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The small brown planthopper (SBPH), Laodelphax striatellus (Fallen) is a major pest insect of rice, wheat, and maize in China and other countries. SBPH not only damage rice plants through sucking plant sap, but also transmits rice virus diseases, for example, striped virus disease (RSV), black streaked dwarf, and maize rough disease virus. Therefore, understanding of pesticide-induced stimulation of reproduction in SBPH is of great significance for the pest management. Our previous study discovered that triazophos (TZP) increased reproduction of SBPH. But the molecular mechanisms are unclear. Here, by using proteomic analysis, we screened and cloned the gene of long chain fatty acid coenzyme A ligase ( FACL ), and silenced FACL to examine influences of TZP on reproduction and glycerin content in SBPH females. In TZP-treated females vs control females, there were 41 differential proteins in 18 pathways related to reproduction, of which 8 were up-regulated and 33 were down-regulated. TZP + dsFACL eliminated TZP-induced stimulation of reproduction of SBPH females (↓about 73.92%) and decreased glycerin content and body weight (↓about 19.93% and 13.62%). TZP + dsFACL treatment led to reduced expression of FACL (↓about 61.88%). FACL is a key gene of TZP-induced increase of reproduction of SBPH.

The widespread use of pesticides in rice has caused the resurgence of the small brown planthopper (SBPH), Laodelphax striatellus. In addition to inciting damage by feeding on phloem cells, SBPH also functions as a vector for rice stripe virus (RSV), which can cause serious yield losses. In general, studies focused on pesticide-induced stimulation of SBPH populations have focused on the insects; little information is available on the impact of pesticides on RSV transmission by SBPH. The present study investigated the effects of two pesticides (validamycin and triazophos) on the fecundity and RSV transmission ability of SBPH. Our results demonstrated that the fecundity of non-viruliferous (naive) or viruliferous SBPH was enhanced by exposure to triazophos at the LC20 and validamycin at 200 mg L− 1. Meanwhile, the increased number of eggs produced by viruliferous females treated with pesticides was larger than those from naive females. Exposure to validamycin caused an increase in horizontal transmission of RSV; furthermore, vertical viral transmission rates of SBPH were significantly increased by exposure to triazophos. The present study provides valuable information for understanding the mechanisms underlying the resurgence of SBPH and subsequent outbreaks of RSV.

The small brown planthopper (SBPH), Laodelphax striatellus (Fallen), is a serious pest insect of rice, wheat, and maize in China. SBPH not only sucks plant sap but also transmits plant disease viruses, causing serious damage. These viruses include rice striped virus disease (RSV disease), black streaked dwarf, and maize rough disease virus. SBPH outbreaks are related to the overuse of pesticides in China. Some pesticides, such as triazophos, stimulate the reproduction of SBPH, but an antibiotic fungicide jinggangmycin (JGM) suppresses its reproduction. However, mechanisms of decreased reproduction of SBPH induced by JGM remain unclear. The present findings show that JGM suppressed reproduction of SBPH (↓ approximately 35.7%) and resulted in the down-regulated expression of glucose dehydrogenase (GDH). GDH- silenced control females (control + dsGDH) show that the number of eggs laid was reduced by 48.6% compared to control females. Biochemical tests show that the total lipid and fatty acid contents in JGM-treated and control + dsGDH females decreased significantly. Thus, we propose that the suppression of reproduction in SBPH induced by JGM is mediated by GDH via metabolic pathways.

The antibiotic jinggangmycin (JGM) is mainly used in controlling the rice sheath blight, Rhizoctonia solani, in China. JGM also enhances reproduction of the brown planthopper (BPH), Nilaparvata lugens (Stål). To date, however, molecular mechanisms of the enhancement are unclear. Our related report documented the influence of foliar JGM sprays on ovarian protein content. Here, we used isobaric tags for relative and absolute quantitation (iTRAQ) protocols to analyze ovarian proteins of BPH females following JGM spray (JGM-S) and topical application (JGM-T). We recorded changes in expression of 284 proteins (142↑ and 142↓) in JGM-S compared to the JGM-S control group (S-control); 267 proteins were differentially expressed (130↑ and 137↓) in JGM-T compared to the JGM-T control group (T-control), of which, 22 proteins were up-regulated in both groups. Comparing the JGM-S to the JGM-T group, 114 proteins were differentially expressed (62↑ and 52↓). Based on the biological significance of fatty acids, pathway annotation and enrichment analysis, we designed a dsRNA construct to silence a gene encoding fatty acid synthase (FAS). FAS was more highly expressed in JGM-S vs S-control and JGM-S vs JGM-T groups. The dsFAS treatment reduced fecundity by about 46% and reduced ovarian and fat body fatty acid concentrations in JGM-S-treated females relative to controls. We infer FAS provides critically needed fatty acids to support JGM-enhanced fecundity in BPH.

Aside from their intended actions, fungicides can drive pest insect outbreaks due to virtually continuous use and pest evolution. Small brown planthopper (SBPH), Laodelphax striatellus, outbreaks occurred recently in many provinces in China, with devastating rice losses. Because exposure to the fungicide jinggangmycin (JGM) increased reproduction of the brown plant hopper, Nilaparvata lugens, via its influence on fatty acid synthase, we posed the hypothesis that JGM and carbendazim (CBM) influence SBPH reproduction via their influence on enzymes involved in other aspects of lipid metabolism. Exposure to the fungicide CBM stimulated SBPH reproduction (egg-laying up by 78%) and to another fungicide, JGM, led to decreased egg-laying (down by 47.3%). These inverse effects are mediated by down-regulated expression of l-3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) in JGM-treated females and up-regulated expression of hydroxysteroid dehydrogenase-like protein 2-like (HSD) in CBM-treated females. RNAi knockdown of, separately, LCHAD and HSD led to reduced egg-laying (down by 52% for dsLCHAD and by 73% for dsHSD). dsLCHAD, dsHSD, and JGM treatments also led to severely reduced ovarian development in experimental SBPH, with shorted and thinned valvula and lack of egg cells in ovaries. Valvula of CBM-treated females enlarged, with banana-shaped eggs in ovaries. These data strongly support our hypothesis.

The cAMP/PKA intracellular signaling pathway is launched by adenylyl cyclase (AC) conversion of adenosine triphosphate (ATP) to 3', 5'-cyclic AMP (cAMP) and cAMP-dependent activation of PKA. Although this pathway is very well known in insect physiology, there is little to no information on it in some very small pest insects, such as the brown planthopper (BPH), Nilaparvata lugens Stal. BPH is a destructive pest responsible for tremendous crop losses in rice cropping systems. We are investigating the potentials of novel pest management technologies from RNA interference perspective. Based on analysis of transcriptomic data, the BPH AC like-9 gene (NlAC9) was up-regulated in post-mating females, which led us to pose the hypothesis that NlAC9 is a target gene that would lead to reduced BPH fitness and populations. Targeting NlAC9 led to substantially decreased soluble ovarian protein content, yeast-like symbiont abundance, and vitellogenin gene expression, accompanied with stunted ovarian development and body size. Eggs laid were decreased and oviposition period shortened. Taken together, our findings indicated that NlAC9 exerted pronounced effects on female fecundity, growth and longevity, which strongly supports our hypothesis.

