Electroantennogram Responses Research Articles

Behavioral and electrophysiological response of sugarcane aphid and imported fire ant to 2,4,6-trimethylpyridine, an alkaloid from the pink-spotted lady beetle

Many predatory coccinellids conflict with hemipteran tending ants, because they both use hemipterans as resources. Lady beetles are important in the ecology of ants and their reciprocal relationship with hemipterans. Volatiles released by lady beetles have diverse biological significance in intraspecific communication, attraction, and aggregation. However, whether the semiochemicals from lady beetles influence the sympatric members, such as aphids and ants, is still obscure. Sugarcane aphids Melanaphis sacchari was closely associated with honeydew collecting ants and coccinellid predators. Herein, we investigated the behavioral and electrophysiological responses of M. sacchari and their attending red imported fire ants, Solenopsis invicta, to an alkaloid, 2,4,6-trimethylpyridine (TMP) from the pink-spotted lady beetle Coleomegilla maculata. The response of C. maculata to this alkaloid was also evaluated. The results showed that TMP elicited significant electroantennogram (EAG) responses in M. sacchari, S. invicta, and C. maculata. In addition, it triggered significant preference and aggregation in both C. maculata males and females at 100 μg/μL, while induced a strong avoidance in M. sacchari. It significantly decreased the digging and residing preference of S. invicta workers at high concentration, but showed certain attractiveness to workers at a lower concentration. Moreover, TMP inhibited aphid-tending efficiency of S. invicta thereby curbing the benefits to M. sacchari. The findings provide important evidence that TMP is a pheromone in C. maculata and a semiochemical to both S. invicta and M. sacchari. It may affect the mutualistic interactions between S. invicta and M. sacchari by mediating the behaviors of both species.

Mating-induced changes in responses of female Queensland fruit fly to male pheromones and fruit: A mechanism for mating-induced sexual inhibition

In order to reproduce, female tephritid fruit flies need both mates for fertilization and fruit for oviposition. Virgin females are prone to mating and approach males, attracted by their pheromones. Mated females, however, may experience an abrupt reduction of mating propensity and prioritise the search for suitable fruit rather than additional mates. Accordingly, mating in fruit flies may induce a switch in olfactory preferences of females from pheromones to fruit stimuli, and this switch may also be an important mediator of mating-induced sexual inhibition. To test for mating-induced switches in olfactory preference of female Queensland fruit fly, Bactrocera tryoni, we used wind tunnel assays to assess attraction of mated and virgin females to (1) male sex pheromone delivered through a perforated glass sphere or (2) an entire fruit. Electroantennogram (EAG) responses were also used to test for mating-induced changes in olfactory sensitivity to pheromones and fruit odours. Pheromones elicited quicker upwind responses in virgin females than in mated females; during the first six minutes of trials more virgin females than mated females were observed in the upwind end of the wind tunnel where pheromone odours were released. Fruit cues, in contrast, elicited stronger association with the upwind end of the wind tunnel in mated females than in virgin females from the fifth minute onwards. Also, mated females were observed on the fruit for longer periods than virgin females. EAG responses to pheromones and fruit odours were similar in virgin and mated females, indicating that changes in preferences are not a consequence of changes in peripheral sensitivity of antennae to odours but instead appear to be mediated by post-receptor processing. Our results show that mating reduces attraction to male-produced pheromones and increases attraction to fruit stimuli in B. tryoni females. We propose that this behavioural switch from mating stimuli to oviposition stimuli is an important mediator of mating-induced sexual inhibition in this species.

