Female-produced Sex Pheromone Research Articles

Identification of the Sex Pheromone of the Asparagus Moth, Parahypopta Caestrum (Lepidoptera, Cossidae).

Chemical, electrophysiological, and field trapping experiments were carried out to identify the female-produced sex pheromone of the asparagus moth, Parahypopta caestrum, a very serious pests of asparagus cultivations in southern Europe. Gas chromatography coupled with mass spectrometry and electroantennogram detection (GC-MS-EAD) analysis of hexane and solid-phase microextraction (SPME) extracts of sex pheromone glands of calling females consistently detected four compounds eliciting EAG responses in male moth antennae. According to their GC retention times, mass spectra, and comparative EAG analyses with reference standards, these EAD-active compounds were identified as (Z)-9-tetradecenol (Z9-14:OH), (Z)-5-tetradecenyl acetate (Z5-14:Ac), (Z)-7-tetradecenyl acetate (Z7-14:Ac), and (Z)-9-tetradecenyl acetate (Z9-14:Ac), respectively. In the SPME extracts from the head-space of individual abdominal tips, Z9-14:Ac, Z5-14:Ac, Z7-14:Ac, and Z9:14 OH were detected in the ratio of 82:9:5:4. In EAG dose-response experiments, Z9-14:Ac was the strongest antennal stimulant at different doses tested. In field trapping experiments, Z9-14:Ac, Z7-14:Ac, and Z5-14:Ac proven to be essential for male attraction and a their 85:5:10 blend loaded onto green rubber septum dispensers was significantly more effective than single-, two-, and any other three-component blend of these compounds. The addition of Z9-14:OH to the optimal blend resulted in a significant reduction of male catches. The attractive blend here identified allowed for an effective and accurate monitoring of P. caestrum flight activity in southern Italy.

Identification, synthesis, and field evaluation of components of the female-produced sex pheromone of Helopeltis cinchonae (Hemiptera: Miridae), an emerging pest of tea.

Helopeltis cinchonae (Hemiptera: Miridae) is a major pest of tea plantations in Asia. Conventional control of pests with pesticides is unsustainable. Therefore, safe and eco-friendly alternatives, such as pheromones, are required to manage the pest. In gas chromatography-electroantennographic detection (GC-EAD) analysis of whole-body extracts of virgin female H. cinchonae, two compounds elicited electroantennogram (EAG) responses from male antennae. These were identified as hexyl (R)-3-acetoxybutyrate and (R)-1-acetoxy-5-butyroxyhexane using gas chromatography-mass spectrometry (GC-MS) analysis compared to synthetic compounds. This is the first study to report 1-acetoxy-5-butyroxyhexane as an insect pheromone component. The synthetic compounds elicited dose-dependent EAG responses from the antennae of male H. cinchonae. In two field trapping experiments, the individual compounds were highly attractive to male H. cinchonae when dispensed from polyethylene vials. However, higher catches were obtained with blends of the two compounds in a 1:10 ratio. The blend of racemic compounds was as attractive as the blend of (R)-enantiomers. We reported that 1-acetoxy-5-butyroxyhexane and hexyl 3-acetoxybutyrate are components of the female-produced sex pheromone of H. cinchonae, but further work is required on the blend and loading of pheromone and on trap design to provide an optimized system for monitoring and control of this pest. The results may also facilitate the identification of the pheromones of other Helopeltis species, which are major pests in many crops. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Gymnandrosoma aurantianum (Lepidoptera: Tortricidae): Calling Rhythm and Effect of Age on Female Sex Pheromone Titer and Male Antennal Responses.

The macadamia nut borer, Gymnandrosoma aurantianum Lima (Lepidoptera: Tortricidae), is the main pest of Macadamia integrifolia Maiden & Betche (Proteales: Proteaceae) in Central America. Despite its importance, there is little information on its reproductive behavior. We studied the calling behavior and effect of age on female sex pheromone production and male antennal response to the pheromone. Calling behavior of G. aurantianum females occurred at the onset of scotophase, between 17:00 and 20:00h. The mean time spent calling was 64min. It was observed that 30% of the 50 females exhibited a calling posture characterized by extrusion of the pheromone gland from the tip of the abdomen and they spread their wings slightly. Female age had no influence on the sex pheromone production, while male antennal response increased with age and pheromone dosage. The information obtained in this work contributes to understanding the sexual behavior of G. aurantianum and thus to the creation of strategies to control this important pest in macadamia.