Three planthopper species, the brown planthopper (BPH), Nilaparvata lugens Stål, the white-backed planthopper (WBPH), Sogatella furcifera Horvath, and the small brown planthopper (SBPH), Laodelphax striatella Fallén, often co-occur in rice grown regions of China. The present investigation examined effects of two pesticides, triazophos (TZP) and jinggangmycin (JGM) (a fungicide), on reproduction of BPH, WBPH, and SBPH. The results showed that TZP stimulated the fecundity of the three planthopper species. Interestingly, JGM stimulated the fecundity of BPH but suppressed the fecundity of WBPH. In addition, TZP and JGM had a significant effect on the preoviposition period (PVD), the oviposition period (OPD), and the longevity of adult females (LAF) of BPH and WBPH. Based on these findings, to avoid resurgence occurrence of planthoppers, we suggest that the application of TZP should be banned in rice fields, that JGM should be used to control rice sheath blight at the early growth stages of rice (with WBPH occurrence and without BPH occurrence).

The brown planthopper (BPH) is a devastating pest of rice throughout Asia. In this paper we document the BPH biogeographic range expansion in China over the 20-year period, 1992 to 2012. We posed the hypothesis that the range expansion is due to a syndrome of adaptations to the continuous presence of agricultural chemicals (insecticides and a fungicide) over the last 40 years. With respect to biogeography, BPH ranges have expanded by 13% from 1992 to 1997 and by another 3% from 1997 to 2012. In our view, such expansions may follow primarily from the enhancing effects of JGM, among other agricultural chemicals, and from global warming. JGM treatments led to increased thermotolerance, recorded as decreased mortality under heat stress at 40 ± 1 °C (down from 80% to 55%) and increased fecundity (by 49%) at 34 °C. At the molecular level, JGM treatments led to increased abundances of mRNA encoding Acetyl Co-A carboxylase (Acc) (up 25%) and Hsp70 (up 32%) in experimental BPH. RNAi silencing of Hsp70 and Acc eliminated the JGM effects on fecundity and silencing Hsp70 reduced JGM-induced thermotolerance. Integrated with global climate change scenarios, such syndromes in pest insect species have potential for regional- and global-scale agricultural disasters.

Potassium (K) is a key component of plant nutrition, significantly influencing crop growth. Levels of this nutrient in plants can also influence a number of pest infestations. The brown planthopper, Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), is an important pest of rice in Asia. In this study, we examined K contents in rice grown in hydroponic solution, and its relationship to the fecundity and expression of the vitellogenin (Nlvg) gene of N. lugens which was reared on the rice. Our findings indicated that K contents in rice increased with the increasing K concentration within the hydroponic solution, but reduced at the highest K concentration (160 mg/L). The number of eggs laid by N. lugens which was reared on the rice varied significantly with K concentration, and increased by 0.12 and 0.22 fold under 20 mg/L and 160 mg/L K level compared to that of the control (40 mg/L), decreasing by 0.57 fold under 0 mg/L K. Nlvg mRNA expression increased 1.17 and 1.94 fold in individuals which were reared on rice grown in 20 mg/L and 160 mg/L K level, compared to that of the control before mating; and by 3.36 and 2.97 after mating, respectively. However, Nlvg mRNA expression fold decreased by 0.99 under 0 mg/L K level before mating and 0.91 after mating. The variation of eggs may be attributed to the change of Nlvg mRNA expression, because there was a positive correlation between the eggs and Nlvg mRNA expression. These results demonstrated low (20 mg/L) and highest K levels (160 mg/L) in hydroponic solution showed the lower K level in plants than the control, which facilitated the fecundity of N. lugens. The study of the effects of K levels on the fecundity should have significance for insect control.

Climate change is likely to have marked ecological effects on terrestrial ecosystems, including the activities of insect pests. Most attention has focused on the increasing geographical ranges of pests; however, if extrinsic factors enhance their thermotoler- ance, populations may express increased voltinism and longer daily and annual activ- ity periods. These changes in pest populations have the potential for severe consequences, including increased crop losses and decreased food security at the glo- bal level. The brown planthopper (BPH) Nilaparvata lugens Stal (Hemiptera: Delphaci- dae) is a serious pest of rice crops in temperate and tropical regions of Asia. It is often present in rice microclimates at temperatures close to its maximum thermotolerance. Recent BPH outbreaks in tropical Asia are considered to be associated with excess use of pesticides and increasing temperature. This study tested whether exposure to suble- thal concentrations of triazophos (tzp), an insecticide widely used in Asian rice pro- duction, enhances thermotolerance of BPH. Tzp exposure (40 ppm at 40 °C) significantly decreased mortality (from 94% in controls to 50% at 48 h post-treatment) and increased lethal mean time (LT50) of adults by 17.2 h. To investigate the underly- ing molecular mechanism of this tzp-enhanced thermotolerance, we selected Hsp70 and Arginine kinase (Argk) for detailed study. Transcripts encoding both proteins in third-instar nymphs and brachypterous adult females were up-regulated, compared with controls, after exposure to tzp. RNAi silencing of both genes demonstrated that Hsp70 and Argk are essential for survival and tzp-increased thermotolerance. We pro- pose that tzp induces thermotolerance in BPHs by increasing the expression of genes that act in cell protection mechanisms. The significance of our proposal relates to the importance of understanding the influence of sublethal concentrations of insecticides on pest biology. In addition to its influence on thermotolerance, tzp also enhances BPH reproduction. We infer that exposure to a pesticide stressor can produce cross- tolerance, that is, increased tolerance to one stressor also increases tolerance to other stressors, including temperature. Aside from needing a better understanding of these effects in nature and in other pest/cropping systems, we suggest that pest management programmes can be improved with better understanding of the influences of stressors, including increased environmental temperatures and sublethal concentrations of insec- ticides, on pest biology.

