Fuscumol and Fuscumol Acetate Are General Attractants for Many Species of Cerambycid Beetles in the Subfamily Lamiinae

DOI: 10.1111/j.1570-7458.2011.01167.x Fuscumol and fuscumol acetate are general attractants for many species of cerambycid beetles in the subfamily Lamiinae Robert F.Mitchell1*, Elizabeth E. Graham1§, Joseph C. H. Wong1, Peter F.Reagel1,Becca L. Striman1,GabrielP.Hughes2, Matthew A. Paschen2, Matthew D. Ginzel2, Jocelyn G. Millar3 & Lawrence M. Hanks1 1Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA, 2Department of Ento- mology, Purdue University, West Lafayette, IN 47907, USA, and 3Department of Entomology, University of California, Riverside, CA 92521, USA Accepted: 1 August 2011 Key words: longhorned beetle, chemical attractant, pheromone, quarantine, invasive species, Coleoptera, Acanthocinini, Cerambycidae Abstract (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol) is an important component of male-produced aggregation pheromones for several species of cerambycid beetles in the genus Tetropium (subfamily Aseminae ⁄ Spondylidinae). Here, we describe the experiments that tested the hypothesis that fuscumol and ⁄ or fuscumol acetate also are general attractants for species in the cerambycid subfamily Lamiinae. At field sites in northwestern Indiana and central Texas (USA), panel traps baited with fuscumol or its acetate captured 331 lamiine beetles, compared to 11 beetles captured in control traps. Three species were attracted to traps baited with fuscumol as a single component, whereas another four species were attracted to fuscumol acetate alone. Surprisingly, fuscumol acetate also attracted two species in the subfamily Cerambycinae: Xylotrechus colonus (Fabricius) (males of which produce a pheromone composed only of stereoisomers of 2,3-hexanediol and 3-hydroxyhexan-2-one), and Obrium maculatum (Olivier) (for which a pheromone has yet to be identified). In an independent field experiment in east-central Illinois (USA), traps baited with fuscumol and ⁄ or its acetate captured 136 beetles of eight lamiine species, all but one species of which were also captured in the other experiment. Blending fuscumol and its acetate did not inhibit responses of species to either of the individ- ual compounds, but synergized their activity for one species. Our results support the hypothesis that fuscumol and fuscumol acetate are widespread pheromone components or attractants for a variety of cerambycid species, especially lamiines in the tribe Acanthocinini. 2011). Male beetles of the subfamily Cerambycinae emit Introduction pheromones that attract both sexes when on larval host Volatile aggregation pheromones produced by males, and plants (Lacey et al., 2004), suggesting that these phero- sex pheromones produced by females have been described mones may signal the presence of breeding material that is recently for several species of cerambycid beetles (e.g., Mil- scarce and ephemeral (Hanks, 1999). Similarly, beetles of lar et al., 2009; Ray et al., 2009, 2011; Rodstein et al., the genus Tetropium (subfamily Aseminae ⁄ Spondylidinae; Monne´ & Hovore, 2005; Bousquet et al., 2009) are only attracted to aggregation pheromones when odors of host *Correspondence: Robert Mitchell, Department of Entomology, Uni- plants are present (Silk et al., 2007). versity of Illinois at Urbana-Champaign, 320 Morrill Hall, 505 South There appears to be considerable parsimony within the Goodwin Avenue, Urbana, IL 61801, USA. E-mail: rmitche3@life. illinois.edu family Cerambycidae in relation to pheromone biosynthe- §Present address: Department of Entomology, Michigan State Univer- sis and closely related species of cerambycids often share sity, East Lansing, MI, USA, 48823 pheromone components or even produce pheromones of Ó 2011 The Authors Entomologia Experimentalis et Applicata 141: 71–77, 2011 Entomologia Experimentalis et Applicata Ó 2011 The Netherlands Entomological Society 71 72 Mitchell et al. identical composition. For example, (R)-3-hydroxyhexan- Materials and methods 2-one is a common, and often the sole component of vola- Synthesis of compounds tile pheromones of many species in the large subfamily Ce- Geranylacetone (97 g, 0.5 mol; Aldrich Chemical, Flavor rambycinae (Hanks et al., 2007; Millar et al., 2009; Ray and Fragrance Division, Milwaukee, WI, USA) was pur- et al., 2009). This similarity in pheromone composition chased as a 1:1.25 mixture of (Z)- and (E)-isomers due to across cerambycine species can result in simultaneous the prohibitive cost of the pure (E)-isomer. Lithium alu- attraction of multiple species to traps baited with a single minum hydride (6.3 g, 166 mmol) was added in portions synthetic pheromone component. Thus, in field bioassays, over 20 min to 1 l of dry ether at 0 °C under argon atmo- racemic 3-hydroxyhexan-2-one and the structurally sphere. Geranylacetone in 100 ml dry ether was added related 2,3-hexanediols serve as general attractants for dropwise to the resulting slurry over 40 min, and the mix- many cerambycine species, and may even attract species ture was warmed to room temperature overnight, during that do not actually produce them (Lacey et al., 2004; which time, it became