Early Season Monitoring of Tarnished Plant Bug, Lygus lineolaris, in Wild Hosts Using Pheromone Traps.

The tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), has a wide host range of over 700 plant species, including 130 crops of economic importance. During early spring, managing the field edges with weeds and other wild hosts is important in preventing early-season infestations of L. lineolaris in cotton to prevent damage to the squares and other fruiting structures. Scouting fields for L. lineolaris is time- and labor-intensive, and end-user variability associated with field sampling can lead to inaccuracies. Insect traps that combine visual cues and pheromones are more accurate, sustainable, and economically feasible in contrast to traditional insect detection methods. In this study, we investigated the application of red or white sticky cards baited with the female-produced sex pheromone to monitor overwintering L. lineolaris populations in early spring. Field experiments demonstrated that the red sticky cards baited with a pheromone blend containing hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal in 4:10:7 ratio are highly effective in trapping L. lineolaris adults in early spring before the row crops are planted, and in monitoring their movement into a cotton crop. The monitoring of L. lineolaris should help growers to make judicious decisions on insecticide applications to control early pest infestations, thereby reducing economic damage to cotton.

Pheromone and Host Plant Odor Detection in Eastern Spruce Budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae).

Spruce budworm, Choristoneura fumiferana Clemens, is an ecologically significant defoliator of spruce and balsam fir in North America. Optimization of semiochemical-mediated control is needed to improve the existing integrated pest management systems such as mating disruption and population estimation. This study used single sensillum recordings (SSR) to identify the responses of olfactory receptor neurons (ORNs) in the antennal sensilla of adult male and female C. fumiferana to host plant volatiles, and female sex pheromones. There have been few SSR studies done on spruce budworm, and to our knowledge, the present study represents the first attempt to examine the responses of ORNs from antennal sensilla in response to a range of host and conspecific stimuli. A total of 86 sensilla were characterized and sorted into 15 possible sensillum categories based on odor responses. We observed that specialist sensilla responding to few ligands were more abundant in both male and female than sensilla exhibiting more generalized odorant responses. (E/Z)-11-tetradecenal elicited responses from ORNs from any sensilla which were sensitive to pheromones in both males and females. Female C. fumiferana ORNs were able to detect and physiologically respond to female-produced sex pheromones with the same degree of sensitivity as their male counterparts. Together, these data improve our knowledge of mechanisms by which adult budworms respond to pheromone and host plant volatiles and provide insights that may be complementary to existing integrated pest management (IPM) strategies based on the chemical ecology of spruce budworm.

Post-fumigation sub-lethal activities of phosphine and ethyl formate on survivorship, fertility and female sex pheromone production of Callosobruchus chinensis (L.)

Phosphine (PH3) and ethyl formate (EF), the two popular fumigant disinfectants of stored product insect pests, are primarily evaluated for their knock down effects without considering their post-fumigation sub-lethal activities. The sub-lethal activities (adult survivorship, fecundity, sterility and female sex pheromone production) of the fumigants were evaluated on a field-to-storage insect pest adzuki bean beetle, Callosobruchus chinensis (L.). The adults’ survivorship and female fecundity, both were dose-dependently affected by sub-lethal PH3 and EF fumigation exposures. Hatchability of the eggs laid by fumigated female adults were also significantly affected. Gas-chromatography mass-spectrometry analysis of solid-phase micro-extraction from virgin fumigated C. cinensis females revealed that the PH3 LC25 (the lethal concentration required to kill the 25% of the population) fumigated female C. chinensis released significantly less amount of the pheromone components. In contrast, EF LC25 exposure did not affect the pheromone release. This study unveils the facts that the EF and PH3 fumigation have detrimental bioactivities against C. chinensis. Notably, this suggests to consider the sub-lethal EF and PH3 fumigation rather than the dose required to instantly kill all the C. chinensis individuals for disinfestation of stored adzuki bean.

