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Thirteen volatile compounds were identified from Flemingia macrophylla plants. Eight major components significantly attracted the tea green leafhoppers, Empoasca flavescens F. Based on their relative abundances, following synthetic blends were made for field experiments: 1) eight-component-attractant blend included Z-3-hexen-1-ol, Z-3-hexenyl acetate, Z-ocimene, MeSA, Z-3-hexenyl butyrate, dodecane, hexadecane and nonanal at 10, 10, 1, 11, 2, 6, 2 and 4 mg mL−1 in n-hexane, respectively; 2) four-component-attractant blend #1 contained hexadecane, Z-3-hexenyl acetate, Z-3-hexen-1-ol and nonanal at 2, 10, 10 and 4 mg mL−1 in n-hexane, respectively; 3) four-component-attractant blend #2 contained hexadecane, Z-3-hexenyl acetate, Z-3-hexen-1-ol and MeSA at 2, 10, 10 and 11 mg mL−1 in n-hexane, respectively. Thymol and 1-methoxy-4-methyl-2-(1-methylethyl)-benzene, identified from Lavandula angustifolia aeration samples, significantly repelled the leafhopper as strong repellents when tested alone or in combination at 10 mg mL−1. For field bioassays, each attractant lure was attached to a bud green sticky board hung from a bamboo stick at above tea plant level for catching the leafhoppers, whereas the repellent dispenser was tied to a tea branch inside tea clump for pushing the leafhoppers away from tea clumps. The results showed that the eight-component-attractant blend caught similar numbers of the leafhopper as did the four-component-attractant blend #1 at about 53–79 leafhoppers/trap/day, which were significantly higher than those on the hexane-control bud green sticky boards. Average leafhopper catches from un-baited sticky boards were about 51–73 leafhoppers/trap/day when pushed by the repellents placed inside tea plants, with the two-component-repellent blend being more effective than their single components. When the two-component-repellent blend was further tested with the three attractant blends in a push-pull fashion, average trap catches ranged from 62 to 92 leafhoppers/trap/day. Control efficacy on the leafhoppers within the push-pull zones increased progressively from day 1 (43%) to day 5 (73%). This push-pull approach might have a great potential as a green control strategy for combating the tea green leafhoppers.

The tea aphid, Toxoptera aurantii, also called the “black citrus aphid”, is one of the most destructive insect pests in commercial tea plantations and gardens in southern China. In autumn, declining day length triggers production of winged T. aurantii sexuparae, which produce both winged males and wingless oviparae. Oviparous females then release sex pheromone that attracts potential mates. GC–MS analysis of volatile headspace extracts of T. aurantii oviparae revealed that they emit (4aS,7S,7aR)-nepetalactone (I) and (1R,4aS,7S,7aR)-nepetalactol (II) in a ratio of 4.3–4.9:1. Field-trapping experiments with synthetic I and II singly or as two-component blends of different doses and ratios showed significant attraction of T. aurantii males, as well as weak attraction of sexuparae. Identification of the T. aurantii sex pheromone provides a new opportunity for developing a pheromone-based monitoring and management strategy for the sexual phase of tea aphids and, possibly, the alate sexparous generation in late summer and fall.

