Can chemical cues from blossom buds influence cultivar preference in the apple blossom weevil (Anthonomus pomorum)?

The post-hibernating adults of the apple blossom weevil, Anthonomus pomorum (L.), show preferences for certain cultivars in mixed apple tree orchards. The degree of infestation of various cultivars was positively correlated with the density of flower buds at a comparable phenological stage, but the numbers of collected beetles were not linearly proportional to the bud density of different cultivars. Hence other possible factors, namely chemical ones, were investigated. Chromatographic analysis of apple tree bud emanations showed that volatiles from two different apple cultivars that show a different attractiveness to the beetles, differed in chemical composition. Several less volatile components of the bud emanation bouquet elicited antennographic responses in both male and female antennae. Four terpene hydrocarbons, namely 3-carene, perillene, caryophyllene and (E,E)--farnesene, were identified among the components that produced distinct electrophysiological responses in the antennae. These findings support a hypothesis that the adult weevils use chemical cues for olfactory discrimination during host-searching behaviour.     

Diapause dynamics, seasonal phenology, and pupal color dimorphism of Papilio polyxenes in southern Florida, USA

In the European grapevine moth, Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae), it has recently been shown that volatiles emitted from the main host plant, grapevine, are attractive to adult females. Here, using wind tunnel experiments, we tested the attractiveness of various grapevine, Vitis vinifera L. (Vitaceae), plant parts at different phenological stages, including ripe berries infested with the pathogenic fungus Botrytis cinerea (Persoon: Fries) (Sclerotiniaceae) to laboratory‐reared virgin and mated male and female moths. We also tested the attractiveness of the non‐host plant, tansy [Tanacetum vulgare (L.) (Asteraceae)], as flowers and flower volatiles were previously shown to be attractive to L. botrana females in the field. Mated female moths were the only adults to exhibit upwind orientation to grape plant parts in the flight tunnel. The most attractive parts of the grapevine plants were leaves, flower buds, and ripe berries. No attraction was observed to flowers. This corresponds to the phenological stages available when females of the 2–3 generations during a year are present in the field. No attraction was observed to leaves and flowers of tansy.     

Caterpillar‐induced plant volatiles attract conspecific herbivores and a generalist predator

Plants release volatiles in response to caterpillar feeding that attracts natural enemies of the herbivores, a tritrophic interaction which has been considered to be an indirect plant defence against herbivores. On the other hand, the caterpillar‐induced plant volatiles have been reported to either repel or attract conspecific adult herbivores. This work was undertaken to investigate the response of both herbivores and natural enemies to caterpillar‐induced plant volatiles in apple orchards. We sampled volatile compounds emitted from uninfested apple trees, and apple trees infested with generalist herbivore the pandemis leafroller moth, Pandemis pyrusana (Lepidoptera, Tortricidae) larvae using headspace collection and analysed by gas chromatography/mass spectrometry. Infested apple trees uniquely release six compounds (benzyl alcohol, phenylacetonitrile, phenylacetaldehyde, 2‐phenylethanol, indole and (E)‐nerolidol). These compounds were tested on two species of herbivores and one predator in apple orchards. Binary blends of phenylacetonitrile + acetic acid or 2‐phenylethanol + acetic acid attracted a large number of conspecific male and female adult herbivores. The response of pandemis leafroller to herbivore‐induced plant volatiles (HIPVs) was so pronounced that over one thousand and seven hundred conspecific male and female adult herbivores were caught in traps baited with HIPVs in three‐day trapping period. In addition, significantly higher number of male and female obliquebanded leafroller, Choristoneura rosaceana (Lepidoptera, Tortricidae), was caught in traps baited a binary blend of 2‐phenylethanol + acetic acid, or a ternary blend contains 2‐phenylethanol and phenylacetonitrile + acetic acid. This result challenges the current paradigm hypothesized that HIPVs repel herbivores and question the indirect defensive function proposed for these compounds. On the other hand, a ternary blend of phenylacetonitrile and 2‐phenylethanol + acetic acid attracted the largest numbers of the general predator, the common green lacewing, Chrysoperla plorabunda. To our knowledge, this is the first record of the direct attraction of conspecific adult herbivores as well as a predator to the caterpillar‐induced plant volatiles in the field.     

