Bark Beetle Pheromone Components Research Articles

Stereospecific synthesis of S-(−)-trans-verbenol and its antipode by inversion of sterically hindered alcohols

S-(−)-trans-Verbenol (1) and its antipode, R-(+)-trans-verbenol (1′) have been confirmed as the critical pheromone components of bark beetles. Synthesis of these two active secondary alcohols (1 and 1′) from commercially available starting materials S-α-pinene and R-α-pinene was reported. The key steps were mainly depended on the effective SN2 stereo-inversion of the hydroxy group of sterically hindered alcohols (3 and 3′), using Mitsunobu reaction or hydrolysis of mesylate ester, alternatively. Our results provide a new and stereo-selectivity way to obtain optically active insect pheromones.

Using synthetic semiochemicals to train canines to detect bark beetle\u2013infested trees

Key messageThe dog detection allows timely removal by sanitation logging of first beetle-attacked trees before offspring emergence, preventing local beetle increases. Detection dogs rapidly learned responding to synthetic bark beetle pheromone components, with known chemical titres, allowing search training during winter in laboratory and field. Dogs trained on synthetics detected naturally attacked trees in summer at a distance of > 100 m.ContextAn early detection of first beetle-attacked trees would allow timely sanitation felling before offspring emergence, curbing local beetle increase.AimsWe tested if detection dogs, trained off-season on synthetic pheromone components from Ips typographus, could locate naturally bark beetle–infested spruce trees.MethodsIndoor training allowed dogs to discriminate between the infestation odours (target) and natural odours (non-target) from the forest. Odour stimuli were shown by chemical analysis to be bioactive at extremely low-levels released (< 10−4 ng/15 min) in the laboratory.ResultsDetection dogs, trained to recognise four different synthetic pheromone compounds in the wintertime, were able to detect naturally infested spruce trees unknown to humans the following summer. The dog-handler pairs were able to detect an infested spruce tree from the first hours of beetle attack until several weeks after first attack, long before discolouration of the crown. Trained sniffer dogs detected infested spruce trees out to ≥ 100 m, as measured by GPS-collar tracks.ConclusionDog-handler pairs appear to be more efficient than humans alone in timely detecting bark beetle infestations due to the canine’s ability to cover a greater area and detect by olfaction infestations from a far longer distance than can humans.

ChemInform Abstract: Stereoselective Synthesis of (R)‐ and (S)‐Ipsdienols (I), Pheromone Components of Bark Beetles of the Ips Family.

ChemInform Abstract: Stereoselective Synthesis of (R)‐ and (S)‐Ipsdienols (I), Pheromone Components of Bark Beetles of the Ips Family.

Stereoselective synthesis of (R)- and (S)-Ipsdienols, pheromone components of bark beetles of the Ips family

(R)- and (S)-Ipsdienols, components of pheromones of bark beetles of the Ips family, were synthesized with high enantiomeric purity (>98%) from 8-chloro-2-methyl-6-methylideneoct-2-en-4-ol prepared from ethyl 3-chloropropionate via cyclopropanation according to Kulinkovich. 8-Chloro-2-methyl-6-methylideneoct-2-en-4-ol was converted into the corresponding hydrogen phthalate whose stereoisomeric salts with (R)- and (S)-1-phenylethanamines were separated by crystallization, and subsequent hydrolysis of the latter and dehydrohalogenation with potassium tert-butoxide gave targeted (R)- and (S)-ipsdienols.

Identification and Field Activity of a Male-Produced Aggregation Pheromone in the Pine Sawyer Beetle, Monochamus galloprovincialis