There are many top-quality,prestigious teas cultivated and processed in the Southern Jiangshu Province,China;however,serious damages to tea plants caused by various pests occur frequently in the region.In order to better understand the insect community structures and their phototaxis,we tested 12 colors(pure white,peach red,dark green,apple green,lake blue,sky blue,jasmine yellow,bud green,earth yellow,orange,bright red and purple) of sticky plates in a non-pollution tea plantation at Danyang City during late fall in 2012.The trapping results showed that: 1) within the 4 days trapping period,in total of 30455 individuals of 85 insect species belonged to 7 orders were caught,with Homoptera(86.5% of total individuals) being the most dominant order group,followed by Hymenoptera(8.8%) and Diptera(2.5%);2) the tea aphid and the tea green leafhopper were the two most dominant pest insect species,accounting for 71.5% and 15% of the total individuals,respectively;3) the Chinese honey bees were the major beneficial insects captured,accounting for 8.2% of the total individuals;4) in addition,a total of 1034 individuals of other beneficial insects(natural enemies) were caught,including 582 green lacewings(e.g.Chrysopa sinica Tjedea,Chrysopa septempunctata Wesmeal and Chrysopa formosa Branar),111 tachinids(Exorista civilis Rondani,Crossocosmia zebina Walk,Exorista sorbillans Wiedemann,plus three other species),110 hoverflies(Sphaerophoria menthastri L.,Syrphus balteatus De Geer,Syrphus corolla F.,Paraqus guadifasciatus Meigen,Syrphus serarius Wiedemann,Leucopis puncticornis Meigen plus two other species),97 braconids with Apanteles spp.being the dominant species,40 ichneumons(Itoplectis naranyae(Ashmead),Gotra octocinctus(Ashmead) and other three species) and 32 ladybeetles with Leis axyridis(Pallas) and Coelophora saucia Mulsant being the major species.5) Bud green,jasmine yellow and orange sticky plates captured significantly higher numbers of the tea green leafhoppers and the tea aphids;bud green and jasmine yellow sticky plates were also strongly attractive to ichneumons and braconids;bud green,earth yellow and apple green sticky plates attracted lacewings;apple green,sky blue and purple sticky plates trapped many flies and mosquitoes.The numbers of insect species captured were highest on the Jasmine yellow sticky plates,whereas the highest diversity index of various groups of trapped insects was detected on the pure white plates,indicating its broad generic attraction to diverse groups of insects.In late fall,knowing the species richness and the abundance of overwintering pest and beneficial insects,the beneficial/pest ratios,and the dominant pest and beneficial insect species and their population levels,as well as their differential phototaxis behaviors would help tea farmers better preparing and executing their environmentally safe pest control measures for efficiently reducing overwintering pest population density,before the field season is over.

The tea green leafhopper, Empoasca vitis Gothe, is one of the most serious insect pests of tea plantations in mainland China. Over the past decades, this pest has been controlled mainly by spraying pesticides. Insecticide applications not only have become less effective in controlling damage, but even more seriously, have caused high levels of toxic residues in teas, which ultimately threatens human health. Therefore, we should seek a safer biological control approach. In the present study, key components of tea shoot volatiles were identified and behaviorally tested as potential leafhopper attractants. The following 13 volatile compounds were identified from aeration samples of tea shoots using gas chromatography-mass spectrometry (GC-MS): (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, 2-ethyl-1-hexanol, (E)-ocimene, linalool, nonanol, (Z)-butanoic acid, 3-hexenyl ester, decanal, tetradecane, β-caryophyllene, geraniol and hexadecane. In Y-tube olfactometer tests, the following individual compounds were identified: (E)-2-hexenal, (E)-ocimene, (Z)-3-hexenyl acetate and linalool, as well as two synthetic mixtures (called blend 1 and blend 2) elicited significant taxis, with blend 2 being the most attractive. Blend 1 included linalool, (Z)-3-hexen-1-ol and (E)-2-hexenal at a 1 : 1 : 1 ratio, whereas blend 2 was a mixture of eight compounds at the same loading ratio: (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, 2-penten-1-ol, (E)-2-pentenal, pentanol, hexanol and 1-penten-3-ol. In tea fields, the bud-green sticky board traps baited with blend 2, (E)-2-hexenal or hexane captured adults and nymphs of the leafhoppers, with blend 2 being the most attractive, followed by (E)-2-hexenal and hexane. Placing sticky traps baited with blend 2 or (E)-2-hexenal in the tea fields significantly reduced leafhopper populations. Our results indicate that the bud-green sticky traps baited with tea shoot volatiles can provide a new tool for monitoring and managing the tea leafhopper.

Electrophysiological and behavioral responses of the wingless tea aphid, Toxoptera aurantii (Boyer), to 14 synthetic volatiles identified from tea shoots, their partial (GLV mixture) and full (ACB mixture) blends, and fresh young tea leaves, buds, tender stems, adult tea leaves and tea aphid-damaged young leaves (ADYL) were studied by using an electroantennography (EAG) and a four-arm olfactometer. ACB elicited the largest EAG responses. Major volatile components, Z -3-hexen-1-ol, E -2-hexenal, n-hexanol, methyl salicylate and benzylalcohol, from the tea shoots were strongly EAG active. All the 4 tested tea shoot tissues also elicited significant EAG responses, with the young tea leaves being the strongest, followed by buds, tender stems and adult tea leaves. Surprisingly, ADYL elicited a weakly negative EAG response. In the olfactory assays, the fresh and tender tea leaves, as well as the individual major volatile components, e.g. Z -3-hexenyl acetate, methyl salicylate, E -2-hexen-1-ol and Z -3-hexen-1-ol, from the tender shoots (EAG-active) were all attractive. This result might indicate that the wingless tea aphids may use tea shoot volatiles as kairomone to find their optimal feeding sites, e.g. fresh tender tea shoots.

