERα+ luminal cells, promotes mammary gland stem cell and basal/myoepithelial cell expansion, promotes mammary gland ductal branching, and restrains TGF-β action in the pubertal mammary gland.

International audience; Aphids constitute a group of major wheat crop pests in northern China and severe infestations at heading and flowering stages lead to important yield loss. Natural enemies may increase yield by reducing aphid density but alteration in cropping pattern can cause changes in their species composition. We observed strong evidence for top-down control of the wheat aphid population growth in winter wheat during 2011-2013 at Langfang Experimental Station (CAAS, China), e.g., a significant increase in the control efficiency of natural enemies in open field cages accounted for 98, 53.8 and 59.3% in the 2011, 2012 and 2013, respectively as compared to exclusion cages. We observed peak population of wheat aphids in the middle growth stage in open field survey. Overall, the population densities of wheat aphids and natural enemies were highest in the middle and late growth stages, respectively while lowest densities recorded in late stage for aphids and in early plant stage for natural enemies. The potential natural enemies were coccinellids, and Aphidiinae aphid parasitoids, especially Aphidius gifuensis (Ashmead) following the aphid peaks each season. Yield difference among the three exclosure cages were substantially different during 2011-2012, the highest yield was recorded in the treatment without aphids as compared the others. Compared to previous studies conducted in northern China, the control efficiency of natural enemies has been greatly increased by coccinellids and parasitoid community in the absence of chrysopids and spiders. These biocontrol services will provide improved IPM strategies for the wheat ecosystem in northern China.

The clover cutworm, Scotogramma trifolii Rottemberg (Lepidoptera: Noctuidae), is a serious polyphagous insect pest of Triticum aestivum Linnaeus, Zea mays Linnaeus, Gossypium herbaceum Linnaeus, and cruciferous vegetables in Asia and Europe. Although S. trifolii has been documented as a long-distance migratory species, the seasonal pattern of migration and the mating status associated with migration in this species have not been fully understood. In this paper, a set of multi-year monitoring data concerning S. trifolii migration was reported. The monitoring study was conducted by searchlight trapping on a small isolated island at the center of the Bohai Strait in northern China in 2003–2015. Data analyses showed that there were significant seasonal differences in the migration of S. trifolii moths across the sea, in which the expected numbers of moths caught per day in July through September were much higher than in the rest of months. The percentage of trapped moths was significantly female biased. The vast majority of females trapped in August and September were virgins, with little or no ovarian development. In contrast, most females trapped in May to July had mated and been sexually mature. The results suggest that S. trifolii migrates toward the north in prevailing southerly winds during late-spring (May) and early-summer (June and July), and returns to the south in prevailing northerly winds during late-summer and early-autumn. These findings may help improve the regional forecast and management of S. trifolii.

Evolution of pest resistance reduces the efficacy of insecticidal proteins from the gram-positive bacterium Bacillus thuringiensis (Bt) used widely in sprays and transgenic crops. In some previously studied strains of three major lepidopteran pests, resistance to Bt toxin Cry1Ac is associated with mutations disrupting the extracellular or cytoplasmic domains of cadherin proteins that bind Cry1Ac in the midgut of susceptible larvae. Here we report the first case of a cadherin transmembrane mutation associated with insect resistance to Bt. We discovered this mutation in a strain of the devastating global cotton pest, the pink bollworm (Pectinophora gossypiella), derived from a field population in the Yangtze River Valley of China. The mutant allele analyzed here has a 207 base pair deletion and encodes a cadherin protein lacking its transmembrane domain. Relative to a susceptible strain, a strain homozygous for this allele had 220-fold resistance to Cry1Ac and 2.1-fold cross-resistance to Cry2Ab. On transgenic cotton plants producing Cry1Ac, no susceptible larvae survived, but the resistant strain completed its life cycle. Inheritance of resistance to Cry1Ac was autosomal, recessive and tightly linked with the cadherin gene. Transportation of cadherin protein to the cell membrane and susceptibility to Cry1Ac occurred in transfected insect cells expressing the wild type cadherin allele, but not in transfected insect cells expressing the mutant cadherin allele. The results imply that the mutant allele analyzed here confers resistance to Cry1Ac by disrupting cellular trafficking of cadherin.

Interspecific competition among different species of insect parasitoids may affect the establishment or efficacy of species used for biological control of a target pests. Peristenus spretus Chen & van Achterberg and Peristenus relictus Loan (syn. P. stygicus) (Hymenoptera: Braconidae) are two dominant solitary parasitoids of mirid bugs in China. In this study, interspecific competition between larvae of P. spretus and P. relictus for the nutrients inside their common host, the green plant bug (Apolygus lucorum Meyer-Durin), as well as their extrinsic competition for host resources were investigated in the laboratory. We examined the effect of four different time intervals between oviposition by the two species (10 min, 24 h, 48 h, and 72 h) and two parasitoid sequences (i.e., P. spretus before P. relictus [Ps-Pr] and P. relictus before P. spretus (Pr-Ps)] in no-choice tests to measure nutrient competition between the two species. In choice tests, three densities of A. lucorum nymphs (40, 80, and 120) were presented to various combinations of P. spretus and P. relictus (1,1; 2,2; or 3,3 pairs). In addition, the developmental times of the immature stage (from egg to late instar larva) of P. spretus and P. relictus were determined. We found that neither the time interval between oviposition by the two competing species, nor the order the parasitoids attacked (Ps-Pr or Pr-Ps) had any influence on the percentage of parasitoid offspring that belonged a particular parasitoid species. Peristenus spretus dominated, accounting for 89.2–97.9% of parasitoid offspring in the no-choice nutrient competition experiment. Parasitoid sequence did, however, affect sex ratio in the dominant parasitoid’s offspring, with 48.2% of P. spretus offspring being female in the Pr-Ps sequence, while only 29.2% were female in the Ps-Pr sequence. Overall, in the host resource competition experiment, 64.7–82.2% of all emerged adult parasitoids of the offspring generation, for all host density treatments, were P. spretus. The percentage of emerged parasitoids that were a given species was significantly affected by host density, but neither by the number of pairs of P. spretus or P. relictus nor by the parasitoid density × host density interaction. The developmental time of the immature stage of P. spretus was 2.2 days shorter than that of P. relictus, an important factor in making P. spretus a superior competitor over P. relictus in all the competition trials. Based on these results, we conclude P. spretus will have an important advantage when competing with P. relictus, a factor that should be considered in any biological control program using these two parasitoids in China.

