Kye Chung Park

Attraction and Antennal Response of the Common Wasp, Vespula vulgaris (L.), to Selected Synthetic Chemicals in New Zealand Beech Forests

BACKGROUND The common wasp, Vespula vulgaris (L.), and the German wasp, Vespula germanica (F.), are significant problems in New Zealand beech forests (Nothofagus spp.), adversely affecting native birds and invertebrate biodiversity. This work was undertaken to develop synthetic attractants for these species to enable more efficient monitoring and management. RESULTS Seven known wasp attractants (acetic acid, butyl butyrate, isobutanol, heptyl butyrate, octyl butyrate and 2,4-hexadienyl butyrate) were field tested, and only heptyl butyrate and octyl butyrate attracted significantly higher numbers of wasps than a non-baited trap. Accordingly, a series of straight-chain esters from methyl to decyl butyrate were prepared and field tested for attraction of social wasps. Peak biological activity occurred with hexyl butyrate, heptyl butyrate, octyl butyrate and nonyl butyrate. Polyethylene bags emitting approximately 18.4-22.6 mg day(-1) of heptyl butyrate were more attractive than polyethylene bags emitting approximately 14.7-16.8 mg day(-1) of heptyl butyrate in the field. Electroantennogram (EAG) studies indicated that queens and workers of V. vulgaris had olfactory receptor neurons responding to various aliphatic butyrates. CONCLUSION These results are the first to be reported on the EAG response and the attraction of social wasps to synthetic chemicals in New Zealand beech forests and will enable monitoring of social wasp activity in beech forests.

Repellent effect of santalol from sandalwood oil against Tetranychus urticae (Acari: Tetranychidae).

ABSTRACT Thirty-four essential oils were screened for their repellent activities against the twospotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), at 0.1% concentration level using choice and no-choice laboratory bioassays. Of these, 20 essential oils showed significant repellencies against T. urticae in the choice tests. In subsequent no-choice tests using these 20 essential oils, only sandalwood oil showed significant repellency against T. urticae. Total number of eggs oviposited by T. urticae was significantly lower than controls in the choice tests when the kidney bean leaves were treated with 1 of 14 essential oils. The significant repellency of sandalwood oil against T. urticae lasted at least for 5 h at the 0.1% concentration level. Our GC-MS analysis indicated that the major components of the sandalwood oil were &agr;-santalol (45.8%), &bgr;-santalol (20.6%), &bgr;-sinensal (9.4%), and epi-&bgr;-santalol (3.3%). Santanol, a mixture of the two main components in the sandalwood oil, appears to be responsible for the repellency of sandalwood oil against T. urticae.

Characterization of olfactory receptor neurons for pheromone candidate and plant volatile compounds in the clover root weevil, Sitona lepidus

Antennal olfactory receptor neurons (ORNs) for pheromone and plant volatile compounds were identified and characterized in male and female clover root weevil, Sitona lepidus (Gyllenhal), using the single sensillum recording technique with five pheromone-related compounds, and 40 host and non-host plant volatile compounds. Overall, seven different types of olfactory sensilla containing specialized ORNs were identified in each sex of S. lepidus. Among them, three different types of sensilla in the males and two types in the females housed ORNs specialized for pheromone-related compounds. The ORNs in males were specialized for 4-methyl-3,5-heptanedione or one or more of four stereoisomers of 5-hydroxy-4-methyl-3-heptanone. In contrast, female sensilla did not contain ORNs sensitive to 4-methyl-3,5-heptanedione while they contained ORNs sensitive to and specialized for the stereoisomers of (4S,5S)-5-hydroxy-4-methyl-3-heptanone. In addition to the pheromone-related ORNs, four types of olfactory sensilla contained ORNs responsive to plant volatile compounds in male S. lepidus, and five types in females. Most of the ORNs identified in S. lepidus showed a high degree of specificity to specific volatile compounds although some of the active compounds showed overlapping response spectra in the ORNs across different types of sensilla. The most active plant volatile compounds were the four green leaf volatile compounds, (E)-2-hexenol, (Z)-2-hexenol, (Z)-3-hexenol and (E)-2-hexenal, and isomers of two monoterpenols, (±)-linalool and (±)-α-terpineol, all eliciting strong responses from relatively large numbers of ORNs in male and female S. lepidus. Our study indicates that S. lepidus has a set of highly sensitive and selective ORNs for pheromone and plant volatile compounds. Further work is needed to elucidate the behavioral implications of these findings.

