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.

 References:

Flint, Hoflis M., and Charles C. Doane.1996. Understanding semiochemicals with emphasis on insect sex pheromones in integrated pest management programs." Radcliffe’s IPM world textbook, URL: http://​ ipmworld.​ umn.​ edu, University of Minnesota, St. Paul, MN.

Aukema, Brian H., and Kenneth F. Raffa.2004. Gender-and sequence-dependent predation within group colonizers of defended plants: a constraint on cheating among bark beetles?." Oecologia 138(2): 253-258.

Cognato, Anthony I., Steven J. Seybold, David L. Wood, and Stephen A. Teale.1997.A cladistic analysis of pheromone evolution in Ips bark beetles (Coleoptera: Scolytidae)." Evolution 51(1):313-318.

Schiebe, Christian, M. Blaženec, R. Jakuš, C. Rikard Unelius, and Fredrik Schlyter.2011.Semiochemical diversity diverts bark beetle attacks from Norway spruce edges." Journal of Applied Entomology 135(10): 726-737.

Golub, Mitzi A., and Iain Weatherston.1984.Techniques for extracting and collecting sex pheromones from live insects and from artificial sources. InTechniques in Pheromone Research, pp. 223-285. Springer New York.

Raffa, Kenneth F., THOMAS W. Phillips, and SCOTT M. Salom.1993. Strategies and mechanisms of host colonization by bark beetles." Beetle-pathogen interactions in conifer forests,103-120.

Sun, Xiao-ling, Qing-yin Yang, Jonathan David Sweeney, and Chang-qi Gao. 2006. A review: chemical ecology of Ips typographus (Coleoptera, Scolytidae)."Journal of forestry research 17(1):65-70.

Holsten, Edward H., Roger E. Burnside, and Steven J. Seybold.2001.Verbenone interrupts the response to aggregation pheromone in the northern spruce engraver, Ips perturbatus (Coleoptera: Scolytidae), in south-central and interior Alaska." Journal of the Entomological Society of British Columbia 98:251-256.

Dodds, Kevin J., Darrell W. Ross, and Gary E. Daterman. 2000. A comparison of traps and trap trees for capturing Douglas-fir beetle, Dendroctonus pseudotsugae (Coleoptera: Scolytidae)." Journal of the Entomological Society of British Columbia 97: 33-38.

Gillette, Nancy E., and A. Steve Munson.2009. Semiochemical sabotage: Behavioral chemicals for protection of western conifers from bark beetles.

Shea, Patrick J., Mark D. McGregor, and Gary E. Daterman. 1992.Aerial application of verbenone reduces attack of lodgepole pine by mountain pine beetle." Canadian Journal of Forest Research 22(4): 436-441.

Lindgren, B. Staffan, and Daniel R. Miller.2002.Effect of verbenone on attraction of predatory and woodboring beetles (Coleoptera) to kairomones in lodgepole pine forests." Environmental Entomology 31(5): 766-773.

Zhang, Qing‐He, and Fredrik Schlyter.2004. Olfactory recognition and behavioural avoidance of angiosperm nonhost volatiles by conifer‐inhabiting bark beetles." Agricultural and Forest Entomology 6(1): 1-20.

Ueda, Akira, and Masahide Kobayashi.2001. Aggregation of Platypus quercivorus (Murayama)(Coleoptera: Platypodidae) on oak logs bored by males of the species." Journal of forest research 6(3):173-179.

Miller, D. R., G. Gries, and J. H. Borden.1990. "E-myrcenol: a new pheromone for the pine engraver, Ips pini (Say)(Coleoptera: Scolytidae)." The Canadian Entomologist 122(3):401-406.

Borden, John H., and John A. McLean.1981.Pheromone-based suppression of ambrosia beetles in industrial timber processing areas." In Management of Insect Pests with Semiochemicals, pp:133-154. Springer US.

Bakke, A.1983. Host tree and bark beetle interaction during a mass outbreak of Ips typographus in Norway1." Zeitschrift für angewandte Entomologie 96(1-5)118-125.

Romón, Pedro, Juan Carlos Iturrondobeitia, Ken Gibson, B. Staffan Lindgren, and Arturo Goldarazena.2007. "Quantitative association of bark beetles with pitch canker fungus and effects of verbenone on their semiochemical communication in Monterey pine forests in northern Spain." Environmental Entomology 36(4):743-750.

Birkinshaw, Lucy A.1998. Mate choice in prostephanus truncatus (horn)(coleptera: bostrichidae): the role of male-produced aggregation pheromone." PhD disserattion., Theses, Dept. of Biology. University of Leicester.