Accurate monitoring of locust migration is the basis for early warning and emergency control programs. This article integrates laboratory recordings with the use of Ku-band vertical insect radar to assess migration of the yellow-spined bamboo locust Ceracris kiangsu (Orthoptera: Arcypteridae) in the China-Laos border area. Under laboratory conditions, field-caught individuals engaged in flight at temperatures above 20℃ and exhibited a wingbeat frequency of 18.5–31.1 Hz. Between July 6 and August 23, 2020, a total of 39C. kiangsu migration events were recorded by radar. Locust individuals only engaged in diurnal migration, with peak activity after 15:00. Flight was recorded at an average height, flight speed and density of 410 m above ground level, 35.8 km/h, and 1305.9 individuals/km3, respectively. High-density C. kiangsu swarms exhibited high flight speeds. Departing from Laos, locusts migrated north by west 27.4–35.0° into Jiangcheng county (Yunnan, China). Migration flight was affected by ambient temperature, while its speed was determined by that of prevailing wind currents. Individual locusts autonomously adjusted their heading direction in order to unify the travel direction of the migrant swarm. Ku-band high-resolution fully polarimetric insect radar can thus accurately assess the migration patterns of C. kiangsu locusts and thereby constitutes an important forecasting tool.

Spodoptera exigua (Hubner) is an important agricultural pest with worldwide distribution. Monitoring the population dynamics of adults and predicting the occurrence of next generation are the basis of prevention and control. Insect attractants are based on preferences for foods or their volatiles and have great potential for pest monitoring and management. To evaluate the monitoring success of food attractants on S. exigua populations in the field, we first quantitatively analyzed the reproductive organ development of adults in a laboratory population. The ovarian development of females was divided into four stages. The length range of the testis major axis of males at different ages was established according to the principle of testis development. This allowed documentation of the reproductive status of adults trapped in the field. In 2019 and 2020, we used food attractant trapping combined with reproductive system examination to monitor the population dynamics and reproductive development of S. exigua adults in natural environment. The results showed obvious generational changes in the population density dynamics of males and females of S. exigua. During the two-year monitoring period, the ovarian development level and mating times of trapped females in the second generation increased at first and then decreased with time. The number of eggs within ovarioles trapped initially decreased and then increased over time. The ovarian development level and mating times of trapped females in the third-generation adults increased gradually over time, and the number of eggs in female ovarioles decreased gradually over time. The age of trapped males in the second generation initially increased and then decreased over time. The age of males in the third generation increased gradually over time. There were significant differences in the reproductive development of female and male moths trapped in different generations in 2019. This study showed that trapping using food attractants can monitor field population dynamics of S. exigua. Combined with examination of reproductive system anatomy, it can monitor the reproductive organ development, mating, and oviposition status of wild adults.

Preclinical data suggest that head and neck cancer is an intrinsically immunosuppressive disease with abnormal inflammatory components in the tumor microenvironment. The development of immune checkpoint inhibitors, which are monoclonal antibodies capable of inhibiting immune suppressive signals to prime anticancer immunity, has revolutionized the therapeutic landscape in recurrent/metastatic head and neck cancer. However, patients with head and neck cancer present primary resistance to immunotherapy. Many ongoing trials include combinations of immunotherapy with different therapeutic interventions, aiming to improve response rates and overall survival. As novel therapy strategies are leveraged, the significance of immunotherapy in recurrent/metastatic head and neck cancer continues to be revealed. This review aims to summarize combinational immunotherapy in head and neck cancer.

The polyphagous mirid bug Apolygus lucorum (Hemiptera: Miridae) is an important pest of cotton and other crops in China. It would be useful to examine the reproductive biology of A. lucorum for the development of management strategies. In this study, the effect of mating on ovarian development, egg maturation, and oviposition of A. lucorum was investigated. The results showed that mating could induce ovary development and oviposition. During the preoviposition period (

The white-backed planthopper Sogatella furcifera (Horvath) is a major pest of rice in Asia. In spring and summer, this species migrates thousands of kilometers northward from tropical and subtropical regions into temperate climate zones, such as northern China, Korean Peninsula, and Japan. Previous studies on the migration behavior of S. furcifera have been done mainly in southern and eastern China. However, the species' pattern of seasonal migration in northern China remains unknown. In northern China, occurrence and flight trajectories of S. furcifera migration across the Bohai Sea were studied on Beihuang Island (BH) in the center of the Bohai Strait from spring to autumn 2003–2016 using searchlight trapping and trajectory simulation. During the period 2003–2016, all S. furcifera adults were captured in July, August and September; the earliest capture occurred on 12 July 2013 and the latest on 26 September 2007. The longest annual migration span at BH was 60 d in 2014. Simulation of possible migration trajectories demonstrates that S. furcifera mainly migrates between Shandong Province and Liaoning Province (or the Korean Peninsula) in both directions. Overall, our research will contribute to a better understanding of the occurrence of S. furcifera in China and to the construction of a real-time prediction system in future.

