Sublethal effects of chlorantraniliprole on Paederus fuscipes (Staphylinidae: Coleoptera), a general predator in paddle field.

Paederus fuscipes is a general predator in rice fields and a non-target organism of chlorantraniliprole, an effective insecticide for insect-pest control in paddy fields. Pesticide hazards to non-target organisms have been a growing global problem for decades. This study was designed to evaluate the toxicity of chlorantraniliprole at lethal and sublethal levels against P. fuscipes larvae and adults. The LC50 of chlorantraniliprole against P. fuscipes adults and larvae were respectively 535.49 and 111.24 mg a.i. L-1, which is higher than the dosage recommended for use in the field (59.38 mg a.i. L-1), but the LC30 and LC10 for larvae are lower than the recommended field dose which showed that the sublethal effects on immature stages are inevitable. Treatment at larval stage with LC30 of chlorantraniliprole significantly elongated the pre-imaginal developmental and pre-oviposition periods. Also, adults exposed directly to chlorantraniliprole oviposited significantly less number of eggs in both LC10 and LC30 treatments. Furthermore, the larval predation efficiency and female bodyweight were also reduced due to exposure to sublethal doses. Meanwhile, the activities of antioxidant (SOD, POD and CAT) and detoxification (P450, AChE and GST) enzymes were also significantly affected by the exposure to these sublethal concentrations. These findings showed that sublethal doses of chlorantraniliprole adversely influenced P. fuscipes development and physiology, and therefore its use as part of integrative pest management should be given further considerations.

An InR/mir-9a/NlUbx regulatory cascade regulates wing diphenism in brown planthoppers.

Wing polymorphism significantly contributes to the ecological success of some insect species. For example, the brown planthopper (BPH) Nilaparvata lugens, which is one of the most destructive rice pests in Asia, can develop into either highly mobile long-winged or highly fecund short-winged adult morphs. A recent study reported a highly provocative result that the Hox gene Ultrabithorax (Ubx) is expressed in BPH forewings and showed that this wing development gene is differentially expressed in nymphs that develop into long-winged versus short-winged morphs. Here, we found that Ubx may be a mir-9a target, and used dual luciferase reporter assays and injected micro RNA (miRNA) mimics and inhibitors to confirm the interactions between mir-9a and NlUbx. We measured the mir-9a and NlUbx expression profiles in nymphs and found that the expression of these two biomolecules was negatively correlated. By rearing BPH nymphs on host rice plants with different nutritional status, we were able to characterize a regulatory cascade between insulin receptor genes, mir-9a, and NlUbx that regulate wing length in BPHs. When host quality was low, NlInR1 expression in the nymph terga increased and NlInR2 expression decreased; this led to a higher mir-9a level, which in turn reduced the NlUbx transcript level and ultimately resulted in longer wing lengths. Beyond extending our understanding of the interplay between host plant status and genetic events that modulate polymorphism, we demonstrated both the upstream signal and miRNA-based regulatory mechanism that control Ubx expression in BPH forewings.

A new method for evaluating the effects of insecticidal proteins expressed by transgenic plants on ectoparasitoid of target pest.

Transgenic Bt insect-resistant plants are highly resistant to Lepidoptera stockpile pest Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae), a storage pest. Habrobracon hebetor (Say) (Hymenoptera: Braconidae), which is an ectoparasitic wasp of Indian meal moth, may be exposed to the Bt protein through the food chain. In the current study, high dose of Cry1C protein was injected into the hemolymph of P. interpunctella by microinjection, and the hemolymph was used as the carrier to deliver Bt protein to the H. hebetor. Using this method, we developed a new Tier-1 risk assessment system for ectoparasitoid, successfully avoided "host/prey quality-mediated effect," and improve the accuracy of safety evaluation. Results showed that injected Cry1C was stable and bioactive in the hemolymph of P. interpunctella parasitized by H. hebetor, and high dose of Cry1C has no negative impacts on egg hatching rate, developmental duration from egg to adult, survival egg to adult, pupa weight, adults weight (male and female), adult longevity and reproduction, and activity of stress-related enzymes of H. hebetor. However, the hemolymph of P. interpunctella injected into Galanthus nivalis L. agglutinin (the positive control) had significant negative impact on these biological parameters of H. hebetor. The results indicate that H. hebetor are not sensitive to Cry1C protein at the tested concentration and there were no detrimental effects of Cry1C protein on any biological parameters tested in the present study. More importantly, we constructed a new efficient and simple system for the biosafety assessment on the larvae of ectoparasitoid of target pest.

