Attractants for the scotylid beetle, Cryphalus fulvus

Biogenetic oxidations of α-pinene along three different routes in Scheme 1 were conducted in vitro, and the activities of the oxidation products in attraction of the pine beetle, Cryphalus fulvus, were compared in field tests. Oxidation with selenium dioxide along route A in Scheme 1, resulting in production of myrtenal and myrtenol, revealed increased activity compared to that of the parent hydrocarbon. A greater increase of activity was observed when β-pinene was oxidized with the same reagent. Detection of myrtenal and myrtenol in host volatiles revealed their contribution to host attraction, but the presence or absence of pinocarvone and trans-pinocarveol in the host remained uncertain.     

Oxidation products of pinene in the bark beetle,Dendroctonus frontalis

Southern pine beetles were collected as they emerged from infested pine bolts and exposed in Petri dishes to α- and β-pinene for 20 hr. Changes in the volatile contents of the beetles' hindguts were detected by gas chromatography, and previously unidentified components were characterized by mass, i.r., and n.m.r. spectroscopy. A prominent compound in hindguts of both sexes before and after treatment was identified as myrtenol, and a less conspicuous, male-specific compound proved to be myrtenal. Upon exposure to α-pinene, males produced cis- and trans-verbenol, and 4-methyl-2-pentanol was found in both sexes. Compounds present after treatment with β-pinene vapour were identified as trans-pinocarveol in both sexes, and pinocarvone in the males.     

An operative kairomonal lure for managing pine sawyer beetle Monochamus galloprovincialis (Coleoptera: Cerymbycidae)

Abstract:  Monochamus galloprovincialis Olivier (Col., Cerambycidae) is a vector of the pine wood nematode, Bursaphelenchus xylophilus , causing the destructive pine wilt disease. An effective lure for monitoring and/or mass-trapping would be of great interest in the management of this pine sawyer. Males and females of this species show an attractive kairomonal response to blends composed of four pheromone compounds used by Ips spp. bark beetles and two host volatiles from pines. This six-component lure is highly attractive but may to be too complex and costly for practical use as each component is released from a separate lure. The role of each component, ipsdienol, ipsenol, cis -verbenol, methyl butenol, α -pinene and ethanol as attractants for M. galloprovincialis was field tested in Spain to obtain a simpler but equally effective bait. Ipsenol was confirmed as the strongest kairomonal signal to M. galloprovincialis synergizing response to α -pinene by 95 times. The addition of methyl butenol to this blend doubled the number of males and females trapped. On the other hand, neither ipsdienol, cis -verbenol nor ethanol improved the results when incorporated into the above three-component blend. A lure consisting of ipsenol, methyl butenol and α -pinene may be very cost-efficient in operational monitoring or mass trapping of M. galloprovincialis . Three potentially repellent candidates, (−)verbenone, methyl cyclohexenone and trans -conophthorin, were also tested against the attractive three-component bait. trans -Conophthorin significantly reduced male catches of M. galloprovincialis ; methyl cyclohexenone had no effect. Verbenone significantly enhanced the response of females to the attractive combination of α -pinene, ipsenol and methyl butenol.     

Pine shoot beetle, Tomicus piniperda (Col., Scolytidae), responses to common green leaf volatiles

We tested the hypothesis that green leaf volatiles (GLVs) disrupt the response of overwintered pine shoot beetles, Tomicus piniperda (L.) to multiple-funnel traps baited with the attractive host volatile α-pinene. A combination of four GLV alcohols, 1-hexanol ( E )-2-hexen-1-ol ( Z )-2-hexen-1-ol, and ( Z )-3-hexen-1-ol, caused 54 and 36% reduction in the number of pine shoot beetles captured in two separate trapping experiments. Similarly, a combination of the four alcohols plus two GLV aldehydes, hexanal and ( E )-2-hexenal, caused 38% reduction in the number of pine shoot beetles captured compared with α-pinene alone. A blend of the two GLV aldehydes was not disruptive. None of the four GLV alcohols nor the two GLV aldehydes were disruptive when tested individually. The finding that the blend of four GLV alcohols reduced attraction of T. piniperda supports the general hypothesis that GLVs common to nonhost angiosperms are disruptive to conifer-attacking bark beetles (Scolytidae).     