Spotted cucumber beetle/southern corn rootworm: profile of a polyphagous native pest

Abstract Spotted cucumber beetle, Diabrotica undecimpunctata (Coleoptera: Chrysomelidae), a North American native leaf beetle species also known as southern corn rootworm (SCRW), is a polyphagous pest of various crops including cucurbits (Cucurbitaceae), corn (Zea mays), soybeans (Glycine max), snap beans (Phaseolus vulgaris), peanut (Arachis hypogaea), and sweetpotato (Ipomoea batatas). Larvae are below-ground pests of corn, sorghum (Sorghum spp.), peanut, and sweetpotato. Adult damage impacts cucurbits by damage to seedlings and fruit and transmission of bacterial wilt (causal agent Erwinia tracheiphila) by eastern populations. Adult feeding also damages fresh market beans and occasionally leafy and fruiting vegetables. Damage on many other crops such as field soybeans, dry beans, and sorghum, is often cosmetic and/or inconsequential. Adults overwinter in mild climates and spread seasonally northward, with multiple generations and populations increasing into the late summer. Diverse natural enemies attack all stages, but their ecology and impact are poorly known, particularly below ground. A female-produced sex pheromone and floral volatiles are known attractants, and cucurbitacins (bitter phytochemicals) are feeding stimulants, offering potential selective behavioral control. Management practices are directed against pest complexes, including other below- and above-ground pests, depending on the crop. Chemical controls are soil-applied for protection from root-feeding larvae, systemic seed treatments for early-state crop feeding, and broadcast application in fruiting cucurbits and beans. Action thresholds and monitoring are not well developed. Cultural controls include field and cultivar choice, row covers in high-value crops, and available crop resistance. The wide host range, abundance, and mobility of adults make prediction and monitoring challenging.

Components of the Female Sex Pheromone of the Newly-Described Canola Flower Midge, Contarinia brassicola

The canola flower midge, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), is a newly-described species that induces galls on canola, Brassica napus Linnaeus and Brassica rapa Linnaeus (Brassicaceae). Identification of the sex pheromone of C. brassicola is essential to developing monitoring tools to elucidate the geographic range and hosts of this new pest, and the extent to which it threatens the $30 billion Canadian canola industry. The aim of this study was to identify and synthesize the female-produced sex pheromone of C. brassicola and demonstrate its effectiveness in attracting males to traps in the field. Two peaks were identified through GC-EAG analysis of female-produced volatiles which elicited electrophysiological responses in male antennae. These peaks were initially characterized through GC–MS and synthesis as 2,7-diacetoxynonane (major component) and 2-acetoxynonane (minor component), and the racemic compounds elicited EAG responses in male antennae. All four stereoisomers of 2,7-diacetoxynonane were synthesized and the naturally-produced compound was shown to be primarily the (2R,7S)-isomer by analysis on an enantioselective GC column, with a small amount of (2R,7R)-2,7-diacetoxynonane also present. The configuration of the minor component could not be determined because of the small amount present, but this was assumed to be (2R)-2-acetoxynonane by comparison with the configuration of the other two components. In field trials, none of the four stereoisomers of 2,7-diacetoxynonane, presented individually or as a racemic mixture, was attractive to male C. brassicola. However, dispensers loaded with a 10 µg:1 µg blend of (2R,7S)- and (2R,7R)-2,7-diacetoxynonane caught large numbers of male C. brassicola and significantly more than other blends tested. The addition of 0.5 µg of (2R)-2-acetoxynonane to this blend further increased the number of males caught. In future work, we will seek to identify the optimum trapping protocol for the application of the pheromone in monitoring and surveillance.

