Search

Background The tea leafhopper, Empoasca onukii Matsuda (Hemiptera: Cicadellidae), is a major pest of tea plants in China. Here, we evaluated the repellent properties of eight volatile chemicals alone and in various combinations as tools for the management of this pest in tea gardens. These chemicals were from the Alliaceae and other aromatic plants, and are known to repel various insect species. Results Among the eight volatile compounds, dimethyl disulfide (DMDS), 1,8-cineole and allyl methyl sulfide were significantly repellent towards E. onukii adults. DMDS and 1,8-cineole were mixed to formulate a binary repellent. Under field conditions, spraying and slow-release applications of the mixture significantly decreased the density of E. onukii adults. The repelling effect after spraying was very short, only ∼ 2 days, but the slow-release mixture had a longer term repelling effect on E. onukii adults. High emission of the slow-release mixture, which was achieved by increasing the number of slow-release bottles, had a stronger repellent effect than low emission. Moreover, when the amount emitted was sufficient, the slow-release mixture significantly decreased the number of leafhopper nymphs in a treated tea-plant line, and significantly decreased the number of leafhopper adults and nymphs in a tea-plant line adjacent to the treated area. Conclusion This study demonstrates the repellent action of a mixture of DMDS and 1,8-cineole applied by a slow-release method against E. onukii in a tea plantation. This mixture has potential applications in integrated pest management schemes. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The tea plant (Camellia sinensis) suffers heavily from a harmful piercing pest, the tea green leafhopper (TLH) Empoasca (Matsumurasca) onukii Matsuda. In the present study, we studied the effect of an efficient elicitor of plant disease resistance, the β-1,3-glucan laminarin, on the induced defense against TLH in tea plants. Defense responses elicited by laminarin in tea include the activation of mitogen-activated protein kinases and WRKY, the burst of H2O2, salicylic acid, and abscisic acid, and the accumulation of direct-defense chemicals (including chitinase, phenylalanine ammonia lyase, callose, polyphenol oxidase, and flavonol synthase), as well as the production of volatile compounds. The laminarin-treated tea plants reduced the performance of TLH and enhanced the attractiveness to the egg parasitoid wasp of TLH, Stethynium empoascae Subba Rao. In the field experiment, laminarin application effectively reduced the number of TLH by attracting parasitoids. These results suggest that laminarin can induce protection against TLH by regulating signaling pathways in tea plant. Our study also proposes an environment friendly strategy for the integrated management of an economically important piercing pest.

Ectropis grisescens Warren 1894 (Lepidopotera: Geometridae) and Ectropis obliqua Prout 1915 (Lepidopotera: Geometridae) are the most destructive chewing pests in China's tea plantations. Ectropis grisescens sex pheromone lures and E. obliqua nucleopolyhedrosis virus (EoNPV) are two species-specific and effective bio-control technologies to control these pests. Because these two species are morphologically similar, tea growers are unable to discriminate them by visual inspection. Hence, determining whether to use E. grisescens sex pheromone lures or EoNPV is difficult without knowledge on the geographical distribution of these two Ectropis species in China. In this study, we developed an efficient identification method, which is considerably cheaper and faster than sequencing the cytochrome c oxidase I gene. Overall, 2,588 E. grisescens and E. obliqua samples, collected from 13 provinces and municipalities in China covering the major regions where these pests have been reported, were identified. All insect samples from southern Jiangsu Province were identified as E. obliqua. Both Ectropis species were mix-distributed at the Anhui-Zhejiang Province border areas, whereas E. grisescens was mostly collected from the other sampling sites. Thus, E. obliqua might be mainly distributed at the junction of Jiangsu, Anhui, and Zhejiang Provinces. In contrast, E. grisescens has a considerably wide distribution area and is the main lepidopteran pest in the tea plantations of China. Our results contribute to improve the management of E. grisescens and E. obliqua populations and provide new insights for further studies on these two species.