Safety assessment of transgenic Cry2Aa rice to a generalist predator, Paederus fuscipes Curtis (Coleoptera: Staphylinidae).

The insecticidal crystal proteins of Cry2A family from Bacillus thuringiensis (Bt) are important candidate proteins expressed in gene pyramiding Bt crops. A transgenic rice line (T2A-1) harboring a synthetic Cry2A* (Cry2Aa) gene showed effective resistance to some lepidopteran rice pests. As a generalist predator in rice ecosystems, the rove beetle (Paederus fuscipes) can prey on many rice insect pests such as planthoppers. Considering the possible exposure of Cry2Aa to P. fuscipes through tritrophic food chain, it is necessary to assess the potential risks of T2A-1 rice to this predator. In this study, a tritrophic experiment was conducted to assess the prey-mediated effects of Cry2Aa on P. fuscipes through the T2A-1 rice-Nilaparvata lugens-P. fuscipes food chain. After preying on N. lugens nymphs reared on T2A-1, no accumulated Cry2Aa could be detected in P. fuscipes adults, despite Cry2Aa being detected in N. lugens. In addition, no harmful effects were detected on the life table parameters of P. fuscipes in this tritrophic chain. Additionally, direct exposure to a high dose of purified Cry2Aa protein, representing the worst case scenario, showed no significant adverse effects on the development of P. fuscipes. These results showed that transgenic Cry2Aa rice had no harmful effects on P. fuscipes.

Assessing the effects of Cry2Aa protein on Habrobracon hebetor (Hymenoptera: Braconidae), a parasitoid of Indian meal moth, Plodia interpunctella (lepidoptera: Pyralidae).

Transgenic crops express Cry proteins exhibit high resistant to target insect pests. When we evaluate the effects of Cry proteins on the parasitoid of target insect pest via tritrophic experiments (transgenic plant-target insect pest-parasitoid) host quality of parasitoids might decrease because of insecticidal protein ingestion, this would cause host-quality mediated effects and influence the accuracy of biosafety assessment. In the current study, high dose of Cry2Aa protein was injected into the hemolymph of Plodia interpunctella by microinjection, and the hemolymph was used as the carrier to deliver Cry protein to Habrobracon hebetor, which has been previously reported as an ectoparasitoid of P. interpunctella larval, in order to avoid the "host-quality mediated effects". Results showed that injected Cry2Aa remained at high concentration and bioactive in the hemolymph of P. interpunctella parasitized by H. hebetor, the hemolymph of P. interpunctella could be used as carriers of Cry protein to H. hebetor, and high dose of Cry2Aa have no negative impacts on the development time, weight of pupa, sex ratio, adults weight (male and female), adult longevity and fecundity, and the activity of stress-related enzymes of H. hebetor. However, the hemolymph of P. interpunctella injected into Galanthus nivalis agglutinin (the positive control) showed significant negative impact on these parameters measured in the present study of H. hebetor. This indicated that Cry2Aa protein had no detrimental effects on the biological parameters of H. hebetor measured in the current study. Meanwhile, this study provides a new method for the safety evaluation of the ectoparasitoids of target pest and might be expanded to the other species of ectoparasitoids of target insects of Cry proteins in biosafety risk assessment.

Ultrabithorax is a key regulator for the dimorphism of wings, a main cause for the outbreak of planthoppers in rice.

Rice planthoppers, the most devastating rice pests, occur in two wing forms: the short-wing form for rapid population growth and long-wing form for long-distance migration, which together create the mechanism for outbreak. Here we show that Ultrabithorax (Ubx) is a key regulator for switching between the long- and short-wing forms of rice planthoppers. Ubx is expressed in both forewing and hindwing pads, which is different from the canonical model of Ubx expression. In brown planthoppers, expression of Ubx (NlUbx) is regulated by nutritional status of the rice host. High-quality young plants induce NlUbx expression leading to the short-wing form; low-quality ripe plants reduce NlUbx expression resulting in long-wing form. We also showed that NlUbx is regulated by the insulin receptors NlInR1 and NlInR2. The default expression of NlInR1 inhibits NlUbx resulting in long-wings, while high-quality hosts induce NlInR2 expression, which represses NlInR1 thus promoting NlUbx expression to produce short-wings.

