Yunfan Zou

The Influence of Host Plant Volatiles on the Attraction of Longhorn Beetles to Pheromones.

Host plant volatiles have been shown to strongly synergize the attraction of some longhorn beetle species (Coleoptera: Cerambycidae) to their pheromones. This synergism is well documented among species that infest conifers, but less so for angiosperm-infesting species. To explore the extent of this phenomenon in the Cerambycidae, we first tested the responses of a cerambycid community to a generic pheromone blend in the presence or absence of chipped material from host plants as a source of host volatiles. In the second phase, blends of oak and conifer volatiles were reconstructed, and tested at low, medium, and high release rates with the pheromone blend. For conifer-infesting species in the subfamilies Spondylidinae and Lamiinae, conifer volatiles released at the high rate synergized attraction of some species to the pheromone blend. When comparing high-release rate conifer blend with high-release rate α-pinene as a single component, species responses varied, with Asemum nitidum LeConte being most attracted to pheromones plus α-pinene, whereas Neospondylis upiformis (Mannerheim) were most attracted to pheromones plus conifer blend and ethanol. For oak-infesting species in the subfamily Cerambycinae, with the exception of Phymatodes grandis Casey, which were most attracted to pheromones plus ethanol, neither synthetic oak blend nor ethanol increased attraction to pheromones. The results indicate that the responses to combinations of pheromones with host plant volatiles varied from synergistic to antagonistic, depending on beetle species. Release rates of host plant volatiles also were important, with some high release rates being antagonistic for oak-infesting species, but acting synergistically for conifer-infesting species.

Synthesis of the pheromone of the longtailed mealybug, a sterically congested, irregular monoterpenoid.

A straightforward and scaleable synthesis of the sterically congested pheromone of the longtailed mealybug, with two adjacent quarternary carbons in a cyclopentene ring, was accomplished in 13.5% overall yield. Key steps included regiospecific cyclization of an alpha-diazo-beta-ketoester to build the cyclopentane ring, followed by reduction of the enol triflate of the ketone to place the double bond.

Identification of a pheromone component and a critical synergist for the invasive beetle callidiellum rufipenne (coleoptera: Cerambycidae)

Abstract The invasive Asian cerambycid beetle Callidiellum rufipenne (Motschulsky), informally known as the Japanese cedar longhorned beetle, was first detected in North America in North Carolina in 1997. The beetle has since been detected in neighboring states and is expected to further expand its range. However, delineating the current distribution of C. rufipenne has been hindered by the lack of efficient sampling methods. Here, we present the results of research on the chemistry of volatile pheromones of C. rufipenne. Analyses of headspace odors revealed that males produce (R)-3-hydroxyhexan-2-one, with lesser amounts of (S)-3-hydroxyhexan-2-one, and (R)- and (S)-2-hydroxyhexan-3-one. In field bioassays conducted over several years in Connecticut, where populations of the beetle were well established, no reconstructed blend of these compounds was significantly attractive to beetles of either sex. However, during field trials in Japan that targeted another species, we discovered that adult male and female C. rufipenne were attracted to a blend of racemic 3-hydroxyhexan-2-one and a novel natural product, 1-(1H-pyrrol-2-yl)-1,2-propanedione. Attraction to (R)-3-hydroxyhexan-2-one and the pyrrole subsequently was confirmed in field trials in Connecticut. Although it is unclear why the pyrrole acts as a synergist for a species that apparently does not produce it, the serendipitous discovery that adult C. rufipenne are attracted by the blend of ketone and pyrrole provides a badly needed method for monitoring its ongoing range expansion within North America, and for detecting new introductions in other parts of the world.

Field optimization of the sex pheromone of Stenoma catenifer (Lepidoptera: Elachistidae): evaluation of lure types, trap height, male flight distances, and number of traps needed per avocado orchard for detection.

