Anti-aphrodisiac pheromone:Pheromone Resources

Anti-aphrodisiac pheromone (diminish sexual desire):

This pheromone is reported in Heliconius melpomene Linnaeus (Lepidoptera:Nymphalidae) (Schulz, 2008). The pheromones of Heliconius melpomene, of males contained the volatile compound (E)-β-ocimene along woth volatile matrix of esters of common C₁₆- and C₁₈-fatty acids with the alcohols ethanol, 2-propanol, 1-butanol, isobutanol, 1-hexanol, and (Z)-3-hexenol. The  investigation showed that β-ocimene is an antiaphrodisiac pheromone of H. melpomene (Schulz S Estrada et al., 2008).

It is reported that male of Lygus hesperus delivers a large spermatophore and fatty molecule myristyl acetate,which  absent in virgin females. When they found myristyl acetate was as effective reducing the attractiveness of virgin females. Hence, already mated males are less attractive to males compered to virgin fmales  (Colin S. Brent and  John A. Byers, 2011).

In the male ejaculate,P. brassicae females receive the anti-aphrodisiac benzyl cyanide (BC) that reduces the females' attractiveness for subsequent mating. It was  detected this pheromone in the accessory gland secretion released by mated female butterflies. When applied onto leaves, BC alone induced phytochemical changes that arrested females of the egg parasitoid. Microarray analyses revealed a similarity in induced plant responses that may explain the arrest of T. brassicae to egg-laden and BC-treated plants. Thus, a male-derived compound endangers the offspring of the butterfly by inducing plant defense (Fatouros et al.,2008).

Behavioural mating assays showed that males mount nymphs significantly shorter time compared to females, although initial mounting preference was the same. In support of our hypothesis, nymphs experienced the same percentage of mating with sperm transfer as females if they were unable to emit (E)-2-hexenal, (E)-2-octenal 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal, from their dorsal abdominal glands. We report that the aldehydes and 4-oxo-(E)-2-hexenal are detected by olfactory receptor neurons housed in smooth and grooved peg sensilla, respectively, on the adult antennae, at biologically relevant concentrations. Behavioural experiments showed that application of 4-oxo-(E)-2-hexenal or the two aldehydes at a nymph-emitted ratio, to a male/female pair during mounting initiation, decreased mating frequency to a rate comparable to that of a male/nymph pair (Harraca et al.,2010).

Courtship conditioning is an associative learning paradigm in Drosophila melanogaster, wherein male courtship behavior is modified by experience with unreceptive, previously mated females. While the training experience with mated females involves multiple sensory and behavioral interactions, we hypothesized that female cuticular hydrocarbons function as a specific chemosensory conditioned stimulus in this learning paradigm. The effects of training with mated females were determined in courtship tests with either wild-type virgin females as courtship targets, or with target flies of different genotypes that express distinct cuticular hydrocarbon (CH) profiles. Results of tests with female targets that lacked the normal CH profile, and with male targets that expressed typically female CH profiles, indicated that components of this CH profile are both necessary and sufficient cues to elicit the effects of conditioning. Results with additional targets indicated that the female-specific 7,11-dienes, which induce naive males to court, are not essential components of the conditioned stimulus. Rather, the learned response was significantly correlated with the levels of 9-pentacosene (9-P), a compound found in both males and females of many Drosophila strains and species. Adding 9-P to target flies showed that it stimulates courting males to attempt to copulate, and confirmed its role as a component of the conditioned stimulus by demonstrating dose-dependent increases in the expression of the learned response. Thus, 9-P can contribute significantly to the conditioned suppression of male courtship toward targets that express this pheromone (Siwicki, et al.,2005).

Closely related egg parasitoids,Trichogramma brassicae and Trichogramma evanescens, exploit the anti-aphrodisiac pheromone benzyl cyanide of one of their hosts, the gregarious large cabbage white butterfly Pieris brassicae that deposits a clutch of more than 20 eggs per oviposition bout. The pheromone is transferred by male butterflies to females during mating to enforce female monogamy. On detecting the anti-aphrodisiac, the tiny parasitic wasps ride on a mated female butterfly to a host plant and then parasitize her freshly laid eggs. The present study demonstrates that both wasp species similarly exploit the anti-aphrodisiac mixture of methyl salicylate and indole of another host, the more common solitary small cabbage white butterfly Pieris rapae that deposits only one egg at a time. Interestingly, this behavior is innate in T. brassicae, whereas T. evanescens learns it after one successful ride on a mated female butterfly. Moreover, we show that the wasps only respond to the anti-aphrodisiacs of the 2 cabbage white butterflies when the ubiquitous compounds are part of a complete mated female odor blend  (Huigens et al.,2010).

In Drosophila melanogaster, the male ejaculatory bulb is the site of synthesis of a male-specific pheromone, cis-vaccenyl acetate, which functions as both an attractant and an anti-aphrodisiac. This long monounsaturated acetate is structurally similar to a number of shorter gland-synthesized moth pheromones. The cell monolayer that forms the Drosophila male ejaculatory bulb wall is responsible for the production and secretion of cis-vaccenyl acetate into the seminal fluid. When dissected bulbs were incubated with sodium [14-C]-acetate (or deuterated acetate), a labeled acetate ester was synthesized. The labeled acetate ester co-migrated with cis-vaccenyl acetate in thin layer chromatography. Incubation of the abdomens of males from which the ejaculatory bulbs had been removed, or the abdomens of females, with radiolabeled acetate did not yield any acetate ester, but did yield other lipid products, including hydrocarbons. When the isolated labeled acetate ester was hydrolyzed, no radioactive vaccenol was formed. This strongly suggests that the acetyl group is incorporated via a transacetylation reaction, but that the vaccenyl moiety is not synthetized in the blub. The transacetylation enzyme activity was localized in the microsomal subfraction of the bulb homogenate, and its affinity for vaccenol was not very different from that reported for monounsaturated alcohol substrates in moths (Guiraudie et al.,2007).