Pea plant volatiles guide host location behaviour in the pea moth

Identification of plant volatiles that attract mated insect females for oviposition can provide important information about plant–insect relationships that can be used to develop pest control strategies involving manipulation of the female host search. Our study represents a first step towards identifying volatiles that affect the host location behaviour of the pea moth Cydia nigricana. The behaviours of virgin and mated males and females were analysed in cage experiments testing a two-choice situation at close range and in wind tunnel experiments evaluating upwind orientation over a distance. In both experimental setups, flowering pea plants constituted the most attractive phenological stage for mated females, with 58 % landing on such plants in the wind tunnel. Testing headspace extracts of different phenological stages of pea and of detached pea buds and flowers in the wind tunnel, mated females showed the highest landing responses to volatiles during flower development (budding 42 % and flowering 56 %) and from detached buds (46 %) and flowers (66 %). Volatile compounds collected from the various phenological stages of pea were analysed by gas chromatography–mass spectrometry, and the antennal responses to these headspace collections were evaluated by gas chromatography–electroantennography. Ten antennally active compounds were identified, nine of which were present in the headspace extracts of the whole pea plants at all tested phenological stages and in detached buds and flowers. Overall, our results demonstrate a clear link between host plant phenology, the corresponding plant odour, and the behaviour of mated C. nigricana females.     

Antagonist effects of non-host fruit volatiles on discrimination of host fruit by Rhagoletis flies infesting apple (Malus pumila), hawthorn (Crataegus spp.), and flowering dogwood (Cornus florida)

In previous flight‐tunnel tests Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) flies originating from domestic apple (Malus pumila), hawthorn (Crataegus spp.), and flowering dogwood (Cornus florida), displayed greater numbers of upwind flights to blends of volatiles identified from their natal fruit compared to non‐natal fruit. Here, we show that when certain non‐host volatiles were added to the host blend, significantly fewer apple, hawthorn, and dogwood flies exhibited sustained upwind flight to the source. Specifically, the upwind flight of apple flies to the apple blend was significantly antagonized by the addition of the hawthorn or dogwood blends, the addition of 3‐methylbutan‐1‐ol alone (a key volatile for hawthorn and dogwood flies), or the combination of 3‐methylbutan‐1‐ol and another key dogwood volatile, 1‐octen‐3‐ol. Similarly, the upwind flight of dogwood and hawthorn flies to their respective natal blends was antagonized by the addition of the apple blend or the key apple volatile butyl hexanoate. Experiments were also conducted to determine whether non‐natal fruit volatiles could disrupt the close‐range flight response of flies to the visual stimulus of fruit alone, represented by an odorless red sphere. Tests with apple‐origin flies showed that when the hawthorn blend, the dogwood blend, or the key antagonist volatiles from each (3‐methylbutan‐1‐ol and 1‐octen‐3‐ol) were added to a red sphere fruit mimic, significantly lower proportions of flies were captured, compared with captures when no odor was present. Our results support the hypothesis that agonist and antagonist properties of fruit volatiles can play an important role in host recognition/discrimination by Rhagoletis flies.     

Response of the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae), to conophthorin and other angiosperm bark volatiles in the avoidance of non-hosts

1 Seventeen non‐host angiosperm bark volatiles, seven of which are antennally active to Ips pini (Say), the pine engraver (PE), were tested for their ability to disrupt the response of the PE to pheromone‐baited traps. 2 Four green leaf volatiles (GLVs) were tested [1‐hexanol (Z)‐3‐hexen‐1‐ol, hexanal, and (E)‐2‐hexenal]. None had any disruptive effect singly, as a group or in all possible blends based on functional groups, despite the fact that the two aldehydes were antennally active. These compounds may have, in some instances, actually masked the disruptive effect of other compounds. The PE thus differs in its response from other Scolytidae, including other Ips spp. 3 Eight non‐host volatiles that were antennally active to other bark beetles, but not to PEs, had no disruptive effect, validating the use of coupled gas chromatographic‐electroantennographic detection analyses to detect compounds with potential behavioural activity. 4 The bicyclic spiroacetal conophthorin, (E)‐7‐methyl‐1,6‐dioxaspiro[4.5]decane, was disruptive when tested alone. When blends of two aldehydes [salicylaldehyde and nonanal] plus an alcohol and a phenol [benzyl alcohol and guaiacol] were combined with conophthorin, an enhanced disruptive effect was revealed. No single compound, other than conophthorin, disrupted the pheromone‐positive response and no blend that did not contain conophthorin was consistently disruptive to both sexes. Conophthorin seems to be a critical component in the non‐host angiosperm message for I. pini during its host selection phase. 5 Combination of the repellent synomones, verbenone and ipsenol, with the five disruptive non‐host volatiles may provide a potent treatment to protect trees, logs or stands from attack by the PE.     