The brown planthopper (BPH), Nilaparvata lugens Stal, is a serious rice pest throughout Asia. Recent outbreaks of N. lugens populations were mainly associated with the overuse of pesticides and resistance to insecticides. Warmer global temperatures that are associated with anthropogenic climate change are likely to have marked ecological effects on terrestrial ecosystems. However, the effects of elevated CO2 concentrations on the biochemical, physiological and nutrient quality of transgenic Bt rice that has been treated with pesticides and on the control efficacy of the pesticides are not understood. The present study investigated changes in soluble sugar content, free amino acid levels, oxalic acid levels, flavonoids levels, and triazophos residues in transgenic Bt rice (TT51) and the control efficacy of triazophos for N. lugens following triazophos foliar spray under conditions of elevated CO2 (eCO2). Our findings showed that the soluble sugar content of TT51 treated with triazophos under eCO2 was significantly higher than that under ambient CO2 (aCO2) and also higher than that of the non-transgenic parent (MH63) under aCO2. However, the results for free amino acid levels were the opposite of those for soluble sugar levels. The oxalic acid and flavonoid contents of rice plants significantly decreased with increases in triazophos concentration, CO2 concentration, and days after treatment (DAT). The oxalic acid and flavonoid contents of TT51 treated with triazophos under eCO2 were significantly lower than those under aCO2 and also lower than those of MH63 under aCO2. The residue concentration of triazophos varied with CO2 concentration, rice variety, and DAT. The residues in TT51 treated with 80 ppm of trizaopos under eCO2 were significantly lower than those under aCO2 and those in MH63 under aCO2. The survival rate of nymphs N. lugens in TT51 under eCO2 was significantly higher than that under aCO2 and that in MH63 under aCO2 at 1 DAT or 15 DAT after the release of 2nd instars nymphs. These findings indicated that (1) for TT51, triazophos reduced the resistance of rice plants to N. lugens with an elevated CO2 concentration, as N. lugens consumed more phloem sap on TT51 plants; (2) triazophos dissipation in TT51 under eCO2 was significantly faster than that under aCO2 and that in MH63 under aCO2; (3) the control efficacy of triazophos for N. lugens significantly decreased under eCO2. The present findings provide important information for integrated pest management among transgenic varieties.

The brown planthopper (BPH), Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), is a long-distance migratory insect pest in temperate eastern Asia and is a classical resurgent rice pest that is induced by insecticides. Knowledge of the effect of insecticides on the flight capacity of insects is needed to understand their migration, which may help to improve the management of insect pests. Our previous study demonstrated that some insecticides enhance the flight capacity of BPH. However, the effect of insecticides on the flight muscle of BPH is not well understood. Thus, the present study examined the effect of triazophos, a classical insecticide that induces the resurgence of BPH, on the ultrastructure of macropterous females using transmission electron microscopy. The results showed that the diameter of myofibrils one and two days after adult female emergence (DAE) following treatment with 40 ppm triazophos was significantly greater than that of the control, increasing by 31.4 and 21.5%, respectively. In addition, the length of the sarcomeres at two and three DAE was significantly greater than that of the control, increasing by 73.8 and 50.8%, respectively. The percentage of mitochondrial volume in the muscle fibres at one and two DAE was 146.2 and 67.7% greater than that of the control, respectively. These findings show that the mechanisms of triazophos-induced enhancement of the flight capacity of BPH involve changes in the ultrastructure of the flight muscle.

The brown planthopper, Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), is a classic example of a pest that experiences insecticide-induced fecundity. The insecticides indoxacarb and chlorantraniliprole were recently developed with high insecticidal activity in the control of rice yellow stem borer, Tryporyza incertulas (walker) and rice leaffolder, Cnaphalocrocis medinalis (Guenee). We examined the changes in the fecundity of N. lugens , the vitellogenin ( Nlvg ) gene expression and the vitellin contents of adult females exposed to these new insecticides. Our findings showed that indoxacarb and chlorantraniliprole significantly suppressed the fecundity of the females and the expression of Nlvg mRNA. Treatment with 10, 20, 40 and 80 mg/L indoxacarb decreased Nlvg mRNA expression by 35.4%, 74.4%, 79.6% and 61.9%, respectively, and treatment with 7.5, 15, 30, 60 and 80 mg/L chlorantraniliprole decreased Nlvg mRNA expression by 79.3%, 40.2%, 40.0%, 79.8% and 51.8%, respectively. The vitellin contents in both the ovaries and fat bodies of the adult females also decreased, indicating that the two insecticides suppressed the synthesis of vitellin in the fat bodies and the transfer of vitellin to the ovaries. This decrease in the vitellin contents of the ovaries may be attributed to the low Nlvg expression, as there was a positive correlation between the vitellin content and the expression of this gene, indicating that these insecticides influenced the fecundity of N. lugens by affecting the expression of Nlvg mRNA. The study of the effects of indoxacarb and chlorantraniliprole on fecundity should have significance for the wide usage in rice plants.

In our previous study with the brown planthopper (BPH), Nilaparvata lugens, triazophos (tzp) treatments led to substantial up-regulation of a male spermatogenesis-associated protein 5-like gene (NlSPATA5) compared to untreated controls. Mating with tzp-treated males significantly increased fecundity (as numbers of eggs laid), relative to females mated with untreated males. Because SPATA5 acts in mammalian sperm development and is expressed in testes, we posed the hypothesis that NlSPATA5 occurs in BPH seminal fluid and it operates in fecundity via mating. We tested the hypothesis by investigating the influence of suppressing NlSPATA5 expression in BPH males on fecundity. Reduced expression of NlSPATA5 led to decreased male accessory gland protein content and reproductive system development compared to controls. These changes in males led to prolonged pre-oviposition periods and decreased fecundity in females. For both genders, we recorded no difference in the body weight, oviposition periods, and longevity compared to controls. NlSPATA5 suppression in males also led to decreased fat body and ovarian protein content, yeast-like symbionts abundance and ovarian development as well as vitellogenin gene expression in their mating partners. We infer that increased NlSPATA5 expression may be one molecular mechanism of tzp-driven reproduction and population increases in BPH.

Previous studies have demonstrated that the agricultural antibiotic jinggangmycin (JGM) stimulates reproduction in the brown planthopper Nilaparvata lugens Stal and that the stimulation of brown planthopper reproduction induced by JGM is regulated by the fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC) genes. However, a key issue in the stimulation of reproduction induced by pesticides involves the growth and development of oocytes. Therefore, the present study investigated oocyte changes via transmission electron microscopy (TEM) and changes in hormone levels (juvenile hormones (JH) and 20-hydroxyecdysone (20 E)) in JGM-treated females. TEM observations showed that the size of the lipid droplets in the oocytes of JGM-treated females, compared with those in the oocytes of the control females, significantly reduced by 32.6 and 29.8% at 1 and 2 d after emergence (1 and 2 DAE), respectively. In addition, the JH levels of JGM-treated females at 1 and 2 DAE were increased by 49.7 and 45.7%, respectively, whereas 20 E levels decreased by 36.0 and 30.0%, respectively. We conclude that JGM treatments lead to substantial changes in lipid metabolism, which are directly and indirectly related to stimulation of reproduction of brown planthopper together with our previous findings.