Olfactory attraction to aggregation pheromone is mediated by disti-flagellum of antennal segments in Riptortus pedestris

Riptortus pedestris (Hemiptera: Alydidae) is a serious pest of soybean and sweet persimmon and uses male produced aggregation pheromone, (E)-2-hexenyl (Z)-3-hexenoate, (E)-2-hexenyl (E)-2-hexenoate, and tetradecyl isobutyrate to facilitate food location and recognition by conspecifics. Using electroantennogram (EAG) and greenhouse bioassay, we determined which antennal segment is involved in the detection of their aggregation pheromone. In the first EAG test using individual antennal segments, significant EAG responses to 1:1:1 mixture of the aggregation pheromone were observed only from the disti-flagellum segments of both male and female antennae at both pheromone doses tested (1 µg and 100 µg). In the following EAG tests using gradually removed antennal segment(s), EAG response was still maintained when the distal half of a disti-flagellum was surgically removed, while EAG response was lost when whole segment of disti-flagellum or other whole segments were gradually removed from intact antenna of both sexes. In greenhouse experiment, removing one or both segment(s) of disti-flagellum from male or female antennae resulted in significant reduction in their attraction to the aggregation pheromone. Together, these findings support that the disti-flagellum of R. pedestris houses olfactory neurons associated with attraction to their aggregation pheromone.

Electrophysiological and behavioral responses of Asian and European honeybees to pear flower volatiles

Honeybee pollination behavior is influenced by flower volatiles, which honeybees sense via olfactory receptors. Honeybees are only weakly attracted to pear flowers. To investigate the potential reasons, we extracted and determined the floral volatile compounds from three pear cultivars (Su, Ya, and Xuehua) using headspace solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC–MS). The effects of pear flower volatiles on the Asian honeybee (Apis cerana cerana Fabricius) and the European honeybee (Apis mellifera ligustica Spinola) were determined by electroantennogram (EAG) assays and behavioral tests in a three-arm olfactometer. Among the 76 flower volatiles detected with GC–MS, 21 were found in all three pear cultivars, accounting for approximately 70% of the total volatile content. 3-Methyl-1-butanol and (+)-limonene volatiles had the highest relative content. Five compounds elicited strong EAG responses in both bee species: 2-methylbutyraldehyde, 1-nonanal, 6-methyl-5-hepten-2-one, 3-methyl-1-butanol, and (+)-limonene. Neither bee species showed positive taxis to these volatiles. In behavioral tests, A. mellifera ligustica showed a low preference for 6-methyl-5-hepten-2-one (20%, 400 µg/µL) and 2-phenethyl alcohol (16.7%, 400 µg/µL). Apis cerana cerana showed a low preference for 6-methyl-5-hepten-2-one (6.7%, 400 µg/µL) and 1-nonanal (10%, 400 µg/µL), whereas its preferences for 3-methyl-1-butanol (43.3%, 400 µg/µL) and α-farnesene (40%, 400 µg/µL) were similar to that for the control. Therefore, a lack of attractive volatile compounds could explain why honeybees are only weakly attracted to pear flowers. Therefore, to achieve acceptable pollination in pear orchards, we suggest using flower-scent sugar syrup feeding and a saturation pollination strategy.

Electroantennogram and behavioral responses of Agrilus mali to the volatiles from Malus sieversii trees induced by pest and disease