Gas-liquid chromatography was used to investigate the role of cis-vaccenyl acetate, cis-vaccenol and esterase 6 in the inhibition of male courtship in D. melanogaster. Results indicate that (1) cis-vaccenyl acetate is not converted tocis-vaccenol, (2) esterase 6 has no effect on the rate of cis-vaccenyl acetate loss from the reproductive tracts of mated females, (3) in vivo concentrations of cis-vaccenyl acetate transferred to females during copulation fall below effective courtship-inhibitory levels within 4 h, (4) cis-vaccenyl acetate is not translocated from the female reproductive tract to the abdominal cuticle, and that (5) mutant male flies that do not reduce the post-mating sexual attractiveness of females contain and transfer normal amounts of cis-vaccenyl acetate (Vander Meer et al.,1996).

A recent study in BMC Biology has determined that the immature stage of the bed bug (the nymph) signals its reproductive status to adult males using pheromones and thus avoids the trauma associated with copulation in this species. The success of this nymphal strategy of deterrence is instructive. Against the background of increasing problems with bed bugs, this research raises the question whether pheromones might be used to control them (Haynes et al.,2010).

After Drosophila males are rejected by mated females, their subsequent courtship is inhibited even when encountering virgin females. Molecular mechanisms underlying courtship conditioning in the CNS are unclear. In this study, we find that tyramine β hydroxylase (TβH) mutant males unable to synthesize octopamine (OA) showed impaired courtship conditioning, which could be rescued by transgenic TβH expression in the CNS. Inactivation of octopaminergic neurons mimicked the TβH mutant phenotype. Transient activation of octopaminergic neurons in males not only decreased their courtship of virgin females, but also produced courtship conditioning. Single cell analysis revealed projection of octopaminergic neurons to the mushroom bodies. Deletion of the OAMB gene encoding an OA receptor expressed in the mushroom bodies disrupted courtship conditioning. Inactivation of neurons expressing OAMB also eliminated courtship conditioning. OAMB neurons responded robustly to male-specific pheromone cis-vaccenyl acetate in a dose-dependent manner. Our results indicate that OA plays an important role in courtship conditioning through its OAMB receptor expressed in a specific neuronal subset of the mushroom bodies (Zhou et al.,2012).

In polyandrous butterflies males transfer a large, nutritious ejaculate at mating. Larger ejaculates delay female remating and confer an advantage in sperm competition. However, large ejaculates are costly, potentially selecting for male adjustment of ejaculate size to the risk of sperm competition. Here, we test if male ejaculate size in the butterfly Pieris napivaries with male density, and whether males assess sperm competition risk using the male sex pheromone citral as a cue. The results conformed to sperm competition theory and showed that male P. napi tailored their reproductive investment in response to the risk of sperm competition; ejaculates transferred by males in the high male density treatments were on average 23% larger than ejaculates transferred at low male densities. The results also show for the first time that the sex pheromone citral was used by males to assess male density; ejaculates transferred by males in presence of added male sex pheromone were 19% larger than ejaculates transferred in the control. In conclusion, the study shows how the sex pheromone not only facilitates female acceptance when dispensed by courting males but also allows males to assess the degree of male competition for matings (Mellström, et al.,2009).

Chemical cues play a major role in the process of host selection by parasitoids, a process that has been discriminated into several steps such as habitat location, host location, and host acceptance. Egg parasitoids are known to rely on infochemicals of the adult host stage, e.g., pheromones, rather than cues emitted by the inconspicuous host eggs themselves. Here, we show that three different Trichogramma(Hymenoptera: Trichogrammatidae) species were attracted to the synthetic sex pheromone of the olive, Olea europea L., pest Prays oleae(Bern) (Lepidoptera: Yponomeutidae). In Y-tube olfactometer experiments, we revealed differences in the behavior of four testedTrichogramma strains to different concentrations of the host pheromone. Although wasps of Trichogramma oleae (Voegele & Poitale) (IO47) were significantly attracted to two concentrations of the host pheromone, another strain of the same species (IO24) did not show a response to any offered concentrations. Trichogramma cacoeciaeMarchai females showed greatest attraction toward the pheromone to three of five offered concentrations. Bioassays with Trichogramma bourarachae Pintureau & Babault wasps showed a positive response of the parasitoids to three concentrations of the host pheromone. Detection of the moth sex pheromone may result in an enhanced searching effort by Trichogramma wasps in an area with host eggs and eventually lead to an increased parasitism rate of these eggs (Milonas et al.,2009).

During mating in many butterfly species, males transfer spermatophores that contain anti-aphrodisiacs to females that repel conspecific males. For example, males of the large cabbage white, Pieris brassicae (Lepidoptera: Pieridae), transfer the anti-aphrodisiac, benzyl cyanide (BC) to females. Accessory reproductive gland (ARG) secretion of a mated female P. brassicae that is deposited with an egg clutch contains traces of BC, inducing Brussels sprouts plants (Brassica oleracea var. gemmifera) to arrest certainTrichogramma egg parasitoids. Here, we assessed whether deposition of one egg at a time by the closely related small cabbage white, Pieris rapae, induced B. oleracea var. gemmifera to arrest Trichogramma wasps, and whether this plant synomone is triggered by substances originating from maleP. rapae seminal fluid. We showed that plants induced by singly laid eggs ofP. rapae arrest T. brassicae wasps three days after butterfly egg deposition. Elicitor activity was present in ARG secretion of mated female butterflies, whereas the secretion of virgin females was inactive. Pieris rapae used a mixture of methyl salicylate (MeSA) and indole as an anti-aphrodisiac. We detected traces of both anti-aphrodisiacal compounds in the ARG secretion of mated female P. rapae, whereas indole was lacking in the secretion of virgin female P. rapae. When applied onto the leaf, indole induced changes in the foliar chemistry that arrested T. brassicae wasps  (Fatouros et al.,2009).