The antibiotic jinggangmycin (JGM) is an agrochemical product widely used in China for controlling rice sheath blight, Rhizoctonia solani. Unexpectedly, it stimulates reproduction in the brown planthopper (BPH), Nilaparvata lugens (Stål). However, the underlying molecular mechanisms of the stimulation are unclear. The present investigation demonstrates that adipose triglyceride lipase (Atgl) is one of the enzymes involved in the JGM-stimulated reproduction in BPH. Silence of Atgl in JGM-treated (JGM + dsAtgl) females eliminated JGM-stimulated fecundity of BPH females. In addition, Atgl knockdown significantly reduced the protein and glycerin contents in the ovaries and fat bodies of JGM + dsAtgl females required for reproduction. We conclude that Atgl is one of the key enzymes responsible for JGM-stimulated reproduction in BPH.

Extreme temperatures are thought to be one of the main factors suppressing natural population growth of the brown planthopper Nilaparvata lugens (Stal) (Hemiptera: Delphacidae). In contrast, sublethal doses of some pesticides (such as triazophos) stimulate reproduction of adult males and adult females of N. lugens. However, the combined effects of high or low temperature and sublethal doses of pesticides on the reproduction of adult males or adult females have not been investigated. This study examined the effects of high (34 °C), typical (26 °C) and low (20 °C) temperature and the insecticide triazophos on the protein content of male accessory glands (MAGs) and adult female ovaries and on the fecundity of adult females. The study demonstrated that temperature and triazophos concentration significantly influence the protein content of MAGs and of adult female ovaries before and after mating. The protein content in MAGs before mating attained a maximum value at 26 °C (45.1 μg per adult male, grand mean of all concentrations), followed by an intermediate value of 38.0 μg at 20 °C and a minimum value of 10.4 μg at 34 °C. These results indicate that the reproduction of males is more sensitive to high temperature compared to adult females. Protein content in MAGs after mating at 26 °C remained at a maximum value (25.6 μg per adult male, grand mean of all concentrations), followed by 21.9 μg at 20 °C and a minimum value of 8.3 μg at 34 °C. The protein content of MAGs after mating decreased with increasing triazophos concentration at the three temperatures. This result indicates that treated males transferred more MAG protein to adult females through mating. For example, MAG protein after mating at 26 °C for 0, 10, 20, 40 and 80 ppm triazophos treatments decreased by 16.5, 39.2, 42.8, 53.5 and 58.2%, respectively, compared with the corresponding values before mating. The protein content of adult female ovaries both before and after mating at three temperatures for all concentrations was significantly higher than in the control. However, the increase of ovary protein (percent) both before and after mating for all concentrations attained its maximum value at 34 °C, an intermediate value at 26 °C, and its minimum value at 20 °C, compared with the control. Similarly, percent increases in the number of eggs laid for 10, 20, 40 and 80 ppm triazophos treatments at 34 °C and 20 °C (except for 80 ppm) were greater than those at 26 °C.

Graphical abstract Insecticide imidacloprid application induced the susceptibility of rice to the brown planthopper and changes of gene expression levels of rice. Highlights ► Microarray was used to identify changes in imidacloprid-induced rice gene expression. ► A total of 225 genes were differentially expressed following imidacloprid treatment. ► These differentially expressed genes were mainly classified into eight functional groups., The chemical pesticide, imidacloprid (IMI) has long-lasting effectiveness against Hemiptera. IMI is commonly used to control the brown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacidae). Some chemical pesticides, however, can induce the susceptibility of rice to BPH, which has indirectly led to the resurgence of BPH. The mechanism of the chemical induction of the susceptibility of rice to BPH was not previously understood. Here, a 44 K Agilent Rice Expression Microarray was used to identify changes in gene expression that accompany IMI-induced rice susceptibility to BPH. The results showed that 225 genes were differentially expressed, of which 117 were upregulated, and 108 were downregulated. Gene ontology annotation and pathway analysis revealed that differentially expressed genes were mainly classified into the eight functional groups: oxidation reduction, regulation of cellular process, response to stress, electron carrier activity, metabolic process, transport, signal transducer, and organismal development. The genes encoding plant lipid transfer protein, lignin peroxidase, and flavonol-3-O-methyltransferenase may be important responses to the IMI-induced susceptibility of rice to BPH. The reliability of the microarray data was verified by performing quantitative real-time PCR and the data provide valuable information for further study of the molecular mechanism of IMI-induced susceptibility of rice.

Jinggangmycin is an antibiotic fungicide against the rice sheath blight, Rhizoctonia solani, in China. Previous investigations have shown that jinggangmycin leaf spray stimulated the fecundity of Nilaparvata lugens Stal (Hemiptera:Delphacidae), but the effects of different application methods and concentrations of jinggangmycin on the reproduction of N. lugens have not been investigated. Here, we investigated three treatment methods (foliar and stem sprays and topical treatment) and four concentrations (100, 200, 400 and 800 ppm) of jinggangmycin on the reproduction of adult female N. lugens. The results showed that leaf spray significantly stimulated the fecundity of N. lugens and increased the vitellin content in female ovaries and the gene expression level of vitellogenin (Nlvg), but there was no significant effect on reproduction found for stem spray. In four concentrations of jinggangmycin, leaf sprays at concentrations of 100, 200 and 400 ppm and topical treatments of 100 and 200 ppm significantly increased the number of eggs laid, the vitellin content and the gene expression level of Nlvg compared to the control. Therefore, we suggest that stem spray at high concentration should be applied (if possible) when jinggangmycin is used against rice sheath blight to facilitate harmonious control of rice pests.

The brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is a classic example of a resurgent pest induced by insecticides. It has been demonstrated that triazophos treatment causes an increase in the content of male accessory gland proteins (Acps) that can be transferred to females via mating, influencing female reproduction. However, the mechanism of this type of insecticide-induced Acps in males and the subsequent stimulation of reproduction in females are not well understood. To identify changes in the types of Acps and reproductive proteins in mated females, we conducted a comparative proteomic analysis. Six samples were categorized into four different groups: (1) untreated unmated males compared to treated unmated males (UUM vs TUM); (2) treated unmated males compared to treated mated males (TUM vs TMM); (3) untreated unmated females compared to treated unmated females (UUF vs TUF); (4) treated unmated females compared to treated mated females (TUF vs TMF). Protein expression changes among the four different groups were examined by two-dimensional gel electrophoresis (2-DE) and liquid chromatography tandem mass spectrometry (LC-MS/MS). Of the 500-600 reproducibly detected protein spots on each gel, 107 protein spots were differentially expressed between the four different groups. Of the 63 proteins identified by LC-MS/MS analysis, 38 were up-regulated and 25 were down-regulated in the four different groups. Some novel proteins related to fecundity were observed including spermatogenesis-associated protein 5, testis development protein NYD-SP6, arginine kinase, actin-5C, vitellogenin, and ovarian serine protease nudel. The elevated expression of novel fecundity proteins in six samples of N. lugens females and males due to exposure to triazophos was confirmed by quantitative real-time PCR (qRT-PCR). The results suggest that these proteins may participate in the reproductive process of N. lugens adult females and males. Our findings fill a gap in understanding the relationship between insecticide-treated males and the stimulated reproduction of N. lugens females.

