Chemical composition of sex pheromone of oriental fruit moth and rates of release by individual female moths

Role of plant volatiles and hetero-specific pheromone components in the wind tunnel response of male Grapholita molesta (Lepidoptera: Tortricidae) to modified sex pheromone blends

Female Grapholita molesta (Busck) release a pheromone blend composed of two stereoisomeric acetates (Z8-12:Ac and E8-12:Ac), which in a 100:6 ratio stimulate maximum conspecific male approach. Z8-12:OH is described as a third pheromone component that increases responses to the acetate blend. Departures from the optimal pheromone blend ratio, or too high or low pheromone doses of the optimal blend ratio, result in lower male response. In a previous study, we show that plant volatiles synergize male response to a suboptimal-low pheromone concentration. In the present study, we show that the plant blend does not synergize male response to a suboptimal-high pheromone dose. The plant blend, however, synergized male response to pheromone blends containing unnatural Z:E-acetate isomer ratios. We revisited the role of alcohols in the pheromone response of G. molesta by replacing Z8-12:OH with conspecific and heterospecific pheromone alcohols or with plant odors. Codlemone, the alcohol sex pheromone of Cydia pomonella L., E8, E10-12:OH, did supplant the role of Z8-12:OH, and so did the plant volatile blend. Dodecenol (12:OH), which has been described as a fourth pheromone component of G. molesta, also increased responses, but not as much as Z8-12:OH, codlemone or the plant blend. Our results reveal new functions for plant volatiles on moth sex pheromone response under laboratory conditions, and shed new light on the role of alcohol ingredients in the pheromone blend of G. molesta.

Measure your septa release ratios: pheromone release ratio variability affected by rubber septa and solvent

The type of solvent and the volume used to load pheromone components onto rubber septa had significant effects on pheromone release ratios, the variability of those release ratios, and the recoverability of the volatile components during subsequent extraction with hexane. Volatile release ratios of synthetic Oriental fruit moth (OFM) pheromone and additional volatile compounds were determined using a gas chromatograph column as a volatile trap for rapid (≤1 hr) analysis from individual rubber septa. Volatile compound solutions were prepared in hexane, pentane, CH2Cl2, and methyl tert-butyl ether, and a 10, 33, or 100 μl aliquot of each solution was applied to rubber septa. Septa loaded with 100 μl of CH2Cl2 emitted significantly (P < 0.05) higher alcohol: acetate (OH:Ac) ratios than septa loaded with the other solvents, which were all similar. Release ratios of the alcohol and acetate components of the OFM pheromone components were assessed over a 3 week period using septa loaded with each solvent. Regardless of loading solvent, the OFM OH:Ac ratios declined logarithmically over 3 weeks; however, the decay slope from septa loaded with CH2Cl2 solutions was different from those of the other three solvents, which were nearly all the same. A high variability in OH:Ac release ratios was measured overall, regardless of the solvent used or the volume it was applied in. Four compounds of near-equal mass: 1-dodecanol, 1-dodecanal, methyl decanoate, and tridecane emitted different release ratios dependent on the solvent, hexane or CH2Cl2, with which a septum was loaded. The more polar and the greater the mass of the test compound, the slower it was emitted from a septum regardless of solvent. These combined results plus comparisons to earlier reports, suggest that researchers should empirically assess the release ratios from septa to be used in bioassays rather than just reporting the type of septum, ratios of compounds applied and solvent used to prepare them.

Similar worldwide patterns in the sex pheromone signal and response in the oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae)

The response of Grapholita molesta (Busck) males to three-component sex pheromone blends containing a 100% ratio of the major sex pheromone component, (Z)-8-dodecenyl acetate and a 10% ratio of (Z)-8-dodecenol, but with varying ratios of (E)-8-dodecenyl acetate (0.4, 5.4, 10.4, 30.4, and 100.1% E-blends) was tested with populations in eight stone and pome fruit orchards in Europe, Asia, and North and South America. Traps baited with the 5.4% E-blend caught significantly more males than traps with any other blend with all populations. Significantly more males were caught in traps baited with the 10.4% E-blend than in traps with the remaining blends, except with the 0.4% E-blend in Turkey. Significant differences in male moth catches occurred between the other blends with the 0.4>30.4% E-blend, and the 30.4>100.1% E-blend. Male moth catches with the 100.1% E-blend only differed from the hexane control in Chile. No apparent differences were noted to these blends in populations collected from pome or stone fruits. Flight tunnel assays to synthetic blends with a subset of populations were similar to the field results, but the breadth of the most attractive E-blends was wider. Flight tunnel assays also demonstrated a high level of male-female cross-attraction among field-collected populations. Female gland extracts from field-collected populations did not show any significant variation in their three-component blends. The only exceptions in these assays were that long-term laboratory populations were less responsive and attractive, and produced different blend ratios of the two minor components than recently collected field populations.