A new synthesis of (Z,Z)-11,11-dimethoxy-6,9-heneicosadiene and 2-((Z,Z)-1,4-decadienyl)-2-ndecyl-1,3-dioxolane, precursors of (Z,Z)-6,9-heneicosadien-11-one, a pheromone component of the whitemarked tussock moth, Orgyia leucostigma (J.E. Smith) (Lepidoptera: Erebidae)

The straightforward synthesis of two long-chain diene ketals, (Z,Z)-11,11-dimethoxy-6,9-heneicosadiene and 2-ndecyl-2-((Z,Z)-1,4-decadienyl)-1,3-dioxolane, is described. These two ketals are synthetic propheromones, or pheromone precursors, of the whitemarked tussock moth (WMTM, Orgyia leucostigma (J.E. Smith) (Lepidoptera: Erebidae)), whose unstable female-produced sex pheromone component, (Z,Z)-6,9-heneicosadien-11-one, lasts only 1–2 days in traps in the field. The two propheromones were synthesized by terminal alkyne/propargylic bromide couplings, facilitated by cesium carbonate, which assembled the 21-carbon chains with skipped diynes. Semi-reduction of the diynes gave the requisite dienes. These two diene ketals were then formulated into lures, which converted them in situ into the attractive (Z,Z)-6,9-heneicosadien-11-one. The performance of these lures is briefly described.

Both male- and female-produced pheromones influence Colorado potato beetle movement in the field.

Colorado potato beetle [Leptinotarsa decemlineata (Say); Coleoptera: Chrysomelidae] is a widespread key pest of potatoes and other solanaceous crops of the temperate Northern Hemisphere. Its evolution of multiple pesticide resistance is a continuing threat if chemical control is relied upon for pest management. An integrated approach including semiochemicals and other non-pesticidal tactics is essential to sustainable management. In addition to the known volatile aggregation pheromone produced by male adult beetles that is attractive to both females and males, there is a yet-unidentified female-produced sex pheromone. Using caged 'bait plants' in the field in Maryland, USA, we tested the attraction of male and female beetles to groups of male-only, female-only, larvae, and uninfested bait plants. Results of five field experiments demonstrate that the female-produced sex pheromone is attractive to male beetles, whereas the male-produced pheromone is attractive to both females and males. Male attraction increased with higher densities of females on bait plants, but female attraction did not change with female density on bait plants. This is the first study to demonstrate male attraction to the female sex pheromone in the field, and to our knowledge, the first to demonstrate a beetle species using bidirectional communication between males and females. Use of semiochemicals for monitoring and management of Colorado potato beetle should consider male-, female-, as well as plant-produced volatiles as important tools for pest manipulation in potato integrated pest management. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Electrophysiological and Behavioral Responses of Dasychira baibarana (Lepidoptera: Lymantriidae) to Tea Plant Volatiles.

Tea black tussock moth, Dasychira baibarana (Matsumura) (Lepidoptera: Lymantriidae), is a devastating pest species of the tea plant in China. Here, we evaluated the responses of D. baibarana to tea plant volatiles using gas chromatography coupled electroantennographic detection (GC-EAD), eleclectroantennography (EAG), and a Y-tube olfactometer. In total, 11 of 18 analyzed compounds elicited GC-EAD responses from test insects. GC-EAD bio-active compounds were further investigated using EAG and behavioral responses. In the EAG analysis, male moths had significantly greater responses to four compounds [(Z)-3-hexenyl butyrate, (Z)-3-hexen-1-ol, ocimene and benzyl alcohol] than female moths. For females, maximum EAG amplitudes, were recorded in response to linalool, (Z)-3-hexenyl hexanoate and (Z)-jasmone. In EAG and behavioral bio-assays, the responses of both sexes were dose independent. In behavioral bio-assays male moths responding significantly to (Z)-3-hexen-1-ol, ocimene, (Z)-3-hexenyl butyrate, linalool, benzyl alcohol, and (Z)-jasmone at various concentrations. For females, significant behavioral responses were observed to (Z)-3-hexenyl hexanoate, followed by (Z)-jasmone, linalool, ocimene, and benzyl alcohol. However, neither sex was sensitive to 4 of the 11 tested compounds, phenyethyl alcohol, phenylacetonitrile, (E)-nerolidol, and indole. The present results showed that tea plant volatiles influenced the behavior of D. baibarana moths, which will greatly contribute in developing eco-friendly control strategies for D. baibarana, through the application of a blend of compounds that showed significant EAG and behavioral responses or a blend combined with female-produced sex pheromones.