The pine sawyer beetle, Monochamus galloprovincialis, is a pest of pine trees in Europe and North Africa. Previously considered a secondary pest of stressed and dying trees, it is now receiving considerable attention as a vector of the pine wood nematode, Bursaphelenchus xylophilus, the causal agent of a lethal wilting disease in susceptible species of pines. Adult beetles are attracted to traps baited with a kairomone blend consisting of a host volatile, alpha-pinene, and two bark beetle pheromone components, ipsenol and 2-methyl-3-buten-2-ol. More recently it has been shown that mature male M. galloprovincialis produce a pheromone that attracts mature females in a laboratory bioassay. Here, volatiles were collected from mature male and female M. galloprovincialis, and a compound produced specifically by mature males was identified as 2-undecyloxy-1-ethanol from its gas chromatographic retention times, its mass spectrum, and by comparison with synthetic standards. The naturally-derived and synthetic compounds elicited electroantennographic responses from both females and males. Sealed polyethylene vials and polyethylene sachets were shown to be effective dispensers with zero-order release, the latter giving a higher release rate than the former. In two field tests, multiple-funnel traps baited with synthetic 2-undecyloxy-1-ethanol caught both female and male M. galloprovincialis, with higher catches at the higher release rate. This compound also synergized the attractiveness of the kairomone blend, the combined mixture catching 80-140% more beetles than the sum of the catches to each bait separately and luring up to two beetles/trap/d in a moderate-density population. We conclude that 2-undecyloxy-1-ethanol is a male-produced aggregation pheromone of M. galloprovincialis. This is the first example of a sex-specific compound in the cerambycid subfamily Lamiinae with significant behavioral activity in the field at a range sufficient to make it a useful trap bait. The possible roles of this pheromone in the chemical ecology of M. galloprovincialis and its potential use in pine wilt disease management are discussed.

Antennal responses of the western pine beetle, Dendroctonus brevicomis (Coleoptera: Curculionidae), to stem volatiles of its primary host, Pinus ponderosa, and nine sympatric nonhost angiosperms and conifers

Summary. Stem volatile extracts from ten trees that are sympatric with the western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae) were assayed by gas chromatographic-electroantennographic detection analysis (GC-EAD). The extracts were from the primary host, ponderosa pine, Pinus ponderosa Dougl. ex Laws. (Pinaceae); two nonhost angiosperms, California black oak, Quercus kelloggii Newb. (Fagaceae), and quaking aspen, Populus tremuloides Michx. (Salicaceae); and seven nonhost conifers, white fir, Abies concolor (Gord. & Glend.) Lindl. ex Hildebr. (Pinaceae), incense cedar, Calocedrus decurrens (Torr.) Florin (Cupressaceae), Sierra lodgepole pine, P. contorta murrayana Grev. & Balf. (Pinaceae), Jeffrey pine, P. jeffreyi Grev. & Balf. (Pinaceae), sugar pine, P. lambertiana Dougl. (Pinaceae), Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco (Pinaceae), and mountain hemlock, Tsuga mertensiana (Bong.) Carr. (Pinaceae). Sixty-four compounds were identified from the ten trees, 42 of which elicited antennal responses in D. brevicomis, usually in both sexes. In addition, several synthetic compounds, including a number of the antennally-active compounds from the extracted trees and some bark beetle pheromone components, elicited antennal responses in a manner similar to that observed with the extracts. Of the antennally-active compounds known to be present in trees sympatric with D. brevicomis, only geraniol was unique to its host. Four antennally-active compounds were found in the host and in other conifers; five compounds were found only in nonhost conifers; eight compounds were found in either or both of the nonhost angiosperms; eight compounds were found in either or both of the angiosperms and in nonhost conifers, but not in the host; and 19 were found in both the host and in angiosperms and/or nonhost conifers. Several bark beetle pheromone components were found in the stem volatile extracts. Conophthorin was identified from both nonhost angiosperms; exo-brevicomin was identified in A. concolor; verbenone was identified from a number of nonhost conifers; and chalcogran was identified from P. tremuloides. The number of nonhost volatile chemicals that D. brevicomis encounters and is capable of detecting, and the diversity of sources from which they emanate, highlight the complexity of the olfactory environment in which D. brevicomis forages. This provides a basis for further work related to chemically-mediated aspects of foraging in this insect and perhaps other coniferophagous bark beetles, and highlights the need to consider foraging context in the design and implementation of semiochemical-based management tactics for tree protection.