Plants release large amounts of volatile organic compounds (VOCs) in response to attackers. Several VOCs can serve as volatile signals to elicit defense responses in undamaged tissues and neighboring plants, but many questions about the ecological functions of VOCs remain unanswered. Tea plants are impacted by two harmful invaders, the piercing herbivore Empoasca (Matsumurasca) onukii Matsuda and the pathogen Colletotrichum fructicola. To determine the VOC signals in tea, we confirmed CsOPR3 as a marker gene and set up a rapid screening method based on a 1.51 kb CsOPR3 promoter fused with a β-glucuronidase (GUS) reporter construct (OPR3p::GUS) in Arabidopsis. Using this screening system, a terpenoid volatile (E)-nerolidol was identified as a potent signal that elicits plant defenses. The early responses triggered by (E)-nerolidol included the activation of a mitogen-activated protein kinase and WRKY, an H2O2 burst, and the induction of jasmonic acid and abscisic acid signaling. The induced plants accumulated high levels of defense-related chemicals, which possessed broad-spectrum anti-herbivore or anti-pathogen properties, and ultimately triggered resistance against Empoasca onukii and Colletotrichum fructicola in tea. We propose that these findings can supply an environmentally friendly management strategy for controlling an insect pest and a disease of tea plants.

Moths can biosynthesize sex pheromones in the female sex pheromone glands (PGs) and can distinguish species-specific sex pheromones using their antennae. However, the biosynthesis and transportation mechanism for Type II sex pheromone components has rarely been documented in moths. In this study, we constructed a massive PG transcriptome database (14.72 Gb) from a moth species, Ectropis grisescens, which uses type II sex pheromones and is a major tea pest in China. We further identified putative sex pheromone biosynthesis and transportation-related unigenes: 111 cytochrome P450 monooxygenases (CYPs), 25 odorant-binding proteins (OBPs), and 20 chemosensory proteins (CSPs). Tissue expression and phylogenetic tree analyses showed that one CYP (EgriCYP341-fragment3), one OBP (EgriOBP4), and one CSP (EgriCSP10) gene displayed an enriched expression in the PGs, and that EgriOBP2, 3, and 25 are clustered in the moth pheromone-binding protein clade. We considered these our candidate genes. Our results yielded large-scale PG sequence information for further functional studies.

The tea leafhopper, Empoasca onukii Matsuda, is a serious pest of the tea plant. E. onukii prefers to inhabit vigorously growing tender tea leaves. The host selection of E. onukii adults may be associated with plant volatile compounds (VOCs). We sought to identify potentially attractive VOCs from tea leaves at three different ages and test the behavioral responses of E. onukii adults to synthetic VOC blends in the laboratory and field to aid in developing an E. onukii adult attractant. In darkness, the fresh or mature tea leaves of less than 1-mo old could attract more leafhoppers than the mature branches (MB) that had many older leaves (leaf age >1 mo). Volatile analysis showed that the VOC composition of the fresh leaves was the same as that of the mature leaves, but linalool and indole were not at detectable levels in VOCs from the MB. Moreover, the mass ratio differed for each common volatile in the three types of tea leaves. When under competition with volatiles from the MB, the leafhoppers showed no significant tropism to each single volatile but could be attracted by the synthetic volatile blend imitating the fresh leaves. With the removal of some volatile components, the effective synthetic volatile blend was mixed with (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, and linalool at a mass ratio of 0.6:23:12.6. These three volatiles may be the key components for the host selection of E. onukii adults and could be used as an attractant in tea gardens.