Limoniic Acid - Major Component of the Sex Pheromones of the Click Beetles Limonius canus and L. californicus.

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are soil-dwelling insect pests inflicting major economic damage on many types of agricultural crops worldwide. The objective of this work was to identify the female-produced sex pheromones of the Pacific Coast wireworm, Limonius canus LeConte, and the sugarbeet wireworm, L. californicus (Mannerheim) (Coleoptera: Elateridae). Headspace volatiles from separate groups of female L. canus and L. californicus were collected on Porapak Q and analyzed by gas chromatography with electroantennographic detection (GC-EAD) and GC-mass spectrometry. GC-EAD recordings revealed strong responses from male L. canus and male L. californicus antennae to the same compound, which appeared below GC detection threshold. The structure of this candidate pheromone component was deduced from the results of micro-analytical treatments of extracts, retention index calculations on four GC columns, and by syntheses of more than 25 model compounds which were assessed for their GC retention characteristics and electrophysiological activity. The EAD-active compound was identified as (E)-4-ethyloct-4-enoic acid, which we name limoniic acid. In field experiments in British Columbia and Alberta, Canada, traps baited with synthetic limoniic acid captured large numbers of male Limonius click beetles, whereas unbaited control traps captured few. Compared to traps baited with the analogue, (E)-5-ethyloct-4-enoic acid, traps baited with limoniic acid captured 9-times more male L. californicus, and 6.5-times more male western field wireworms, L. infuscatus Motschulsky, but 2.3-times fewer male L. canus. Limoniic acid can now be developed for detection, monitoring and possibly control of L. californicus, L. infuscatus and L. canus populations.

Identification of Two Additional Behaviorally Active Gland Constituents of Female Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae)

The sugarcane borer, Diatraea saccharalis (Fabricius), is the major pest insect attacking sugarcane crops in Brazil. Population control by insecticide treatment is not efficient due to simultaneous presence of all developmental stages of the insect throughout the year, and alternative control methods are needed. Two female-produced sex pheromone components, (Z,E)-hexadeca-9,11-dienal and (Z)- hexadec-11-enal, have previously been reported to elicit antennal activity and behavioral response of males in flight tunnel experiments. However, the attractiveness of these compounds in field tests has been very low. In this study, two additional female-produced compounds in D. saccharalis eliciting consistent antennal response in males were identified as (Z)-hexadec-9-enal and hexadecanal. In flight tunnel assays, the behavioral response to a quaternary blend was significantly higher when compared with the previously identified binary blend. Subtracting (Z)-hexadec-9-enal or hexadecanal from the full blend did not reduce attraction, indicating redundancy in the communication channel. We conclude that additional compounds are part of the sex pheromone of D. saccharalis, which may improve the efficiency of trap lures for monitoring of this pest.

Rectal gland exudates and emissions of Bactrocera bryoniae: chemical identification, electrophysiological and pheromonal functions

Bactrocera bryoniae is a polyphagous and economically significant fruit fly found in Indonesia, Papua New Guinea and Australia. To understand chemical-mediated sexual communication, and the potential for novel pheromone-based attractants for monitoring and mass-trapping of B. bryoniae, rectal gland exudates and emissions from sexually mature males and females were investigated. Gas chromatography–mass spectrometry showed that male rectal glands contained six compounds, of which 1,7-dioxaspiro[5,5]undecane elicited electroantennographic (EAD) and electropalpographic (EPD) responses in both sexes, ethyl 3-acetoxybutanoate elicited EPD responses in both sexes, N-(3-methylbutyl)acetamide elicited EAD response from males and 4-hydroxy-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and females and EPD responses in females. Female rectal glands contained 23 compounds with the esters ethyl laurate and ethyl myristate as major components. Amongst the female rectal gland constituents, ethyl laurate, ethyl myristate and ethyl palmitate elicited EAD responses in males and females, N-(3-methylbutyl)acetamide elicited EAD responses in males only, (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane elicited EAD responses in males and EPD responses in females, and 2,7-dimethyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]decane, (E,E)-2-ethyl-8-methyl-1,7-dioxaspiro[5.5]undecane, (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, (E,E)-2-propyl-8-methyl-1,7-dioxaspiro[5.5]undecane and ethyl caprate elicited EPD responses in females only. Y-tube bioassays indicated that male rectal gland extracts and headspace volatiles attracted females and males, while female rectal gland extracts and headspace volatiles only attracted males. The results suggest that ethyl 3-acetoxybutanoate, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male-produced sex pheromone in B. bryoniae while (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, N-(3-methylbutyl)acetamide, ethyl laurate, ethyl myristate and ethyl palmitate may be components of female-produced sex pheromone. Ethyl 3-acetoxybutanoate, N-(3-methylbutyl) acetamide, 1,7-dioxaspiro[5,5]undecane and 4-hydroxy-1,7-dioxaspiro[5.5]undecane may be components of male aggregation pheromone. These findings contribute to the understanding of pheromone communication in B. bryoniae and provide a foundation for developing pheromone-based monitoring and control methods.