Parasitoid exploitation of the seasonal variation in host plant volatile emission for herbivore location

Volatile compounds from the apple, Malus domestica Borkh. (Rosaceae), change considerably as the season progresses, and this is successfully exploited by the female codling moth Cydia pomonella L. (Lepidoptera, Tortricidae), as it searches for oviposition sites. In this study, we investigated the effect of seasonal emissions of apple fruit volatiles on the host location behaviour of a parasitoid of the codling moth larvae, Hyssopus pallidus (Askew) (Hymenoptera: Eulophidae). In dual choice olfactory bioassays, the behaviour of the parasitoid in response to apple cues was observed over the complete 2003 growing season. Our results show that codling moth infested apples evoked a strong response from the parasitoid at the beginning of the season, until July. Then, attraction dropped drastically, increasing again at the beginning of August. At the end of the growing season, just prior to harvest, infested apples hardly evoked any behavioural response. Interestingly enough, mid‐season emissions of healthy apples were per se attractive to the parasitoid, and even preferred over volatiles from infested apples. Simultaneous volatile collections from healthy apples on twigs in the field were analysed throughout the season, showing that the overall quantity of headspace volatiles peaks at the beginning of June and mid‐August. The seasonal volatile emission is correlated with the behaviour of the parasitoid during the fruit ripening stage. The results are discussed in relation to the use of H. pallidus as a potential biocontrol agent, in order to enhance current integrated pest management (IPM) programs.     

Apple and peach fruit volatiles and the apple constituent butyl hexanoate attract female oriental fruit moth, Cydia molesta, in the laboratory

Volatiles emitted from immature and mature peach and apple fruits were all attractive to mated female oriental fruit moth, Cydia molesta (Busck), in a dual choice arena. Females did not discriminate between odours emitted by these two major host plants. The same natural blends were behaviourally ineffective for virgin females. A major component of apple fruit volatiles, butyl hexanoate, also attracted female C. molesta. Mated females were attracted to two medium dosages, while virgin females responded positively to the lowest of the five dosages tested. The time course of the captures of the moths shows a diurnal activity cycle known from the field. The possible implications of a semiochemical which attracts females are discussed in the context of previous findings that gravid females may immigrate from peaches into apple orchards particularly in the later phase of the season.     

Antennal and behavioural response of codling moth Cydia pomonella to plant volatiles

Identification of host volatile compounds attractive to codling moth Cydia pomonella, a most important insect of apple, will contribute to the development of safe control techniques. Synthetic apple volatiles in two doses were tested for antennal and behavioural activity in codling moth. Female antennae strongly responded to (Z)3‐hexenol, (Z)3‐hexenyl benzoate, (Z)3‐hexenyl hexanoate, (±)‐linalool and E,E‐α‐farnesene. Two other compounds eliciting a strong antennal response were the pear ester, ethyl (E,Z)‐2,4‐decadienoate, and its corresponding aldehyde, E,E‐2,4‐decadienal, which is a component of the larval defence secretion of the European apple sawfly. Attraction of codling moth to compounds eliciting a strong antennal response was tested in a wind tunnel. Male moths were best attracted to a blend of (E,E)‐α‐farnesene, (E)‐beta‐farnesene and ethyl (E,Z)‐2,4‐decadienoate. The aldehyde E,E‐2,4‐decadienal had an antagonistic effect when added to the above mixture.     

Interaction of Anthonomus grandis and cotton genotypes: biological and behavioral responses