Chemical ecology meets conservation biological control: identifying plant volatiles as predictors of floral resource suitability for an egg parasitoid of stink bugs

Conservation biological control aims to enhance natural enemy populations in crop habitats, e.g. by providing flowering plants as food resources. Suitable flower species must enhance the survival and fecundity of natural enemies but in addition they also need to be highly attractive and thus frequently visited. To date, few examples exist that have considered both criteria. In this study, we tested the effects of the flowering plants alyssum (Lobularia maritima), buckwheat (Fagopyrum esculentum), French marigold (Tagetes patula) and sweet basil (Ocimum basilicum) on the fecundity and olfactory attractiveness of the egg parasitoid Trissolcus basalis, an important biological control agent of the stink bug Nezara viridula. Our results showed that access to buckwheat and basil flowers increased the parasitoid offspring. However, in olfactometer experiments where T. basalis was allowed to choose between flowering and non-flowering plants, only buckwheat floral scent was attractive. Headspace analyses of the odour emitted by the four plant species revealed very distinct profiles with little overlap in compounds. Buckwheat floral scent was characterized by an unpleasant smell for the human nose due to the presence of short-chain carboxylic acids. Headspace extracts of buckwheat flowers and a blend of six buckwheat plant volatiles consisting of butanoic, 2-methylbutanoic, 3-methylbutanoic and pentanoic acids, (Z)-3-hexenyl acetate and α-farnesene were significantly attractive in olfactometer bioassays. Furthermore, electrophysiological experiments showed most of these compounds elicited significant responses in T. basalis antennae. Integrating chemo-ecological methods into conservation biological control allowed us to identify a potential resource plant and attractive compounds for field studies.

Antennal Sensillum Morphology and Electrophysiological Responses of Olfactory Receptor Neurons in Trichoid Sensilla of the Diamondback Moth (Lepidoptera: Plutellidae)

Abstract Plant chemical signals are important olfactory cues for the survival and reproduction of phytophagous insects. The diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) is a Brassica spp. (Brassicales: Brassicaceae) specialist pest, with most of its life events occurring on Brassica spp. hosts. We conducted a scanning electron microscopy study on the morphology and distribution of antennal sensilla of male and female P. xylostella. Seven morphological types of sensilla were identified in the antennae of P. xylostella: 3 types of sensilla trichodea (Tr I, Tr II and Tr III), sensilla chaetica, sensilla coeloconica, sensilla auricillica and sensilla styloconica. One particular type of trichoid sensillum (Tr III) was present only in the males. The presence of numerous pores or deep longitudinal grooves on the surfaces of 5 morphological types of sensilla indicated that their major function is olfactory. Single sensillum recordings were also carried out on the trichoid sensilla of the female diamondback moth to identify the olfactory receptor neurons (ORNs) and to determine the response spectra of the ORNs, using a panel of 39 host and non-host volatile compounds. Based on the response profiles, 42 responsive trichoid sensilla could be segregated into 4 sensillum classes. Each sensillum appeared to contain 3 co-compartmentalized ORNs, and therefore a total of 12 classes of ORNs were identified from these sensilla. Each ORN class showed a narrow response spectrum, with some ORNs specialized for green leaf volatiles and (±)-linalool that are present in brassicaceous hosts, while several other ORNs responded to 2 non-host volatile sesquiterpenes, (E)-β-farnesene and germacrene D, as well as (E)-β-caryophyllene, a host-related sesquiterpene volatile. The sensitivity and selectivity of the female diamondback moth towards certain host plant volatiles warrants further investigation for potential behavioral manipulation to control this pest.