Borden, J. H., D. R. Devlin, and Dan R. Miller.1992.Synomones of two sympatric species deter attack by the pine engraver, Ips pini (Coleoptera: Scolytidae)."Canadian Journal of Forest Research 22(3):381-387.

Hunt, D. W. A., J. H. Borden, B. S. Lindgren, and G. Gries.1989.The role of autoxidation of α-pinene in the production of pheromones of Dendroctonus ponderosae (Coleoptera: Scolytidae)." Canadian Journal of Forest Research19(10):1275-1282.

Dodds, Kevin J., and Darrell W. Ross.2002.Sampling range and range of attraction of Dendroctonus pseudotsugae pheromone-baited traps." The Canadian Entomologist 134(3): 343-355.

Ross, Darrell W., Kenneth E. Gibson, Ralph W. Their, and Steve A. Munson.1996. Optimal Dose of an Antiaggregation Pheromone (3-Methylcyclohex-2-en-1-one) for Protecting Live Douglas-Fir from Attack by Dendroctonus pseudotsugae (Coleopera: Scolytidae)." Journal of economic entomology 89(5):1204-1207.

Gillette, Nancy E., John D. Stein, Donald R. Owen, Jeffrey N. Webster, Gary O. Fiddler, Sylvia R. Mori, and David L. Wood.2006. Verbenone‐releasing flakes protect individual Pinus contorta trees from attack by Dendroctonus ponderosae and Dendroctonus valens (Coleoptera: Curculionidae, Scolytinae)." Agricultural and Forest Entomology 8(3): 243-251.

Symonds, Matthew RE, and Mark A. Elgar.2004.The mode of pheromone evolution: evidence from bark beetles. Proceedings of the Royal Society of London, Series B: Biological Sciences 271(1541): 839-846.

Ben-Yehuda, S., T. Tolasch, W. Francke, R. Gries, G. Gries, D. Dunkelblum, and Z. Mendel.2002. Aggregation pheromone of the almond bark beetle Scolytus amygdali (Coleoptera: Scolytidae)." IOBC-WPRS Bull., 25: 259-270.

Phillips, Michael A., and Rodney B. Croteau.1999.Resin-based defenses in conifers." Trends in plant science 4 (5): 184-190.

Aluja, M., and E. F. Boller.1992. Host marking pheromone of Rhagoletis cerasi: field deployment of synthetic pheromone as a novel cherry fruit fly management strategy." Entomologia Experimentalis et Applicata 65(2): 141-147.

Vanderwel, Desiree.1994.Factors affecting pheromone production in beetles.Archives of insect biochemistry and physiology., 25(4): 347-362.

Blomquist, Gary J., Rubi Figueroa-Teran, Mory Aw, Minmin Song, Andrew Gorzalski, Nicole L. Abbott, Eric Chang, and Claus Tittiger.2010.Pheromone production in bark beetles." Insect biochemistry and molecular biology 40(10): 699-712.

Miller, Daniel R., John H. Borden, and B. Staffan Lindgren.1995.Verbenone: dose-dependent interruption of pheromone-based attraction of three sympatric species of pine bark beetles (Coleoptera: Scolytidae)."Environmental entomology 24(3): 692-696.

Erbilgin, Nadir, Nancy E. Gillette, Donald R. Owen, Sylvia R. Mori, Andrew S. Nelson, Fabian Uzoh, and David L. Wood.2008.Acetophenone superior to verbenone for reducing attraction of western pine beetle Dendroctonus brevicomis to its aggregation pheromone." Agricultural and Forest Entomology 10(4): 433-441.

Loughrin, John H., Daniel A. Potter, and Thomas R. Hamilton-Kemp.1995.Volatile compounds induced by herbivory act as aggregation kairomones for the Japanese beetle (Popillia japonica Newman)." Journal of chemical ecology.,21(10):1457-1467.

Lindgren, B. Staffan, and Daniel R. Miller. 2002.Effect of verbenone on five species of bark beetles (Coleoptera: Scolytidae) in lodgepole pine forests."Environmental Entomology., 31(5):759-765.

Erbilgin, Nadir, Jaimie S. Powell, and Kenneth F. Raffa.2003.Effect of varying monoterpene concentrations on the response of Ips pini (Coleoptera: Scolytidae) to its aggregation pheromone: implications for pest management and ecology of bark beetles." Agricultural and Forest Entomology., 5(4): 269-274.