The sibling species Ectropis grisescens and E. obliqua are the major chewing tea pests in China. A difference in sex pheromone components plays a central role in premating isolation in these two species. To investigate the mechanism of premating isolation in these two Ectropis species, we sequenced the transcriptomes of the antennae of female and male E. obliqua individuals and performed phylogenetic analyses, abundance analyses, and tissue expression profile analyses to compare the olfactory genes involved in the detection of sex pheromones. A total of 36 odorant-binding proteins (OBPs) and 52 olfactory receptors (ORs) were identified in E. obliqua. Phylogenetic analyses showed that EoblOBP2, 3, and 25 were grouped in the pheromone-binding protein clade with EgriOBP2, 3, 25, and another lepidopteran PBP. EoblOR25 and 28 were grouped with EgriOR25, 28, and pheromone receptors for the detection of Type-I sex pheromone components. EoblOR24, 31, 37, and 44 were grouped with EgriOR24, 31, 37, and 44. All of these 4 EoblORs and 4 EgriORs showed higher abundance in male antennae than in female ones. Therefore, OBP2, 3, 25 and OR24, 31, 37, 44 of E. grisescens and E. obliqua might be responsible for sex pheromone component detection. However, the sequences of these genes in E. grisescens and E. obliqua were more than 90% identical. This indicates that these orthologous genes might play similar roles in the detection of sex pheromones. In contrast, the observed OBPs and ORs differed in abundance between the antennae of the two Ectropis species. Therefore, we speculate that these two Ectropis species use the different transcript levels of PRs to differentiate sex pheromone components. The results of the present study might contribute in deciphering the mechanism for premating isolation in these species and may be of use in devising strategies for their management.

Ectropis grisescens and Ectropis obliqua (Lepidoptera: Geometridae) are sibling pest species that co-occur on tea plants. The sex pheromone components of both species contain (Z,Z,Z)-3,6,9-octadecatriene and (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene. E. obliqua has (Z,Z)-3,9-cis-6,7-epoxy-nonadecadiene as an additional sex pheromone component, which ensures reproductive segregation between the two species. To ascertain the detection mechanism of olfactory organs for sex pheromone components of E. grisescens and E. obliqua, we applied scanning electron microscopy and single sensillum recording to compare antennal morphology and sensillum physiology in the two species. There was no apparent morphological difference between the antennae of the two species. Both species responded similarly to all three sex pheromone components, including, E. obliqua specific component. The distribution patterns of antennal sensilla trichodea differed between the two species. Sex pheromone olfactory sensing in these sibling species appears to be determined by the density of different types of olfactory sensing neurons. Dose-dependent responses of sensilla trichodea type 1 to (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene, the most abundant component, showed an "all or none" pattern and the other two components showed sigmoidal dose-response curves with a half threshold of 10-4 (dilution equal to the concentration of 10 μg/μl). These results suggest that the major sex pheromone component functions as an on-off controller while secondary components function as modulators during olfactory transmission to the primary olfactory center.

A species of lichen moth, Miltochrista striata (Bremer & Grey, 1852), feeds on lichens in Chinese tea plantations (Camellia sinensis (L.) O. Kuntze (Ericales:Theaceae)). A previous sex attractant screening test showed that male moths of M. striata were attracted by a mixture of (Z,Z,Z)-3,6,9-octadecatriene (Z3,Z6,Z9-18:H), (Z,Z,Z)-3,6,9-nonadecatriene (Z3,Z6,Z9-19:H), and their monoepoxy derivatives. To determine which of the component is an effective sex attractant for M. striata, the sex pheromone glands of female moths were excised and extracted with n-hexane. By comparison with the retention time and mass spectra of synthetic chemicals, two compounds in the crude extracts were identified as Z3,Z6,Z9-18:H and (Z,Z)-3,6-cis-9,10-epoxy-octadecadiene (Z3,Z6,epo9-18:H) using gas chromatography-mass spectrometry. The results of electroantennographic tests showed that the electrophysiological activities of Z3,Z6,Z9-18:H and Z3,Z6,epo9-18:H were distinctly higher than those of (Z,Z)-6,9-cis-3,4-epoxy-octadecadiene, (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene, (Z,Z,Z)-3,6,9-nonadecatriene, (Z,Z)-6,9-cis-3,4-epoxy-nonadecatriene, (Z,Z)-3,9-cis-6,7-epoxy-nonadecatriene, and (Z,Z)-3,6-cis-9,10-epoxy-nonadecatriene. Field trapping showed that only a mixture of Z3,Z6,Z9-18:H and Z3,Z6,epo9-18:H attracted male moths, and the optimal mixture of these compounds was the ratio of 4:6 at 1.0-mg dosage. The results represent the first determination of the sex pheromone of a lichen moth in a tea plantation and provide a scientific basis to develop an effective protocol using sex pheromone to monitor populations of M. striata.