Selective manipulation of predators using pheromones: responses to frontalin and ipsdienol pheromone components of bark beetles in the Great Lakes region

Abstract 1 One proposed approach to improving biological control of bark beetles (Coleoptera: Scolytidae; alt. Curculionidae: Scolytinae) is to manipulate predator movement using semiochemicals. However, selective manipulation is impeded by attraction of both predators and pests to bark beetle pheromones.2 The primary bark beetle affecting pine plantations in Wisconsin, U.S.A., is the pine engraver, Ips pini (Say). Other herbivores include Ips grandicollis (Eichhoff) and Dryophthorus americanus Bedel (Curculionidae). The predominant predators are the beetles Thanasimus dubius (Cleridae) and Platysoma cylindrica (Histeridae).3 We conducted field assays using two enantiomeric ratios of ipsdienol, and frontalin plus α‐pinene. Ipsdienol is the principal pheromone component of I. pini, and frontalin is produced by a number of Dendroctonus species. α‐Pinene is a host monoterpene commonly incorporated into commercial frontalin lures.4 Thanasimus dubius was attracted to frontalin plus α‐pinene, and also to racemic ipsdienol. By contrast, I. pini was attracted to racemic ipsdienol, but showed no attraction to frontalin plus α‐pinene. Platysoma cylindrica was attracted to 97%‐(–)‐ipsdienol and, to a lesser extent, racemic ipsdienol, but not to frontalin plus α‐pinene. Ips grandicollis was attracted to frontalin plus α‐pinene but not to ipsdienol. Dryophthorus americanus was attracted to both ipsdienol and frontalin plus α‐pinene.5 This ability to selectively attract the predator T. dubius without attracting the principal bark beetle in the system, I. pini, provides new opportunities for research into augmentative biological control and basic population dynamics. Moreover, the attraction of T. dubius, but not P. cylindrica, to frontalin plus α‐pinene creates opportunities for selective manipulation of just one predator.6 Patterns of attraction by predators and bark beetles to these compounds appear to reflect various degrees of geographical and host tree overlap with several pheromone‐producing species.

Frontalin: De novo biosynthesis of an aggregation pheromone component by Dendroctonus spp. bark beetles (Coleoptera: Scolytidae)

The pheromone component, frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) is thought to be formed in Dendroctonus spp. bark beetles through the cyclization of oxygenated 6-methyl-6-hepten-2-one (6-MHO). Unlike many of the isoprenoid pheromone components of bark beetles, there is no obvious immediate host conifer precursor for 6-MHO or frontalin. To elucidate the biosynthetic pathway of frontalin, juvenile hormone-treated male Dendroctonus jeffreyi were injected separately with [1- 14C]acetate, [2- 14C]mevalonolactone, [1- 14C]isopentenol, [1- 14C]:[1- 3H]isopentenol, and [4,5- 3H]leucine. Subsequently volatiles were collected on Porapak Q from these males and abdominal tissues were extracted. Radio-HPLC analyses of extracts from males injected with each radiolabeled substrate showed that radioactivity from the injected precursors eluted in a peak with a retention time that matches that of unlabeled frontalin. In all cases, HPLC fractions containing radiolabel that eluted at the same time as a frontalin standard were analyzed by GC-FID and GC-MS to confirm the presence of frontalin. In a separate study, male D. jeffreyi were injected with [1- 13C]acetate and an abdominal tissue extract from these insects was analyzed by tandem gas chromatography-isotope ratio monitoring-mass spectrometry (GC-IRM-MS), which unequivocally showed incorporation of 13C into frontalin. Because mevalonate is the key intermediate in the isoprenoid pathway, its incorporation (as mevalonolactone) into frontalin provides compelling evidence that the biosynthesis of frontalin involves that pathway in some form. In the experiment with [1- 14C]:[1- 3H]isopentenol, there was no significant difference in the mean percentage incorporation of either radioisotope into frontalin. This supports the role of the classical isoprenoid pathway, as tritium would be lost if only a hybrid pathway were involved. Confirming that de novo synthesis may be general to all Dendroctonus spp., 14C-acetate was also incorporated into frontalin by females of D. rufipennis and D. simplex. A radiolabeled precursor/pathway inhibitor study showed that the fatty acid synthase inhibitor, 2-octynoic acid, increased (although not significantly) the mass of frontalin produced and significantly increased the percentage incorporation of radioactivity from [1- 14C]acetate into frontalin. This suggests that as fatty acid biosynthesis is blocked, an increased amount of acetate is funneled into frontalin production via the isoprenoid pathway.