Candidate detoxification-related genes in brown planthopper, Nilaparvata lugens, in response to ß-asarone based on transcriptomic analysis.

Nilaparvata lugens(Stål) is a serious pest of rice and has evolved different levels of resistance against most chemical pesticides. ß-asarone is the main bioactive insecticidal compound of Acorus calamus L. that shows strong insecticidal activity against pests. In this study, we conducted a bioassay experiment to determine the contact toxicity of ß-asarone to N. lugens nymphs. The LD30 sublethal dose was 0.106 µg per nymph, with 95% confidence limits of 0.070-0.140 µg. We applied the LD30 concentration of ß-asarone to nymphs for 24 h or 72 h and then performed a transcriptome sequence analysis by referencing the N. lugens genome to characterize the variation. The transcriptomic analysis showed that several GO terms and KEGG pathways presented significant changes. Individually, 126 differentially expressed genes (DEGs), including 72 upregulated and 54 downregulated genes, were identified at 24 h, and 1771 DEGs, including 882 upregulated and 889 downregulated genes, were identified at 72 h. From the DEGs, we identified a total of 40 detoxification-related genes, including eighteen Cytochrome P450 monooxygenase genes (P450s), three Glutathione S-transferase genes, one Carboxylesterase gene, twelve UDP-glucosyltransferases and six ATP-binding cassette genes. We selected the eighteen P450s for subsequent verification by quantitative PCR. These findings indicated that ß-asarone presented strong contact toxicity to N. lugens nymphs and induced obvious variation of detoxification-related genes that may be involved in the response to ß-asarone.

Decapentaplegic function in wing vein development and wing morph transformation in brown planthopper, Nilaparvata lugens.

The decapentaplegic (dpp) gene plays a variety of roles in diverse cellular and molecular processes of the growth and development. In insects, dpp is mainly required for dorsal-ventral patterning and appendage formation. The brown planthopper (BPH) Nilaparvata lugens, a major pest of rice, possesses two distinct wing morphs described as long-winged (LW) and short-winged (SW) morphs. With our lab-maintained stable strains of LW and SW BPH, RNA interference (RNAi) was used to research the functions of N. lugens dpp (Nldpp) on wing development. Silencing of Nldpp in the SW strain led to the significant lengthening of the forewing, while Nldpp-knockdown in the LW strain resulted in distorted wings. Moreover, knockdown of Nldpp caused the complete absence of wing veins. During the development of wing-pads, the Nldpp abundance in the terga of the SW strain was significantly higher than that of the LW strain. Through controlling the direction of wing morph transformation, we found that the expression level of Nldpp increased in the NlInR1-knockdown BPH (tending to SW) and abundance of Nldpp declined after dsNlInR2 injection (tending to LW). Our results showed that Nldpp is mainly responsible for the formation and development of veins in BPH. Also, Nldpp can be regulated by NlInR1/2 and participate in the wing morph transformation.

Lethal and sublethal effects of emamectin benzoate on the rove beetle, Paederus fuscipes, a non-target predator of rice brown planthopper, Nilaparvata lugens.

The use of pesticides in rice can not only manage the pest but also influence non-target organisms. The rove beetle (Paederus fuscipes), which is an important predator of the brown plant hopper (Nilaparvata lugens) in rice ecosystems, was tested to investigate acute and chronic effects of emamectin benzoate. The results from this study show that the LC50 of emamectin benzoate to adults of P. fuscipes at 72 h was 3.07 (1.84-4.54) mg a.i. L-1, whereas the LC50 of emamectin benzoate to the second instar larvae of P. fuscipes at 72 h was 2.58 (1.95-3.19) mg a.i. L-1. Tested sublethal doses (LC10 and LC30) had significant effects on the second instar developmental time of P. fuscipes compared with that of the control. The LC30 dose had a negative influence on the pre-imaginal developmental duration and the feeding potential of treated P. fuscipes larvae. Additionally, the LC30 reduced the pre-oviposition period, the fecundity and the body weight of adults emerged from treated larvae of P. fuscipes. In the sublethal experiment with adults, the fecundity and the feeding potential were significantly reduced at the LC30 dose. These results revealed that sublethal doses of emamectin benzoate negatively affected the development and biological activities of P. fuscipes, and we conclude that more attention should be paid to the use of this chemical as part of integrated pest management strategies.

