An omnivorous arthropod, <Emphasis Type="Italic">Nesidiocoris tenuis</Emphasis>, induces gender-specific plant volatiles to which conspecific males and females respond differently

Nesidiocoris tenuis Reuter (Heteroptera: Miridae) is an omnivorous mirid bug that preys on diverse generalist herbivorous arthropods. N. tenuis adults are attracted to volatiles from plants induced by their prey, such as tobacco cutworms (CCW) (Spodoptera litura larvae) and two-spotted spider mites (Tetranychus urticae). N. tenuis adults also induce volatiles when they infest plants. In this study, we focused on olfactory responses of N. tenuis males and females to volatiles from eggplants and sesame plants induced by conspecifics of the same or different gender by using a Y-tube olfactometer. Males were attracted to volatiles from plants of both species induced by either males or females. The male preference was biased to volatiles from plants of both species induced by females, probably because the biased response would facilitate their mate-finding. Females were attracted only to volatiles from plants of both species induced by females. Mating occurs multiple times in this species. Thus, the responses would indirectly affect mating of males and females. Slight but significant qualitative and quantitative differences were detected between the volatiles of plants of both species induced by N. tenuis females and those of the plants induced by conspecific males. N. tenuis might use such differences in their gender-specific responses.     

Biological activity and specificity of Miridae-induced plant volatiles

The ability of zoophytophagous predators to produce defensive plant responses due to their phytophagous behavior has been recently demonstrated. In the case of tomatoes, the mirids Nesidiocoris tenuis and Macrolophus pygmaeus are able to attract or repel pests and/or natural enemies in different ways. Nevertheless, the herbivore-induced plant volatiles (HIPVs) released by the phytophagy of both mirids, which are responsible for these behaviors, are unknown. In this work, the HIPVs produced by the plant feeding of N. tenuis and M. pygmaeus were characterized. In addition, the role of each HIPV in the repellence or attraction of two tomato pests, Bemisia tabaci and Tuta absoluta, and of the natural enemy Encarsia formosa was evaluated. Six green leaf volatiles (GLVs) plus methyl salicylate and octyl acetate clearly stood out as major differential peaks on the chromatogram in a directed analysis. The six GLV and methyl salicylate were repellent for B. tabaci and attractive to E. formosa, whereas they showed no effect on T. absoluta. Octyl acetate, which was significantly present only in the M. pygmaeus-punctured plants, was significantly attractive to T. absoluta, repellent to E. formosa and indifferent to B. tabaci. Unlike the remaining HIPVs, octyl acetate was emitted directly by M. pygmaeus and not by the plant. Our results showed that mirid herbivory could modulate the pest and natural plant enemy locations, since tomato plants release a blend of volatiles in response to this activity. These results could serve as a basis for future development of plant protection.     

Genetic diversity and reproductive traits in triploid and tetraploid populations of <Emphasis Type="Italic">Gladiolus tenuis</Emphasis> (Iridaceae)

Most perennial herbaceous plants are able to reproduce vegetatively as well as sexually. Sometimes, such plants may lose the capacity for sexual reproduction. We have studied the case of sterility in triploid populations (2n = 3x = 45) of Gladiolus tenuis M.Bieb. in a considerable part of its area of distribution. Initially, we recorded the presence of a large clone of G. tenuis to the east of the Volga River, as a result of isozyme analysis. We also used AFLP fingerprinting to genotype 55 samples from 10 populations of G. tenuis and one population of the closely related G. imbricutus L. This analysis revealed an extremely low genetic diversity in sterile triploid populations of G. tenuis and a rather high genetic diversity in fertile tetraploid populations (2n = 4x = 60) over most of the area of this species. Genetic distances between fertile and sterile populations of G. tenuis were similar to those between different species of gladioli. It appears that a single sterile genotype has spread vegetatively over 800 km, propagating by daughter corms. The study of the reproductive features of G. tenuis suggests that the cause of sterility may be self-incompatibility between individuals of the clone.     