The brown planthopper, Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), is a long-distance migratory insect pest in temperate eastern Asia and a typical recurrent pest induced by pesticides. We investigated the effect of sublethal concentrations of insecticides on the flight capacity on this species. An automated flight-mill system was used to assess the flight capacity of adults reared on untreated and insecticide-treated plants. In most instances, the flight duration of adult females exposed to high concentrations of imidacloprid, triazophos or deltamethrin was significantly greater than that of untreated controls. Compared to the controls, the flight duration of females increased by 140% (from 103 to 245.9 min), 119% (from 103 to 226 min) and 78% (from 103 to 183.3 min) with 10 ppm imidacloprid, 40 ppm triazophos and 3 ppm deltamethrin, respectively, yet no significant difference in the flight duration of males was found between the insecticide treatments and the controls. The high concentrations of the three insecticides significantly enhanced the flight speed and the flight distance of both males and females, with the exception of the flight speed of adult males treated with deltamethrin. For example, the flight speed of adult females and males treated with 10 ppm imidacloprid, 40 ppm triazophos and 6 ppm deltamethrin increased by 75% (from 0.39 to 0.68 km/h), 154% (from 0.39 to 0.98 km/h) and 124% (from 0.39 to 0.87 km/h) for females and by 141% (from 0.32 to 0.77 km/h), 73% (from 0.32 to 0.55 km/h) and 48% (from 0.32 to 0.47 km/h) for males, respectively, compared to the controls. In addition, the percentages of individuals treated with imidacloprid and triazophos flying for over 60 min doubled compared to the control. These findings are relevant for understanding the migration and outbreak patterns of N. lugens .

Graphical abstract A previous study demonstrated that the flight capacity of Nilaparvata lugens adults treated with triazophos was enhanced significantly. However, the physiological and regulative mechanisms of the flight enhancement are not well understood. Trehalose is a primary blood sugar in insects, and the enzyme trehalase is involved in energy metabolism. The present study investigated the effects of triazophos on the trehalose content, trehalase activity (soluble trehalase and membrane-bound trehalase) and the mRNA transcript levels of their corresponding genes (NlTre-1 and NlTre-2) in fifth instar nymphs, as well as in the brachypterous and macropterous N. lugens adult females. Our findings showed that the trehalose content in fifth instar nymphs as well as in the brachypterous and the macropterous adults significantly decreased following triazophos treatment. However, the glucose content, soluble trehalase activity and expression level of NlTre-1 mRNA increased significantly compared to the controls. No significant enhancement of NlTre-2 expression was found, indicating that regulation of energy metabolism of triazophos-induced flight capacity in N. lugens was not associated with NlTre-2 expression. In addition, soluble trehalase activity and the expression level of NlTre-1 mRNA in the macropterous females was significantly higher than that in the brachypterous females. The present findings provide valuable information on the molecular and regulative mechanisms of the increased flight capacity found in adult N. lugens after treatment with triazophos. Highlights ► The physiological and regulative mechanisms of insecticide-induced the flight enhancement are not well understood. ► The trehalose content in fifth instar nymphs, and in the brachypterous and the macropterous adults of the insect decreased following triazophos treatment. ► The glucose content, soluble trehalase activity and expression level of NlTre-1 mRNA increased significantly compared to the controls. ► Soluble trehalase activity and the expression level of NlTre-1 mRNA in the macropterous females was higher than that in the brachypterous females., A previous study demonstrated that the flight capacity of Nilaparvata lugens adults treated with triazophos was enhanced significantly. However, the physiological and regulative mechanisms of the flight enhancement are not well understood. Trehalose is a primary blood sugar in insects, and the enzyme trehalase is involved in energy metabolism. The present study investigated the effects of triazophos on the trehalose content, trehalase activity (soluble trehalase and membrane-bound trehalase) and the mRNA transcript levels of their corresponding genes (NlTre-1 and NlTre-2) in fifth instar nymphs, as well as in the brachypterous and macropterous N. lugens adult females. Our findings showed that the trehalose content in fifth instar nymphs as well as in the brachypterous and the macropterous adults significantly decreased following triazophos treatment. However, the glucose content, soluble trehalase activity and expression level of NlTre-1 mRNA increased significantly compared to the controls. No significant enhancement of NlTre-2 expression was found, indicating that regulation of energy metabolism of triazophos-induced flight capacity in N. lugens was not associated with NlTre-2 expression. In addition, soluble trehalase activity and the expression level of NlTre-1 mRNA in the macropterous females was significantly higher than that in the brachypterous females. The present findings provide valuable information on the molecular and regulative mechanisms of the increased flight capacity found in adult N. lugens after treatment with triazophos.

The brown planthopper Nilaparvata lugens (Stal) (Hemiptera: Delphacidae) is a classical resurgent rice pest induced by insecticides. The past focus on resurgence mechanisms has been on the stimulation of the reproduction of adult females induced by insecticides. To date, the role that males play as a resurgence of N. lugens has not been investigated. The present study examined changes in protein levels in both male accessory glands and female ovaries induced by the insecticides triazophos and deltamethrin as well as the stimulating effect of treated males on the fecundity of adult females via mating following foliar sprays of the insecticides. For adults that had been exposed as nymphs to treated rice plants, the protein content in both the male accessory glands and in the female ovaries of N. lugens were significantly affected by male mating status, insecticide and insecticide concentration. There was a higher protein content in male accessory glands when males were exposed to triazophos as third instars compared to fifth instars, and there was a higher protein content before mating compared to after mating. In addition, the protein levels in male accessory glands after mating for individuals exposed to high doses of the two insecticides as 3rd and 5th instars were significantly lower than untreated control except for exposed to triazophos as 3rd instar, indicating that treated males transferred more male accessory gland protein to adult females via mating. The protein content was also affected by different combinations of treated mating pairs. Adult males (♂t) developed from third instar nymphs treated with triazophos stimulated the fecundity of the female significantly via mating (♂t × ♀ck) with untreated females (♀ck) (control females), increasing the reproductive rate by 43.5% as compared to the mating (♂ck × ♀ck) of untreated males and females. Also, the fecundity of the females after the mating (♂t × ♀t) of treated males and females was significantly higher than that after the mating (♂ck × ♀t) of untreated males with treated females. These findings indicated that the reproductive effects of insecticide on males can be transferred to females via mating. The present findings provide valuable information for understanding the potential role that males play in the pesticide-induced resurgence of N. lugens.