Drosophila melanogaster males court mated females significantly less actively than they court virgins. Courtship-inhibiting chemicals (anti-aphrodisiacs) released by mated females when males are present could play a role in controlling the sexual attractiveness of mated females. To test this hypothesis, the attractiveness of intact mated females, which are able to release aversive chemical signals, was compared to that of decapitated mated females, which do not release the signals. By 24 h after mating, reduced female sexual attractiveness was due almost entirely to anti-aphrodisiacs released when males were present. Anti-aphrodisiacs vary between strains, and have been identified as hydrocarbons found primarily on the cuticle of mature males. The quantity of these hydrocarbons on mated females increases when males are present, but the increase is not due to tranfer from the males. When males with radiolabelled cuticular hydrocarbons were paired with mated females, no transfer of label could be detected. Interstrain comparisons showed that males from one strain do not necessarily respond to the anti-aphrodisiac of another, and that male cuticular hydrocarbons may provide a chemical stimulus that induces release of anti-aphrodisiac by mated females. (Scott et al.,1990).

Gregarious mature males of the desert locust (Schistocerca gregaria) emit a courtship-inhibiting pheromone continuously to repel rivals. This signal evokes a strong response from males with recent experience of mature females. However, if males have been female deprived for some time, they start to ignore the pheromone and attempt to usurp females that are guarded by males. The probability and intensity with which males struggle for an occupied mate was found to depend on the time previously spent without a female. This adaptive behaviour is similar to the response to host-marking pheromones in phytophagous insects and parasitoids (Seidelmann et al.,2006).

Males of the beetle Tenebrio molitor produce a volatile sex pheromone which attracts females of the same species. The pheromone level peaks 8 days after emergence and then reaches a plateau. Elimination of endocrine centers by decapitating male adults 24 hr following adult ecdysis did not impair pheromone production. Treatment of decapitated males with juvenile hormone analogues did not make any detectable difference in the levels of pheromone activity. However, undecapitated males treated with juvenile hormone analogue showed a significant increase in pheromone activity when compared with those that had been decapitated and subsequently treated with juvenile hormone analogue. This observation is discussed in the light of published research on the effect of juvenile hormone on pheromone activity of females of T. molitor (Menon et al.,1976).

Phoretic insects utilize other animals to disperse to new environments. We recently discovered how egg parasitoids use an exciting phoretic strategy to reach egg-laying sites of their butterfly hosts. In the laboratory, femaleTrichogramma wasps detect and mount mated female cabbage white butterflies that emit an anti-aphrodisiac pheromone. Hardly any information exists about the natural occurrence of phoresy in wasps of this genus. Therefore, we monitored the presence of phoretic Trichogramma wasps on lepidopteran hosts in the field. Only female wasps were found at low prevalence on six lepidopteran species. Wasps were mostly found on female hosts and mainly on abundant solitary host species. This is the first report of phoretic Trichogramma wasps on butterflies in nature. We suggest that phoresy is only one of several strategies used by these polyphagous egg parasitoids. The evolution of phoresy is discussed in relation to the nutritional ecology of egg parasitoids (Fatouros et al.,2012).

References:

Colin S. Brent and  John A. Byers.2011. Female attractiveness modulated by a male-derived anti-aphrodisiac pheromone in a plant bug. Animal Behaviour, 82:937-943.

Fatouros, Nina E., and Martinus E. Huigens.2012."Phoresy in the field: natural occurrence of Trichogramma egg parasitoids on butterflies and moths."BioControl 57(4): 493-502.

Fatouros, Nina E., Colette Broekgaarden, Gabriella Bukovinszkine'Kiss, Joop JA van Loon, Roland Mumm, Martinus E. Huigens, Marcel Dicke, and Monika Hilker. 2008. Male-derived butterfly anti-aphrodisiac mediates induced indirect plant defense." Proceedings of the National Academy of Sciences105(29):10033-10038.

Fatouros, Nina E., Foteini G. Pashalidou, Wilma V. Aponte Cordero, Joop JA van Loon, Roland Mumm, Marcel Dicke, Monika Hilker, and Martinus E. Huigens.2009. Anti-aphrodisiac compounds of male butterflies increase the risk of egg parasitoid attack by inducing plant synomone production." Journal of chemical ecology 35(11):1373-1381.

Guiraudie‐Capraz, Gaëlle, Dang Ba Pho, and Jean‐Marc Jallon.2007.Role of the ejaculatory bulb in biosynthesis of the male pheromone cis‐vaccenyl acetate in Drosophila melanogaster." Integrative zoology 2,(2): 89-99.

Harraca, Vincent, Camilla Ryne, and Rickard Ignell.2010.Nymphs of the common bed bug (Cimex lectularius) produce anti-aphrodisiac defence against conspecific males." BMC biology 8(1): 121.

Haynes, Kenneth F., Mark H. Goodman, and Michael F. Potter.2010. Bed bug deterrence." BMC biology 8(1): 117.

Huigens, Martinus E., Jozef B. Woelke, Foteini G. Pashalidou, T. Bukovinszky, Hans M. Smid, and Nina E. Fatouros.2010. Chemical espionage on species-specific butterfly anti-aphrodisiacs by hitchhiking Trichogramma wasps." Behavioral Ecology 21(3): 470-478.

Mellström, Helena Larsdotter, and Christer Wiklund.2009. Males use sex pheromone assessment to tailor ejaculates to risk of sperm competition in a butterfly." Behavioral Ecology 20(5):1147-1151.