Although farmers in China have grown transgenic Bt-Cry1Ac cotton to resist the major pest Helicoverpa armigera since 1997 with great success, many secondary lepidopteran pests that are tolerant to Cry1Ac are now reported to cause considerable economic damage. Vip3AcAa, a chimeric protein with the N-terminal part of Vip3Ac and the C-terminal part of Vip3Aa, has a broad insecticidal spectrum against lepidopteran pests and has no cross resistance to Cry1Ac. In the present study, we tested insecticidal activities of Vip3AcAa against Spodoptera litura, Spodoptera exigua, and Agrotis ipsilon, which are relatively tolerant to Cry1Ac proteins. The bioassay results showed that insecticidal activities of Vip3AcAa against these three pests are superior to Cry1Ac, and after an activation pretreatment, Vip3AcAa retained insecticidal activity against S. litura, S. exigua and A. ipsilon that was similar to the unprocessed protein. The putative receptor for this chimeric protein in the brush border membrane vesicle (BBMV) in the three pests was also identified using biotinylated Vip3AcAa toxin. To broaden Bt cotton activity against a wider spectrum of pests, we introduced the vip3AcAa and cry1Ac genes into cotton. Larval mortality rates for S. litura, A. ipsilon and S. exigua that had fed on this new cotton increased significantly compared with larvae fed on non-Bt cotton and Bt-Cry1Ac cotton in a laboratory experiment. These results suggested that the Vip3AcAa protein is an excellent option for a “pyramid” strategy for integrated pest management in China.

Transgenic plants that produce Bacillus thuringiensis (Bt) crystalline (Cry) toxins are cultivated worldwide to control insect pests. Resistance to B. thuringiensis toxins threatens this technology, and although different resistance mechanisms have been identified, some have not been completely elucidated. To gain new insights into these mechanisms, we performed multiple back-crossing from a 3000-fold Cry1Ac-resistant BtR strain from cotton bollworm (Helicoverpa armigera), isolating a 516-fold Cry1Ac-resistant strain (96CAD). Cry1Ac resistance in 96CAD was tightly linked to a mutant cadherin allele (mHaCad) that contained 35 amino acid substitutions compared with HaCad from a susceptible strain (96S). We observed significantly reduced levels of the mHaCad protein on the surface of the midgut epithelium in 96CAD as compared with 96S. Expression of both cadherin alleles from 96CAD and 96S in insect cells and immunofluorescence localization in insect midgut tissue sections showed that the HaCAD protein from 96S localizes on the cell membrane, whereas the mutant 96CAD-mHaCad was retained in the endoplasmic reticulum (ER). Mapping of the mutations identified a D172G substitution mainly responsible for cadherin mislocalization. Our finding of a mutation affecting membrane receptor trafficking represents an unusual and previously unrecognized B. thuringiensis resistance mechanism.

Persistent infection or chronic inflammation contributes significantly to tumourigenesis and tumour progression. C-X-C motif ligand 8 (CXCL8) is a chemokine that acts as an important multifunctional cytokine to modulate tumour proliferation, invasion and migration in an autocrine or paracrine manner. Studies have suggested that CXCL8 and its cognate receptors, C-X-C chemokine receptor 1 (CXCR1) and C-X-C chemokine receptor 2 (CXCR2), mediate the initiation and development of various cancers including breast cancer, prostate cancer, lung cancer, colorectal carcinoma and melanoma. CXCL8 also integrates with multiple intracellular signalling pathways to produce coordinated effects. Neovascularisation, which provides a basis for fostering tumour growth and metastasis, is now recognised as a critical function of CXCL8 in the tumour microenvironment. In this review, we summarize the biological functions and clinical significance of the CXCL8 signalling axis in cancer. We also propose that CXCL8 may be a potential therapeutic target for cancer treatment.

Cotton bollworm (Helicoverpa armigera) is the major insect herbivore of cotton plants. As its larvae feed and grow on cotton, H. armigera can likely tolerate gossypol, the main defense metabolite produced by cotton plants, through detoxification and sequestration mechanisms. Recent reports have shown that various P450 monooxygenases and UDP-glycosyltransferases in H. armigera are involved in gossypol detoxification, while the roles of ABC transporters, another gene family widely associated with metabolite detoxification, remain to be elucidated. Here, we show that ingestion of gossypol-infused artificial diet and cotton leaves significantly induced the expression of HaABCB6 in H. armigera larvae. Knockdown and knockout of HaABCB6 increased sensitivity of H. armigera larvae to gossypol. Moreover, HaABCB6-GFP fusion protein was localized on lysosomes in Hi5 cells and its overexpression significantly enhanced gossypol tolerance in vitro. These experimental results strongly support that HaABCB6 plays an important role in gossypol detoxification by H. armigera.

The Notch pathway is involved in cell proliferation, differentiation and survival. The Notch signaling pathway is one of the most commonly activated signaling pathways in cancer. Alterations include activating mutations and amplification of the Notch pathway, which play key roles in the progression of cancer. Accumulating evidence suggests that the pharmacological inhibition of this pathway can overcome chemoresistance. Efforts have been taken to develop Notch inhibitors as a single agent or in combination with clinically used chemotherapeutics to treat cancer. Some Notch inhibitors have been demonstrated to have therapeutic efficacy in preclinical studies. This review summarizes the recent studies and clinical evaluations of the Notch inhibitors in cancer.

As the rapid development of Genetically Modified crops, Chinese government has been increasing its efforts in GM crop biosafety management. However, the rapid expansion of Bacillus thuringiensis (Bt) cotton varieties and less regulated seed industry also resulted in a large amount of Bt cotton varieties that bypassed China's biosafety regulations. This study shows that the Bt cotton varieties without biosafety certificates (BC) have been widely used by farmers in practice. Econometric analysis further shows that the Bt cotton varieties with BC outperform the varieties without BC in terms of pesticide use. The paper concludes with policy implications. (C) 2015 Elsevier Inc. All rights reserved.