The brown planthopper, Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), is an insect pest in which offspring are produced by the mating of adult males with adult females. This species is a classic case in which pest resurgence is induced by insecticides. In the past, studies of resurgence mechanisms have focused on insecticide-induced stimulation of reproduction in adult females. To date, however, the role that males play in the resurgence mechanisms of N. lugens has not been investigated. The aim of the present study is to examine changes in protein levels in male accessory glands (MAGs) induced by the insecticides triazophos and deltamethrin and to determine their relationship with vitellin content in the fat bodies and ovaries of adult females in the context of mating pairs. Our results show that protein content in MAGs is significantly affected by male mating status, insecticide type, and insecticide concentration. Insecticide application induced increased protein levels in MAGs. A greater quantity of MAG products was transferred to females via mating. Thus, protein levels in MAGs significantly decreased after mating. Experimental matings indicate that vitellin content in both fat bodies and ovaries of adult females in mating pairs consisting of a treated male and an untreated female (♂ t × ♀ ck ) is significantly greater than that of females in pairs consisting of an untreated male and an untreated female (♂ ck × ♀ ck ). Under various concentrations of the two insecticides, vitellin levels are highest in mating pairs consisting of a treated male and a treated female (♂ t × ♀ t ), followed by mating pairs consisting of an untreated male with a treated female (♂ ck × ♀ t ). These findings demonstrate that (1) insecticides have an effect on males; (2) insecticide effect can be transferred to females; and (3) the reproductive effect of insecticides is strongest in mating pairs in which both the males and females are treated compared to pairs in which only one individual is treated. These findings provide valuable information about the role of males in pesticide-induced resurgence of N. lugens.

The widespread use of imidacloprid against insect pests has not only increased the rate of the development of target pest resistance but has also resulted in various negative effects on rice plants and Nilaparvata lugens resurgence. However, the effect of imidacloprid on elements in rice plants and the transference of these element changes between rice and N. lugens are currently poorly understood. The present study investigated changesofCu,Fe,Mn,Zn,Ca,K,MgandNacontentsinriceplantsfollowingimidacloprid foliarspraysintheadultfemaleofN. lugens thatdevelopsfromnymphsthatfeedontreated plants and honeydew produced by females. The results indicated that imidacloprid foliar spray significantly increased Fe and K contents in leaf sheaths. Generally, Fe, Mn, K and Na contents in leaf blades were noticeably decreased, but Ca contents in leaf blades for 10 and 30 mg/kg imidacloprid treatments were significantly increased. The contents of most elements except K and Mg in the adult females and honeydew were significantly elevated. Multivariate statistical analysis showed that Fe, Mn and Na in leaf blades and Fe and Mn in leaf sheaths could be proportionally transferred to N. lugens. The relationship between most elements in adult female bodies and in the honeydew showed a positive correlation coefficient. There were significant differences in the contents of some elements in rice plants and N. lugens from different regions.

The rice brown planthopper, Nilaparvata lugens (Stal) (Homoptera: Delphacidae), is the type of insect pest whose resurgence is induced by pesticides. Outbreaks of the pest frequently occur in Asia. We investigated the effects of series of concentrations of four insecticides, imidacloprid, buprofezin, deltamethrin and triazophos, on the durations of the preoviposition (DPP) and oviposition period (DOP), female longevity (LOF), realized fecundity (RFE) and egg hatchability of N. lugens on two rice varieties: TN1 and Xieyou 963. DPP, DOP, LOF, NLE and hatchability varied with insecticide type, concentration, number of applications, and rice variety. For imidacloprid and buprofezin, RFE and hatchability decreased, DPP increased, and DOP and LOF lessened significantly with increasing concentration. In contrast, for deltamethrin and triazophos, DPP and DOP shortened, and LOF, RFE and hatchability increased significantly with increasing concentration. Increase in the number of applications for the four insectici...

This study concerns elucidating the physiology of insecticide-induced stimulation reproduction in Nilaparvata lugens (Stal) (Homoptera : Delphacidae). In insects, vitellogenesis involves the synthesis of the yolk protein precursor in the fat body and its deposition in the oocytes. Our investigations were specifically targeted at the dynamics of the protein content of both the fat body and ovary of adult females developed from the nymphs on rice plants treated with imidacloprid, triazophos and deltamethrin. The results show that the protein contents of the fat body and the ovary increased significantly in insects from rice plants which were subjected to insecticide foliar sprays at both tillering and yellow maturation stages, as compared to the controls from untreated plants. However, the amount of increase varied with insecticide, treatment concentrations and adult age. In general, the percent increase induced by triazophos and deltamethrin was generally greater than that induced by imidacloprid, and the ...

Imidacloprid is a foliar and systemic insecticide used for controlling hemipteran insect pests such as planthoppers and aphids. The extensive use of imidacloprid to control rice planthoppers has increased the risk of resistance development for many other insect pests in the rice agroecosystem. We measured insecticide residue concentrations in leaves and stems of two varieties of rice plants after either a water or foliar application and evaluated the efficacy of imidacloprid residues in plants for control of the brown planthopper, Nilaparvata lugens (Stal) in rice. The concentration of imidacloprid residues varied with application method, plant part and developmental stage of rice. Residue concentration in plants receiving insecticide as a water application was significantly higher than in plants receiving insecticide as foliar sprays. Residues were higher in fully expanded leaves than in unexpanded new leaves and stems. Residues were higher at the booting stage than at the tillering stage. Correspondingl...

The manifestation of brown planthopper Nilaparvata lugens (Stal) hopperburn damage was investigated with damage due to rice leaffolder, Cnaphalocrocis medinalis (Guenee) simulated by leaf cutting and root pests by root cutting. Plants were grown under hydroponic culture, with a nutrient solution (PK) foliar applied to assess the effect on the onset of the damage symptoms. The effect of both root and leaf removal on the time (days) before hopperburn symptoms (DHS) depended on the rice variety. DHS was significantly shortened with TN1 variety (BPH susceptible), but not with root cutting. Removal of both leaves and roots from Xieyou 63 variety (BPH tolerant), did not affect DHS. However, multiple comparisons of means of combined treatments for leaf and root cutting showed that removal of two thirds of root and leaves significantly shortened DHS. Foliar P sprays with root cutting had no impact of DHS on TN1 compared to no spray, but with leaf cutting DHS of TN1 was shortened significantly. In contrast to TN1, foliar P sprays significantly prolonged DHS of Xieyou 63. For the two rice varieties, foliar K sprays did not affect DHS, nor did doubling P and K concentrations in hydroponics solutions with TN1 under root removal. There was a significant interaction between leaf removal and doubling P and K with leaf cutting, the DHS being shortest for the combined treatment of two thirds of leaf cut and double K. Doubling P and K concentrations did not affect DHS of Xieyou 63 with both root and leaf removal. The understanding of the relationship between DHS and root/leaf cutting, and application of P and K fertilizer for two rice varieties can provide valuable information for determining a control threshold of BPH when two pests coexist and for rational application of fertilizers. A high damage rate of rice leaves by C. medinalis can enhance the damage inflicted by BPH due to an interaction effect. Thus the control threshold of BPH should be decreased when C. medinalis outbreaks occur. In contrast, the threshold of BPH should be increased when there is a low damage rate caused by C. medinalis. The variety that delays DHS indicates that it has some tolerance to BPH infestation, thus control threshold should be increased or pesticide application be reduced.