The boll weevil, Anthonomus grandisBoheman (Coleoptera: Curculionidae), is a key pest of cotton, Gossypium hirsutumL. (Malvaceae). Knowledge about boll weevil feeding and oviposition behavior and its response to plant volatiles can underpin our understanding of host plant resistance, and contribute to improved monitoring and mass capture of this pest. Boll weevil oviposition preference and immature development in four cotton genotypes (CNPA TB90, TB85, TB15, and BRS Rubi) were investigated in the laboratory and greenhouse. Volatile organic compounds (VOCs) produced by TB90 and Rubi genotypes were obtained from herbivore‐damaged and undamaged control plants at two phenological stages – vegetative (prior to squaring) and reproductive (during squaring) – and four collection times – 24, 48, 72, and 96 h following herbivore damage. The boll weevil exhibited similar feeding and oviposition behavior across the four tested cotton genotypes. The chemical profiles of herbivore‐damaged plants of both genotypes across the two phenological stages were qualitatively similar, but differed in the amount of volatiles produced. Boll weevil response to VOC extracts was studied using a Y‐tube olfactometer. The boll weevil exhibited similar feeding and oviposition behavior at the four tested cotton genotypes, although delayed development and production of smaller adults was found when fed TB85. The chemical profile of herbivore‐damaged plants of both genotypes at the two phenological stages and time periods (24–96 h) was similar qualitatively, with 30 identified compounds, but differed in the amount of volatiles produced. Additionally, boll weevil olfactory response was positive to herbivory‐induced volatiles. The results help to understand the interaction between A. grandis and cotton plants, and why it is difficult to obtain cotton genotypes possessing constitutive resistance to this pest.     

Plant volatiles mediate attraction to host and non-host plant in apple fruit moth, Argyresthia conjugella

Plant volatiles mediate host finding in insect herbivores and lead to host fidelity and habitat‐specific mating, generating premating reproductive isolation and facilitating sympatric divergence. The apple fruit moth, Argyresthia conjugella Zeller (Lepidoptera: Argyresthiidae), is a particularly suitable species to study the cues and behavioural mechanisms leading to colonization of a new host: it recurrently oviposits on the non‐host plant, apple Malus domestica Borkh. (Rosaceae), where the larvae cannot complete their development. The larval host of the apple fruit moth (Lepidoptera, Argyresthiidae), is rowan Sorbus aucuparia L. (Rosaceae). Fruit setting in rowan, however, fluctuates strongly over large areas in Scandinavia. Every 2–4 years, when too few rowanberries are available for egg laying in forests, apple fruit moth females oviposit instead on apple in nearby orchards, but not on other fruits, such as pear or plum. This poses the question of which cues mediate attraction to rowan and apple, and how apple fruit moth discriminates rowan from apple. Chemical analysis and antennal recordings showed that 11 out of 15 rowan volatiles eliciting an antennal response in A. conjugella females co‐occur in rowan and apple headspace, in a different proportion. In the field, A. conjugella was attracted to several of these plant volatiles, especially to 2‐phenyl ethanol, methyl salicylate, and decanal. Addition of anethole to 2‐phenyl ethanol had a strong synergistic effect, the 1 : 1 blend is a powerful attractant for A. conjugella males and females. These results confirm that volatiles common to both plants may account for a host switch in A. conjugella from rowan to apple. Some of the most attractive compounds, including 2‐phenyl ethanol, anethole, and decanal, which have been found in several apple cultivars, were not present in the headspace of the apple cultivar, Aroma, which is also susceptible to attack by A. conjugella. This supports the idea that the odour signal from apple is suboptimal for attraction of A. conjugella, but is nonetheless sufficient for attraction, during times when rowan is not available for egg laying.     

Induced volatiles in soybean and pigeon pea plants artificially infested with the neotropical brown stink bug, Euschistus heros, and their effect on the egg parasitoid, Telenomus podisi

Herbivory is known to increase the emission of volatiles, which attract natural enemies to herbivore‐damaged plants in laboratory and agricultural systems. We report on signalling through volatiles induced by Euschistus heros (F.) (Heteroptera: Pentatomidae) in two legumes that influence the attraction and retention of the egg parasitoid Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). Air‐borne extracts obtained from two host plants of E. heros, soybean, Glycine max, and pigeon pea, Cajanus cajan (Leguminosae), produce a different blend of emitted volatiles when attacked by adult males or females and nymphs of the pest species, compared with the undamaged plants. The same results were obtained when the plants were treated with extracted saliva of E. heros which had been mechanically introduced into the plants. This indicates that some substance in the saliva contributed to the release of the volatiles. Bioassays in a Y‐tube olfactometer with female T. podisi and treated plants confirmed the significant preference of the egg parasitoid for plants attacked by either males, females, or fourth instar nymphs of the pest species. On the other hand, volatile extracts obtained from soybean subjected to the velvetbean caterpillar, Anticarsia gemmatalis, a non‐host species for T. podisi, showed a different blend of volatiles compared to those obtained from plants subjected to E. heros. Additionally, the volatiles obtained from this plant–host complex were not attractive to T. podisi. These results indicate that E. heros causes an increase in the emission of specific plant volatiles, and that the induction is possibly caused by an elicitor present in the pest saliva. The possibility that these plant volatiles play an important role in the attraction and retention of the egg parasitoid T. podisi is discussed.     