Management of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae) in strawberry fields with <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> (Acari: Phytoseiidae) and acaricides

The purpose of this study was to evaluate the performance of Neoseiulus californicus (McGregor) for the control of Tetranychus urticae Koch in commercial strawberry fields, under greenhouse conditions, in association or not with the use of acaricides. The N. californicus strain used in this study was tolerant or resistant to several pesticides. Three experiments were carried out in the State of São Paulo, Brazil. For the first experiment, the initial infestation of T. urticae was 87.1 active stages per leaflet. Two applications of propargite were made on the first and the 14th day of the experiment. Approximately 2 h after each propargite application, N. californicus was released at a rate of 3.0 and 1.9 adult mites per plant, respectively, for each application. The population of T. urticae decreased from 87.1 to 2.8 mites per leaflet in the first three weeks. After this period, the population of T. urticae was maintained at low levels (≤1.5 mites/leaflet) until the end of the experiment (10th week). Propargite and dimethoate sprayed on the strawberry field did not affect significantly the population of this predaceous mite. For the second experiment, the infestation of T. urticae was 29.1 mites per leaflet, when the acaricide chorfenapyr was applied on the strawberry field. The release of N. californicus (2 mites per plant) was made 2 weeks after spraying the acaricide. The population of T. urticae was maintained at low levels (≤2.8 mites/leaflet) for 8 weeks (evaluation period). The T. urticae infestations in plots with N. californicus were significantly lower than in non-release plots, for the experiments 1 and 2. In the third experiment, the initial infestation of T. urticae was 40.5 mites per leaflet (55.5 active stages/leaflet on release plants; 25.5 active stages/leaflet on non-release plants). Three releases of N. californicus (average rate of 3.0 adult mites/plant), without any acaricide application, were not sufficient to reduce significantly the T. urticae population in release plots (release plants + non-release plants) in 6 weeks from the first release, however, the spider mite population decreased from 55.5 to 7.8 active stages per leaflet on release plants, during this period. Interplant dispersal of N. californicus was low in this strawberry field with high infestation of T. urticae. The studies indicate the viability of the use of this strain of N. californicus for the control of T. urticae in strawberry fields under greenhouse conditions, especially in association with selective acaricides.     

Behavioral responses of <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis> to floral volatiles combined with different background visual cues

The Western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), is one of the most destructive sucking pests of flowering plants. We examined behavioral responses of F. occidentalis adults to the floral volatiles of Rosa chinensis, Gardenia jasminoides, and Tagetes erecta in a Y-tube olfactometer with background visual cues (green, red, white, yellow, and blue backgrounds). The results show that F. occidentalis adults had similar responses under all the different background colors, but the responses by sex varied significantly when offered floral volatile or clean air. In pairings of floral volatiles, female F. occidentalis adults presented significant preferences (R. chinensis > G. jasminoides > T. erecta) in each treatment, while male F. occidentalis adults had no significant preference. Furthermore, the responses of female F. occidentalis adults to the three different floral volatiles compared with each other were greater under green and blue backgrounds than red, white, or yellow backgrounds. However, the responses of male F. occidentalis adults to floral volatiles were similar to all five backgrounds. These results indicate that female thrips could discriminate different floral volatiles, while male thrips could not. Both male and female thrips performed steady preferences of floral volatiles under all the five visual backgrounds, and the behavioral responses of female thrips to the floral volatiles could be enhanced under the green and blue backgrounds. These findings could hopefully aid in the development of effective trapping and monitoring strategies for this pest.     

Attraction to Host Plant Volatiles and Feeding Performance of <Emphasis Type="Italic">Naupactus Xanthographus</Emphasis> (Coleoptera: Curculionidae) is Affected by Starvation

The grape weevil, Naupactus xanthographus Germar (Coleoptera: Curculionidae), is a polyphagous insect which is a cause of important damage to several economically relevant crops, including grape (Vitis vinifera) and avocado (Persea americana), in several countries of Latin America. The larvae cause damage to the roots and rootlets of plants, and adults feed on leaves of their host plant. Despite its economic importance, there are few reports on the behavioral and nutritional ecology of this weevil. In this context, laboratory feeding and olfactometer bioassays with N. xanthographus were performed. The feeding performance was evaluated by measuring the weight variation of the insects after 1 and 6 h of feeding on grape or avocado leaves, respectively. After 1 h of feeding, insects showed no significant differences in weight increase. However, after a period of 6 h of feeding, males had continued feeding on grape leaves, but not on avocado leaves. Bioassays using a Y-tube olfactometer showed that males are attracted to volatiles of both host plants. Furthermore, starved males and females showed no preference to volatiles of grape or avocado. However, non-starved males and females preferred grape volatiles over avocado volatiles. Based on the combined results of the assays, we conclude that grape is preferred over avocado for N. xanthographus. Furthermore, this is the first report on the effect of starvation on the attraction to host plant volatiles in Curculionidae.     