Disruption of male oriental fruit moth to calling females in a wind tunnel by different concentrations of synthetic pheromone

Disruption of male Oriental fruit moth orientation to calling females was studied in a wind tunnel by surrounding calling female moths with septa loaded with synthetic pheromone. At the lowest loadings, 0.01 and 0.1µg, which produced release rates well below those of calling females, some males flew to septa instead of the females. At loadings of 1 and 10µg, which produced release rates close to those of a calling female, more than half the males flew to septa instead of the females, but there was little evidence of habituation at any of these loadings. At higher loadings, 100 and 1000µg, upwind flight of males was arrested, and many males remained inactive, indicating habituation. Preexposure of the males for 3 hr to ambient pheromone concentrations in the tunnel had no significant effect on numbers of disrupted males. However, at the 1000-µg loading, most of the males that had been preexposed to the synthetic pheromone remained inactive. This may indicate a higher level of habituation than among males that had not been preexposed, most of which flew, although they subsequently showed flight arrestment. Levels of disruption were similar to those found for the spruce budworm in comparable experiments. In both species, less than 1% of the males were able to locate females when time-averaged concentrations of synthetic pheromone were above 20 ng/m(3). However, levels of inactivity and flight arrestment were higher among male Oriental fruit moths than among male spruce budworms, which may explain why Oriental fruit moths are more susceptible to disruption than are spruce budworms.

Plant odour plumes as mediators of plant-insect interactions

Insect olfactory orientation along odour plumes has been studied intensively with respect to pheromonal communication, whereas little knowledge is available on how plant odour plumes (POPs) affect olfactory searching by an insect for its host plants. The primary objective of this review is to examine the role of POPs in the attraction of insects. First, we consider parameters of an odour source and the environment which determine the size, shape and structure of an odour plume, and we apply that knowledge to POPs. Second, we compare characteristics of insect pheromonal plumes and POPs. We propose a 'POP concept' for the olfactory orientation of insects to plants. We suggest that: (i) an insect recognises a POP by means of plant volatile components that are encountered in concentrations higher than a threshold detection limit and that occur in a qualitative and quantitative blend indicating a resource; (ii) perception of the fine structure of a POP enables an insect to distinguish a POP from an unspecific odorous background and other interfering plumes; and (iii) an insect can follow several POPs to their sources, and may leave the track of one POP and switch to another one if this conveys a signal with higher reliability or indicates a more suitable resource. The POP concept proposed here may be a useful tool for research in olfactory-mediated plant-insect interactions.

Evolution of insect olfaction

Neuroethology utilizes a wide range of multidisciplinary approaches to decipher neural correlates of natural behaviors associated with an animal's ecological niche. By placing emphasis on comparative analyses of adaptive and evolutionary trends across species, a neuroethological perspective is uniquely suited to uncovering general organizational and biological principles that shape the function and anatomy of the nervous system. In this review, we focus on the application of neuroethological principles in the study of insect olfaction and discuss how ecological environment and other selective pressures influence the development of insect olfactory neurobiology, not only informing our understanding of olfactory evolution but also providing broader insights into sensory processing.

Cryoprotection in dampwood termites (Termopsidae, Isoptera)

In contrast to the majority of the Order, the dampwood termites of the family Termopsidae found in colder regions can experience frost and snow, either in cool temperate areas at high latitudes (45 degrees ), or alpine areas at high elevations (>1000m). This suggests that dampwood termites are adapted to cold climates. We investigated this hypothesis in two dampwood termites, Porotermes adamsoni Froggatt and Stolotermes victoriensis Hill. We measured nest temperatures and atmospheric temperatures of their alpine habitat during winter, and measured survival and recovery at subzero temperatures. We also determined the minimum temperature at which these species remain active and the LT50 values. We used a novel gas chromatographic strategy to examine eight metabolites from individuals of both species collected in winter and summer to identify possible cryoprotectants. Both P. adamsoni and S. victoriensis had significantly higher levels of trehalose, a known cryoprotectant, in winter than in summer; in addition S. victoriensis also had higher levels of unsaturated fatty acid ligands in winter than in summer, consistent with patterns observed for cold adaptation in other organisms. These results are the first to reveal that dampwood termites are adapted to cold climates and use trehalose and unsaturated lipids as cryoprotectants.