Plant genotype and the preference and performance of herbivores: cultivar affects apple resistance to the florivorous weevil Anthonomus pomorum

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Semiochemical attractants for the beech leaf‐mining weevil,Orchestes fagi

The beech leaf‐mining weevil, Orchestes fagi L. (Curculionidae: Curculioninae: Rhamphini), a pest of European beech, Fagus sylvatica L. (Fagaceae), was recently discovered infesting American beech, Fagus grandifolia Ehrh., in Nova Scotia, Canada. Adult O. fagi feed on both young and mature leaves of beech as well as on other species (e.g., raspberry, Rubus spp.), but oviposition and larval feeding are restricted to beech. Females oviposit in young developing beech leaves at the time of bud burst. We characterized volatiles emitted from buds, leaves, and sapwood of American beech and examined their potential as attractants alone or when combined with other weevil pheromones for O. fagi. We predicted that adults would be attracted to volatiles emitted from beech leaves, especially those emitted from bursting beech buds. Gas chromatography/mass spectrometry (GC/MS) analyses of volatiles collected from buds at pre‐ and post‐budburst identified two diterpene hydrocarbons, 9‐geranyl‐p‐cymene ( 1 ) and 9‐geranyl‐α‐terpinene ( 2a ), that were emitted in large amounts at the time of bud burst. Compound 1 significantly increased mean catch of males and total O. fagi (but not females) on sticky traps compared with unbaited controls. Y‐tube bioassays confirmed attraction of male O. fagi to bursting beech buds and compound 1 . Attraction of male O. fagi to 1 , emitted in large quantities from American beech, is likely adaptive because both oviposition and mating of O. fagi coincide with budburst. Our data suggest that traps baited with 1 may be useful for monitoring the spread of O. fagi in North America.     

Significance of shelter traps for spring monitoring of Anthonomus pomorum in apple orchards

The significance of the apple blossom weevil, Anthonomus pomorum L. (Coleoptera: Curculionidae), as a potential threat to apple, Malus domestica Borkh., has increased over the past two decades in many regions of Europe. The apple blossom weevil immigrates into orchards and colonises apple trees in early spring. Females deposit single eggs into closed blossom buds, which leads to capped blossoms. This study was designed to test the suitability of transparent shelter traps for the surveillance of colonisation under different population pressures, and to assess the quantitative relationship between number of weevils caught and: (1) absolute injury, expressed as number of infested buds, as well as (2) relative injury, expressed as a percentage of infested buds relative to all buds on the tree. The findings with the new shelter traps were contrasted to results from limb jarring. Numbers of weevils caught with the transparent shelter trap were positively correlated with absolute injury, as well as with relative injury across the five study sites, whereas weevil counts with limb jarring were not correlated with absolute injury, but only with relative injury. Our data validate the transparent shelter trap as a method for accurately monitoring the course of spring colonisation of A. pomorum and demonstrate its potential for predicting injury by the weevils to blossom buds. In contrast, the significance of limb jarring for monitoring both the time course of colonisation and subsequent injury is limited. The significant linear relationship between the number of weevils caught in shelter traps and the relative injury allows for predictions of potential damage before oviposition takes place, i.e., early enough for an insecticide application where necessary.     

Behavioral responses for evaluating the attractiveness of specific tea shoot volatiles to the tea green leafhopper,Empoaca vitis

Abstract The tea green leafhopper, Empoasca vitis Göthe, 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.     

Temporal relationship between emitted and endogenous floral scent volatiles in summer‐ and winter‐blooming Jasminum species

Jasminum spp. is cultivated for their fragrant flowers used in essential oil production and cosmetic uses. An attempt was made to study the temporal variations in floral scent volatiles composition including emitted, free endogenous and glycosyl‐linked volatile compounds from two summer‐blooming species namely, Jasminum auriculatum and Jasminum grandiflorum as well as from two winter‐blooming species namely, Jasminum multiflorum and Jasminum malabaricum. The overall emitted volatile organic compounds (VOCs) were found to be highest when the matrix Porapak Q 80/100 was used with dichloromethane (DCM) as elution solvent. The floral volatile emission from bud to senescence exhibited nocturnal maxima pattern for both the summer‐blooming species. Both the winter‐blooming species emitted its highest concentration at noon. The free endogenous concentrations of all VOCs were low when corresponding emitted concentrations were high. Enzymatic treatment of petal extract revealed that several aromatic volatiles including aromatic alcohols and monoterpenols are synthesized and stored in the flowers as water‐soluble glycosides; these compounds were shown to accumulate in higher amounts in flowers at late bud stage. These findings indicate the utilization of the precursors, i.e. the volatile‐conjugates, through hydrolysis followed by their release as free‐volatiles at flower opening stage. The outcome as a whole suggests a linkage among the temporal pattern of emitted volatiles, free‐endogenous volatiles and glycoside‐bound volatile compounds in all above studied Jasminum spp. and provided an overview of their floral volatilome.     