The probing behaviors of the tea green leafhopper, Empoasca vitis (Gothe), on 9 tea cultivars were studied using video-text Direct Current-Electrical Penetration Graph, i.e., DC-EPG. The following 7 types of waveforms produced by the leafhopper stylet probing were determined: A, stylet pathway formation; S, salivation when stylets pierce into and stay in phloems; C, active ingestion before stylets reach phloems; E and F, passive ingestion in phloems; R, the insect resting with its stylet inserted into the leaf tissue and NP without probing. The 9 tested tea cultivars were categorized into 3 groups by the cluster analysis according to the number of probes per insect, waveform durations, or duration per probe of various waveforms on different tea cultivars. Waveforms S, E and F correlated to the main feeding activity of the leafhopper and may provide valuable information on predicting the resis-tance level of the tea plants to the leafhopper. The resistance level of the 9 tea cultivars to the leafhopper was ranked based on the durations of waveforms S, E and F, as well as the duration per probe including various waveforms. The ranking order of the resis-tance was: Longjingchangye > Hangdan > Zhenghedabaicha > Qianmei 601 > Hongyafoshuo > Zhongcha 102 > Zhongcha 302 > Longjing 43 > Anjibaicha, which corresponded to the resistance level determined by the population density (infestation) of the leaf-hopper on the 9 tea cultivars in the tea fields. Our study suggests that this simple and convenient DC-EPG technique might have great potential as a reliable tool to predict the resistance of tea cultivars to the tea leafhopper.

The rhythm of honeydew excretion by the tea aphid Toxoptera aurantii (Boyer) and its attraction to following 9 species (or subspecies) of beneficial insects, Aphidius sp., Chrysopa sinica Tjeder, Chrysopa septempunctata Wesmael, Sphaerophoria menthastri L., Coccinella septempunctata L., Leis axyridis (Pallas) ab. bimaculata Hemmelmann, L . axyridis (Pallas) ab. conspicua Faldermaenn, L. axyridis (Pallas) var. spectabilis Faldermaenn and L. axyridis (Pallas) var. novemdecimpunctata Faldermaenn, were investigated. Forty-five wingless virginoparae nymphs, reproduced by the same wingless virginogenia adult within 1 h, were introduced onto tea seedlings with one aphid per seedling. The honeydews excreted from different instars of nymphs and adults were collected under 21°C, 85% RH, 3500 lx and 12 L:12 D photoperiod. It took 32.4 d ±5.8 d for the tested tea aphids to complete the development of their nymph and adult stages, during which 325.6±35.8 droplets (ca. 41.98 μl ±6.14 μl and 45.34 mg ± 8.76 mg) of honeydews were secreted. During the 1st and 4th instars, there was a logistic regression relationship between the amount of honeydews excreted and the time (days). The honeydew secretion during the first two instars was less than that from the later instars. Adult aphids survived for 22.0 d ± 0.0 d, and excreted 176.31 ± 22.38 droplets (ca. 30.38 μl ± 5.32 μl) of honeydews in a rate of 1 drop per ca. 30–50 min for 5–8 h with a pause for 2–5 h before next secretion series. A batch of forty-five virginoparae female adults, reproduced by the same virginoparae female adult within 1 h, were introduced onto the tea seedlings (one aphid/seedling) under 13–21°, 85% RH, 3500 lx and 12 L:12 D photoperiod. Temperature showed a significant effect on the amounts of honeydews excreted within the range of 13–21°. Honeydews excreted by the aphids significantly increased the searching and retention time of the tested 9 species of natural enemies in a positive dose-response fashion. The searching times of Aphidius sp. and S. menthastri were the longest and the shortest, respectively, among all the 9 species, while the searching and retention time of L. axyridis (Pallas) var. spectabilis was the longest among the four varieties of L. axyridis . Tea aphid oneydew is considered as an important contact kairomone for the tested natural enemies.

Electrical penetration graph (EPG) investigation showed that the secreting (E1) and sucking (E2) times of tea aphid stylet in tea phloem were much longer than that on non-host plants such as soybean and wheat. However, non-feeding wave (np) was shorter than that on soybean and wheat. Duration of both E1 and E2 of stylet in tea phloem of 1st leaf, bud, 4th leaf and tender stem occupied 30.2%, 22.3%, 9.2% and 8.2% of the total experimental time, respectively. E2 wave was accompanied by honeydew secretion, with a time lag. Tea aphid preferred the tender parts, in which amino acids and other nutritional components were very rich. While the stylet of hungry tea aphid was forced to pierce phlom of non-host plant (soybean or wheat), E1 and E2 waves were also produced, but the action of stylet could be disrupted by tea shoot volatile (10~(-6) V/V linalool, etc.) emitted near to the antennae. It was considered that before and under probing tea aphid made use of olfactory clues.