Centromeric and non-centromeric satellite DNA organisation differs in holocentric <Emphasis Type="Italic">Rhynchospora</Emphasis> species

Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R. tenuis) revealed linear signals at both chromatids, non-centromeric, species-specific satDNAs formed distinct clusters along the chromosomes. Colocalisation of both repeat types resulted in a ladder-like hybridisation pattern at mitotic chromosomes. In interphase, the centromeric satDNA was dispersed while non-centromeric satDNA clustered and partly colocalised to chromocentres. Despite the banding-like hybridisation patterns of the clustered satDNA, the identification of chromosome pairs was impaired due to the irregular hybridisation patterns of the homologues in R. tenuis and R. ciliata. These differences are probably caused by restricted or impaired meiotic recombination as reported for R. tenuis, or alternatively by complex chromosome rearrangements or unequal condensation of homologous metaphase chromosomes. Thus, holocentricity influences the chromosomal organisation leading to differences in the distribution patterns and condensation dynamics of centromeric and non-centromeric satDNA.     

A PCR-based analysis of plant DNA reveals the feeding preferences of <Emphasis Type="Italic">Apolygus lucorum</Emphasis> (Heteroptera: Miridae)

The mirid bug Apolygus lucorum (Meyer-Dür) (Heteroptera: Miridae) is a severe pest of cotton and other crops in China. The feeding preferences of this pest are unclear due to its frequent movement among different host plants and the inconspicuous signs of its feeding. Here, we present results of a field trial that used direct observation of bug densities and a PCR-based molecular detection assay to detect plant DNA in bugs to explore relationships between A. lucorum population abundance and its feeding preference between two host plants, Humulus scandens (Loureiro) Merrill and Medicago sativa L. The field-plot samples showed that A. lucorum adults generally prefer flowering host plants. Its density was significantly higher on flowering H. scandens than on seedlings of M. sativa, and a similarly higher bug density was observed on flowering M. sativa than on seedlings of H. scandens. In the laboratory, we designed two pairs of species-specific primers targeting the trnL-F region for H. scandens and M. sativa, respectively. The detectability of plant DNA generally decreased with time post-feeding, and the half-life of plant DNA detection (DS₅₀) in the gut was estimated as 6.26 h for H. scandens and 3.79 h for M. sativa with significant differences between each other. In mirid bugs exposed to seedlings of H. scandens and flowering M. sativa, the detection rate of M. sativa DNA was significantly higher than that of H. scandens. Meanwhile, in mirid bugs exposed to seedlings of M. sativa and flowering H. scandens, a significantly higher detection rate of H. scandens DNA was found. We developed a useful tool to detect the remaining plant food species specifically from the gut of A. lucorum in the current study. We provided direct evidence of its feeding preference between H. scandens and M. sativa at different growth stages, which strongly supported a positive correlation between population abundance and feeding preference of A. lucorum on different plants under field conditions. The findings provide new insights into the understanding of A. lucorum’s feeding preference, and are helpful for developing the strategies to control this pest.     

Effects of imidacloprid on the orientation behavior and parasitizing capacity of <Emphasis Type="Italic">Anagrus nilaparvatae</Emphasis>, an egg parasitoid of <Emphasis Type="Italic">Nilaparvata lugens</Emphasis>

Anagrus nilaparvatae (Pang et Wang) (Hymenoptera: Mymaridae), is an egg parasitoid of rice planthoppers, Nilaparvata lugens (Stål) (Homoptera: Delphacidae). This study evaluated effects of the insecticide imidacloprid on orientation behavior and parasitizing capacity of A. nilaparvatae. Sub-lethal concentrations of imidacloprid (LC₂₀ and LC₁₀) disrupted the foraging ability of A. nilaparvatae exposed to imidacloprid through contact or oral routes. Some survivors did not respond to volatiles from N. lugens-infested plants. Responsive individuals were equally attracted to volatiles from N. lugens-infested and healthy plants. Volatiles emitted from rice plants treated with a low concentration of imidacloprid were more attractive to A. nilaparvatae than those from plants treated with a high concentration of imidacloprid. Parasitism of N. lugens by A. nilaparvatae that survived contact with sub-lethal concentrations of imidacloprid did not decrease significantly. When A. nilaparvatae were fed imidacloprid-honey mixture, parasitism rates were 1.49% and 0%, respectively, significantly lower than those of the control (9.58%). Parasitism of N. lugens eggs in high concentration of imidacloprid treated rice plants by A. nilaparvatae decreased significantly. These effects involving disturbed foraging ability and reduced parasitizing capacity of A. nilaparvatae indicated that imidacloprid could decrease the performance of this parasitoid.     