Transcriptomic analysis of differentially expressed genes and related pathways in Harmonia axyridis after sulfoxaflor exposure.

Harmonia axyridis (Pallas) is a major biological control agent that is indirectly threatened by sulfoxaflor insecticide applications targeting pests in agro-ecosystems. However, the genome-wide response of H. axyridis to sulfoxaflor remains largely unknown. Here, we used high-throughput RNA-seq technology to characterize the variation in the transcriptomic profile of second-instar H. axyridis larvae after exposure to sulfoxaflor. Two libraries were generated, with 50,702,976 and 47,005,096 clean reads for the sulfoxaflor treatment and control, respectively; these were grouped into 112,497 transcripts and 52,229 unigenes, of which 33,820 and 25,175 unigenes were respectively matched to proteins in the NCBI (Nr) and Swiss-Prot databases. From these unigenes, 794 significant differentially expressed genes (DEGs) consisting of 446 up- and 348 down-regulated genes, namely P450s, GSTs, USTs, ESTs, and others, were identified between the sulfoxaflor-treated and control groups. Furthermore, these DEGs were involved in several KEGG pathways including drug metabolism and metabolism of xenobiotic pathways. For transcriptome validation, 10 specifically expressed genes were selected and verified by quantitative real-time PCR analysis. Together, these results demonstrated that sulfoxaflor induces notable variation in the transcriptome profile and pathways of H. axyridis, which establishes a basis for further molecular investigations.

Repellency, toxicity, and anti-oviposition of essential oil of Gardenia jasminoides and its four major chemical components against whiteflies and mites.

We examined the repellent, insecticidal, and anti-oviposition activities of the ethanol-extracted essential oil of Gardenia jasminoides against Bemisia tabaci and Tetranychus urticae adult and nymph stages under laboratory and greenhouse conditions. We used GC-MS to identify the main chemicals in the essential oil and selected four compounds, squalene, ethyl linoleate, n-hexadecanoic acid and 9-12-octadecadienoic, to evaluate their activity on whiteflies and mites. In the laboratory experiments, the essential oil of G. jasminoides showed maximum effects in fumigation against whitefly adults (81.48%) and contact toxicity against whitefly nymphs (46.44%), adult mites (49.81%), and mite nymphs (66.46%). In the greenhouse experiments, squalene showed maximum repellency against whitefly adults at 24 (89.59%) and 48 h (84.76%), whitefly nymphal toxicity at 24 (80.08%) and 48 h (77.28%), and mite toxicity at 24 (78.74%) and 48 h (73.86%). The essential oil showed maximum anti-oviposition activity against whiteflies at 24 (63.58%) and 48 h (59.56%) and toxicity to mite nymphs at 24 (82.45%) and 48 h (57.14%) in the bioassay. The essential oil had LC50 values of 2396.457, 2844.958, 56,990.975 and 21,468.619 against whitefly adults, whitefly nymphs, mite adults and mite nymphs, respectively. G. jasminoides and its major chemicals may effectively control the whiteflies and mites.

Silencing of juvenile hormone epoxide hydrolase gene (Nljheh) enhances short wing formation in a macropterous strain of the brown planthopper, Nilaparvata lugens.

The rice brown planthopper, Nilaparvata lugens, is an important migratory pest in many rice planting areas of Asia. The typical wing dimorphism of N. lugens gives them flexibility to adapt to different environmental cues. As an important hormone in the insect's endocrine regulation, juvenile hormone (JH) has previously been shown to participate in the wing morph determination of N. lugens. In this paper, we investigated the possible wing morph determination roles of two JH metabolic enzymes, JH esterase (JHE) and JH epoxide hydrolase (JHEH). A 1957-bp full-length cDNA sequence encoding JHEH in N. lugens (NlJHEH) was first cloned from a hemipteran insect. Except for an uncertain transmembrane segment prediction, the deduced 454-amino-acid sequence of Nljheh has all of the conserved domains of JHEHs such as the H147GWP150, Tyr293 and Tyr368 motif corresponding to the oxyanion hole and the residues Asp222, Glu398, and His425 in the catalytic triad. qRT-PCR results showed that both Nljhe and Nljheh had different expression timeframes between a predominantly brachypterous strain (BS) and a macropterous strain (MS) of N. lugens, indicating that these two enzymes may participate in wing dimorphism regulation in brown planthopper. Silencing Nljheh expression by dsRNA injection enhanced short wing formation in the macropterous strain of N. lugens, while the brachypterizing individuals were mainly females. Compared to the dsgfp injection control, silencing Nljhe had no brachypterizing effect. Our results indicated that NlJHEH plays an important role in the wing morph determination of N. lugens.