viscous. After checking that the Hanks et al., 2007). In a different subfamily, the Prioninae, reduction was complete using thin layer chromatography the female-produced pheromone of Prionus californicus on silica gel [the reactant and product had virtually identi- Motschulsky (3,5-dimethyldodecanoic acid; Rodstein cal retention times by gas chromatography (GC) on a DB- et al., 2011) has been shown to attract males of seven cong- 5 column], the magnetic stir-bar was replaced with a eners (Barbour et al., 2011). Similarly, in the subfamily mechanical stirrer, and the mixture was cooled in an ice- Lamiinae, 2-(undecyloxy)-ethanol not only serves as the bath while adding, sequentially and dropwise, 6.64 ml male-produced aggregation pheromone for Monochamus water (caution: vigorous hydrogen evolution!), 5 ml aque- galloprovincialis (Olivier) (Pajares et al., 2010), but also ous 20% NaOH, and 23.5 ml water. The mixture was stir- attracts both sexes of other congeners (Teale et al., 2011; red for an additional 20 min, during which time, the metal unpubl.). salts formed a granular white precipitate. The mixture was (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol) has filtered with suction, rinsing the filter cake with ether. The been identified as a male-produced aggregation phero- filtrate was extracted with water and brine, then dried over mone for the invasive European cerambycid Tetropium anhydrous Na SO , and concentrated on a rotary evapora- fuscum (Fabricius) and its North American congener Tet- 2 4 tor at room temperature. The residue was purified by ropium cinnamopterum (Kirby) (Silk et al., 2007). It also Kugelrohr distillation (oven temperature ca. 80 °C, attracts and is likely a pheromone component for another 0.2 mm Hg), yielding racemic fuscumol [hence (E ⁄ Z)- European species, Tetropium castaneum (L.) (Sweeney fuscumol] as a clear, colorless oil [94.6 g, 97% yield, >98% et al., 2010). In addition, this same compound has been chemically pure by GC, 1:1.25 mixture of racemic (Z)- and identified as a pheromone component for two South (E)-isomers]. The nuclear magnetic resonance (NMR) American species in the subfamily Lamiinae: Hedypathes and mass spectra were analogous to those recently betulinus (Klug) (Fonseca et al., 2010) and Steirastoma reported (Fonseca et al., 2010; Sweeney et al., 2010). breve (Sulzer) (Liendo et al., 2005; C Liendo, pers. (E ⁄ Z)-Fuscumol acetate was synthesized by adding comm.). Males of both species also produce (E)-6,10- (E ⁄ Z)-fuscumol (44 g, 224 mmol) to a solution of pyri- dimethyl-5,9-undecadien-2-one (common name: gerany- dine (20.2 ml, 250 mmol) and methylene chloride lacetone; Fonseca et al., 2010; C Liendo, pers. comm.) (400 ml), and the mixture was stirred and cooled in an and H. betulinus produces (E)-6,10-dimethyl-5,9-undeca- ice-bath while acetyl chloride (17.8 ml, 250 mmol) was dien-2-yl acetate (‘fuscumol acetate’; Fonseca et al., added dropwise. The mixture was then warmed to room 2010). These findings suggest that fuscumol and its ana- temperature and stirred overnight. The small excess of logs may be common pheromone components for a acetyl chloride was destroyed by addition of ethanol diversity of species across subfamilies of the Cerambyci- (1.4 g, 30 mmol), followed by stirring for an additional dae. In fact, in recent years, we have consistently captured 4 h. The mixture was then poured into water and the lay- several lamiine species in traps baited with the blend of ers were separated. The aqueous layer was extracted with fuscumol and its acetate during field trials in east-central ether and the combined organic extracts were washed Illinois that targeted asemine species (RF Mitchell, un- successively with water, 1 M HCl, saturated aqueous publ.). Herein, we describe experiments, conducted in NaHCO , and brine. After drying over anhydrous Indiana, Illinois, and Texas, that specifically address 3 Na SO , the solution was concentrated by rotary evapora- the hypothesis that fuscumol and fuscumol acetate 2 4 tion followed by Kugelrohr distillation of the residue represent another widespread motif for cerambycid beetle (oven temperature ca. 80 °C, 0.15 mm Hg), yielding pheromones, analogous to the 3-hydroxyalkan-2-one and (E ⁄ Z)-fuscumol acetate (52.4 g, 98%, >98% pure by GC). 2,3-alkanediol motifs. Fuscumol and its acetate are attractants for cerambycids 73 Mass and NMR spectra were analogous to those reported of Texas AgriLife Research and Extension Center in Fonseca et al. (2010). (32°14¢27.7965¢¢N, 98°11¢18.7731¢¢W). The experiment was conducted from 24 May to 8 June 2010 (air tempera- Field bioassays ture 21–34 °C, skies usually clear, 2 cm total precipitation; Two experiments were conducted to test for attraction of Weather Underground). lamiine species to (E ⁄ Z)-fuscumol and its acetate. Experi- Experiment 2 included the same treatments as Experi- ment 1 tested for attraction of beetles to each compound ment 1, but lures were loaded with 100 mg of synthetic separately, and was replicated at study sites in northwestern pheromone and included a treatment that was a blend Indiana and central Texas.

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