Differential Bio-Activity ofIpsandDendroctonus(Coleoptera: Scolytidae) Pheromone Components forMonochamus clamatorandM. scutellatus(Coleoptera: Cerambycidae)

Male and female Monochamus clamator (LeConte) and M. scutellatus (Say) are able to detect bark beetle pheromone components electrophysiologically and are attracted to traps baited with blends of pheromone components of scolytid bark beetles. We investigated the effect of individual pheromone components (ipsenol, ipsdienol, 3-methyl-2-cyclohexen-1-one (MCH), frontalin, verbenone, cis- and trans-verbenol, and endo- and exo-brevicomin) on Monochamus Dejean trap catches. Only traps baited with ipsenol and/or ipsdienol together with the host volatiles ethanol and α-pinene caught significantly more male and female M. scutellatus and M. clamator than traps baited with host volatiles alone. Ipsenol and ipsdienol are aggregation pheromones of secondary bark beetles in the genus Ips DeGeer while the other components are pheromones of primary bark beetles in the genus Dendroctonus Erichson. The former should be the most reliable indicators of suitable host material because most Ips spp. attack weakened or moribund trees or trees already successfully under attack by primary bark beetles, and their pheromones may be more persistent in space and time than those of Dendroctonus spp. In two successive years in an operational (commercial) mass-trapping program, traps baited with ethanol, α-pinene, and ipsenol captured twice as many beetles as traps baited with host volatiles alone. These results suggest that operational monitoring or mass-trapping programs could be improved significantly by the inclusion of ipsenol in baits at a minimal cost.

Incomplete barriers to mitochondrial gene flow between pheromone races of the North American pine engraver,Ips pini(Say) (Coleoptera, Scolytidae)

The pine engraver Ips pini (Say) is known to include three pheromone races, but gene flow between these races has not been investigated. We used maternally inherited mitochondrial DNA (mtDNA) variation to infer gene flow between 22 widely distributed North American populations of I. pini for a total of 217 individuals, based on 354 bp of the cytochrome oxidase I gene. Gene flow was estimated cladistically as migrants per generation (Nm) and as haplotype variation between populations (Nst). Three distinct mtDNA haplotype lineages, generally corresponding to eastern (I), Rocky Mountain (II) and western (III) regions of North America, were resolved with a total of 34 distinct I. pini haplotypes. The distributions of these lineages were largely congruent with the geographical ranges of the 'New York', 'California' and 'Idaho–Montana' pheromone races. Only individuals with lineage I mtDNA were observed among eastern populations, whereas individuals with lineage II or III mtDNA predominated among western populations. Gene flow (Nm and Nst) was generally moderate between all populations. However, the presence of lineage I mtDNA on the eastern side of western North America and the absence of lineage II and III mtDNA in eastern North America suggest directional gene flow from east to west. These results indicate that female-controlled assortative mating among pheromone races may disrupt gene flow between conspecifics, reflecting incomplete pre-mating barriers.

Randomization algorithms in BASIC for experimental design

Six BASIC programs for randomization of treatments with respect to space and time are presented. Program 1 is used to obtain randomization of several treatments in an equal number of positions for any number of replicates such that identical treatments are not replicated successively in the same position. Program 2 randomly assigns different treatments as specified in a grid of any size either (a) without constraints or (b) so that similar treatments do not occur next to each other either horizontally or vertically, or (c) horizontally, vertically, or diagonally. Program 3 assigns from five to 100 different treatments in equal proportions to a grid of specified size with treatments separated as in Program 2 (c) above. Program 4 randomly assigns any number of different treatments in equal proportions to a Latin square-like grid containing row and column cells with a multiple number of the treatments such that no identical treatments are replicated successively in the same row, column, or both row and column. Program 5 produces Latin squares of letters with unique numbered subscripts randomized. Program 6 makes Greco-Latin squares with an odd number of letters per side. These programs will aid in randomization of treatments within positions and replicates when a degree of uniformity or spacing of treatments is desired in order to increase the power of statistical tests. Examples of program output are discussed for tests with bark beetle pheromone components.