Since the identification of the Ectropis grisescens sex pheromone, no effective control technology based on this pheromone has yet been developed and evaluated. In this study, pheromone proportion and dosage, sustained-release dispensers, and pheromone lure-matched traps were optimized. The mass trapping technology developed with the above optimized parameters was tested in a field trial. The results show that two compounds, (Z,Z,Z)-3,6,9-octadecatriene and (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene, at a ratio of 30:70 and impregnated into rubber septa at 1 mg, were the most attractive to male moths. These compounds provided the best performance when combined with a sticky wing trap. Adult male moth monitoring data showed that there was a lower population density in the trapping plot compared with the control plot, and there was a clear difference during the peak adult occurrence of the first five insect generations in 2017. The effect of mass trapping on the larva population was investigated in 2018, the control efficiency reached 49.27% after trapping of one generation of adults and was further reduced to 67.16% after two successive adult moth generations, compared with the control plot. The results of the present study provide a scientific basis for the establishment of sex pheromone-based integrated pest management strategies.

The tea green leafhopper, Empoasca vitis (Gothe) (Hemiptera: Cicadellidae), is a serious pest of tea plants. We examined the behavioral responses of E. vitis adults to odors from the shoots of three host plants in a Y-tube olfactometer with background visual cues. The host plants were tea [Camellia sinensis (L.) Kuntze (Theaceae)], peach [Prunus persica (L.) Siebold & Zucc. (Rosaceae)], and grapevine [Vitis vinifera L. (Vitaceae)]. Volatiles from the shoots were analyzed. Both yellow-green and gold backgrounds enhanced the olfactory responses of E. vitis adults to tea plant odors, and this enhancement was stronger under a high light intensity. On the yellow-green background, E. vitis adults significantly preferred the odors from shoots of the three host plants compared with clean air. Moreover, E. vitis adults preferred grapevine odor over the tea plant odor. The volatile blends of the three plant species were distinctly different. Peach plant shoots emitted the greatest amount of volatiles, whereas grapevine shoots released the greatest diversity of compounds. These results provide evidence that background visual cues could enhance the response of E. vitis adults to host-plant volatiles. The leafhoppers can discern different host odors, suggesting the possibility of using peach plant and grapevine odors to monitor and manage this pest in tea plantations.

Tea grey geometrid (Ectropis grisescens), a devastating chewing pest in tea plantations throughout China, produces Type-II pheromone components. Little is known about the genes encoding proteins involved in the perception of Type-II sex pheromone components. To investigate the olfaction genes involved in E. grisescens sex pheromones and plant volatiles perception, we sequenced female and male antennae transcriptomes of E. grisescens. After assembly and annotation, we identified 153 candidate chemoreception genes in E. grisescens, including 40 odorant-binding proteins (OBPs), 30 chemosensory proteins (CSPs), 59 odorant receptors (ORs), and 24 ionotropic receptors (IRs). The results of phylogenetic, qPCR, and mRNA abundance analyses suggested that three candidate pheromone-binding proteins (EgriOBP2, 3, and 25), two candidate general odorant-binding proteins (EgriOBP1 and 29), six pheromone receptors (EgriOR24, 25, 28, 31, 37, and 44), and EgriCSP8 may be involved in the detection of Type-II sex pheromone components. Functional investigation by heterologous expression in Xenopus oocytes revealed that EgriOR31 was robustly tuned to the E. grisescens sex pheromone component (Z,Z,Z)-3,6,9-octadecatriene and weakly to the other sex pheromone component (Z,Z)-3,9-6,7-epoxyoctadecadiene. Our results represent a systematic functional analysis of the molecular mechanism of olfaction perception in E. grisescens with an emphasis on gene encoding proteins involved in perception of Type-II sex pheromones, and provide information that will be relevant to other Lepidoptera species.