Objective This study aims to explore the electroantennogram and behavioral responses of Agrilus mali to the volatiles from Malus sieversii trees in different damaged states to provide reference for the research and development of highly effective attractants. Method The volatiles were collected by using dynamic headspace adsorption from branches and limbs of M. sieversii trees. Result There are total of 46 volatile compounds in 9 categories has been obtained, including alcohols, lipids, aldehydes, alkanes, alkenes, ketones, terpenes, ethers and others. Compared with healthy branches, the relative contents of eicosane and pentadecane increased in A. mali damaged branches, while the relative contents of 8 volatiles such as butenol, 2-methylacrolein, heptadecane, heneicosane, cycloheptatriene, cyclohexanone, α-pinene and chamomile decreased. Fourteen compounds were added such as cis-3-hexenol, hexanal, decanal, nonanal, (+)-limonene etc. In Valsa mali damaged branches, pentadecane, heptadecane, 3,7-dimethyldecane, eicosane and α-pinene increased, and heneicosane, cyclohexanone, cycloheptatriene, azulene decreased. Twelve compounds were added such as cis-3-hexenol, butyl butyrate, hexanal, (+)-α-pinene, (+)-limonene, etc. Compared with the volatilides released from healthy limbs, the relative contents of cis-3-hexenol, α-pinene, (−)-α-pinene and camphene were increased in A. mali damaged limbs, and hexanal, cycloheptane, β-pinene, cycloheptatriene, azulene contents decreased. Seventeen compounds were added such as 3-octene-2-alcohol, butyl butyrate, decanal pentadecane, (+)-aromadendrene, etc. In Valsa mali damaged limbs, hexanal increased, and cis-3-hexenol, acrolein, cyclohexanone, α-pinene, (−)-α-pinene, β-pinene and azulene decreased. Eleven compounds were added such as benzaldehyde, pentadecane, dipentene, etc. EAG responses and behaviour of A. mali towards volatiles released by host were tested. The results showed that strong EAG reactants could be produced in the antennae of male and female adults of A. mali, these compounds were (−)-α-pinene, nonanal, (+)-α-pinene, benzaldehyde, decanal, butyl acrylate. A. mali were attracted by (−)-α-pinene, α-pinene, (+)-β-pinene, β-pinene, decanal, nonanal in the behavior bioassay. Conclusion According to the results of EAG responses and behavioral orientation, the (−)-a-pinene, nonanal and decanal had good attraction to the adult of Agrilus mali.[Ch, 1 fig. 3 tab. 27 ref.]

Electrophysiological Responses to Cuelure of Raspberry Ketone-Fed Queensland Fruit Flies.

The sterile insect technique (SIT) and male annihilation technique (MAT) are important tools for the control of Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), a major insect pest of horticultural crops in Australia. In MAT, mature Q-fly males are attracted to a toxic bait using Cuelure, a synthetic analog of raspberry ketone (RK). Substantial improvements in control could be achieved by simultaneous use of SIT and MAT, but this requires suppression of the Cuelure response in released sterile flies. Recent studies report that prerelease feeding with RK during the first 48 h after emergence can reduce the response of mature Q-fly males to Cuelure, but the mechanism underpinning this is unknown. Here, to test whether reduced sensory sensitivity to Cuelure is involved, we evaluated the effects of RK supplements, adult diet (yeast-supplemented diet throughout adult stage vs yeast-supplemented diet only for 48 h), and age on electroantennogram (EAG) and electropalpogram (EPG) responses of Q-flies to Cuelure stimuli. EAG responses did not vary with RK supplements, sex, or age of Q-flies fed yeast-supplemented diet throughout the adult stage, but the responses of Q-flies fed other diet regime decreased with age. EPG responses of both sexes of Q-flies were affected by RK supplements, age, and their interaction, but without patterns that might indicate reduced maxillary palp response of RK supplemented flies to Cuelure. Our findings do not support the hypothesis that reduced Cuelure response of male Q-flies fed RK supplements is explained by reduced electrophysiological response in antennae or maxillary palps.

Synthesis and Biological Testing of Ester Pheromone Analogues for Two Fruitworm Moths (Carposinidae).

A range of ester pheromone analogues for carposinid moths were synthesized and evaluated for biological activity. The analogues aimed to take advantage of the structural commonality of (7Z)-alken-11-ones found in this family. Analogues were tested on two pest species: Heterocrossa rubophaga and Coscinoptycha improbana. Two of the analogues, (2Z)-nonenyl nonanoate and (4Z)-heptyl undecenoate, elicited significant electroantennogram responses. Only (4Z)-heptyl undecenoate gave consistent responses with both moth species in single sensillum recording. Field trapping trials were conducted with these two analogues both individually and in combination with the pheromone of each of the two moth species. No attraction was observed to either of the analogues alone, by either moth species. However, when (4Z)-heptyl undecenoate was coupled with the pheromone, it produced a strong inhibitory effect in H. rubophaga, reducing male moth trap catch by over 95%. No inhibitory effect on male moth trap catch was observed in C. improbana.