Production of pheromone components, chalcogran and methyl ( E,Z)-2,4-decadienoate, in the spruce engraver Pityogenes chalcographus

Capillary gas chromatography and mass spectrometry were used to quantify the amounts of E- and Z- chalcogran and methyl ( E,Z)-2,4-decadienoate ( E,Z-MD), pheromone synergists of the bark beetle Pitygenes chalcographys (Coleoptera: Scolytidae). Males were exposed or not to vapours of host (Norway spruce, Picea abies) oleoresin or allowed to feed in host logs prior to extraction of body parts and hindguts for pheromone synergists. E,Z-MD and chalcogran were produced sex-specifically in males, and only after feeding on host-plant tissue. The pheromone synergists were not produced during exposure to oleoresin vapours. Several oxygenated monoterpenes (including trans-verbenol, myrtenol, and trans-myrtanoy) were found in feeding males. The amounts of the pheromone synergists in unmated feeding males remained relatively constant over a 3.5 day period. In contrast to many other pheromone components of bark beetles, including chalcogran, E,Z-MD was found primarily in the male's body (head and thorax) with less in the hindgut (abdomen). The probable acetogenic origins of both pheromone components indicate that the species has evolved control over production and is thus not dependent on host precursors as expected in many other bark beetles.

Violence and children.

<h3>Abstract</h3> In this proof of concept study, we report the off season training of two detection dogs on a series of synthetic semiochemicals associated with <i>Ips typographus</i> pest bark beetle infestations of spruce trees. Scent detection training allowed dogs to discriminate between physiologically-relevant infestation (target) odours, quantified by GC-MS using extracted ion chromatogram to be bio-active at levels of &lt; 10⁻⁴ ng /15 min or lower, and natural non-target odours that might be encountered in the forest. Detection dogs trained to recognize four different synthetic pheromone compounds in the winter time, well before beetle flight, were able to detect natural infested spruce trees unknown to humans the following summer. The trained detection dogs were able to detect an infested spruce tree from the first hour of bark beetle attack until several weeks after the attack. Trained detection dogs appear to be more efficient than humans in detecting early bark beetle infestations because the canines ability to cover a greater area and by olfaction detect infestations from a far greater distance than can humans. Infested spruce trees could be detected by trained detection dogs out to more than 100 m. <h3>Key Message</h3> Detection dogs were rapidly trained to locate release of synthetic bark beetle pheromone components Synthetics allowed dog training off-season both in laboratory and field Dogs trained on synthetics detected naturally target pest insect attacked trees at a distance of more than 100 m. The method allows rapid removal of single, first attacked trees before offspring emergence, thus curbing local pest increase and lowering spread of attacks in the landscap

Convenient synthetic route to 6,8-dioxabicyclo[3.2.1]octanes, the aggregation pheromone components of bark beetles

Convenient syntheses of (±)-frontalin (I) and (±)-brevicomins (IIa) and (IIb) were achieved from pent-4-en-1-ol (2) and pent-4-yn-1-ol (3). In a few simple and unambiguous steps, the alkenol (2) and the alkynol (3) were transformed into the acetal bromide (7) and the alkenyl bromides (14) and (17), respectively. Acylation of the Grignard reagents of these bromides provided the corresponding methyl ketones (8), (15), and (18), the key intermediates for the synthesis of the title bicyclic acetals. The ketone (8) was converted into the olefin (9) which, on epoxidation followed by acid hydrolysis, yielded (±)-frontalin, whereas epoxidation of the alkenones (15) and (18) and subsequent cyclisation afforded exo-and endo-brevicomin, stereoselectively.

Determination of enantiomer composition of several bicyclic ketal insect pheromone components

Details are given for the determination by a chiral shift reagent of enantiomer compositions of several bark beetle pheromone components, which are bicyclic ketals. The procedure was carried out on three samples in the range of 200 micrograms. For one sample, the determination was achieved at the level of 5 micrograms.