We investigated the effect of the SHAM treatment of tea plants on their induced defense on a tea geometrid (TG), Ectropis obliqua Prout. Treatment of tea leaves with SHAM reduced the performance of TG and TG-elicited level of the lipoxygenase gene CsiLOX1 and the putative allene oxide synthase gene CsiAOS1. The release of wound-induced green leaf volatiles (GLVs) and the expression of the hydroperoxide lyase (HPL) gene CsiHPL1 were also reduced by SHAM treatment. The negative effect of SHAM dramatically reduced the total hebivore-induced plant volatiles (HIPVs) and the attractiveness to the parasitoid wasp Apanteles sp. These results indicated that SHAM may negatively mediate tea defense response against TG by modulating the wound-induced emission of GLVs, the expression of genes involved in oxylipin pathway, and the emission of other HIPV compounds that mediate direct and indirect defenses.

BACKGROUND A plant-based ‘push-pull’ strategy for Ectropis obliqua (Prout) (Lepidoptera: Geometridae) is being developed using semiochemicals in the volatiles of Rosmarinus officinalis (Lamiaceae). The aim of this study was to identify and quantify the bioactive components within R. officinalis by gas chromatography–electroantennographic detection (GC-EAD) and gas chromatography–mass spectrometry (GC-MS), and to test the antennal and behavioural responses of E. obliqua to these chemicals. The emission dynamics of bioactive chemicals was also monitored. RESULTS GC-EAD experiments indicated that E. obliqua antennae responded to the following volatile compounds from R. officinalis: myrcene, α-terpinene, γ-terpinene, linalool, cis-verbenol, camphor, α-terpineol and verbenone, which were the minor constituents. Based on the dose-dependent antennal and behavioural responses of E. obliqua to these bioactive compounds, myrcene, γ-terpinene, linalool, cis-verbenol, camphor and verbenone were found to play a key role in repelling the moths, and the mixture that included all eight compounds was significantly more effective. The maximum emissions of these semiochemicals occurred at nightfall. CONCLUSIONS The specifically bioactive compounds in R. officinalis volatiles are responsible for repelling E. obliqua adults. Results indicate that R. officinalis should be considered as a potential behaviour-modifying stimulus for ‘push’ components when developing ‘push-pull’ strategies for control of E. obliqua using semiochemicals. © 2014 Society of Chemical Industry

Volatile organic compounds derived from non-host plants, Ocimum basilicum, Rosmarinus officinalis, Corymbia citriodora, and Ruta graveolens, can be used to mask host plant odors, and are repellent to the tea geometrid, Ectropis obliqua. Volatile compounds were collected by headspace absorption, and the components were identified and quantified by using gas chromatography/mass spectrometry. The responses of antennae of female E. obliqua to the compounds were evaluated with gas chromatography/electroantennography detection. Qualitative and quantitative differences were found among the four odor profiles. Consistent electroantennographic activity was obtained for eight of the volatiles from the four plants: β-myrcene, α-terpinene, γ-terpinene, linalool, cis-verbenol, camphor, α-terpineol, and verbenone. In a Y-tube bioassay, six chemicals, β-myrcene, γ-terpinene, (R)-(-)-linalool, (S)-(-)-cis-verbenol, (R)-(+)-camphor, and (S)-(-)-verbenone, were the main compounds responsible for repelling E. obliqua. An eight-component mixture including all of the bioactive compounds (in a ratio of 13:2:13:8:1:24:6:17) from R. officinalis was significantly more effective at repelling the moths than any single compound or a mixture of equal amounts of the eight compounds. Field results demonstrated that intercropping tea plants with R. officinalis effectively suppressed E. obliqua infestations in a tea plantation. Our findings suggests that odor blends of R. officinalis play a role in disturbing host orientation behavior, and in repelling E. obliqua adults, and that R. officinalis should be considered when developing "push-pull" strategies aimed at optimizing the control of E. obliqua with semiochemicals.