The brown planthopper (BPH), Nilaparvata lugens, sugar transporter gene 6 (Nlst6) is a facilitative glucose/fructose transporter (often called a passive carrier) expressed in midgut that mediates sugar transport from the midgut lumen to hemolymph. The influence of down regulating expression of sugar transporter genes on insect growth, development and fecundity is unknown. Nonetheless, it is reasonable to suspect that transporter-mediated uptake of dietary sugar is essential to the biology of phloem-feeding insects. Based on this reasoning, we posed the hypothesis that silencing, or reducing expression, of a BPH sugar transporter gene would be deleterious to the insects. To test our hypothesis, we examined the effects of Nlst6 knockdown on BPH biology. Reducing expression of Nlst6 led to profound effects on BPHs. It significantly prolonged the pre-oviposition period, shortened the oviposition period, decreased the number of eggs deposited and reduced body weight, compared to controls. Nlst6 knockdown also significantly decreased fat body and ovarian (particularly vitellogenin) protein content as well as vitellogenin gene expression. Experimental BPHs accumulated less fat body glucose compared to controls. We infer that Nlst6 acts in BPH growth and fecundity and has potential as a novel target gene for control of phloem-feeding pest insects.

A major challenge in ecology lies in understanding the coexistence of intraguild species, well documented at the organismal level, but not at the molecular level. This study focused on the effects of the antibiotic, jinggangmycin (JGM), a fungicide widely used in Asian rice agroecosystems, on reproduction of insects within the planthopper guild, including the brown planthopper (BPH) Nilaparvata lugens and the white-backed planthopper (WBPH) Sogatella furcifera, both serious resurgence rice pests. JGM exposure significantly increased BPH fecundity and population growth, but suppressed both parameters in laboratory and field WBPH populations. We used digital gene expression and transcriptomic analyses to identify a panel of differentially expressed genes, including a set of up-regulated genes in JGM-treated BPH, which were down-regulated in JGM-treated WBPH. RNAi silencing of Acetyl Co-A carboxylase (ACC), highly expressed in JGM-treated BPH, reduced ACC expression (by > 60%) and eliminated JGM-induced fecundity increases in BPH. These findings support our hypothesis that differences in ACC expression separates intraguild species at the molecular level.

The brown planthopper, Nilaparvata lugens (Stal), is a destructive insect pest on rice throughout Asia. As a visible genetic marker, red eye mutant colony of brown planthopper is a valuable material. Here, we established the near-isogenic lines, NIL-BB and NIL-rr, through mating red eye females to brown eye brothers for eight successive generations. Biological experiments showed that NIL-BB had big fitness cost; however, NIL-rr had comparable survival and fertility parameters with BB, a normal laboratory brown planthopper strain. Significantly lower number eggs per female and egg hatchability were the key factors resulting in big fitness cost of NIL-BB. The population trend indexes of BB, NIL-rr, and NIL-BB were 52.18, 43.80, and 4.19, respectively. Real-time PCR study suggested that the poorer fertility of NIL-BB was not mediated by the differential expression of genes relating to oogenesis. The stronger fitness of NIL-rr compared with NIL-BB may be caused by the eye mutant gene or its closely linked genes having stronger compensation ability for reproduction. The comparable fitness of NIL-rr with BB indicated that NIL-rr may be used in field research. The NIL-BB strain with significantly declined fecundity and survival ability can be used as study model for the signal pathways relating to fecundity.

This study investigates the uptake of nitrogen (N), phosphorus (P), and potassium (K) by rice roots as a response to infestation by the rice brown planthopper, Nilaparvata lugens (Stal) (Homoptera: Delphacidae) at two developmental stages (i.e. beginning-heading and grain-filling) of two rice varieties, Zhendao 2 (japonics rice) and Xieyou 63 (hybrid indica rice), respectively. The results show that the impact of N. lugens infestation at the beginning-heading stage on N, P, and K uptake was not only more serious, but also that the recovery rate of root uptake after the removal of N. lugens was slower, as compared to the grain-filling stage. The percent reduction of N uptake following N. lugens infestations at the beginning-heading stage of Xieyou 63 was significantly greater in comparison to Zhendao 2 at the same stage. There was no significant difference in N uptake between two developmental stages, but P and K uptake by roots following N. lugens infestation were significantly different between ...

Changes of the uptake function of rice roots to nitrogen (N), phosphorus (P), and potassium (K) in a hydroponics culture solution were studied in three experiments: a single factor experiment involving rice leaffolder, Cnaphalocrocis medinalis, larval infestations or simulated damages (cutting of leaves); paired combinations of two factors (leaf and root cuts); and combination of three factors (Nilaparvata lugens infestation and leaf and root removal). In the single-factor experiment, both C. medinalis feeding and leaf cutting significantly reduced the uptake of N by rice roots compared with the control. There were no significant differences in N concentration in hydroponics culture solution between treatments of one, two, and four larvae per hill, but there were significant differences between two rates of leaf cutting. Also, C. medinalis feeding and the cutting of leaves reduced the uptake of P by roots significantly but did not affect K uptake except when two-thirds of the leaf area was remove...

Effects of different BPH densities and pesticide applications on the uptake of nitrogen (N), phosphorus (P) and potassium (K), by the root system were investigated using a hydroponics culture. Infestations of 30 BPH had a significant effect on the uptake function of the rice root. A high dose (225 g.a.i. ha −1 ) of jingganmycin reduced the uptake of P and K significantly, but there was little effect on the uptake of N. At a low dose (15 g.a.i. ha −1 ) of imidacloprid the uptake of P and K was promoted significantly. There was also a significant interaction effect between BPH density and pesticide treatments. Field experiment during rice-grain filling showed that both low and high doses of imidacloprid reduced active growth stage (Δ t ) and maximum (K) of grain growth of superior grains significantly and a high dose reduced K and growth rate of inferior grains significantly. All doses of imidacloprid and jingganmycin significantly reduced accumulative grain weight during Δ t . A high dose of imidacloprid reduced the growth rate of inferior grains significantly.

The effective durations of pesticide-induced susceptibility of rice to brown planthopper (BPH), Nilaparvata lugens (Stal) (Homoptera: Delphacidae), and physiological and biochemical changes in rice plants following pesticide applications, were studied. The effective duration of the herbicide butachlor on the susceptibility of rice variety Zhengdao 2 to BPH exceeded 16 days. The difference in damage rating between rice plants with pesticide treatments and control plants gradually decreased with days after treatment (DAT). There was a significant correlation between damage rating and DAT. The number of rice tillers at 3 – 10 DAT and plant heights at 7 – 10 DAT declined on Zhengdao 2 with the butachlor treatment. On the other hand, there were no effects of butachlor on damage rating, number of rice tillers and plant height for Xiushui 63. This might be related to tolerance of Xiushui 63 to butachlor. For Zhengdao 2, the fungicide jingganmycin and the insecticide bisultap had a significant influence on BPH da...