Menon, Maya.1976. Hormone-pheromone relationships of male Tenebrio molitor."Journal of Insect Physiology 22 (7):1021-1023.

Milonas, P. G., A. F. Martinou, D. Ch Kontodimas, F. Karamaouna, and M. A. Konstantopoulou. 2009.Attraction of different Trichogramma species to Prays oleae sex pheromone." Annals of the Entomological Society of America 102(6):1145-1150.

Schulz, S., Estrada, C., Yildizhan, S., Boppré, M., and Gilbert, L.E. 2008. An antiaphrodisiac in Heliconius melpomene butterflies. J. Chem. Ecol. 34:82-93.

Scott, David, and Larry L. Jackson.1990. The basis for control of post-mating sexual attractiveness by Drosophila melanogaster females." Animal behaviour 40(5): 891-900.

Seidelmann, Karsten.2006.The courtship-inhibiting pheromone is ignored by female-deprived gregarious desert locust males." Biology letters 2(4): 525-527.

Siwicki, Kathleen K., Paul Riccio, Lisa Ladewski, Fabrice Marcillac, Laurence Dartevelle, Stephanie A. Cross, and Jean-François Ferveur.2005.The role of cuticular pheromones in courtship conditioning of Drosophila males."Learning & Memory 12(6): 636-645

Vander Meer, Robert K., Martin S. Obin, Stephen Zawistowski, Kathy B. Sheehan, and Rollin C. Richmond. 1996.A reevaluation of the role of cis-vaccenyl acetate, cis-vaccenol and esterase 6 in the regulation of mated female sexual attractiveness in Drosophila melanogaster." Journal of insect physiology 32(8):681-686.

Zhou, Chuan, Hai Huang, Susy M. Kim, Hsuanwen Lin, Xianglan Meng, Kyung-An Han, Ann-Shyn Chiang, Jing W. Wang, Renjie Jiao, and Yi Rao.2012. Molecular genetic analysis of sexual rejection: roles of octopamine and its receptor OAMB in Drosophila courtship conditioning." The Journal of Neuroscience 32(41): 14281-14287.

Anti-aggregation pheromone:Pheromone Resources

Anti-aggregation pheromone:

Disrupt Micro-Flake Verbenone Bark Beetle Anti-Aggregant flakes (Hercon Environmental, Inc., Emigsville, Pennsylvania) were applied in two large-scale tests to assess their efficacy for protecting whitebark pine Pinus albicaulis Engelm. from attack by mountain pine beetle Dendroctonus ponderosae Hopkins (Coleoptera: Scolytinae) (MPB). At two locations, five plots of equivalent size and stand structure served as untreated controls. All plots had early- to mid-outbreak beetle populations (i.e. 7.1–29.2 attacked trees/ha). Verbenone was applied at 370 g/ha in both studies. Intercept traps baited with MPB aggregation pheromone were placed near the corners of each plot after the treatment in order to monitor beetle flight within the plots. Trap catches were collected at 7- to 14-day intervals, and assessments were made at the end of the season of stand structure, stand composition and MPB attack rate for the current and previous years (Gillette et al.,2012). 

When applied a blend of NHV and verbenone, released from dispensers fixed at 2 and 6 m height at forest edges with high Ips typographus populations. In Slovakia, three different doses (0.2–0.7 dispensers/m forest edge) were tested in 20-tree zones of spruce stand edges. The Swedish experiments used only the middle dose. In Slovakia, there was high tree mortality but dispensers with the anti-attractants reduced killed trees in a dose-dependent manner. The reduction in tree killing ranged from 35 to 76% compared to untreated zones. Regression analysis of relative tree kill on log dispenser density was highly significant ( = 0.34, corresponding effect size d≈ 0.98). In Sweden, with lower beetle populations, most attacks (99%) were found outside the experimental areas, with high attack rates (15 trees/ha) in a range of 15–30 m from treated groups, indicating an active inhibitory radius exceeding the previous estimates (Schiebe et al.,2011). 

Description of currently available semiochemical methods for use in monitoring and controlling bark beetle pests in western conifer forests. Delivery systems include hand-applied methods, such as semiochemical-releasing bubblecaps, pouches, and "puffers," as well as products that can be applied by aircraft such as semiochemical-releasing flakes. Descriptions of both attractant-based ("pull") and anti-attractant-based ("push") strategies are provided. Examples are provided for the major bark beetle pests in western North America, including the mountain pine beetle (Dendroctonus ponderosae Hopkins), western pine beetle (Dendroctonus brevicomis LeConte), the Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins), the spruce beetle [Dendroctonus rufipennis (Kirby)], and the red turpentine beetle (Dendroctonus valens LeConte) (Gillette  and  Steve,2009).

Attraction of a major predator, Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), to the aggregation pheromone ofD. brevicomis was reduced by verbenone, but not by acetophenone. Moreover, the T. chlorodia : D. brevicomis ratio for the pooled acetophenone treatment was 1.7-fold greater than that for the attractant alone and two-fold greater than the ratio for the pooled verbenone treatment, suggesting that acetophenone would not disrupt populations of this natural enemy  (Erbilgin et al.,2008). 

Catches of I. sexdentatus, an opportunistic species normally attacking fresh dead host material, were also gradually reduced with increasing verbenone dose. Catches of Tomicus piniperda L., O. erosus, Dryocoetes autographus (Ratzeburg), H. eruditus, Xyleborus dryographus (Ratzeburg), Hylastes ater (Paykull), Hylurgus ligniperda (F.), H. attenuatus, and B. incanus were not significantly affected by verbenone. The effects of verbenone were consistent with differences in host-age preference. Semiochemical disruption by verbenone in P. pubescens and I. sexdentatus could represent an integrated pest management strategy for the prevention of the spread of pitch canker disease between different stands. However, several species associated with F. circinatum were unaffected by verbenone, not supporting this compound for prevention of the establishment of potential vectors in Northern Spain (Romón et al.,2007). 