The diamondback moth, Plutella xylostella (L.), is one of the most destructive pest species of cruciferous vegetables worldwide. Previous studies on the migration of P. xylostella in China were mostly carried out in its ‘year-round breeding region’ (YBR) or ‘winter diapause region’ (WDR). However, the pattern of monthly movements in its ‘summer breeding region’ (SBR) (i.e. northern China, where they cannot overwinter) remains unknown. Here we present data from an 11-year study of P. xylostella made by searchlight trapping on Beihuang (BH) Island in the center of the Bohai Strait, which provides direct evidence that P. xylostella moths must have been migrants, and undertook regular long-distance migration across the sea. There was considerable annual and monthly variation in the number of P. xylostella trapped on BH, with the vast majority was trapped in the summer. The mean time from the earliest trapping to the latest trapping within a year was 117 ± 19 d in the five mass-migration years, with the shortest time span of 51 d in 2005 and the longest of 157 d in 2010. Some females trapped in May and June showed a relatively higher proportion of having mated and a degree of ovarian development suggesting that the migration of this species is not completely bound by the ‘oogenesis-flight syndrome’. These findings provide a good starting point of research on P. xylostella migration between its WDR (or YBR) and SBR, which will help us develop more effective regional management strategies against this pest.

Cotton is one of the most economically important crops in China, while insect pest damage is the major restriction factor for cotton production. The strategy of integrated pest management (IPM), in which bio- logical control plays an important role, has been widely applied. Nearly 500 species of natural enemies have been reported in cotton systems in China, but few species have been examined closely. Seventy- six species, belonging to 53 genera, of major arthropod predators and parasitoids of lepidoptera pests, and 46 species, belonging to 29 genera, of natural enemies of sucking pests have been described. In addi- tion, microsporidia, fungi, bacteria and viruses are also important natural enemies of cotton pests. Tricho- gramma spp., Microplitis mediator, Amblyseius cucumeris, Bacillus thuringiensis and Helicoverpa armigera nuclear polyhedrosis virus (HaNPV) have been mass reared or commercially produced and used in China. IPM strategies for cotton pests comprising of cultural, biological, physical and chemical controls have been developed and implemented in the Yellow River Region (YRR), Changjiang River Region (CRR) and Northwestern Region (NR) of China over the past several decades. In recent years, Bt cotton has been widely planted for selectively combating cotton bollworm, H. armigera, pink bollworm, Pectinophora gos- sypiella, and other lepidopteran pest species. As a result of reduced insecticide sprays, increased abun- dance of natural enemies in Bt cotton fields efficiently prevents outbreaks of other pests such as cotton aphids. In contrast, populations of mirid plant bugs have increased dramatically due to a reduction in the number of foliar insecticide applications for control of the bollworms in Bt cotton, and now pose a key problem in cotton production. In response to this new pest issue in cotton production, control strat- egies including biological control measures are being developed in China.

The mealybug, Oracella acuta Lobdell, is native to southern USA. It was unintentionally introduced to Guangdong Province, southern China, in 1988 as a result of the importation of infested scions of slash pine, Pinus elliottii Engelm . Infestations were first detected in 1990, rapidly spreading in P. elliottii plantations throughout Guangdong and inflicting severe damage. The mealybug has damaged or threatened both native and introduced pine species in its invaded range because of the suitability of climate, presence of hosts as well as the lack of effective natural enemies. In this paper, we review the current literature and government reports and data to summarize the history, present status and ecology of the species. We then analyze the potential O. acuta invasion in Asia. Available studies are mostly centered on the invasion timing and pathway of this species from USA to China, its current distribution in China, the biological and ecological traits of the species, damage and impacts on forests and ecosystems, and the strategies for its prevention and control. There remain substantial gaps in scientific knowledge of the invasion mechanisms and cost-effective measures for early detection and practical management of O. acuta, including options for biological control . Research on these aspects is required in order to prevent further spread of this pest in China and neighboring countries, and to provide better management in invaded regions.

Transgenic crops producing Bacillus thuringiensis (Bt) toxins kill some major insect pests, but pests can evolve resistance and thereby reduce the effectiveness of such Bt crops. The main approach for slowing pest adaptation to Bt crops uses non-Bt host plants as "refuges" to increase survival of susceptible pests. To delay evolution of pest resistance to cotton producing Bt toxin Cry1Ac, several countries have required refuges of non-Bt cotton, while farmers in China have relied on "natural" refuges of non-Bt host plants other than cotton. This strategy is designed for cotton bollworm (Helicoverpa armigera), which attacks many crops and is the primary target of Bt cotton in China, but it does not apply to pink bollworm (Pectinophora gossypiella), which feeds almost entirely on cotton in China. Here we review evidence of field-evolved resistance to Cry1Ac by cotton bollworm in northern China and by pink bollworm in the Yangtze River Valley of China. For both pests, results of laboratory diet bioassays reveal significantly decreased susceptibility of field populations to Cry1Ac, yet field control failures of Bt cotton have not been reported. The early detection of resistance summarized here may spur countermeasures such as planting Bt cotton that produces two or more distinct toxins, increased planting of non-Bt cotton, and integration of other management tactics together with Bt cotton.