Dispersal From Natal Patch Correlates With the Volatility of Female Sex Pheromones in Parasitoid Wasps

Chemical communication via pheromones is considered the oldest and most widespread form of communication in nature. However, the way that the enormous diversity of species-specific pheromones evolved is still of debate. One possible process driving pheromone evolution is the mate-finding and dispersal behavior, as long-distance mate-finding requires highly volatile compounds. In contrast, less volatile compounds might be sufficient attractants in species that search for mates within proximity. In the parasitoid wasp genus Leptopilina, the composition of species-specific sex pheromones ranges from highly volatile iridoid compounds through combinations of iridoids with low volatile cuticular hydrocarbons (CHCs) to only CHCs. To study the selective forces shaping the composition of sex pheromones in Leptopilina, we examined the dispersal behavior, i.e. the proportion of male and female wasps dispersing after emergence, in four species with known sex pheromone compositions. If males and females disperse immediately, long-range mate attraction might become necessary, favoring volatile iridoids over CHCs. If mating occurs directly on the host patch, short-range mate attraction by low volatile CHCs might suffice. Our analyses have revealed that the dispersal behavior of Leptopilina males and females after emergence does indeed differ between species with differently volatile sex pheromones. Specifically, males of species with iridoid sex pheromones start to disperse immediately before their females’ emergence, whereas males of species with CHC sex pheromones delay dispersal until their conspecific females emerge. While the differences in female dispersal behavior turned out to be species-specific, differences in male dispersal correlated with the volatility of female-produced sex pheromones of each species. This study significantly contributes to our understanding of the evolution of sex pheromones by differences in dispersal behavior.

3,7-Dimethylpentadecane: a Novel Sex Pheromone Component from Leucoptera sinuella (Lepidoptera: Lyonetiidae).

Leucoptera sinuella is a leaf-miner moth present in several regions in the world, which has been recently introduced into Chile. The larvae feed exclusively on the leaves of poplar and willow trees, and the damage caused by the feeding behavior poses a threat to the wood-producing industry. Besides, L. sinuella larvae invade nearby orchards for pupation, causing rejections in Chilean fresh fruit for export. Here we report the identification of the female-produced sex pheromone of L. sinuella as a first step towards the development of pheromone-based methods for pest management of this species. First, we analyzed hexane extracts of the abdominal glands of virgin females by gas chromatography coupled with mass spectrometry and identified the major compound in these extracts to be 3,7-dimethylpentadecane, while minor compounds in the extracts proved to be 3,7-dimethyltetradecane and 7-methylpentadecane. Structure assignments were carried out by comparison of retention times and mass spectra of the natural products with those of authentic reference samples. Second, we conducted field tests, which showed that traps baited with synthetic 3,7-dimethylpentadecane were significantly attractive to males in a dose-dependent response. Our results also showed that a mixture of 3,7-dimethylpentadecane, 3,7-dimethyltetradecane, and 7-methylpentadecane in proportions similar to those found in gland extracts was the most attractive lure.

The Effect of Pheromone Synthesis and Gland Retraction on Translocation and Dynamics of Pheromone Release in the Moth Chloridea virescens.