The complete mitochondrial genome of Empoasca vitis was sequenced. The length of the mitogenome is 15,154 bp with 78.35% AT content (GenBank accession No. KJ815009). The genome encode 37 typical mitochondrial genes including 22 transfer RNA genes, 13 protein-coding genes, 2 ribosomal RNA genes and an A+T-rich region. The gene arrangement is similar to that of Drosophila yakuba, the presumed ancestral insect mitochondrial gene arrangement. Except for cox2 using GTG as start codon, other protein-coding genes (PCGs) share the start codons ATN. Usual termination codon TAA and incomplete stop codon T are using by 13 protein-coding genes. The A+T-rich region has a length of 977 bp with the AT content high to 88.95%.

The volatiles, absorbed by Porapak Q and eluted by hexane, from Chinese cabbage,Brassica campestris chinesis (L.) Makino. var.communis Tsen et Lee, have been identified as allyl isothiocyanate, Z-3-hexenyl acetate, 3,7-dimethyl-l,3,6-octatriene, 2,5-hexanediol, Z-3-hexen-1-ol, nonanol, β-myrcene, α-pinene, E-2-hexen-1-ol, D-limonene, Z-3-hexenyl propanoate, linalool, geraniol, E-4-hexen-1-ol, Z-3-hexenyl isovalerate, α-terpinene, β-caryophyllene, 3-carene and α-caryophyllene, by their mass spectra and retention times in comparison with authentic samples. The first five chemicals are the main components. All components can elicite electroantennogram (EAG) responses of dia-mondback moth (DBM),Plutella xylostella, in which allyl isothiocyanate and C6alcohols and esters, i.e. Z-3-hexen-l-ol, E-2-hexen-1-ol, E-4-hexen-1-ol, Z-3-hexenyl isovalerate and 2,5-hexanediol elicite stronger EAG responses than other components, and EAG responses of female moths to them are slightly larger than those of male moths. However, EAG responses elicited by terpenes are smaller, and EAG responses from females to terpenes are smaller than those from males, but β-myrcene can evoke stronger EAG responses from both females and males. Volatiles from intact Chinese cabbage, allyl isothiocyanate, 2,5-hexanediol and Z-3-hexenyl isovalerate intensely cause DBM directional flying and landing in wind tunnel, in which volatiles from intact Chinese cabbage have the strongest activity, and the next is allyl isothiocyanate. Allyl isothiocyanate is more attractive to females than to males a bit. As for α-terpinene and other subordinate components, EAG and wind tunnel test make sure they have weak activity.

Adult chrysopids have paired prothoracic glands (PG) that are thought to produce defensive secretions (allomones). We analyzed PG extracts of the following green lacewings from North and South America, Australia, and China: Ceraeochrysa cubana (Brazil); Chrysopa (= Co.) oculata, Co. nigricornis, Co. incompleta, Co. quadripunctata (USA), and Co. septempunctata (China); Chrysoperla (= Cl.) rufilabris (USA) and Cl. sp. (Brazil); Plesiochrysa ramburi and Mallada spp. (Australia). PG secretions are characteristic for species within a genus, except for Chrysopa spp. (Z)-4-Tridecene is ubiquitous, but (Z,Z)-4,7-tridecadiene is a major PG constituent in some Chrysopa spp. and in P. ramburi. Earlier reports that Co. oculata and Co. nigricornis produce 1-tridecene were shown to be in error. Chrysopa PG secretions are distinguished by the presence or absence of N-3-methylbutylacetamide, plus skatole (3-methylindole). Skatole is also identified for the first time from the Plesiochrysa and Ceraeochrysa. The PG secretion in Plesiochrysa ramburi is characterized by the presence of (Z)-4-undecene instead of (Z)-4-tridecene, and N-3-methylbutylpropanamide instead of the acetamide, resembling the PG secretions of Chrysopa nigricornis, Co. septempunctata and Co. incompleta. The chemotaxonomic value of PG semiochemicals is discussed, including evidence for subgroups within the genus Chrysopa as it now stands.