Knockdown of TOR causing ovarian diapause in a genetically stable brachypterous strain of Nilaparvata lugens.

Brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is one of the most damaging pests of rice crops. BPH is a migratory insect with a delayed ovarian development in migrants classified as reproductive diapause. The molecular mechanism of reproductive diapause remains unclear, although we suspect it might be regulated by one or more nutrient signaling pathways. The target of rapamycin (TOR) pathway regulates cell growth in response to nutritional information, which raised a hypothesis that TOR mediates BPH reproductive diapause. We used a pure brachypterous strain (BS) and a predominantly macropterous strain (MS) to investigate the roles of NlTOR in BPH reproductive diapause. We found that NlTOR is expressed from the nymphal to adult stages, with a higher expression level of NlTOR in BS adults at 1, 2, and 4 days posteclosion than in MS at the same time points. Injection of dsNlTOR into BS nymphs resulted in the termination of BPH female ovary development and the retardation of nymph development. We infer that TOR signaling functions in BPH reproductive diapause by regulating the expression of NlFoxA and NlVitellogenin.

Toxicity and sublethal effects of chlorantraniliprole on the development and fecundity of a non-specific predator, the multicolored Asian lady beetle, Harmonia axyridis (Pallas).

In order to further develop integrated pest management (IPM) approaches for controlling insect pests, it is important to estimate the effects of pesticides. In this study, the toxicity and sublethal effects of the insecticide chlorantraniliprole on a non-specific predator, the multicolored Asian lady beetle Harmonia axyridis, were evaluated and life table parameter data were analyzed statistically using the age-stage, two-sex life table procedure. The results of this study show that the development time of second and fourth instar larvae as well as pupa was significantly prolonged in populations treated with LC10 (2.42 mg (a.i.) L-1) and LC30 (12.06 mg (a.i.) L-1), while adult longevity and fecundity were both significantly reduced and the preoviposition period (POP) was significantly prolonged following treatment compared to the control. In addition, the net reproductive rate (R0), as well as the intrinsic (r) and finite rate of increase (λ) were significantly decreased in groups treated with the insecticide. These results reveal that because sublethal concentrations of chlorantraniliprole impair the population growth of H. axyridis, more attention should be paid to the use of this chemical as a component of IPM strategies.

The tiered-evaluation of the effects of transgenic cry1c rice on Cyrtorhinus lividipennis, a main predator of Nilaparvata lugens.

T1C-19, a newly developed transgenic cry1C rice line, expresses cry1C under the control of the maize ubiquitin promoter, and is highly resistant to lepidopteran pests of rice. Cyrtorhinus lividipennis is the major predator of the eggs and young nymphs of Nilaparvata lugens, which is the main non-target sap-sucking insect pest of Bt rice. C. lividipennis may be exposed to Cry1C protein, thus biosafety evaluations of transgenic cry1C rice on C. lividipennis should be conducted before the commercialization of T1C-19. In the current study, we tested the direct toxicity of elevated doses of Cry1C to C. lividipennis, effects of T1C-19 on the life-table parameters of C. lividipennis via preying planthoppers, and effects of T1C-19 on the population density and dynamics in rice fields. No detrimental effects on development, survival, female ratio and body weight of C. lividipennis were caused by direct exposure to elevated doses of the Cry1C protein or prey-mediated exposure to realistic doses of the protein. The population density and dynamics did not significantly differ between C. lividipennis in T1C-19 and non-transgenic rice fields. Thus, transgenic cry1C rice had no negative effects on C. lividipennis. This is the first report of the effects of transgenic cry1C rice on C. lividipennis.

Bt rice expressing Cry2Aa does not harm Cyrtorhinus lividipennis, a main predator of the nontarget herbivore Nilapavarta lugens.