Males initiate host location and produce semiochemicals which attract both males and females. A successful mass attack must first overcome the resistance of the host tree. Pioneer I. typographus evolved to use the resin flow of host trees as kairomones in host location, and synthesized semiochemicals initially to detoxify the resin. If small bark beetle populations infest healthy trees, mass attack is prevented by host resistance. Nine monoterpene alcohols were found in male hind-guts, including cis-verbenol (cV) and 2-methyl-3-buten-2-ol (MB) which are regarded as primary aggregation pheromones, and a low proportion of Ipsdienol (Id) which increases attractiveness of cV and MB. Verbenone (Vn) and Ipsenol (Ie) are anti-aggregation pheromones, that play important roles in adjusting attack density and insect density under the bark (Sun et al.,2006). 

In a study site in interior northern California, twenty individual lodgepole pines  Pinus contorta were sprayed with a suspension of DISRUPT Micro-Flake^® Verbenone (4,6,6-trimethylbicyclo(3.1)hept-3-en-2-one) Bark Beetle Anti-Aggregant flakes (Hercon Environmental, Emigsville, Pennsylvania) in water, with sticker and thickener, from ground level to a height of 7 m. Twenty trees sprayed with just water, sticker and thickener served as controls. All trees were baited immediately after spraying with mountain pine beetle Dendroctonus ponderosae aggregation pheromone lures, and lures were refreshed after 4 weeks (Gillette et al.,2006). 

Sex and aggregation pheromones consist of species–specific blends of chemicals. The way in which different species’ blends have evolved has been the subject of some debate. Theoretical predictions suggest that differences between species have arisen not through the accruing of small changes, but through major shifts in chemical composition. Using data on the aggregation pheromones of 34 species of bark beetle from two genera, Dendroctonus and Ips, we investigated how the distributions of the chemical components of their pheromone blends mirror their phylogenetic relationships. It was  tested whether there were consistent patterns that could be used to help elucidate the mode of pheromone evolution. Although there were obvious differences in pheromone blends between the two genera, the differences between species within each genus followed a less clear phylogenetic pattern. In both genera, closely related species are just as different as more distantly related species. Within Dendroctonus, particularly, most chemical components were distributed randomly across the phylogeny. Indeed, for some chemicals, closely related species may actually be more different than would be expected from a random distribution of chemical components (Symonds et al.,2004). 

Recent electrophysiological and behavioural studies clearly indicate that conifer-inhabiting bark beetles are not only able to recognize, but also to avoid, nonhost habitats or trees by olfactory means. Green leaf volatiles (GLV), especially C6-alcohols, from the leaves (and partly from bark) of nonhost angiosperm trees, may represent nonhost odour signals at the habitat level. Specific bark volatiles such as trans-conophthorin, C8-alcohols, and some aromatic compounds, may indicate nonhosts at the tree species level. Flying bark beetles are also capable of determining whether a possible host is unsuitable by reacting to signals from conspecifics or sympatric heterospecifics that indicate old or colonized host tree individuals (Zhang et al.,2004). 

The relative benefits to senders versus receivers of these signals are only partly understood. Because the initial stage of host entry can be hazardous, there may be benefit to a cheating strategy, whose practitioners respond to pheromones but do not engage in host searching. Several disadvantages to cheating have been proposed, but the role of predators has not been considered. Predators exploit bark beetle pheromones to locate prey, accumulate at the breeding site, and consume adult bark beetles before they enter the tree. Preliminary experiments quantified arrival patterns in the field. We used a laboratory assay to investigate relative predation on pioneers (those that initially select and enter hosts) and responders (those that arrive at a host in response to pheromones) during host colonization (Aukema et al.,2004). 

Ips pini demonstrated a parabolic response, in which low concentrations of α-pinene had no effect on attraction to its pheromone, intermediate concentrations were synergistic and high concentrations were inhibitory. These results suggest optimal release rates for population monitoring and suppression programmes. Reduced attraction to a low ratio of α-pinene to pheromone, as occurs when colonization densities become high and the tree's resin is largely depleted, might reflect a mechanism for preventing excessive crowding. Thanasimus dubius, the predominant predator of I. pini, was also attracted to ipsdienol plus lanierone, but its response differed from that of its prey. Attraction increased across all concentrations of α-pinene (Erbilgin et al.2003). 

Volatiles emitted by female ABB boring into plum branches were collected on Porapak Q and eluted with hexane. GC-EAD analyses of volatile extracts, using female antennae as an electroantennographic detector, revealed four EAD-active candidate pheromone components, as follows: (3S,4S)-4-methyl-3-heptanol (SS-I), most abundant and EAD-active component; (3S,4S)-4-methyl-3- hexanol (SS-II); (5S,7S)-7-methyl-1,6-dioxaspiro[4,5]decane (III); and 7-methyl-1,6-dioxaspiro [4,5]dec-8-ene [IV], the first unsaturated spiroaketal found in insects. In field experiments (1994- 1998) using funnel traps baited with polyethylene pheromone dispensers, SS-I unlike SS-II was attractive by itself, while SS-I plus SS-II at a ratio of 2:1 was optimally attractive. Addition of stereoisomeric mixtures of III and/or IV did not affect trap captures. Candidate kairomones ethanol and propanol did not affect total trap catches. Methanol, in contrast, strongly inhibited attraction of beetles to pheromone-baited traps and prevented colonization of cut branches. It failed, however, to reduce damage to tree buds caused by ABB maturation feeding. Although SS-I plus SS-II was twice as attractive as the stereoisomeric mixtures of 4-methyl-3-heptanol plus 4-methyl-3-hexanol, these readily obtainable stereoisomeric mixtures can be used for both pheromone-based monitoring and control of ABB populations (Ben-Yehuda et al.,2002). 