Many aphid species possess wingless (apterous) and winged (alate) stages, both of which can harbor parasitoids at various developmental stages. Winged aphids bearing parasitoid eggs or young larvae can potentially still engage in long-distance flights and thereby facilitate parasitoid dispersal, which has important implications for biological control of aphids by parasitoids. In this study, we determined the effect of parasitism by Binodoxys communis (Hymenoptera: Braconidae) on wing development and flight of the summer alate stage of the soybean aphid, Aphis glycines (Hemiptera: Aphididae), and quantified the effect of aphid flight duration on subsequent B. communis development. Parasitism by B. communis was allowed at alatoid 3rd (L3) and 4th instar (L4) nymphal stages of A. glycines and subsequent aphid flight was measured using a computer-monitored flight mill. Only 25% of aphids parasitized as L3 alatoid nymphs produced normal winged adults, compared to 100% of L4 alatoids. While flight performance of aphids that had been parasitized as 4th-instar alatoid nymphs 24 or 48 h prior to testing was similar to that of unparasitized alates of identical age, it declined sharply for alates that had been parasitized as 4th-instar alatoid nymphs 72 and 96 h prior to testing. Parasitoid larval and pupal development times, percent mummification and adult emergence rates did not differ between treatments in which aphids had flown over varying durations. Our results have implications for natural biological control of A. glycines in Asia and classical biological control of the soybean aphid in North America.

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

Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is a serious pest of cotton and many other crops in northern China. To evaluate the contribution of alternative hosts as an effective refuge for transgenic cotton expressing the Bacillus thuringiensis (Bt) Cry1Ac toxin, the susceptibility to this toxin was measured in progeny derived from field-collected H. armigera larvae and pupae from different hosts in the Xiajin’s region of the Shandong Province in northern China. During 2008–2010, progeny from a total of 258,56,184 and 160 single-pair crosses derived from wheat (first-generation), Bt cotton (second-generation), Bt cotton (third-generation), and corn (third-generation) were screened on Cry1Ac diets, respectively. Based on relative average development rates (RADR) of H. armigera larvae in these F1 tests, the second and third-generation moths emerging from Bt cotton fields were more tolerant to the Bt toxin than the first and third-generation moths emerging from wheat and corn each year. These results suggest that there is significant variation in susceptibility to Bt toxins among H. armigera populations derived from different host crops. Alternate crops, such as corn, that maintain Bt susceptible populations of H. armigera could be used as refugia to minimize the evolution of resistance to Bt cotton.

Two high-quality cDNA libraries were constructed from female and male antennae of the cotton bollworm Helicoverpa armigera (Hubner). The titers were approximately 2.0 × 106 pfu/ml for females and 2.3 × 106 pfu/ml for males, and this complies with the test requirement. From the libraries, 1750 male ESTs and 1640 female ESTs were sequenced and further analyzed. We identified 15 olfactory genes (12 are new), and 14 of them have the characteristic six conserved cysteine residues. With the exception of OBP9, all the genes were classified as classical OBP genes. By alignment and cluster analysis, the 14 classical OBPs were divided into pheromone binding protein (PBP) genes, odorant binding protein (OBP) genes, general odorant binding protein 1 (GOBP1) genes, general odorant binding protein 2 (GOBP2) genes and antennae binding protein (ABP) genes. Among these genes, we obtained three PBP genes (PBP1–PBP3) including two new PBP genes, one new ABP gene, nine new OBP genes (OBP1–OBP9), one known GOBP1 gene and one known GOBP2 gene. Furthermore, the expression patterns of these 14 classical OBP genes were investigated in various tissues by real-time quantitative polymerase chain reaction (qPCR). The results indicated that some OBP genes are expressed differently in different sexes and tissues, but most of them are highly expressed in antennae.

DACH1 (Dachshund homolog 1) is a key component of the retinal determination gene network and regulates gene expression either indirectly as a co-integrator or through direct DNA binding. The current studies were conducted to understand, at a higher level of resolution, the mechanisms governing DACH1-mediated transcriptional repression via DNA sequence-specific binding. DACH1 repressed gene transcription driven by the DACH1-responsive element (DRE). Recent genome-wide ChIP-Seq analysis demonstrated DACH1 binding sites co-localized with Forkhead protein (FOX) binding sites. Herein, DACH1 repressed, whereas FOX proteins enhanced, both DRE and FOXA-responsive element-driven gene expression. Reduced DACH1 expression using a shRNA approach enhanced FOX protein activity. As DACH1 antagonized FOX target gene expression and attenuated FOX signaling, we sought to identify limiting co-integrator proteins governing DACH1 signaling. Proteomic analysis identified transcription elongation regulator 1 (TCERG1) as the transcriptional co-regulator of DACH1 activity. The FF2 domain of TCERG1 was required for DACH1 binding, and the deletion of FF2 abolished DACH1 trans-repression function. The carboxyl terminus of DACH1 was necessary and sufficient for TCERG1 binding. Thus, DACH1 represses gene transcription through direct DNA binding to the promoter region of target genes by recruiting the transcriptional co-regulator, TCERG1.

Transgenic Bt cotton expressing Cry1Ac is important in controlling various agricultural pests, including Helicoverpa armigera. Especially for transgenic crops that are cultivated in large expanses, avoiding resistance development is a key for ensuring sustainability of Bt technologies. Integrated pest management, in which transgenic crops are strategically combined with rational pesticide use, may help to prevent H. armigera resistance acquisition in Bt cotton. In this study, we evaluated the toxicity of a novel insecticide (chlorantraniliprole) on Cry1Ac-susceptible and resistant individuals of H. armigera. More specifically, we assessed the effect of chlorantraniliprole on the activity of two enzymes and conducted laboratory bioassays to determine its toxicity on H. armigera larvae. Chlorantraniliprole increased esterase and glutathione-S-transferase activities in Cry1Ac susceptible and resistant populations of H. armigera. Cry1Ac resistant populations XJ-F (Cry1Ac resistance ratio 21.8-fold), XJ-10.0 (95.8-fold) and BTR (3536.5-fold) did not show cross-resistance to chlorantraniliprole, with LC50 values of 0.0733 (μg/mL) in XJ-F, 0.0545 (μg/ml) in XJ-10.0 and 0.0731 (μg/mL) in BTR, which were close to that in the susceptible strain 96S (0.0954 μg/mL). Our work shows that chlorantraniliprole could be considered to be integrated in Bt cotton management schemes to delay the H. armigera resistance development.

