Using Generic Pheromone Lures to Expedite Identification of Aggregation Pheromones for the Cerambycid Beetles Xylotrechus nauticus, Phymatodes lecontei, and Neoclytus modestus modestus

Abstract

Males of several species of longhorned beetles in the subfamily Cerambycinae produce sex or aggregation pheromones consisting of 2,3-hexanediols and/or hydroxyhexanones. We tested the hypothesis that this diol/hydroxyketone pheromone motif is highly conserved within the subfamily, and the resulting prediction that multiple cerambycine species will be attracted to compounds of this type. We also tested the concept that live traps baited with generic blends of these compounds could be used as a source of live insects from which pheromones could be collected and identified. Traps placed in a mature oak woodland and baited with generic blends of racemic 2-hydroxyhexan-3-one and 3-hydroxyhexan-2-one captured adults of both sexes of three cerambycine species: Xylotrechus nauticus (Mannerheim), Phymatodes lecontei Linsley, and Phymatodes decussatus decussatus (LeConte). Odors collected from male X. nauticus contained a 9:1 ratio of two male-specific compounds, (R)-and (S)-3-hydroxyhexan-2-one. Field trials with synthetic compounds determined that traps baited with (R)-3-hydroxyhexan-2-one (94% ee), alone or in blends with other isomers, attracted similar numbers of X. nauticus of both sexes, whereas (S)-3-hydroxyhexan-2-one (94% ee) attracted significantly fewer beetles. Phymatodes lecontei and P. d. decussatus also were caught in traps baited with hydroxyhexanones, as well as a few specimens of two other cerambycine species, Neoclytus modestus modestus Fall (both sexes) and Brothylus gemmulatus LeConte (only females). Male N. m. modestus produced (R)-3-hydroxyhexan-2-one, which was not present in extracts from females. Neoclytus m. modestus of both sexes also responded to lures that included (R)-3-hydroxyhexan-2-one as one of the components. The only male-specific compound found in extracts from P. lecontei was (R)-2-methylbutan-1-ol, and adults of both sexes were attracted to racemic 2-methylbutan-1-ol in field bioassays. Surprisingly, P. lecontei of both sexes also were attracted to (R)-and (S)-3-hydroxyhexan-2-ones, although neither compound was detected in extracts from this species. Males of all five beetle species had gland pores on their prothoraces that were similar in structure to those that have been associated with volatile pheromone production in other cerambycine species. The attraction of multiple cerambycine species of two tribes to (R)-3-hydroxyhexan-2-one in this study, and in earlier studies with other cerambycine species, suggests that this compound is a widespread aggregation pheromone component in this large and diverse subfamily. Overall, the attraction of multiple species from different cerambycine tribes to this compound at a single field site supports the hypothesis that the hydroxyketone pheromone structural motif is highly conserved within this subfamily.

Efficacy of semiochemical-baited traps for detection of longhorn beetles (Coleoptera: Cerambycidae) in the Russian Far East

“…Our data support the predictions of Hanks et al (2007) that multiple species in the subfamily Cerambycinae would be attracted to compounds in the 2,3-diol/hydroxyketone motif. We found that racemic hydroxyketones (i.e., K6, k8) increased the efficacy of detecting three of eight species of Cerambycinae: A. colobotheoides, P. testaceus, and M. minor.…”

“…In contrast to the Lepidoptera, in which attraction of a particular moth species to a synthetic lure is highly dependent on the relative ratio and chirality of pheromone components (Roelofs & Cardé, 1977), longhorn beetle pheromones often attract several species in the same genus or subfamily and thus have good potential as survey tools of native and exotic Cerambycids (Millar et al, 2009;. Hanks et al (2007) found that individual species of Cerambycinae usually emitted specific enantiomers, e.g., (R)-3-hydroxyhexan-2-one, but the presence of other enantiomers in synthetic lures did not reduce attraction; they hypothesized that the 2,3-diol/hydroxyketone pheromone motif was highly conserved within the subfamily and predicted that multiple Cerambycinae species would be attracted to compounds of this type. Similarly, (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol), the aggregation pheromone of Tetropium fuscum (Fabr.…”

“…For traps baited with either K6 or K8, we placed two pouches per trap to obtain release rates of 40-50 mg/d and did not replace the lures. Unlike some earlier studies (e.g., Hanks et al, 2007), in which the diols/hydroxyketones were formulated in ethanol, our hydroxyketone lures did not use ethanol as a carrier, which allowed us to independently test whether the presence of ethanol increased or decreased attraction to the hydroxyketone lures, and vice versa.…”

Identification and Synthesis of a Female-Produced Sex Pheromone for the Cerambycid Beetle Prionus Californicus

“…However, there is considerable circumstantial evidence that female-produced sex attractant pheromones are widespread within the Prioninae (e.g., Rotrou 1936;Edwards 1961;Benham and Farrar 1976;Gwynne and Hostetler 1978), so we anticipate that pheromones of other species, particularly congeners of P. californicus, will soon be reported, now that the basic methods and a "lead" compound have been characterized. It should also be noted that the pheromone of P. californicus is entirely different in structure from the male-produced pheromones of species in other subfamilies of the Cerambycidae (e.g., Hanks et al 2007;Ray et al 2009), and femaleproduced pheromones of two species that are apparently closely related to the Cerambycidae: Migdolus fryanus Westwood and Vesperus xatarti Dufour (Leal et al 1994;Boyer et al 1997; taxonomy according to Napp 1994;Bense 1995;Dong and Yang 2003).…”

Aggregation-Sex Pheromones and Likely Pheromones of 11 South American Cerambycid Beetles, and Partitioning of Pheromone Channels

“…Accumulating evidence suggests that there is considerable parsimony among cerambycid species with regard to pheromone biosynthesis and use, with closely related species often sharing pheromone components, or even producing pheromones of apparently identical composition (e.g., Hanks et al, 2007;Mitchell et al, 2011Mitchell et al, , 2013Ray et al, 2012Ray et al, , 2015Hanks and Millar, 2013). For example, ∼60 species within the subfamily Cerambycinae have been shown to emit and are attracted to pheromone compounds with 6, 8, or 10 carbon chains, with carbonyl or hydroxyl groups on carbons 2 and/or 3 (listed in Table S1 of Hanks and Millar, 2016).…”