T2A-1 is a newly developed transgenic rice that expresses a synthesized cry2Aa gene driven by the maize ubiquitin promoter. T2A-1 exhibits high resistance against lepidopteran pests of rice. The brown planthopper, Nilapavarta lugens (Stål), is a main nontarget sap-sucking insect pest of rice, and Cyrtorhinus lividipennis (Reuter) is the major predator of the eggs and young nymphs of planthoppers. As C. lividipennis may expose to the Cry2Aa protein via N. lugens, it is therefore essential to assess the potential effects of transgenic cry2Aa rice on this predator. In the present study, three experiments were conducted to evaluate the ecological risk of transgenic cry2Aa rice to C. lividipennis: (1) a direct feeding experiment in which C. lividipennis was fed an artificial diet containing Cry2Aa at the dose of 10-time higher than that it may encounter in the realistic field condition; (2) a tritrophic experiment in which the Cry2Aa protein was delivered to C. lividipennis indirectly through prey eggs or nymphs; (3) a realistic field experiment in which the population dynamics of C. lividipennis were investigated using vacuum-suction. Both direct exposure to elevated doses of the Cry2Aa protein and prey-mediated exposure to realistic doses of the protein did not result in significant detrimental effects on the development, survival, female ratio and body weight of C. lividipennis. No significant differences in population density and population dynamics were observed between C. lividipennis in transgenic cry2Aa and nontransgenic rice fields. It may be concluded that transgenic cry2Aa rice had no detrimental effects on C. lividipennis. This study represents the first report of an assessment continuum for the effects of transgenic cry2Aa rice on C. lividipennis.

Supercritical fluid CO2 extraction of Acorus calamus L. (Arales: Araceae) and its contact toxicity to Sitophilus zeamais Motschusky (Coleoptera: Curculionidae).

Contact toxicities of Acorus calamus L. (Arales: Araceae) extracts obtained from four published extraction methods: soakage, soxhlet, ultrasonic and supercritical fluid CO2 (SFE-CO2), were compared in this study. Under the given extraction conditions, SFE-CO2 extract exhibited the highest contact toxicity against S. zeamais of the four methods. With the SFE-CO2 method, extraction temperature, pressure, time and the amount of EtOH (the extraction solvent) were identified as having a significant effect on the extract. Orthogonal experiments showed that the optimal extraction parameters were: temperature--55°C, pressure--35 MPa, time--40 min and EtOH--150 mL per 200 g of dry powder. Under these conditions, the yield was 4.12% and the LD50 of the extract against S. zeamais after 96 h of treatment was 27.26 µg cm⁻². ß-asarone was the dominant component of the extract derived from the SFE-CO2 method, accounting for 24.39% of the extract. These results may contribute to the designing of large-scale production processes for obtaining A. calamus extract, which proves to be an effective alternative for the control of stored product insect pests.

Field evaluation of effects of transgenic cry1Ab/cry1Ac, cry1C and cry2A rice on Cnaphalocrocis medinalis and its arthropod predators.

The impacts of transgenic Bt rice on target pests and their predators need to be clarified prior to the commercialization of Bt rice. In this study, the percentages of folded leaves of three transgenic Bt rice lines and non-transgenic parental rice line caused by Cnaphalocrocis medinalis were studied over two successive growing seasons. In addition, the population densities, relative abundance and population dynamics of C. medinalis and four species of its natural arthropod predators were investigated at three sites in China. The results showed that rice line significantly affected the percentages of folded leaves and population densities of C. medinalis larvae. Significantly higher percentages of folded leaves were observed on the non-transgenic rice compared with the three transgenic Bt rice on most sampling dates. Significantly higher densities of C. medinalis larvae and higher relative abundance of C. medinalis within phytophages were found on non-transgenic rice compared with three transgenic Bt rice at different sites across the study period. The population dynamics of C. medinalis larvae were significantly affected by rice line, rice line×sampling date, rice line×year, rice line×sampling date×year. However, there was little, if any, significant difference in the relative abundance, population density and population dynamics of the four arthropod predators between the three Bt rice lines and non-transgenic rice. The results of this study indicate that the Bt toxin in transgenic Bt rice can effectively suppress the occurrence of C. medinalis, but has no significant effects on the occurrence of the four predatory arthropod species.