Isolation, identification and field tests of the sex pheromone of the carambola fruit borer, Eucosma notanthes

Two components, (Z)-8-dodecenyl acetate (Z8-12:Ac) and (Z)-8-dodecenol (Z8-12:OH), were isolated from sex pheromone glands of the carambola fruit borer, Eucosma notanthes, and were identified by GC, and GC-MS, chemical derivatization, and comparison of retention times. The ratio of the alcohol to acetate in the sex pheromone extracts was 2.7. However, synthetic mixtures (1 mg) in ratios ranging from 0.5 to 1.5 were more effective than other blends in trapping male moths in field tests.

Effects of residues of deltamethrin in cattle faeces on the development and survival of three species of dung-breeding insect

OBJECTIVE

To assess the toxicity to insects of drug residues excreted in cattle faeces following treatment with deltamethrin.

DESIGN

Bioassays were performed on one species of dung-breeding fly (Musca vetustissima) and two species of dung beetle (Onthophagus binodis and Euoniticellus fulvus).

ANIMALS

Cattle on properties near Kangaroo Valley, Canberra and Gundagai were treated with pour-on formulations of deltamethrin. Untreated animals acted as controls.

PROCEDURES

Faeces from treated and untreated cattle were inoculated with newly emerged fly larvae or fed to adults of two species of dung beetle. Percentage survival and duration of development provided measures of the toxicity of deltamethrin residues in faeces.

RESULTS

Residues of deltamethrin were excreted in concentrations sufficient to inhibit survival of larvae of M vetustissima for 1 to 2 weeks after treatment. Peak concentrations of 0.4 mg deltamethrin/kg dry weight of faeces occurred 3 days after treatment and were sufficient to kill adult beetles for at least twice this period. With one of two formulations tested, there was evidence of a reduction in dung beetle fecundity and an increase in the duration of juvenile development. A model of the effect of deltamethrin on the breeding success of dung beetles in the field suggests that a single treatment, applied when most of the population is in a nonparous condition, may cause up to 75% reduction in beetle activity by the end of the season. Multiple treatments at 10 or 21 day intervals may drive local populations towards extinction.

CONCLUSION

Depending on the time and frequency of treatment, the effect of deltamethrin on insects in cattle faeces may range from negligible to catastrophic.

New mimics of the acetate function in pheromone-based attraction

Several analogues of (Z)-8-dodecenyl acetate (1a), the major pheromone component of the Oriental fruit moth, Cydia molesta, with chloroformate and lactone functional groups in place of the acetate moiety, were synthesized and investigated for their biological activity at four evaluation levels, i.e. by electroantennography (EAG), electrosensillography (ESG), short-range sexual stimulation and activation in the flight-tunnel. We found very strict requirements on the shape as well as on the electron distribution of the acetate group for a productive interaction with the receptor. The behavioral results showed that, among the analogues investigated, the chloroformate 1b, alken-4-olide 2a and also dodecyl acetate (1c) possess significant (60-85%) inhibitory activities. Based on electrophysiological evidence demonstrating that (i) only 1b is competing with the major pheromone component 1a for the same receptor sites on the male antennal sensilla, (ii) 1c elicits moderate EAG but no ESG responses and (iii) 2a does not produce any electrophysiological response at all, three possible inhibitory mechanisms by which these analogues are acting could be distinguished.

Identification and quantification of juvenile hormone biosynthesized by larval and adult Australian sheep blowfly Lucilia cuprina (Diptera: Calliphoridae)

Recent evidence indicates that higher dipterans biosynthesize predominantly the novel juvenile hormone (JH) bisepoxide, methyl (2E,6trans)-6,7,10,11-bisepoxy-3,7,11-trimethyl-2-dodecen oate (JHB3), together with a small proportion of methyl (2E,6E)-10,11-epoxy-3,7,11-trimethyl-2,6-dodecadienoate (JHIII) and possibly its 6,7-epoxy isomer. A strategy of gas chromatography-mass spectrometry (GC-MS) involving cool on-column GC and negative-ion chemical ionization MS has enabled the selective analysis of underivatized JH-like products released in vitro by ring glands and corpora allata of Lucilia cuprina. JHB3 is released to the exclusion of mono-epoxidized and unepoxidized esters. The rate of JHB3 release in adult females increases dramatically after protein feeding from 0.2 to 5.2 pmol/h/gland. Values agree well with the rate of JH biosynthesis determined by radiochemical assay. As revealed by thin-layer chromatography, the radiolabel is predominantly incorporated into JHB3, of which only 2% is retained in the corpus allatum indicating almost immediate release from the gland. Approximately 5% of radioactive material retained in the glands co-migrates with JHIII and may be an intermediate in JHB3 synthesis. We conclude that JHB3 is the only juvenile hormone biosynthesized in vitro by L. cuprina. The data suggest that JHB3 may be the exclusive JH synthesized by higher dipterans.