Two mark–recapture experiments and a trap interference experiment were conducted to determine the sampling range and range of attraction, respectively, of Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae) pheromone-baited traps in northern Idaho. To determine the sampling range, either live beetles or logs containing brood were marked with one of four colors of fluorescent powder. Colored beetles or logs were placed along transects oriented away from a central pheromone-baited trap at distances of 50, 100, 200, and 300 m. A release distance of 400 m was added to one mark–recapture experiment during the 2nd year. To determine the range of attraction, a trap interference study was conducted. For this experiment, groups of three traps were oriented in equilateral triangles with distances of 50, 100, 200, and 300 m between the three traps. Distances between traps were changed daily to allow for adequate replication. Mark–recapture studies indicated that most D. pseudotsugaewere recaptured from distances less than or equal to 200 m from the pheromone-baited trap. On average, 95% of beetles recaptured were males (Dodds et al.,2002). 

The objective was to determine how these bark beetles respond to verbenone, a purported anti-aggregation pheromone of several economically significant bark beetle species. Catches of Dendroctonus ponderosae Hopkins, a species attacking live trees, were unaffected relative to a control trap (no verbenone) at release rates of 0.2 mg/24 h or less, but were significantly reduced at rates of 1.8 mg/24 h or more. Catches of Ips pini (Say) and I. latidens (LeConte), two opportunistic species normally attacking fresh, dead host material, were gradually reduced with increasing verbenone dose. Verbenone did not affect catches of Hylurgops porosus (LeConte) and Hylastes longicollis Swaine, two species normally associated with bark in contact with the ground, where saprophytic microorganisms quickly invade phloem tissue (Lindgren et al.,2002). 

The response of bark beetle predators and woodboring beetles to the bark beetle anti-aggregation pheromone, verbenone, was tested in the field with multiple-funnel traps baited with attractant kairomones. Catches of the predators Thanasimus undatulus (Say), Enoclerus sphegeus (F.), Enoclerus lecontei (Wolcott) (Coleoptera: Cleridae), and Lasconotus complex LeConte (Coleoptera: Colydiidae) declined significantly with increasing release rates of verbenone. Lasconotus subcostulatus Kraus, andCorticeus praetermissus (Fall) (Coleoptera: Tenebrionidae) (in two of three experiments), showed no significant response to verbenone. In a third experiment, catches of C. praetermissus increased with verbenone dose. Likewise, catches of the striped ambrosia beetle, Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae), increased with verbenone dose in one experiment, but there was no effect in two other experiments. Verbenone had no effect on the response of Spondylis upiformis Mannerheim (Coleoptera: Cerambycidae) (Lindgren et al.,2002). 

Large numbers of males and females were attracted to the bored logs, and the total numbers increased as the number of entry holes in the logs increased. This result shows that both male and female beetles aggregate on logs bored by the males. Then collected a large number of beetles attracted to living trees bored by the beetles, and the total number of beetles collected increased as the number of entry holes/m² on the tree trunk increased. Beetles also aggregated on living trees bored by the males  (Ueda et al.,2001). 

Field tests of verbenone, a potential antiaggregation pheromone of the northern spruce engraver, Ips perturbatus (Eichhoff), were conducted in south-central and interior Alaska in stands of Lutz spruce, Picea xlutzii (Little), and white spruce, P. glauca (Moench) Voss, respectively. Addition of 84%-(-)-verbenone at a high release rate to the three-component aggregation pheromone of I. perturbatus (racemic ipsenol, racemic ipsdienol, and 83%-(-)-cis-verbenol), significantly reduced trap catches. The results of this study, combined with previous results on the presence of verbenone in extracts of volatiles collected from feeding I. perturbatus and GC-EAD data, are consistent with antiaggregant behavioral activity of verbenone for I. perturbatus  ( Holsten et al.,2001). 

Compared pheromone-baited traps and trap trees for managing Douglas-fir beetle (DFB), Dendroctonus pseudotsugae Hopkins populations. Pheromone-baited traps caught significantly more DFB than did trap trees. More male DFB were caught in pheromone-baited traps than in trap trees, while significantly higher numbers of females were caught in the trap trees. Additional benefits of pheromone-baited traps include, easy deployment, less mortality of some beneficial insects, and low cost (Dodds et al.,2000). 

Possible examples include chemically disguising the host, adding toxins and altering the levels of pheromone precursors, attractants for predators or hormone mimics to disrupt insect development. Strategies and prospects for generating transgenic conifers with increased defense capability are discussed (Phillips et al.,1999). 

Males produce an aggregation pheromone when on food, that attracts dispersing males and females. P. truncatus aggregation pheromone is being used to monitor the spread of P. truncatus (Larger Grain Borer) across Africa. The biological function of this pheromone is controversial. This thesis investigates the role of aggregation pheromone in mate choice in P. truncatus.;The literature on Coleopteran aggregation pheromones was reviewed, with particular reference to the possible adaptive functions of aggregation pheromones.;Variation in Prostephanus truncatus aggregation-pheromone signalling was detected. Conspecifics can detect these differences and are preferentially attracted to some males more than others. Both males and females 'agree' which males are most attractive (shown in a laboratory bioassay and in trapping experiments in the field). Females also discriminate between potential mates on contact by a stylised pushing behaviour. Some males consistently secure more matings than others when two males are presented at once to a female. Discrimination between males mediated on contact through pushing is not influenced by the male's aggregation pheromone signal (both natural variation and manipulation of the pheromone signal were studied).;Observation of adult beetles in an artificial host sandwiched between two glass plates revealed that males and females pair up, and cohabit within the same tunnel system (Birkinshaw,1998).