Phloem-feeding herbivory on flowering melon plants enhances attraction of parasitoids by shifting floral to defensive volatiles

Emission of herbivore-induced plant volatiles (HIPVs) can differ according to the type of herbivory and the plant development stage, ultimately affecting recruitment of the natural enemy. Little is known about plant defenses induced at the flowering stage by phloem-feeding insects. We investigated the olfactory preference of Encarsia desantisi parasitoids and the chemical profile of flowering melon plants induced or not by the phloem-feeding of Bemisia tabaci whiteflies. In addition, we tested whether the parasitoids were attracted to synthetic defensive HIPVs, which mimicked whitefly-infested flowering melons. The parasitoids recognized volatiles from undamaged melons but preferred the scent of host-infested melons in olfactometry assays. Amounts of most individual volatiles did not differ between plant treatments; however, only whitefly-induced melons released methyl salicylate and tetradecane, compounds known to attract parasitoids. Interestingly, grouping volatiles by chemical classes revealed that whitefly-infested melon released larger amounts of monoterpenes and smaller amounts of benzenoids than undamaged melons, which might underlying the parasitoid attraction and indicate a possible trade-off between defensive and reproductive defenses at the melon flowering stage. Additionally, E. desantisi preferred the mix of synthetic and defensive HIPVs over hexane (control), opening a new avenue for further investigations in using olfactory lures for B. tabaci biological control. This study is the first report of induced defenses in melon plants and their mediation in a tritrophic interaction, as well as the first record of E. desantisi behavioral preference for HIPVs.     

Impact of the invasive painted bug <Emphasis Type="Italic">Bagrada hilaris</Emphasis> on physiological traits of its host <Emphasis Type="Italic">Brassica oleracea</Emphasis> var botrytis

Bagrada hilaris is a herbivorous insect native of Asia and Africa, which has invaded southern Europe and North America where it causes major damage to cole crops. Laboratory experiments were conducted to assess how the infestation of this invasive species damages the host Brassica oleracea var botrytis, and to evaluate the interaction between plant emission of volatile organic compounds (VOC) and B. hilaris adults. Plant responses to insect feeding were evaluated through changes in photosynthesis, stomatal conductance, VOC emission, and visual damage on leaves. The impact of B. hilaris was compared with that of Nezara viridula, a polyphagous species distributed worldwide. Plant VOC role in host plant detection was tested with electroantennography bioassays on B. hilaris antenna. Photosynthesis and stomatal conductance were consistently reduced in plants infested with 40 B. hilaris adults for 24 h. The feeding activity of a single B. hilaris caused larger discolored spots on host leaves in comparison with N. viridula. VOC emitted by B. oleracea changed significantly in response to B. hilaris and N. viridula infestation. In particular, production of limonene was strongly reduced by the infestation of the two pentatomids, while an increase in the emission of acetic acid and 2-ethyl-1-hexanol was observed. EAG dose–response tests using the main plant VOC showed B. hilaris antennal responses to benzaldehyde, octanal, nonanal, and acetic acid, which indicates a role of these compounds in host location.     

Innate Olfactory Responses of <Emphasis Type="Italic">Asobara japonica</Emphasis> Toward Fruits Infested by the Invasive Spotted Wing Drosophila

Insect parasitoids are often manipulated to improve biological control programs for various arthropod pests. Volatile compounds can be a relevant cue used by most parasitoid hymenoptera for host or host microhabitat location. Here, we studied olfactory responses of the braconid Asobara japonica Belokobylskij, an Asiatic endoparasitoid of the invasive pest Drosophila suzukii (Matsumura), toward its host and host substrates. Adult A. japonica displayed an innate attraction to undescribed volatile cues from infested host fruits irrespectively of the juvenile rearing experience, i.e. they respond to a novel cue subsequently used for microhabitat selection. These data suggest that A. japonica parasitoids mass-reared on artificial diet and factitious host (D. melanogaster) can successfully locate their hosts. Naïve female parasitoids did not show a preference towards any of the tested host media. However, the enforced adult experience with the rearing host medium modified the olfactory preference patterns toward non-natal host fruits. These findings provide evidence of associative learning during the adult stage of A. japonica, and demonstrate its plasticity in exploiting the volatiles from various fruits infested by D. suzukii.     