Electroantennogram responses of Plutella xylostella (L.), to sex pheromone components and host plant volatile semiochemicals

AbstractThe diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a notorious insect pest of cruciferous crops worldwide. Attract‐and‐kill strategies to manage the DBM based on insect pheromone and plant volatile semiochemicals have been explored and partially applied in the field. However, little is known about whether the attractant effects of insect pheromone and host plant volatile semiochemicals on insects are affected by insect age or volatile concentrations. Therefore, we examined the electroantennogram (EAG) responses of both DBM males and females varying in age and body size to a range of concentrations of seven host plant volatiles and two main female sex pheromone components. Our results showed that DBM age had no influence on EAG responses to trans‐2‐Hexenal, trans‐2‐Hexenol, Heptanal, cis‐3‐Hexen‐1‐ol and Z11‐16:Ald and significantly influenced the EAG responses to Z11‐16:Ac and three isothiocyanates. Age and sex had interaction effects on EAG responses of DBMs to some tested semiochemicals. DBM females had significantly stronger responses than males to all tested plant volatiles, and values were enhanced with increasing concentrations. Moreover, the degree of enhancement of EAG responses in females was larger than that in males for trans‐2‐Hexenal, trans‐2‐Hexenol, cis‐3‐Hexen‐1‐ol, 2‐Phenylethyl isothiocyanate and Methyl isothiocyanate treatments. Body size seemed to have no influence on EAG responses. Our results might provide a theoretical basis for optimizing attract‐and‐kill strategies for insect pests.

Detecting Host-Plant Volatiles with Odorant Receptors from Grapholita molesta (Busck) (Lepidoptera: Tortricidae).

Grapholita molesta is a global pest of stone and pome fruits. The sensitive olfactory system plays a crucial role in regulating key behavioral activities of insects and G. molesta relies heavily on general odorant receptors (ORs) to detect host-plant volatiles. In this study, three general OR genes from G. molesta (GmolOR12, GmolOR20, and GmolOR21) were identified. Quantitative polymerase chain reaction revealed that GmolORs expression was considerably higher in adults and adult antennae than in any other life stages and body parts, respectively. Moreover, the expression of GmolORs was significantly higher in the antennae of females than in those of males, with a peak in the antennae of 3-days-old adult females. GmolOR20 and GmolOR21 displayed no responses to any of the odorant compounds tested in the Xenopus oocyte system. GmolOR12 was tuned mainly to 5 of the 47 odorant components tested (including decanol, heptanal, octanal, nonanal, and decanal), and the response to aldehydes among the 5 components was the highest. Additionally, they all elicited female and male antennae electroantennogram responses, and the aldehydes elicited the highest response among the 5 components. These results suggested that GmolOR12 in the G. molesta olfactory system plays an important role in sensing aldehydes and that GmolOR12 is involved in sensing host-plant volatiles. These findings provide insight into the possibility of using host-plant volatiles for the control of G. molesta.

Behavioral and Electrophysiological Effects of Ajowan (Trachyspermum ammi Sprague) (Apiales: Apiaceae) Essential Oil and Its Constituents on Nymphal and Adult Bean Bugs, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae).

We investigated the repellent effect of 12 Apiaceae plant essential oils on nymphal and adult (male and female) forms of the bean bug, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae), using a four-arm olfactometer. Among the essential oils tested, ajowan (Trachyspermum ammi Sprague) essential oil showed the strongest repellent activity against the nymphal and adult bean bugs. For female adults, the repellent activity was significantly different between an ajowan oil-treated chamber and an untreated chamber down to a concentration of 14.15 μg/cm2. We also investigated the repellent activity of individual ajowan essential oil constituents. Of the compounds examined, carvacrol and thymol showed the most potent repellent activity against the nymphal and adult bean bugs. Carvacrol and thymol exhibited 73.08% and 70.0% repellent activity for the bean bug nymph at 0.71 and 2.83 μg/cm2, respectively, and 82.6% and 80.7% at 5.66 and 11.32 μg/cm2, respectively, for male adults. Carvacrol and thymol exhibited strong repellent activity against female adult bean bugs down to a concentration of 2.83 μg/cm2. Ajowan essential oil, thymol and carvacrol elicited a negative electroantennogram (EAG) response from adult bean bugs. This could explain the repellent activity of ajowan essential oil and its constituents. Our results indicate that ajowan essential oil and its constituents carvacrol and thymol can be potential candidates as the ‘push’ component in a ‘push-pull’ strategy for bean bug control.