Kairomonal responses of Tomicus destruens (Col., Scolytidae) to host volatiles α-pinene and ethanol

The Mediterranean pine shoot beetle Tomicus destruens is one of the most damaging bark beetles attacking Mediterranean pine forests in southern Europe and north Africa. We studied the attractiveness of the host volatiles α-pinene and ethanol at a range of release rates, alone or in combination, to T. destruens , in order to develop an attractive lure for the management of this beetle. T. destruens was attracted slightly to the host volatile α-pinene, but a strong synergistic effect was found in the attraction towards monoterpene when ethanol was added to the bait. The highest catches of T. destruens were obtained by the optimal blend releasing 300 mg/day of α-pinene and 900 mg/day of ethanol. In contrast to data reported for the related species T. piniperda , Mediterranean pine shoot beetles were clearly attracted to baits releasing ethanol alone (1350 mg/day). trans -Verbenol, which was also added to host volatiles in some tests, did not affect the response. The use of the attractive blend proposed would have a low impact on the natural enemy population of Thanasimus formicarius because of asynchronies in flight periods. Other non-target insects, such as the facultative predator or competitor Oxipleurus nodieri , were also significantly attracted. These results allow the development of an operative lure for the effective monitoring of T. destruens , although improvements by the addition of other host volatiles should be studied.     

New metabolites of α-pinene produced by the mountain pine beetle,Dendroctonus ponderosae (Coleoptera: Scolytidae)

Emergent females of the mountain pine beetle, Dendroctonus ponderosae, contained five previously undetected volatiles: toluene, 4-methylene-6,6-dimethylbicyclohept-2-ene (verbenene), p-mentha-1,5,8-triene, o- and p-cymene. Exposure of wild or axenically reared beetles to protio- and deuterio-α-pinene or protio- and deuterio-trans-verbenol indicated that all compounds except toluene were produced from α-pinene, with trans-verbenol as a probable intermediate. The ratio between these α-pinene metabolites was insensitive to the level of α-pinene to which the beetles were exposed, suggesting a tightly regulated enzymatic and/or acid-catalyzed conversion of α-pinene. Exposure of females to either enantiomer of α-pinene or to the same amount of (±)-α-pinene indicated that female mountain pine beetles possess two enantiospecific enzyme systems for processing α-pinene. Production of p-cymene constitutes the first record in an insect of an aromatic volatile produced from a monoterpene hydrocarbon.     

Influence of sex,maturity and host substances on pheromones in the guts of the bark beetles, Ips paraconfusus and Dendroctonus brevicomis

Pheromones and metabolites of host (ponderosa pine) compounds were found in association with the hindgut of both naturally fed and of non-fed, host vapour-exposed bark beetles, Ips paraconfusus and Dendroctonus brevicomis. Much smaller amounts were found in the corresponding heads and mid guts. Sex-specific differences in content of pheromones were observed as in earlier studies. Exposure of I. paraconfusus to vapours of a pheromone component, ipsenol and other monoterpene alcohols resulted in their accumulation in the hindgut but relatively very low amounts in the head. The possible sites of pheromone biosynthesis are discussed. Exposure of male I. paraconfusus to vapours of host compounds, myrcene and α-pinene, revealed that immature adults do not produce the pheromone components, ipsenol and ipsdienol, as mature adults do while both immature and mature sexes produced another pheromone component, cis-verbenol, as well as trans-verbenol and myrtenol. Immature D. brevicomis adults did not contain pheromones until their exposure to vapours of (?)-α-pinene which caused production of trans-verbenol but only about 10% that of mature adults treated similarly. Verbenone, a male-produced inhibitory pheromone of D. brevicomis, apparently was not synthesized from (?)-α-pinene in females nor was its synthesis in males enhanced by exposure to this host compound.     