The sex pheromone of Stenoma catenifer was evaluated in commercial avocado orchards in Guatemala to determine operational parameters, such as optimal lure type, trap height, trap density and estimates of the distances that male moths fly. Of four pheromone dispensers tested, gray and white rubber septa were of equal efficacy, whereas 1-ml low-density polyethylene vials and 2×3-cm polyethylene ziplock bags were least efficacious. The height at which wing traps were hung did not significantly affect the number of adult male S. catenifer captured. For monitoring S. catenifer, these data suggest that the pheromone should be dispensed from gray rubber septa in wing traps hung inside the tree canopy at 1.75 m, a height convenient for trap placement and monitoring. Mark-recapture studies of male S. catenifer indicated that, on average, males flew 67 m in one night. However, it is likely that this is an underestimate of the distance that male moths are capable of flying in a single night. Probabilistic modeling of S. catenifer capture data from different numbers of pheromone traps deployed in seven commercial avocado orchards of varying sizes and infestation levels suggested that 10-13 randomly deployed traps per orchard for a 7-day period are needed to detect at least one male S. catenifer with 90% confidence. These data provide sufficient information to develop effective protocols for using the S. catenifer pheromone to detect and monitor this pest in countries with endemic populations that are exporting fresh avocados, and for quarantine detection and incursion monitoring in countries receiving avocado imports from high risk areas.

Synergism between Enantiomers Creates Species-Specific Pheromone Blends and Minimizes Cross-Attraction for Two Species of Cerambycid Beetles

Research over the last decade has revealed extensive parsimony among pheromones within the large insect family Cerambycidae, with males of many species producing the same, or very similar aggregation pheromones. Among some species in the subfamily Cerambycinae, interspecific attraction is minimized by temporal segregation, and/or by minor pheromone components that synergize attraction of conspecifics or inhibit attraction of heterospecifics. Less is known about pheromone-based mechanisms of reproductive isolation among species in the largest subfamily, the Lamiinae. Here, we present evidence that the pheromone systems of two sympatric lamiine species consist of synergistic blends of enantiomers of (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol) and the structurally related (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (fuscumol acetate), as a mechanism by which species-specific blends of pheromone components can minimize interspecific attraction. Male Astylidius parvus (LeConte) were found to produce (R)- and (S)-fuscumol + (R)-fuscumol acetate + geranylacetone, whereas males of Lepturges angulatus (LeConte) produced (R)- and (S)-fuscumol acetate + geranylacetone. Field experiments confirmed that adult beetles were attracted only by their species-specific blend of the enantiomers of fuscumol and fuscumol acetate, respectively, and not to the individual enantiomers. Because other lamiine species are known to produce single enantiomers or blends of enantiomers of fuscumol and/or fuscumol acetate, synergism between enantiomers, or inhibition by enantiomers, may be a widespread mechanism for forming species-specific pheromone blends in this subfamily.

Candidate Attractant Pheromones of Two Potentially Invasive Asian Cerambycid Species in the Genus Xylotrechus.

ABSTRACT Research during the 1980s showed that male Xylotrechus pyrrhoderus Bates (Coleoptera: Cerambycidae), a vineyard pest, produce (2S,3S)-2,3-octanediol and (S)-2-hydroxyoctan-3-one as possible pheromone components, but to our knowledge, field tests were not carried out.We confirmed that at least female X. pyrrhoderus were attracted by a 1:1 blend of these two compounds in field trials in Japan. Furthermore, more than 200 males and females of the congener Xylotrechus rufilius Bates were attracted by racemic 2-hydroxyoctan-3-one, and inhibited by syn-2,3-octanediol. Adult X. rufilius recently were intercepted in a shipment from China entering Baltimore, Maryland, raising concerns that this polyphagous species could establish in North America. Our results suggest that traps baited with 2-hydroxyoctan-3-one would be a valuable tool to assess whether X. rufilius has indeed become established, and to monitor for future introductions of X. rufilius.

Synthesis and Bioassay of Racemic and Chiral trans-α-Necrodyl Isobutyrate, the Sex Pheromone of the Grape Mealybug Pseudococcus maritimus

A concise synthesis of the racemic form of the female-produced pheromone of the grape mealybug was developed. The synthesis was readily adapted to production of both enantiomers of the pheromone via lipase-catalyzed kinetic resolution of an intermediate in the synthesis. Replicated field trials revealed that, contrary to a preliminary report, the (R,R)- rather than the (S,S)-enantiomer is the attractive stereoisomer. Lithium aluminum hydride reduction of the insect-produced compound to alpha-necrodol followed by analysis on a chiral stationary phase GC column showed that the insect-produced material was actually an 85:15 mixture of the (R,R)- and (S,S)-enantiomers. The racemic form of the pheromone was highly attractive to male mealybugs, and in one of two field bioassays, the racemic material was significantly more attractive than the pure (R,R)-enantiomer, suggesting that the (S,S)-enantiomer might act synergistically.