Attraction of <Emphasis Type="Italic">Telenomus podisi</Emphasis> to volatiles induced by <Emphasis Type="Italic">Euschistus heros</Emphasis> in three different plant species

Specialized natural enemies that forage for polyphagous hosts need to locate hosts on different plants. Telenomus podisi (Hymenoptera: Platygastridae) is a stink bug egg parasitoid with a preference for Euschistus heros (Hemiptera, Pentatomidae), a polyphagous species. The aim of this study was to evaluate the induction of defences in three E. heros host plants: maize (Zea mays), sunflower (Helianthus annuus) and pigeon pea (Cajanus cajan). We hypothesized that E. heros damage to these three plants enhances the attraction of the parasitoid T. podisi as has been observed in other systems. Using Y-tube olfactometer bioassays, we tested parasitoid responses to combinations of the following odour sources: clean air, undamaged plants and plants damaged by stink bug feeding. Volatiles were collected by means of dynamic headspace collection and analysed by gas chromatography coupled to mass spectrometry. T. podisi did not distinguish odours from undamaged plants against air for any of the three plant species. For maize, the parasitoid preferred the odour from herbivore-damaged plants over both clean air and undamaged plants. For sunflower, the parasitoid only preferred the odour of herbivore-damaged plants over the odour of undamaged plants. For pigeon pea, no preferences were observed. Quantitative differences in the volatile profile of damaged and undamaged plants were observed in each plant species. We conclude that sunflower and maize plants, when damaged by E. heros, release volatiles that attract the parasitoid T. podisi; the parasitoid appears to use a different blend composition to distinguish herbivore-damaged plants of each species.     

Terpenoids dominate the bouquet of volatile organic compounds produced by <Emphasis Type="Italic">Passiflora edulis</Emphasis> in response to herbivory by <Emphasis Type="Italic">Heliconius erato phyllis</Emphasis> (Lepidoptera: Nymphalidae)

In response to injury, plants produce volatile organic compounds (VOCs) that usually differ depending on the type of damage they have suffered (e.g., mechanical damage, herbivory, and oviposition). The objectives of this study were to identify and compare the bouquet of volatiles emitted by passion vine plants (Passiflora edulis) after injury caused by mechanical damage (MD), herbivory (HB), and oviposition (OV) by the lepidopteran, Heliconius erato phyllis. Following injury, extracts of plant emissions were collected from each treatment every 24 h for three days and were analyzed by GC and GC/MS. Results show that plants emitted 12 volatiles before and after damage, namely terpenoids, ketones, and aldehydes. Although no significant differences were detected between the three treatments individually, if the entire bouquet of volatiles is analyzed, samples collected at 24 h were different from samples collected at 48 and 72 h. However, terpenoid emission increased significantly in HB plants after 24 h. HB plants emitted approximately 6300, 50, 46, 11, 6, and 3.6 times more (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), (E)-β-ocimene, (Z)-β-farnesene, (E)-β-caryophyllene, and farnesane, respectively, compared to control plants. OV plants displayed a peak of emission of (E)-β-ocimene after 72 h, which distinguished them from HB plants. MD plants showed a general increase of VOCs versus undamaged control plants. Furthermore, it has been suggested that (E)-β-ocimene may be sequestered by larvae of H. erato phyllis as a component of the odoriferous bouquet of the abdominal scent glands present in adult males, which play a role in sexual communication.     

Physical and biochemical aspects of host plant resistance to mustard aphid, <Emphasis Type="Italic">Lipaphis erysimi</Emphasis> (Kaltenbach) in rapeseed-mustard

Mustard aphid, Lipaphis erysimi (Kaltenbach) is a major constraint in increasing the yield of rapeseed-mustard crops in India. Resistance to mustard aphid infestation and its correlation to some physiological and biochemical traits in selected varieties of different Brassica species were studied. Yield and oil content losses of up to 29.4% and 2.84%, respectively, were observed due to aphid infestation. Eruca sativa var. T-27 and Brassica carinata var. DLSC-2 were less susceptible to aphid infestation and had minimal yield losses. Surface wax, total glucosinolate, and phenol contents were found to correlate negatively with the aphid infestation, whereas the opposite relationship was obtained for the sugar content. The study suggests that physical and chemical barriers potentially play an important role in resistance against aphid infestation.     