Electrophysiological Response of Two Moth Species, Helicoverpa armigera and Maruca vitrata to Host Plant (Cajanus cajan) Volatiles

Host searching and oviposition behavior of insects are influenced by certain plant volatiles which help, especially, gravid females to locate suitable oviposition site. To ascertain the differential behavior, if any, electrophysiological response of two moth species Helicoverpa armigera and Maruca vitrata to the volatiles of their common host, i.e., pigeon pea, was studied. Dynamic headspace collection of volatiles from pigeon pea revealed the presence of 27 volatiles belonging to different classes such as aliphatic hydrocarbons like undecane, dodecane, and tetradecane, green leaf volatiles like (Z)-3-hexen-1-ol acetate and (E)-2-hexen-1-ol acetate, aromatics like acetophenone, an acyclic sesquiterpenes alcohol like farnesol, a cyclic monoterpene like limonene, bicyclic sesquiterpenes like caryophyllene and its oxide and a monoterpene like (z)-β-ocimene. Electroantennogram response of selective volatiles revealed the significant difference between the responses from gravid females of both species suggesting difference in perception of odor by both the insect species. At lowest concentration used (0.1 mg/ml) there was a significant response to phenylacetaldehyde and β-caryophyllene at 5% level of significance, whereas it was significant at both 1% and 5% level of significance for linalool, limonene and β-myrcene. Phenylacetaldehyde and limonene triggered significant response in H. armigera, whereas in M. vitrata phenylacetaldehyde and β-myrcene elicited the significant response.

Electrophysiological responses of banana pseudostem weevil,Odoiporus longicollis Olivier (Coleoptera: Curculionidae) tomethyl jasmonate, 1-hexanol and host plant extract

The banana pseudostem weevil (BSW), Odoiporus longicollis Olivier (Coleoptera: Curculionidae) is one of the mostdestructive pests of banana and plantains. Our laboratory bioassay studies showed that out of 50 host plants related volatilechemicals screened against BSW, only methyl jasmonate (MeJA) and 1-hexanol was electrophysiologically and behaviourallyactive. Here, we investigated the influence of host plant extract (HPE) on two semiochemicals, namely methyl jasmonate(MeJA) and 1-hexanol, both independently and in combination, in the electroantennogram (EAG) response in BSW. The resultsshowed that HPE alone elicited greater EAG response only in males suggesting that males involved predominantly in the hostplant selection. Addition of HPE to MeJA increased significantly higher EAG response in females and the response wasinsignificant in males. Similarly, the addition of HPE to 1-hexanol evoked higher response in females but decreased antennalactivity was recorded in males compared to HPE alone. The HPE showed additive effect on MeJA and 1-hexanol in their EAGresponses only in female BSW. The result also revealed that 1-hexanol+HPE blend exhibited enhanced EAG responsecompared to 1-hexanol alone in both sexes.

Design of odor discrimination system based on insect electroantennogram responses

Design of odor discrimination system based on insect electroantennogram responses

Electrophysiological and Alarm Responses of Solenopsis invicta Buren (Hymenoptera: Formicidae) to 2-Ethyl-3,5-dimethylpyrazine (Short Title: EAG and Behavioral Responses of Fire Ants to Pyrazine).