Identifying Possible Pheromones of Cerambycid Beetles by Field Testing Known Pheromone Components in Four Widely Separated Regions of the United States

Abstract The pheromone components of many cerambycid beetles appear to be broadly shared among related species, including species native to different regions of the world. This apparent conservation of pheromone structures within the family suggests that field trials of common pheromone components could be used as a means of attracting multiple species, which then could be targeted for full identification of their pheromones. Here, we describe the results of such field trials that were conducted in nine states in the northeastern, midwestern, southern, and western United States. Traps captured 12,742 cerambycid beetles of 153 species and subspecies. Species attracted in significant numbers to a particular treatment (some in multiple regions) included 19 species in the subfamily Cerambycinae, 15 species in the Lamiinae, one species in the Prioninae, and two species in the Spondylidinae. Pheromones or likely pheromones for many of these species, such as 3-hydroxyhexan-2-one and syn- and anti-2,3-hexanediols for cerambycine species, and fuscumol and/or fuscumol acetate for lamiine species, had already been identified. New information about attractants (in most cases likely pheromone components) was found for five cerambycine species (Ancylocera bicolor [Olivier], Elaphidion mucronatum [Say], Knulliana cincta cincta [Drury], Phymatodes aeneus LeConte, and Rusticoclytus annosus emotus [Brown]), and five lamiine species (Ecyrus dasycerus dasycerus [Say], Lepturges symmetricus [Haldeman], Sternidius misellus [LeConte], Styloleptus biustus biustus [LeConte], and Urgleptes signatus [LeConte]). Consistent attraction of some species to the same compounds in independent bioassays demonstrated the utility and reliability of pheromone-based methods for sampling cerambycid populations across broad spatial scales.

Likely Aggregation-Sex Pheromones of the Invasive Beetle Callidiellum villosulum , and the Related Asian Species Allotraeus asiaticus , Semanotus bifasciatus , and Xylotrechus buqueti (Coleoptera: Cerambycidae)

Abstract During field trials of the two known cerambycid beetle pheromone components 3-hydroxyhexan-2-one and 1-(1H-pyrrol-2-yl)-1,2-propanedione (henceforth “pyrrole”) in Guangxi and Anhui provinces in China, four species in the subfamily Cerambycinae were attracted to lures containing one of the two components, or the blend of the two. Thus, the invasive species Callidiellum villosulum (Fairmaire) (tribe Callidiini) and a second species, Xylotrechus buqueti (Castelnau & Gory) (tribe Clytini), were specifically attracted to the blend of 3-hydroxy-hexan-2-one and the pyrrole. In contrast, Allotreus asiaticus (Schwarzer) (tribe Phoracanthini) and Semanotus bifasciatus Motschulsky (tribe Callidiini) were specifically attracted to the pyrrole as a single component. In most cases, both males and females were attracted, indicating that the compounds are likely to be aggregation-sex pheromones. The results indicate that the two compounds are conserved as pheromone components among species within at least three tribes within the subfamily Cerambycinae. For practical purposes, the attractants could find immediate use in surveillance programs aimed at detecting incursions of these species into new areas of the world, including the United States.

(2R,3S)-2,3-octanediol, a female-produced sex pheromone of megopis costipennis (Coleoptera: Cerambycidae: Prioninae)

Abstract During field screening trials of a number of known cerambycid pheromones in China, males of Megopis costipennis (White) (Coleoptera: Cerambycidae: Prioninae: Callipogonini) were found to be specifically attracted to racemic anti-2,3-octanediol, suggesting that one of the enantiomers of this compound might be a female-produced sex pheromone of this species. Analysis of volatiles produced by beetles of both sexes confirmed this hypothesis: females produced (2R,3S)-2,3-octanediol, whereas males did not, and in coupled gas chromatography–electroantennogram detection analyses, antennae from male beetles responded strongly to this compound. In field trials, males were equally attracted to traps baited with either (2R,3S)-2,3-octanediol or racemic anti-2,3-octanediol, indicating that the enantiomeric (2S,3R)-2,3-octanediol does not antagonize attraction to the naturally produced enantiomer. Thus, the more economical racemic anti-2,3-octanediol can be used for trap baits for this species. Homologous 2,3-hexanediols previously had been identified as sex pheromones or sex attractants of prionine species in the genus Tragosoma Audinet-Serville of the tribe Meroscelisini.