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

A functional assessment of Bacillus thuringiensis (Bt) toxin receptors in the midgut of lepidopteran insects will facilitate understanding of the toxin mode of action and provide effective strategies to counter the development of resistance. In this study, we produced anti-aminopeptidase (APN) and anti-cadherin sera with purified Cry1Ac toxin-binding APN or cadherin fragments from Heliocoverpa armigera. Antisera were evaluated for their effects on Cry1Ac toxicity through bioassays. Our results indicated that both the anti-APN and anti-cadherin sera reduced Cry1Ac toxicity in vivo, although cadherin antiserum reduced toxicity more than APN antiserum. These results suggest that both APN and cadherin are involved in Cry1Ac intoxication of H. armigera, evidence that the pore formation model may be representative of Cry1Ac toxin mode of action in this insect.

The cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) is one of the most serious crop pests in northern China, calling for accurate prediction of pest outbreaks and strategies for pest control. A computer model is developed to simulate the population dynamics of H. armigera over a wide area in northern China. The area considered covers 12 provinces where serious outbreaks of H. armigera have been observed. In this model, pest development is driven by local ambient temperature, and adults migrate long distances between regions and select preferred hosts for oviposition within a region. Six types of host including cotton, wheat, corn, peanut, soybean and a single category composed of all other minor hosts are considered in this model. Survival rates of eggs and larvae are based on life-table data, and simulated as a function of host type, host phenology and temperature. The incidence of diapause depends on temperature and photoperiod experienced during the larval stage. Survival rate of non-diapause pupae is a nonlinear function of rainfall, and overwinter survival rate is a nonlinear function of temperature. Insecticide is applied when population density exceeds the economic threshold on a host crop within a region. Comparisons of model output with light-trap data indicate that our model reflects the pest population dynamics over a wide area, and could potentially be used for testing novel pest control strategies in northern China.

Midgut membrane-bound alkaline phosphatases (mALP) tethered to the brush border membrane surface by a glycosylphosphatidylinositol (GPI) anchor have been proposed as crucial for Cry1Ac intoxication. In the present work, two full-length cDNAs-encoding alkaline phosphatases in the midgut of Helicoverpa armigera larvae were cloned and named HaALP1 (GenBank accession no. EU729322) and HaALP2 (GenBank accession no. EU729323), respectively. These two clones displayed high identity (above 94%) at the amino acid sequence, indicating that they may represent allelic variants, and were predicted to contain a GPI anchor. Protein sequence alignment revealed that HaALPs were grouped with mALP from the Heliothis virescens midgut. The HaALP1 and HaALP2 ( approximately 68kDa) proteins were heterologously expressed in Sf9 cells using a baculovirus expression system and purified to homogeneity. Ligand blot and dot blot analysis revealed that the Cry1Ac bound to both denatured and native purified HaALPs. Data from lectin blots, competition assays with soybean agglutinin (SBA) lectin and GalNAc binding inhibition assays were indicative of the presence of GalNAc on HaALPs and binding of Cry1Ac toxin to this residue. This observation was further confirmed through N-glycosidase digestion of HaALPs, which resulted in reduced Cry1Ac binding. Our data represent the first report on HaALPs and their putative role as receptors for Cry1Ac toxin in H. armigera.

Many aphid species possess wingless (apterous) and winged (alate) stages, both of which can harbor parasitoids at various developmental stages. Alates can either be parasitized directly or can bear parasitoids eggs or larvae resulting from prior parasitism of alatoid nymphs. Winged aphids bearing parasitoid eggs or young larvae eventually still engage in long-distance flights, thereby facilitating parasitoid dispersal. This may have a number of important implications for biological control of aphids by parasitoids. In this study, we determined the effect of parasitism by Aphelinus varipes (Hymenoptera: Aphelinidae) on wing development and flight of the soybean aphid, Aphis glycines (Hemiptera: Aphididae). We also quantified the influence of aphid flight distance on subsequent A. varipes development. Parasitism by A. varipes was allowed at different A. glycines developmental stages (i.e., alatoid 3rd and 4th-instar nymphs, alates) and subsequent aphid flight was measured using a computer-monitored flight mill. Only 35% of aphids parasitized as L3 alatoid nymphs produced normal winged adults compared to 100% of L4 alatoids. Flight performance of aphids parasitized as 4th-instar alatoid nymphs 24 or 48 h prior to testing was similar to that of un-parasitized alates of identical age, but declined sharply for alates that had been parasitized as 4th-instar alatoid nymphs 72 and 96 h prior to testing. Flight performance of aphids parasitized as alate adults for 24 h was not significantly different from un-parasitized alates of comparable ages. Flight distance did not affect parasitoid larval or pupal development times, or the percent mummification of parasitized aphids. Our results have implications for natural biological control of A. glycines in Asia and classical biological control of the soybean aphid in North America.

It is generally accepted that in most insects adults are sexually immature when they initiate migration and that migratory behaviour terminates with the onset of sexual maturation. However, a few studies examining the mating status of field collected moths have suggested that sexually mature individuals may continue migrating, but in these cases it was impossible to completely eliminate the possibility that the mated females captured came from local, non-migrant populations. In this study we examined the ovarian development of Mythimna separata females captured using a vertical pointing searchlight trap on Beihuang Island in the Bohai Gulf, China, a site >40km from land. Moths were collected from May to October from 2003 to 2008 in order to test the hypothesis that the onset of sexual maturation resulted in the termination of migratory behaviour. While females at the end of the summer had little ovarian development and were unmated, a significant proportion of those migrating northward in the early summer had developed ovaries and often had at least one spermatophore. Given that theses insects were captured while flying up to 500m above sea level, at a site with no local populations, the findings would not support the hypothesis and suggest that both ovarian development and mating may occur during migration.