Responses of a predatory bug to a mixture of herbivore-induced plant volatiles from multiple plant species

The attractiveness of herbivore-induced plant volatiles (HIPVs) from a specific plant species to natural enemies has been well established. However, under natural conditions and polycultural agriculture systems, the interactions among trophic levels are thought to be more complex. For instance, complex mixtures of volatiles emitted from diverse host plant species infested by polyphagous herbivores might affect responses of natural enemies. In this study, we investigated whether a mixture of HIPVs emitted from herbivore-damaged multiple host plant species affect responses of a predatory bug. Therefore, we report (1) olfactory responses of the predatory bug (Orius strigicollis) to volatiles emitted from cotton bollworm (Helicoverpa armigera) first instar larvae-damaged multiple plant species (tomato, French bean and sweet corn), (2) chemical analyses of volatiles emitted from the three plant species exposed to different treatments and (3) olfactory responses of the predators to a reconstituted HIPV blend from multiple plant species based on chemical analyses. O. strigicollis significantly preferred volatiles emanating from H. armigera-damaged multiple plant species to volatiles emanating from a single plant species. In all the three plant species, H. armigera-damaged seedlings emitted significantly a greater amount of volatiles as well as a larger number of volatile compounds than an undamaged or a mechanically injured seedling. The predators preferred the reconstituted HIPVs from multiple plant species to the reconstituted HIPVs from a single plant species. Thus, the mixture of HIPVs from multiple plant species enhanced the attractiveness to the predators.     

Electrophysiological and behavioral response of the oriental fruit moth <Emphasis Type="Italic">Grapholita</Emphasis><Emphasis Type="Italic">molesta</Emphasis> (Busck, 1916) (Lepidoptera: Tortricidae) to the volatiles of apple fruits at different stages of development

The oriental fruit moth, Grapholita molesta, occurs in Southern Brazil throughout the year, and migrates from peach to apple orchards. Because moths rely on volatile organic compounds (VOCs) during the host-location process, variations in the emission of these compounds during fruit maturation can influence the time of infestation and preference of the moths for a particular genotype. The aim of this work was to identify VOCs emitted by the apples “Eva” and “Gala” at different stages of development and to determine the behavioral and electrophysiological responses of G. molesta to these compounds. For this purpose, VOCs from immature, maturing, and mature fruits of both cultivars were collected and analyzed by gas chromatography and gas chromatography-mass spectroscopy. The response of the antennae of virgin males and females and mated females to volatiles released by the three fruit stages was registered by gas chromatography coupled to an electroantennography. A dual-choice behavioral test for the different combinations of insect groups and fruit stage was also performed. Amongst the volatiles released by mature fruits, twelve compounds elicited a response. The antennae of the oriental fruit moth did respond to isoamyl hexanoate and α-farnesene emitted by “Eva” maturing fruits. In general, virgin females did not respond to volatiles in olfactometer bioassays and mated females were attracted to volatiles released by mature fruits. Our results show that the variation in the emission during the maturation of fruits can influence the orientation of G. molesta.     

Herbivore- and MeJA-induced volatile emissions from the redroot pigweed <Emphasis Type="Italic">Amaranthus retroflexus</Emphasis> Linnaeus: their roles in attracting <Emphasis Type="Italic">Microplitis mediator</Emphasis> (Haliday) parasitoids

The redroot pigweed Amaranthus retroflexus Linnaeus (Caryophyllales: Amaranthaceae), an annual weed, is a host plant of the cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Microplitis mediator (Haliday) (Hymenoptera: Braconidae) is a parasitoid of H. armigera. Here, the electrophysiological and behavioral responses of M. mediator to induced redroot pigweed volatiles were investigated. Female parasitoids were significantly attracted to odors from plants induced by H. armigera damage, H. armigera continuous feeding, and 10 mM methyl jasmonate (MeJA) spray. The gas chromatography–mass spectrometry (GC–MS) results demonstrated that there were significant changes in volatiles from these three treatments in comparison with the control. When the constitutive compound 6-methyl-5-hepten-2-one was emitted in significant amounts from treated plants, it could elicit a medium electrophysiological response (0.2?≤?value?<?0.8) , a significant behavioral response of M. mediator females. β-Elemene, emitted from two treatments (plants damaged by H. armigera, plants with H. armigera continuous feeding), showed a very weak electrophysiological response (value?<?0.2), but was significantly attractive to M. mediator. The results showed that 6-methyl-5-hepten-2-one and β-elemene might play important roles in mediating the foraging behavior of M. mediator. Further work will be conducted to evaluate the function of these two compounds under semi-field and field conditions and exploit them as attractants for M. mediator to control H. armigera.