Morphology and distribution of antennal sensilla of two tortricid moths, Cydia pomonella and C. succedana (Lepidoptera)

Morphology of antennal sensilla and their distributions were investigated in male and female adults of two tortricid moths, Cydia pomonella and C. succedana using scanning electron microscopy. The antennae of both sexes of the two species were filiform, and the overall lengths of the antennae and the number of consisting segments were greater in males than in females. Six types of sensilla (s.) were identified from the antennae of both sexes in the two species: s. trichodea, s. basiconica, s. coeloconica, s. auricillica, s. chaetica, and s. styloconica, in varying numbers and distribution along the antennae. Among them, surface of four sensilla types (s. trichodea, s. basiconica, s. coeloconica, s. auricillica) were multiporous in the two species, indicating that the primary function of these sensilla is olfactory. The s. trichodea were the most numerous on the antennae in both sexes of the two species. Male C. pomonella has a greater number of s. trichodea than the female. The four sensilla types were further divided into different subtypes in the two species; s. trichodea into three subtypes, s. basiconica into two subtypes, s. coeloconica into two subtypes in C. pomonella and one subtype in C. succedana, and s. auricillica into two subtypes. Sexual dimorphism was observed in the subtypes of s. trichodea. The long subtype of s. trichodea occurs only on male antennae, whereas the short subtypes mainly on female antennae. These findings would be helpful for further studies on detailed chemo‐receptive functions of each subtype of the antennal sensilla.

Morphology and Distribution of Antennal Sensilla of the Bean Bug Riptortus pedestris (Hemiptera: Alydidae).

The bean bug, Riptortus pedestris is a major pest of bean pods and some tree fruits in north‐east Asian countries. Scanning electron microscopy was conducted to investigate the morphology and distribution of antennal sensilla of R. pedestris to help in understanding the sensory mechanisms of the bug. Average antennal lengths of male and female R. pedestris were 11.00 mm and 9.84 mm, respectively, consisting of four distinct segments, scape, pedicel, basiflagellum, and distiflagellum. Based on the gross appearance, the antennal sensilla were classified into four major types (trichodea, basiconica, chaetica, and coeloconica), which could be further classified into four trichoid, three basiconic, four chaotic, and two coeloconic subtypes, based on their size, tip shape, presence of socket, and surface structure. Among them, two subtypes of trichoid sensilla, all three subtypes of basiconic sensilla, four subtypes of chaetic sensilla and two subtypes of coeloconic sensilla had numerous pores along the surface, suggesting their olfactory function. Nine subtypes (2 trichoid, 1 basiconic, 4 chaetic, and 2 coeloconic subtypes) showed a distinct socket structure at the base. Among the four antennal segments, the distiflagellum possessed highest number of sensilla. Trichoid sensilla were most abundant, followed by basiconic, chaetic, and coeloconic sensilla. Each subtype of sensilla exhibited distinct distribution profile along the four antennal segments. Two subtypes of trichoid sensilla, one subtype of basiconic sensilla and one subtype of chaetica sensilla were distributed on scape, pedicel, and basiflagellum, whereas distribution of other subtypes of sensilla was confined to basiflagellum and distiflagellum. Microsc. Res. Tech. 79:501–511, 2016.

Identification of olfactory receptor neurons in Uraba lugens (Lepidoptera: Nolidae) and its implications for host range.