2-Ethyl-3,5-dimethylpyrazine is an isomer of 2-ethyl-3,6-dimethylpyrazine, the alarm pheromone component of the red imported fire ant, Solenopsis invicta Buren. The pyrazine was synthesized and its alarm activity was investigated under laboratory conditions. It elicited significant electroantennogram (EAG) activities, and released characteristic alarm behaviors in fire ant workers. The EAG and alarm responses were both dose-dependent. Two doses of the pyrazine, 1 and 100 ng, were further subjected to bait discovery bioassays. Fire ant workers excited by the pyrazine were attracted to food baits, and their numbers increased over time. Ants displayed very similar response patterns to both low and high doses of the pyrazine. The pyrazine impregnated onto filter paper disc attracted significantly more fire ant workers than the hexane control for all observation time intervals at the low dose, and in the first 15 min period at the high dose. The pyrazine loaded onto food bait directly tended to attract more fire ant workers than the hexane control. These results support the potential use of 2-ethyl-3,5-dimethylpyrazine to enhance bait attractiveness for the control of S. invicta in invaded regions.

Functional characterization of one sex pheromone receptor (AlucOR4) in Apolygus lucorum (Meyer-Dür)

Traps baited with female-produced sex pheromones have been very effective in the monitoring and management of mirid bugs in numerous field trials. However, none of the target odorant receptors for sex pheromone components in Apolygus lucorum have been identified. Here, we identified one candidate sex pheromone receptor, AlucOR4, from A. lucorum. Quantitative real-time PCR (qPCR) analysis revealed that AlucOR4 was antennae-enriched and male-biased in adult A. lucorum. Xenopus oocyte expression system assays demonstrated that AlucOR4/AlucOrco was sensitive to two major sex pheromone constituents and exhibited high sensitivity to (E)-2-hexenyl butyrate (E2HB) and lower sensitivity to hexyl butyrate (HB). The expression level of target mRNA was significantly reduced (>80%) in dsAlucOR4-injected bugs after five days. The electroantennogram (EAG) responses of male antennae to E2HB and HB were also reduced significantly (~40%). Our findings suggest that AlucOR4 is essential to sex pheromone perception in A. lucorum.

Dropping Counter: A Detection Algorithm for Identifying Odour-Evoked Responses from Noisy Electroantennograms Measured by a Flying Robot.

The electroantennogram (EAG) is a technique used for measuring electrical signals from the antenna of an insect. Its rapid response time, quick recovery speed, and high sensitivity make it suitable for odour-tracking tasks employing mobile robots. However, its application to flying robots has not been extensively studied owing to the electrical and mechanical noises generated. In this study, we investigated the characteristics of the EAG mounted on a tethered flying quadcopter and developed a special counter-based algorithm for detecting the odour-generated responses. As the EAG response is negative, the algorithm creates a window and compares the values inside it. Once a value is smaller than the first one, the counter will increase by one and finally turns the whole signal into a clearer odour stimulated result. By experimental evaluation, the new algorithm gives a higher cross-correlation coefficient when compared with the fixed-threshold method. The result shows that the accuracy of this novel algorithm for recognising odour-evoked EAG signals from noise exceeds that of the traditional method; furthermore, the use of insect antennae as odour sensors for flying robots is demonstrated to be feasible.

The general odorant receptor GmolOR9 from Grapholita molesta (Lepidoptera: Tortricidae) is mainly tuned to eight host-plant volatiles.

Grapholita molesta is one of the most destructive fruit pests distributed worldwide. Odorant receptors (ORs) located on the dendritic membrane of chemosensory neurons are deemed to be key molecules for sensing exogenous chemical signals. In this study, GmolOR9, a general OR from G. molesta, was functionally characterized. Quantitative real-time polymerase chain reaction revealed that GmolOR9 was more highly expressed in adults than in other stages, including eggs, larvae, and pupae. GmolOR9 expression was highly significantly more in the antennae of females than in those of males, and the highest level occurred in the antennae of 3-day-old female adults. GmolOR9 was broadly tuned to eight of 47 odorant components tested, including (Z)-3-hexenyl acetate, butyl propionate, ethyl hexanoate, ethyl heptanoate, 1-hexanol, (Z)-3-hexenol, 2-ethyl-1-hexanol, and linalool, by in vitro heterologous expression. Furthermore, electroantennogram responses indicated that the effects of dsOR9-injected females to (Z)-3-hexenyl acetate dramatically decreased. These results suggested that GmolOR9 might be involved in detecting host-plant volatiles. Moreover, (Z)-3-hexenyl acetate might serve as a potential attractant for the biological control of G. molesta.