Comparative analysis of peach and pear fruit volatiles attractive to the oriental fruit moth,Cydia molesta

Cydia molesta is an important pest of peach and pear fruits late in growing season. We identified and quantified volatiles from immature and mature fruits of peach and pear using gas chromatography-mass spectrometry. Antennally, active compounds were identified by gas chromatography-electroantennogram detection and were further tested in the field. Consistent electroantennographic activity was obtained for nine compounds from headspace collections of the mature fruits of two peach and two pear varieties. Esters were the major components, but qualitative and quantitative differences were found among four odor profiles. Blends mimicking pear fruit volatiles were more attractive to both sexes than blends mimicking peach fruit volatiles in both orchards. Our finding indicated that mixtures mimicking peach and pear fruit volatiles attracted both females and males of C. molesta, and these host volatiles may also be involved in the host switch behavior from peach to pear in mid-late season.     

Orientation of Colorado potato beetle to natural and synthetic blends of volatiles emitted by potato plants

1 Behavioural responses of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), to volatiles emitted from solanaceous host plants (potato and tomato), a non‐host legume (soybean), and 13 synthetic blends or three individual chemicals emitted by potato plants were investigated in laboratory bioassays. 2 Both male and female CPB were attracted to volatiles emitted by mechanically damaged potato foliage, but not to mechanically damaged tomato foliage; CPB offered a choice between the two damaged solanaceous plants did not show a preference. 3 Among 16 odourous blends or individual chemical components of potato plant emissions tested, six blends were attractive, two were repellent, and eight elicited no preference in laboratory bioassays. Volatile blends containing relatively high amounts of the green leaf volatiles (E)‐2‐hexen‐1‐ol and (Z)‐3‐hexen‐1‐ol, or the sesquiterpene β‐ caryophyllene, were unattractive or repellent. Minimal blends attractive to CPB were comprised of (Z)‐3‐hexenyl acetate (±)‐linalool and methyl salicylate: the combination of all three chemicals elicited sexually dimorphic attraction of males; two component blends comprised of (Z)‐3‐hexenyl acetate and either (±)‐linalool and methyl salicylate attracted both sexes. Individual compounds were inactive. No significant difference was noted between two attractive blends, or an attractive synthetic blend vs. mechanically damaged potato foliage. 4 These results show that CPB are attracted to blends of specific chemicals emitted by their host plants and provide a basis for the use of plant attractants as a component of integrated management of pestiferous populations.     

Volatile compounds emitted by Triatoma dimidiata,a vector of Chagas disease: chemical analysis and behavioural evaluation

In this study, we evaluated the responses of Triatoma dimidiata Latreille (Hemiptera: Reduviidae) to volatiles emitted by conspecific females, males, mating pairs and metasternal gland (MG) extracts with a Y‐tube olfactometer. The volatile compounds released by mating pairs and MGs of T. dimidiata were identified using solid‐phase microextraction and coupled gas chromatography‐mass spectrometry (GC‐MS). Females were not attracted to volatiles emitted by males or MG extracts; however, they preferred clean air to their own volatiles or those from mating pairs. Males were attracted to volatiles emitted by males, females, mating pairs, pairs in which the male had the MG orifices occluded or MG extracts of both sexes. However, males were not attracted to volatiles emitted by pairs in which the female had the MG orifices occluded. The chemical analyses showed that 14 and 15 compounds were detected in the headspace of mating pairs and MG, respectively. Most of the compounds identified from MG except for isobutyric acid were also detected in the headspace of mating pairs. Both females and males were attracted to octanal and 6‐methyl‐5‐hepten‐2‐one, and males were attracted to 3,5‐dimethyl‐2‐hexanol. Males but not females were attracted to a seven‐compound blend, formulated from compounds identified in attractive MG extracts.