An investigation was carried out to evaluate the two models of pheromone 
evolution in bark beetles. One of the models depicts pheromone evolution as plastic. Such model predicts that the phylogenetic distribution of pheromone components  (Cognato et al.,1997). 

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, anti aggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), was applied to stands of Douglas-fir, Pseudotsuga menziesii(Mirabel) Franco, at high risk for infestation to determine the lowest effective dose for protecting live trees. MCH was applied at rates of 50, 100, and 150 bubble capsules per hectare (20, 40, and 60 g/ha, respectively) in 1994, and 15, 30, and 50 bubble capsules per hectare (6, 12, and 20 g/ha, respectively) in 1995. Mean release rates throughout the beetle flight periods in 1994 and 1995 were 1.63 and 1.23 milligrams per capsule per day, respectively. For both years, catches of Douglas-fir beetles in pheromone-baited traps located at the plot centers were significantly lower on all MCH-treated plots compared with untreated plots, but there were no differences among the 3 doses of MCH. In contrast, NCR had no effect on the numbers of 3 predators [Thanasimus undatulus (Say), Enoclerus sphegeusF., and Temnochila chlorodia (Mannerheim)] collected in the traps during either year. In 1994, the percentage of Douglas-fir ≥20 cm diameter at breast height (abh) that were mass attacked was significantly lower on MCH-treated plots compared with the untreated control, and all 3 doses were equally effective (Ross et al.,1996). 

The use of semiochemicals, including pheromones, that modify insect behavior is still a developing area of science. The awareness of environmental and safety hazards, associated with insecticides, coupled with the technology to measure their presence, have lead to increasing restrictions on their use. The costs of introducing new insecticides or even re-registration of existing insecticides, is time consuming and expensive. These problems with insecticides have driven the search for new control technology. Pheromones and other behavior-modifying chemicals found naturally in the environment, offer non-insecticidal alternatives which are being commercially pursued by both new companies and established giants of the insecticide industry (Flint et al.,1996). 

Crabapple leaves that had been damaged overnight by Japanese beetles or fall webworms attracted significantly more Japanese beetles than did undamaged leaves. Artificially damaged leaves or leaves freshly damaged by Japanese beetles, however, were not significantly more attractive than undamaged leaves. Leaves that had been damaged overnight by Japanese beetles or fall webworms produced a complex mixture of aliphatic compounds, phenylpropanoid-derived compounds, and terpenoids. In comparison, artificially damaged leaves or leaves with fresh Japanese beetle feeding damage generated a less complex blend of volatiles, mainly consisting of green-leaf odors. Feeding-induced odors may facilitate host location and/or mate finding by the Japanese beetle (Loughrin et al.,1995).

Verbenone significantly reduced catches of Ips latidens(LeConte), I. pini (Say), and Dendroctonus ponderosae Hopkins in multiple-funnel traps, baited with aggregation pheromones, in stands of lodgepole pine in southern British Columbia. Interruption of attraction was dose dependent for all three species. There were no significant differences in attraction between the sexes. Variation in successful use of verbenone in protecting pine stands partially may be explained by the dose-dependent variation in responses (Miller et al.,1995). 

The first aggregation pheromone components from bark beetles were identified in 1966 as a mixture of ipsdienol, ipsenol and verbenol. Since then, a number of additional components have been identified as both aggregation and anti-aggregation pheromones, with many of them being monoterpenoids or derived from monoterpenoids. The structural similarity between the major pheromone components of bark beetles and the monoterpenes found in the host trees, along with the association of monoterpenoid production with plant tissue, led to the paradigm that most if not all bark beetle pheromone components were derived from host tree precursors, often with a simple hydroxylation producing the pheromone. In the 1990s there was a paradigm shift as evidence for de novo biosynthesis of pheromone components began to accumulate, and it is now recognized that most bark beetle monoterpenoid aggregation pheromone components are biosynthesized de novo. The bark beetle aggregation pheromones are released from the frass, which is consistent with the isoprenoid aggregation pheromones, including ipsdienol, ipsenol and frontalin, being produced in midgut tissue. It appears that exo-brevocomin is produced de novo in fat body tissue, and that verbenol, verbenone and verbenene are produced from dietary α-pinene in fat body tissue.  (Blomquist et al.,1995). 

Pheromone production and/or release by beetles is coordinated with a variety of behavioral, physiological, and environmental factors. To data, two basic mechanisms for the regulation of pheromone biosynthesis in beetles have been proposed. Pheromone biosynthesis may simply be dependent on the availability of biosynthetic precursors. Alternatively, certain stimuli or events may trigger pheromone biosynthesis via juvenile hormone (JH) action. JH may either act directly at the site of pheromone biosynthesis to enhance pheromone production or may act indirectly, through a brain hormone (which might be related to the pheromone biosynthesis activating neuropeptide) or through effects on antennal sensory response. Knowledge of the regulation of the initiation and termination of pheromone biosynthesis is reviewed. Mechanisms by which pheromone stereochemistry is controlled are also discussed. This is an important aspect of pheromone production in Coleoptera, since slight changes in the stereochemistry can completely alter the activity of the molecule (Vanderwel et al.,1994). 

Synthetic host marking pheromone (HMP) of the European cherry fruit fly (R. cerasi) as a fruit-infestation-reducing-agent in an experimental cherry orchard. Two different pheromone deployment strategies were compared: covering entire tree canopies with synthetic HMP or treating only one half (top to bottom or lower half) of the tree canopy. Pheromone application caused a tenfold reduction in fruit infestation if the entire tree canopy was covered (0.226 vs 0.021 pupae/fruit in untreated and treated trees, respectively). Results show, nevertheless, that a significant reduction in fruit infestation can be achieved by treating only one half of tree canopies (top to bottom) (0.021 vs 0.048 pupae/fruit when comparing totally vs partially treated trees) (Aluja et al.,1992). 