History of insecticidal control of rice planthoppers in Asia and associated resistance development is summarized. Rice planthoppers have developed resistance against all the insecticides that were commonly used. Experiences of past 30 years of chemical control of the rice planthoppers in many parts of Asia confirm that the use of any kind of insecticide for long time leads to the development of resistance. Overseas migration of rice planthoppers may markedly affect the status of insecticide resistance in populations over long distances, and the effects of migration can be maintained at least until the following year. It is possible that insecticide resistance may spread as a result of intercrossing between resistant immigrant and susceptible domestic populations. When insecticides are used against major pest, such planthoppers also produce selection pressure on the potential pests. It is believed that the resistance of small brown planthopper (SBPH) to insecticides is one of the important factors behind the recent outbreaks of smaller BPH in China. Pesticide-induced resurgence involves ecological and physiological factors. Many of the pesticides stimulate the reproduction of the brown planthopper (BPH), and sublethal dosages increase its reproduction. Decimation of natural enemy by pesticides is an important ecological factor for the induction of BPH resurgence, but stimulation of reproduction by pesticides is more responsible for the occurrence of resurgence. Insecticide resistance and pest resurgence caused by insecticides and their outcome result in occurrence of outbreak or resurgence of pests. Pesticides also affect physiology and biochemistry of rice plant in different ways. Insecticide resistance and insecticide-induced resurgence are closely related, and resultant outcome is pest outbreak or resurgence.

The pesticide-induced stimulation of reproduction in pests is one of the most important mechanisms of pest resurgence. There have been numerous reports on the insecticide-induced stimulation of reproduction. However, the relationship between pesticide application method and pest resurgence (stimulation of reproduction) has received little attention. Here, we studied the effect of two treatment methods, triazophos (TZP) and jinggangmycin (JGM), on the protein content in the ovaries and fat bodies of the brown planthopper (BPH) Nilaparvata lugens Stal. The results showed that pesticide treatment methods significantly affected the protein content in the ovaries and fat bodies of BPH. In addition, grand means (means of main effect) of the protein content at 2 and 3 days after emergence (2 and 3 DAE) for foliar sprays was significantly higher than that observed after topical treatments, which increased by 23.9% (from 1.42 to 1.76) and 8.82% (from 4.42 to 4.81), respectively. No significant differences on the protein content in the ovaries and fat bodies for the JGM topical treatment were observed compared with controls. However, the protein content for JGM foliar sprays was significantly higher than that for the controls. The protein contents in both topical and spray treatments of TZP were significantly higher than those of the controls. Ovarian protein is mainly yolk protein. There is a positive correlation between ovarian protein content and the number of eggs laid. These findings show that foliar spray of the pesticides promotes the resurgence of BPH. Therefore, the foliar spray of some pesticides, such as JGM, should be avoided for the control of pests, which is the sideeffects of the fungicide on non-target insect pests' occurrence.

The brown planthopper Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) is a serious pest of rice crops in the temperate and tropical regions of Asia and Australia, and it is also a classic example of an insecticide-induced resurgent pest. Brown planthopper outbreaks have been reported to be closely associated with pesticide application. Previous studies have shown that the insecticide triazophos enhances thermal tolerance and fecundity in brown planthopper. However, the effects of triazophos and high temperature on reproductive capacity have not been studied in high temperature-conditioned reciprocal pairs of adult males and females. The present experiments showed that triazophos enhanced the reproductive capacity of brown planthopper under high temperature (34°C). The number of eggs laid by females treated with 40 ppm triazophos at 34°C approximately doubled compared with untreated insects. Furthermore, the triazophos-induced fecundity enhancement at 34°C was significantly greater than that at 26°C, and the number of eggs laid for mating pair of adult males at 34°C with adult females under 34°C (♂(34) × ♀(34)) were significantly greater than that of adult males at 26°C (♂(26) × ♀3(4)), suggesting that this insecticide enhances the resistance of brown planthopper to high-temperature stress. Insecticide-induced enhancement of reproductive capacity in brown planthopper under high temperatures should be of great concern, and it has important implications for forecasting future brown planthopper outbreaks as well as the pesticide-selection process.

The effects of rice plants treated with various pesticides (jingganmycin, bisultap and methamidophos) on feeding, survival rates and population growth of Nilaparvata lugens Stal (Homoptera: Delphacidae), susceptibility of the treated rice plants and amounts of free amino acids and sucrose were studied. Experiments indicated that the effects of the tested pesticides were dependent on nymphal age, pesticide and their dose and time after application. Jingganmycin at 75 g a.i. ha −1 significantly increased the N. lugens population. Both jingganmycin and bisultap increased the survival rate of N. lugens nymphs. The feeding rate of the insects was also affected by the pesticide application, but the effect varied between nymphal age and time after application and lasted no longer than 15 d. Results clearly indicated that pesticide application increased the susceptibility of rice plants to N. lugens. Although the free amino acids in rice plants did not change with the pesticide treatments, the concentration of sucrose significantly decreased 5 d after application and the C/N ratio significantly decreased in jingganmycin treated plants 5 d and 10 d after application.

Nilaparvata lugens (Stal) (Hemiptera:Delphacidae) is a serious migratory pest of rice in Asia. Pest resurgence often occurs because of insecticide overuse. Using both susceptible (TN1) and moderately resistant (Xieyou 963) cultivars, we studied the effect of foliar insecticides on the percentage of brachypterous adults, female reproductive rate, and crude fat and soluble sugar contents in third- and fifth-instar nymphs and adults. The percentage of brachypterous adults and reproductive rate of adult females developed from nymphs that fed on insecticide-treated plants varied significantly with rice cultivar, type of insecticide, and its concentration. Feeding on susceptible plants increased the percentage of brachypterous adults and reproductive rate of adult females. Also, deltamethrin increased brachypterous production relative to imidacloprid and triazophos. The highest reproductive rate was on plants treated with triazophos. All insecticide treatments in both cultivars resulted in increase of soluble sugar contents in third- and fifth-instar nymphs and adults developed from nymphs feeding on insecticide-treated rice plants. This effect was stronger on the susceptible cultivar. Changes of crude fat content after N. lugens feeding on insecticide-treated plants were related to its feeding duration. Crude fat content in adult developed from nymphs feeding on treated plants was significantly higher that on control plants. These studies showed that plant and insecticide influences on physiological ecology of this planthopper will influence its population dynamics under commercial production of rice in Asia.