Phytophagous insects detect volatile compounds produced by host and non-host plants, using species-specific sets of olfactory receptor neurons (ORNs). To investigate the relationship between the range of host plants and the profile of ORNs, single sensillum recordings were carried out to identify ORNs and corresponding active compounds in female Uraba lugens (Lepidoptera: Nolidae), an oligophagous eucalypt feeder. Based on the response profiles to 39 plant volatile compounds, 13 classes of sensilla containing 40 classes of ORNs were identified in female U. lugens. More than 95% (163 out of 171) of these sensilla contained 16 classes of ORNs with narrow response spectra, and 62.6% (107 out of 171) 18 classes of ORNs with broad response spectra. Among the specialized ORNs, seven classes of ORNs exhibited high specificity to 1,8-cineole, (±)-citronellal, myrcene, (±)-linalool and (E)-β-caryophyllene, major volatiles produced by eucalypts, while nine other classes of ORNs showed highly specialized responses to green leaf volatiles, germacrene D, (E)-β-farnesene and geranyl acetate that are not produced by most eucalypts. We hypothesize that female U. lugens can recognize their host plants by detecting key host volatile compounds, using a set of ORNs tuned to host volatiles, and discriminate them from non-host plants using another set of ORNs specialized for non-host volatiles. The ORNs with broad response spectra may enhance the discrimination between host and non-host plants by adding moderately selective sensitivity. Based on our finding, it is suggested that phytophagous insects use the combinational input from both host-specific and non-host specific ORNs for locating their host plants, and the electrophysiological characterization of ORN profiles would be useful in predicting the range of host plants in phytophagous insects.

Species- and sex-specific distribution of antennal olfactory sensilla in two tortricid moths, Epiphyas postvittana and Planotortrix octo

We investigated the morphology and distribution of antennal sensilla in males and females of two tortricid moths, Epiphyas postvittana and Planotortrix octo, by scanning electron microscopy. The number and overall length of flagellomeres were significantly greater in females than in males in both species. The antennae of each species bearing six morphological types of sensilla (trichodea, basiconica, coeloconica, auricillica, chaetica, and styloconica), with different numbers and distributions along the antennae. Among these sensilla, four types (trichodea, basiconica, coeloconica, and auricillica) displayed multi-porous cuticular surfaces, indicating that their primary sensory function is olfactory. Each of these four types of sensilla could be further classified into subtypes according to their size, shape, and surface structure. Both E. postvittana and P. octo exhibited sexual dimorphism of the profiles of antennal olfactory sensilla. Trichoid sensilla were the most abundant type in both species. Subtype I trichoid sensilla were male-specific in both species, indicating that they are responsible for the perception of conspecific female sex pheromone. By contrast, subtype II trichoid sensilla were more abundant in female antennae in both species, suggesting that some subtype II trichoid sensilla are involved in female-specific behaviors, such as oviposition. Chaetic and styloconic sensilla displayed relatively even distributions along the antennae. Our results indicate that the antennae of E. postvittana and P. octo have species-specific and sex-specific profiles of olfactory sensilla. The morphological information obtained in our study provides a basis for electrophysiological and behavioral studies of the olfactory sensory function of each morphological type of sensilla.

Olfactory attraction mediated by the maxillary palps in the striped fruit fly, Bactrocera scutellata: Electrophysiological and behavioral study: PARK et al.

Here, we report that the olfactory attraction of the striped fruit fly, Bactrocera scutellata (Hendel; Diptera: Tephritidae), a serious pest of pumpkin and other cucurbitaceae plants, to cue lure and raspberry ketone is mediated by the maxillary palps. The antennae, bearing three morphological types (basiconic, trichoid, and coeloconic) of olfactory sensilla, in male and female B. scutellata exhibited significant electroantennogram (EAG) responses to a plant volatile compound, 3-octanone, and methyl eugenol, whereas cue lure, raspberry ketone, and zingerone that are known to attract several other species of Bactrocera fruit flies elicited no significant EAG responses from both sexes. In contrast, maxillary palps, housing one morphological type of basiconic sensilla, displayed the largest electropalpogram (EPG) responses to cue lure followed by raspberry ketone among the five compounds tested in male and female B. scutellata, with only minor EPG responses to 3-octanone, which indicates that the maxillary palps are responsible for detecting cue lure and raspberry ketone in this species. In field trapping experiments, significant number of male B. scutellata were captured in the traps baited with cue lure or raspberry ketone, in which the attractiveness of cue lure was significantly higher than that of raspberry ketone. Methyl eugenol and zingerone were not behaviorally attractive to B. scutellata although they elicited significant EPG responses. Our study indicates that the behavioral attraction of B. scutellata to cue lure and raspberry ketone is mediated by the olfactory sensory neurons present in the maxillary palps.