The capture of pine engravers, Ipspini (Say), in ipdienol-baited, multiple-funnel traps in British Columbia was significantly reduced when devices releasing ipsenol or verbenone were placed in the traps. These results suggest that ipsenol and verbenone are synomones released byIpslatidens (LeC.) and the mountain pine beetle, Dendroctonusponderosae m centres. The antiaggregant composition of verbenone plus ipsenol has considerable operational potential for use in precommercial thinnings and in areas where standing pines are of high value; e.g., in rural subdivisions, shelterbelts, and recreational forests. 4 grid of 16 release devices at 5- × mg per day per tree, respectively, there was a 66.7% reduction in the number of logs attacked and a 98.8% reduction in attack density. The same treatment caused a 74.1% reduction in attack density on standing trees surrounded by a 4 m apart on felled trees, at 50 and 1.5 Hopk., respectively. When verbenone and ipsenol were released together from five stations ( Borden et al.,1992). 

Verbenone per hectare. There were significantly fewer successfully attacked trees on the treated plots, as evidenced by ( mm plastic beads and applied without benefit of a sticker at the rate of 54 5 × aerial treatments of the antiaggregation pheromone, verbenone, were applied to lodgepole pine stands infested with mountain pine beetle in northwestern Montana. The pheromone was formulated by PHERO TECH Inc. in controlled-release, cylindrical 5i) a fourfold greater incidence of current-year attacked trees per hectare in the untreated check plots and (ii0.05) in the treated plots. = 0.05) ratio of 1988:1987 attacked trees in the treated plots. Further, the number of trees per hectare resisting attacks (as reflected by number of trees pitching out bark beetles) was higher (α = ) the significantly lower (Shea et al.,1992). 

E-Myrcenol reduced catches of the pine engraver, Ips pini (Say), to ipsdienol-baited, multiple-funnel traps in a dose-dependent fashion. The sex ratio was unaffected by E-myrcenol treatments. Lures containing E-myrcenol in ethanol solution failed to protect freshly cut logs of lodgepole pine from attack by I. pini. Rather, I. pini preferentially attacked logs treated with devices releasing E-myrcenol and ethanol, over nontreated, control logs. Our results demonstrate that E-myrcenol is a new pheromone for I. pini, and emphasize the importance of understanding basic pheromone biology before utilisation of a semiochemical in forest pest management (Miller et al.,1990). 

Verbenone: (1R)-cis-4,6,6-Trimethylbicyclo-[3.1.1] hept -3-en- 2-one ) is a synthetic pheromone treatment that replicates the anti-aggregate pheromone in  Mountain Pine Beetleswhere it repels beetles from further attack and encourages them to seek unoccupied host trees (Nils Chr.Slenseth,1989).

The monoterpene α-pinene, a major component of the terpene composition of Pinus spp., has been reported to act as a host-produced kairomone for a variety of bark beetle species, including the mountain pine beetle, Dendroctonusponderosae Hopkins. However, our experiments indicate that α-pinene autoxidizes under normal temperature and atmospheric conditions to form significant quantities of trans-verbenol, an aggregation pheromone for many species of bark beetles. The quantities of α-pinene present in the resin that can flow from small wounds in pine trees appear to be sufficient to produce trans-verbenol at rates similar to those by female beetles that are actively synthesizing the compound.trans-Verbenol can then autoxidize rapidly to form verbenone, with the content of this compound reaching 8% within 13 weeks of exposure to air. Verbenone is often used by scolytids as an antiaggregation pheromone. Approximately 1.9% of the trans-verbenol and 2.7% of the verbenone found in Porapak Q aerations of phloem with boring spruce beetle, Dendroctonusrufipennis (Kirby), females, as well as 0.8% of the trans-verbenol and 0.8% of the verbenone found in aerations of phloem with boring D. ponderosaefemales, was due to the autoxidation of α-pinene and (or) the release of oxygenated compounds found in the phloem before bark beetle attack. The natural interconversion of α-pinene, trans-verbenol, and verbenone under ambient conditions suggests that many experiments involving the behavioral activity of these compounds require re-evaluation  (Hunt et al.,1989). 

It is supposed that the decline in beetle population was a combined effect of cool and wet summer weather, which limited the flight activity of the beetle and restored the resistance of the trees to beetle attack, and an extensive control program where mass trapping of beetles in response to synthetic pheromone was an important part ( Bakke et al.,1983). 

As the field of pheromone research evolved, and it became clear that pheromones possessed great potential as components of pest management strategies, it became necessary (a) to define precisely the pheromonal blend emitted by the insect, (b) to determine the rates of production and release of the blends by the insect, and (c) to develop controlled release systems for use in monitoring, mass trapping, and aerial dissemination control programs (Golub  and Iain, 1984).

There are 3 important species, Trypodendron lineatum (Olivier),Gnathotrichus sulcatus (LeConte) and G. retusus (LeConte). Each spring they infest the sapwood of coniferous trees that have died the previous winter. Female T. lineatum and male Gnathotrichus spp. initiate the attack and produce aggregation pheromones which induce mass attack on suitable hosts (Borden et al.,1981). 

Gillette, Nancy E., E. Matthew Hansen, Constance J. Mehmel, Sylvia R. Mori, Jeffrey N. Webster, Nadir Erbilgin, and David L. Wood.2012. Area‐wide application of verbenone‐releasing flakes reduces mortality of whitebark pine Pinus albicaulis caused by the mountain pine beetle Dendroctonus ponderosae. Agricultural and Forest Entomology 14(4):367-375.

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