Molecular Screening of Behaviorally Active Compounds with CmedOBP14 from the Rice Leaf Folder Cnaphalocrocis medinalis

Odorant binding proteins (OBPs) play a key role in chemoreception in insects. In an earlier study, we identified CmedOBP14 from the rice leaf folder, Cnaphalocrocis medinalis, with potential physiological functions in olfaction. Here, we performed a competitive binding assay under different pH conditions as well as knockdown via RNA interference to determine the specific role of CmedOBP14 in C. medinalis. CmedOBP14 displayed broad binding affinities to many host-related compounds, with higher affinities at pH7.4 compared with pH5.0. After treatment with CmedOBP14-dsRNA, the transcript level of OBP14 was significantly decreased at 72h compared with controls, and the electroantennogram response evoked by nerolidol, L-limonene and beta-ionone was reduced. Furthermore, behavioral assays revealed consistent patterns among these compounds, especially for nerolidol, with adults could no longer able to differentiate 0.1% nerolidol from controls. RNAi experiments suggest that at least in part, CmedOBP14 mediates the ability to smell nerolidol and beta-ionone.

EAG Responses of Adult Lobesia botrana Males and Females Collected from Vitis vinifera and Daphne Gnidium to Larval Host-Plant Volatiles and Sex Pheromone.

We analysed electroantennogram (EAG) responses of male and female adults of the European grapevine moth Lobesia botrana (Denis et Schiffermüller) (Lepidoptera: Tortricidae) collected as larvae from grapevine (Vitis vinifera L.) and flax-leaved daphne (Daphne gnidium L.). The host-plant odorants tested were either V. vinifera-specific [1-octen-3-ol, (E)-β-farnesene, (E)-4,8-dimethyl-1,3,7-nonatriene], D. gnidium-specific (2-ethyl-hexan-1-ol, benzothiazole, linalool-oxide, ethyl benzanoate), or were shared by both host-plants (linalool, methyl salicylate). Sex pheromone compounds were also tested. The male response to the major pheromone component (E7,Z9-12:Ac) was higher than to any other stimuli, whereas the response to the minor pheromone components (E7,Z9-12:OH and Z9-12:Ac) was not different from the response to the plant odorants. The female response to pheromone was lower or not different from that to plant odorants. Methyl salicylate elicited a higher response in females and (E)-β-farnesene elicited a higher response than several other plant odorants in both sexes. Non-significant interactions between host-plant odorant and sex indicated an absence of sex specialization for host-plant volatile detection. The lack of a significant interaction between plant volatiles and larval host-plants suggested that there was no specialization for plant-volatile detection between V. vinifera and D. gnidium individuals.

Two terpenoids activates close mating behavior and enhances trap efficiency of sex pheromone of Grapholita molesta

Grapholita molesta (Busck) (Lepidoptera: Tortricidae) is a notorious pest of many Rosaceae crops worldwide. Enhancement of trap efficiency of its sex pheromone was devised by addition of E-β-ocimene and E-β-farnesene. The addition of E-β-ocimene or E-β-farnesene to sex pheromone increased electroantennogram response of male G. molesta compared to sex pheromone alone. Blend of pheromone and E-β-ocimene or E-β-farnesene in 1:0.1 increased the upwind flight and landing behaviors. Furthermore, field experiments showed that sex lures with E-β-ocimene, or /and E-β-farnesene, enhanced trapping efficiency compared to sex pheromone alone. These results may provide the basis for the development of efficient pest management systems against G. molesta using plant volatiles and insect sex pheromones.