A Cry1Ac-resistant strain (Bt-R) of Helicoverpa armigera, with 2971-fold resistance, was derived by selection with Cry1Ac toxin for 75 generations. We used cDNA-amplified fragment length polymorphism analysis to identify those genes differentially expressed in the Cry1Ac-resistant and -susceptible strains, which revealed 212 differentially expressed transcripts among 2000 screened cDNAs. Among these transcript-derived fragments (TDFs), 37 showed some homology to known sequences, including Aminopeptidase N (APN), which is expressed in the midgut epithelium and has been implicated as a Cry1A subfamily receptor in several moths, including H. armigera. We confirmed the TDF by RT-PCR and identified a deletion mutation of apn1 in the Bt-R strain. We expressed the TDF in bacteria. The partial HaAPN1-96S wild-type protein, bound to Cry1Ac on ligand blots, whereas HaAPN1-BtR did not. This suggested that HaAPN1 is a receptor for Bt Cry1Ac and that its deletion mutation is associated with Cry1Ac resistance in H. armigera. The absence of one binding site is responsible for its resistance to Cry1Ac. We developed an allele-specific PCR to monitor whether the apn1 gene in an H. armigera field population produced a similar mutation. No deleted mutants were found in 2250 individuals collected from the field in 2006-2007.

The (HER2/Neu) ErbB2 oncogene is commonly overexpressed in human breast cancer and is sufficient for mammary tumorigenesis in transgenic mice. Nuclear factor (NF)-kappaB activity is increased in both human and murine breast tumors. The immune response to mammary tumorigenesis may regulate tumor progression. The role of endogenous mammary epithelial cell NF-kappaB had not previously been determined in immune-competent animals. Furthermore, the role of the NF-kappaB components, p50 and p65, in tumor growth was not known. Herein, the expression of a stabilized form of the NF-kappaB-inhibiting IkappaBalpha protein (IkappaBalphaSR) in breast tumor cell lines that express oncogenic ErbB2 inhibited DNA synthesis and growth in both two- and three-dimensional cultures. Either NF-kappaB inhibition or selective silencing of p50 or p65 led to a loss of contact-independent tumor growth in vitro. IkappaBalphaSR reversed the features of the oncogene-induced phenotype under three-dimensional growth conditions. The NF-kappaB blockade inhibited ErbB2-induced mammary tumor growth in both immune-competent and immune-deficient mice. These findings were associated with both reduced tumor microvascular density and a reduction in the amount of vascular endothelial growth factor. The expression of IkappaBalphaSR in breast cancer tumors inhibited angiogenesis. Thus, mammary epithelial cell NF-kappaB activity enhances ErbB2-mediated mammary tumorigenesis in vivo by promoting both growth and survival signaling via the promotion of tumor vasculogenesis.

The changes of inheritance mode and fitness of resistance in Helicoverpa armigera (Hübner) along with its resistance evolution to Cry1Ac toxin were evaluated in the laboratory. The resistance levels reached 170.0-, 209.6- and 2893.3-fold, on selection of the field population in the 16th (BtR-F(16)), 34th (BtR-F(34)) and 87th (BtR-F(87)) generation with artificial diet containing Cry1Ac toxin, respectively. As the resistance levels increased, more larvae feeding on the Bt cotton expressing Cry1Ac toxin survived. Most larvae of BtR-F(87) could develop to the 5th instar and about 3% individuals reached the adult stage. The inheritance of Cry1Ac resistance trait at three resistant levels was autosomal and incompletely recessive, but the degree of dominance decreased as the resistance increased. The resistance was primarily monogenic in BtR-F(16) strain, but polygenic as resistance increased. The relative fitness of H. armigera, measured as a ratio of R(0) (the net replacement rate) of resistant strain divided by R(0) of the susceptible strain, decreased with an increase of the resistance levels, with ratios of 0.79, 0.64 and 0.59 in their respective BtR-F(16), BtR-F(34) and BtR-F(87) strains.

Since the sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B invaded southern China in the mid-1990s, it had spread to most other regions of the country, and become an important pest in agricultural and horticultural production. Investigations on overwintering of B. tabaci biotype B and its spring reproduction in northern China were conducted to determine the main factors that might contribute to an understanding of the population dynamics of this pest for developing improved pest control strategies. A cold hardiness test showed that when exposed for 10 h at −10 °C, mortalities of eggs, nymphs, and adults reached to 86.6%, 88.4%, and 100%, respectively, suggesting that it is probably impossible for feral populations of B. tabaci to survive in the winter under natural environmental conditions in northern China. A survey on vegetables, ornamental plants and weeds in greenhouses at Hebei Province and Beijing in northern China revealed at least 14 species of plants on which B. tabaci fed during the winter and spring. Lycopersicon esculentum Mill, Brassica alboglabra Bailey, Ficus carica L., Euphorbia pulcerrima Wild, and Hemelia patens Haence were the main host plants. Further research on the population dynamics of B. tabaci on three major greenhouse hosts; tomato, cucumber, and melon, indicated that densities remained at a low level during the winter, but increased steadily from February to March until migration into field crops in April. It is concluded that the control of the insect in greenhouse in winter and spring can play an important role for seasonal management of this pest in northern China.