Most species of moths use a female-produced sex pheromone to bring mates together. Typically, sex pheromone is synthesized in a specialized gland and released during the behavior of "calling", in which the ovipositor and gland are extruded, allowing pheromone to evaporate. Although there has been much study on how a gland makes specific pheromone components, we know relatively little about how it actually functions with regard to synthesis, storage and release. In this paper, we investigated three aspects of gland function in the noctuid moth Chloridea virescens (Fabricius): (i) whether translocation of pheromone from site of synthesis to release is dependent on calling or ovipositor movement, (ii) whether pheromone synthesis rate limits release and (iii) how intermittent calling (observed in this and other species) might affect the dynamics of release rate. Firstly, by manipulating the gland to simulate calling (extruded) or non-calling (retracted), we showed that pheromone translocation occurred regardless of whether the gland was retracted or extruded. Secondly, by manipulating pheromone production, we found that females that produced more pheromone had higher release rates. It was especially noticeable that females had a higher release rate at the start of calling, which dropped rapidly and leveled off over time. Together, these data suggest that intermittent calling in C. virescens (and other species) may function to allow females to replenish pheromone stores on the gland surface between calling bouts, so that brief, high release rates occur at the start of a calling bout; thus, potentially increasing a female's chances of attracting a mate.

Female-Produced Sex Pheromone of Tetrastichus planipennisi, a Parasitoid Introduced for Biological Control of the Invasive Emerald Ash Borer, Agrilus planipennis.

The Asian eulophid wasp Tetrastichus planipennisi is being released in North America as a biocontrol agent for the emerald ash borer (Agrilus planipennis), a very destructive invasive buprestid beetle that is devastating ash trees (Fraxinus spp.). We identified, synthesized, and tested a female-produced sex pheromone for the wasp. The key component eliciting behavioral responses from male wasps in flight tunnel bioassays was identified as (6S,10S)-(2E,4E,8E)-4,6,8,10-tetramethyltrideca-2,4,8-triene. Female specificity was demonstrated by gas chromatographic (GC) comparison of male and female volatile emissions and whole body extracts. The identification was aided by coupled gas chromatography/mass spectrometry analysis, microchemical reactions, NMR, GC analyses with a chiral stationary phase column, and matching GC retention times and mass spectra with those of synthetic standards. The tetramethyl-triene hydrocarbon was synthesized as a mixture of two enantiomeric pairs of diastereomers, and as the pure insect-produced stereoisomer. In flight-tunnel bioassays, males responded to both the natural pheromone and the chiral synthetic material by upwind flight and landing on the source. In contrast, the mixture of four stereoisomers was not attractive, indicating that one or more of the "unnatural" stereoisomers antagonized attraction. Field trials, using yellow pan traps baited with natural pheromone, captured significantly more male wasps than control traps over a four week trial. The identified pheromone could increase the efficiency and specificity of the current detection methods for Tetrastichus planipennisi and aid in the determination of parasitoid establishment at release sites.

Male Colorado potato beetles alter search behavior in response to prior female presence on potato plants

For Colorado potato beetle, an integrated approach including semiochemicals and other nonpesticidal tactics is essential to sustainable management. A volatile aggregation pheromone produced by male adult beetles is attractive to both females and males. Yet earlier research also indicates that males respond to a yet-unidentified female-produced sex pheromone. We investigated male Colorado potato beetle behavior on potato plants that had been exposed to females only, males only, mixed-sex groups, or no beetles (clean plants). During observation, these plants hosted no beetles except for the single experimental male beetle. These males (previously mated or unmated) responded very differently to female-exposed plants, spending longer time on these plants, undertaking characteristic active searching behavior, exploring more leaves per plant, and moving more rapidly between leaves, compared to male-exposed or unexposed plants. When presented with a three-way choice, males spent about five times longer on the female-exposed foliage, compared to either male-exposed or clean leaves. Searching parameters differed between mated and unmated males, but both showed similar reactions to female-exposed plants; there was little to no statistical interaction between male mated condition and plant treatment. Results strongly indicate the presence of a persistent female-produced pheromone significantly influencing male searching behavior and between-plant movement.

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.