The lacewing Chrysopa phyllochroma Waesmael is a polyphagous predator of many pests. Releasing lacewings is an important component of biological control programs, but it is difficult to establish populations on field crops. Electrophysiological and behavioral responses to 10 common plant volatiles were recorded to screen for lacewing-attracting compounds. Electroantennographic assays indicated that all of the tested compounds elicited responses from C. phyllochroma. Three green-leaf volatiles-(E)-2-hexenal, (Z)-3-hexenyl acetate, and (Z)-3-hexenol-produced the strongest responses. Weaker responses were observed to six terpenes-ocimene, linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, (E,E)-α-farnesene, limonene, and nerolidol-and to methyl salicylate. Using a Y-tube olfactometer, the behavioral assays of the eight most active compounds demonstrated that four-(Z)-3-hexenyl acetate, (Z)-3-hexenol, (3E)-4,8-dimethyl-1,3,7-nonatriene, and linalool-were significant attractants for C. phyllochroma at specific concentrations. Three common plant volatile compounds-(Z)-3-hexenyl acetate, (3E)-4,8-dimethyl-1,3,7-nonatriene, and linalool-were also found to significantly enhance female ovipositing, resulting in a concentration of eggs. These observations are important for lacewing release as a pest control measure because they suggest means for retaining individuals and establishing populations using common plant volatiles.

Herbivore-induced plant volatiles have been reported to play a role in the host-searching behavior of herbivores. However, next to nothing is known about the effect of volatiles emitted from tea plants infested by Ectropis obliqua larvae on the behavior of conspecific adults. Here, we found that tea plants infested by E. obliqua caterpillars for 24 h were more attractive to both virgin male and female E. obliqua adults than were intact, uninfested tea plants; moreover, mated female E. obliqua moths were more attracted by infested tea plants and preferentially oviposited on these plants, whereas male moths were repelled by infested plants once they had mated. Volatile analysis revealed that the herbivore infestation dramatically increased the emission of volatiles. Among these volatiles, 17 compounds elicited antennal responses from both male and female virginal moths. Using a Y-tube olfactometer, we found that 3 of the 17 chemicals, benzyl alcohol, (Z)-3-hexenyl hexanoate, and (Z)-3-hexenal, were attractive, but two compounds, linalool and benzyl nitril, were repellent to virgin male and female moths. One chemical, (Z)-3-hexenyl acetate, was attractive only to virgin males. Mated females were attracted by three compounds, (Z)-3-hexenyl hexanoate, (Z)-3-hexenyl acetate, and (Z)-3-hexenal; whereas mated males were repelled by (Z)-3-hexenol. The findings provide new insights into the interaction between tea plants and the herbivores, and may help scientists develop new measures with which to control E. obliqua.

More and more users joined in social network. The precise social trust value is critical for application system such as recommendation system. To a user, the egocentric network is formed by the user, his friends and social relationships between him and other users. We proposed an algorithm for inferring dynamic trust based on trust chains and interactions. Indirect trust values are calculated depending on direct trust values and trust chains in the egocentric network. As the social network evolves, the dynamic trust values can be resulted from the interactions between a user and his friends and trust reference. By statistical analysis of trust value in social network, this algorithm improved the accuracy of trust transitivity and trust value computing compared with a classical trust algorithm.

Malicious codes can propagate rapidly by exploiting software vulnerabilities. In order to prevent the explosion of malicious codes in P2P networks, an automatic patching mechanism based on social computing is proposed. The security server generates automatic patches, and then selects the vulnerable nodes to push automatic patches. Automatic patches propagate rapidly along social network, so that the peers in P2P network covered by social network can be patched, which will improve the security of the whole P2P network. Experiments show this mechanism is more efficient than other patching mechanisms in P2P networks.