Detached leaf bioassays, open field tests and cage tests were conducted to evaluate the control efficacy of two transgenic rice lines, expressing Cry1Ac and CpTI, against Cnaphalocrocis medinalis (Guenee) during 2005-2006 in Fuzhou, China. Bioassay results showed that cumulative feeding areas of C. medinalis on transgenic lines were significantly lower than that on control rice lines at different developmental stages. The corrected mortalities at 96 h after infestation on transgenic lines during six rice growth stages were >90% and 100% during experiments conducted in 2005 and 2006, respectively. In the open field test, there was no significant difference in egg density between transgenic and control lines during early days of infestation, but significant differences were detected in late season, due to serious damage on control lines. Larval densities on control lines were significantly higher than the low larval populations observed on transgenic lines during both seasons. The percentages of plants with folded leaves and percentages of folded leaves on transgenic lines were significantly lower than that on control lines with and without insecticide applications, during the entire season. In cage tests the cumulative numbers of C. medinalis adults derived from transgenic lines were significantly lower than that from control lines with and without insecticide treatments. The high level of efficacy of the two transgenic rice lines against C. medinalis may provide an important basis for reduced insecticide applications, an expansion of alternative pest-control strategies and insect resistance management of Bt rice in the future.

The cotton bollworm, Helicoverpa armigera, is one of the most important insect pests in cotton growing regions of China. Transgenic cotton that expresses a gene derived from the bacterium Bacillus thuringiensis (Bt) has been deployed for combating cotton bollworm since 1997. Natural refugees derived from the mixed planting system consisting of cotton, corn, soybean, vegetables, peanut and others on single-family farms of a small scale were used for delaying the evolution of resistance to Bt cotton. Susceptibility of H. armigera field populations to the Bt insecticidal protein Cry1Ac was monitored from 1997 to 2006. The results indicate that the field populations are still susceptible to Cry1Ac, and monitoring indication no apparent shifts in susceptibility in field populations of this important pest.

Evolution of resistance by pests is the greatest threat to the continuous success of the Bacillus thuringiensis (Bt) toxins used in conventional sprays or in transgenic plants. The most common mechanism of insect resistance to Bt is reduced binding of toxins to target sites in the brush border membrane of the larval mid-gut. In this paper, binding experiments were performed with three 125 I-Cry1A toxins and the brush border membrane vesicles from Cry1Ac resistant or susceptible strains of Helicoverpa armigera . The homologous competition test showed that there was no significant difference in Cry1Ac-binding affinity, but the concentration of Cry1Ac-binding sites dramatically decreased in the resistant strain ( R t decreased from 5.87 ± 1.40 to 2.23 ± 0.80). The heterologous competition test showed that there were three Cry1Ac-binding sites in the susceptible strain. Among them, site 1 bound with all three Cry1A toxins, site 2 bound with both Cry1Ab and Cry1Ac, and site 3 only bound with Cry1Ac. In the Cry1Ac resistant strain, the binding capability of site 1 with Cry1Ab decreased and site 2 did not bind with Cry1Ac. It is suggested that the absence of one binding site is responsible for H. armigera resistance to Cry1Ac. This result also showed that the resistance fitted the “mode 1” pattern of Bt resistance described previously.

The androgen receptor (AR) regulates ligand-dependent gene transcription upon binding specific DNA sequences. The AR conveys both trans-activation and trans-repression functions, which together contribute to prostate cellular growth, differentiation, and apoptosis. Like histone H3, the AR is post-translationally modified by both acetylation and phosphorylation. The histone acetyltransferase p300 transactivates the AR and directly acetylates the AR in vitro at a conserved motif. Point mutations of the AR acetylation motif that abrogate acetylation reduce trans-activation by p300 without affecting the trans-repression function of the AR. The current studies assessed the functional relationship between acetylation and phosphorylation of the AR. Herein trans-activation of the AR acetylation site mutants were enhanced by the p42/p44 MAPK pathway but were defective in regulation by protein kinase A (PKA) signaling. PKA inhibition augmented ARwt activity but not AR acetylation mutant gene reporter activity and association at an androgen response element in chromatin immunoprecipitation assays. Mutations of the lysine residues at the AR acetylation site reduced trichostatin A (TSA) responsiveness and ligand-induced phosphorylation of the AR. The AR acetylation site mutant formed ligand-induced phosphorylation-dependent isoforms with distinguishable characteristics from wild type AR as determined with two-dimensional electrophoresis. Conversely, point mutation of a subset of AR phosphorylation sites reduced trichostatin A responsiveness and trans-activation by histone acetyltransferases. Together these studies suggest that acetylation and phosphorylation of the AR are linked events and that the conserved AR lysine motif contributes to a select subset of pathways governing AR activity.

Bt cotton has been planted to the exclusion of non-Bt cotton in the Yellow River cotton-farming region of China since 2000. Alternative non-Bt hosts, such as maize, soybean, peanut, wheat, and other host plants of Helicoverpa armigera (Hubner) may be acting as refuges for Bt-susceptible larvae of this pest, thereby delaying evolution of resistance to Bt cotton. Egg, larval, and adult densities of H. armigera were measured on Bt cotton, and on maize that was planted on dates that reflected local farming practices, in order to assess the role of maize as a refuge during 2001–2002 in Xinxiang County, Henan Province and Anci County, Hebei Province. The results indicated that the average egg densities for the second–fourth generation of the pest on Bt cotton in Xinxiang and the second generation in Anci County were significantly higher than those in maize fields. However, maize typically had much higher larval densities in the third and fourth generation of H. armigera than on Bt cotton. These data indicate that maize is probably serving as an effective refuge for third and fourth generation H. armigera , but is of less value for the second generation. The densities of moths produced by Bt cotton and by maize in a cage experiment confirmed the importance of maize as a refuge in the third and fourth generation.