Development of an improved attractive lure for the pine shoot beetle, Tomicus piniperda (Coleoptera: Scolytidae)

Abstract 1 The pine shoot beetle, Tomicus piniperda (L.) (Coleoptera: Scolytidae), is an exotic pest of pine, Pinus spp., and was first discovered in North America in 1992. 2 Although primary attraction to host volatiles has been clearly demonstrated for T. piniperda, the existence and role of secondary attraction to insect‐produced pheromones have been widely debated. 3 Currently, commercial lures for T. piniperda include only the host volatiles α‐pinene in North America and α‐pinene, terpinolene and (+)‐3‐carene in Europe. Several potential pheromone candidates have been identified for T. piniperda. 4 We tested various combinations of host volatiles and pheromone candidates in Michigan, U.S.A., and Ontario, Canada, to determine an optimal blend. 5 Attraction of T. piniperda was significantly increased when trans‐verbenol (95% pure, 3.2%cis‐verbenol content) was added with or without myrtenol to α‐pinene or to blends of α‐pinene and other kairomones and pheromone candidates. 6 Our results, together with other research demonstrating that trans‐verbenol is produced by T. piniperda, support the designation of trans‐verbenol as a pheromone for T. piniperda. A simple operational lure consisting of α‐pinene and trans‐verbenol is recommended for optimal attraction of T. piniperda.     

Behavioural and electrophysiological responses of the bark beetle, Ips typographus, to potential pheromone components

ABSTRACT. Field tests showed ( S )-(-)- cis -verbenol and ( R )-(+)- trans -verbenol in combination with a second pheromonal component, 2-methyl-3-buten-2-ol, more attractive than the combination with their optical antipodes. Inhibition of response to the attractant component, ( S )-(-)- cis -verbenol, by high concentrations of its optical antipode did not occur. No significant differences were noted for response to the attractant, ( S )-(-)- cis -verbenol and 2-methyl-3-buten-2-ol, with the addition of either ipsdienol enantiomer or a racemic mixture of ipsdienol enantiomers. Electroantennogram (EAG) studies correlated well with the behavioural studies. EAGs recorded from male and female beetles revealed both sexes to have a lower threshold for the pheromone, ( S )-(-)- cis -verbenol, than its host terpene precursor, (-)- alpha -pinene. EAGs showed a greater number of acceptors for (-)- alpha-pinene in males than in females. EAGs at acceptor saturation to the enantiomers of alpha -pinene and the verbenol isomers showed males more responsive to (-)- alpha -pinene, (±)- cis -verbenol, and ( R )-(+)- trans -verbenol. Significantly greater EAGs were elicited in females than in males to (-)- alpha -pinene, and (±)- and ( S )-(-)- cis -verbenol. No significant differences in EAGs of females to the enantiomers of trans -verbenol were noted. EAGs showed similar thresholds in males and females to the pheromone component, 2-methyl-3-buten-2-ol; however, female response at threshold was significantly greater than male response. The results are discussed with regard to olfactory acceptor evolution.     

Attractive responses by Monochamus galloprovincialis (Col., Cerambycidae) to host and bark beetle semiochemicals

Abstract:  The pine sawyer Monochamus galloprovincialis is the European vector of the recently introduced pine wood nematode. This nematode is the causal organism of pine wilt disease, a serious tree killer in East Asia. Efficacious baits and traps to monitor and control this beetle are now required. The effect of bark beetle ( Ips spp.) pheromone components, released individually (ipsenol) or in blends (ipsenol, ipsdienol, cis -verbenol and methyl-butenol), together with host volatiles (turpentine or α -pinene and ethanol) on M. galloprovincialis trap catches has been studied in Spain. A kairomonal response by male and female of M. galloprovincialis to Ips semiochemicals was found. Beetles were more attracted to host blends supplemented with bark beetle pheromones than to host volatiles alone. Ipsenol alone was attractive to pine sawyers, and was synergistic with α -pinene and ethanol. The full blend of the four Ips semiochemicals and the host compounds was highly attractive. Multiple-funnel traps were as effective as black cross-vane traps in capturing this insect when the escape of trapped beetles was prevented. Trapping of non-target bark beetle predators was also evaluated. The trogossitid Temnochila coerulea and clerid Thanasimus formicarius were kairomonally attracted to and killed in traps baited with bark beetle pheromones. These results suggest that effective monitoring of M. galloprovincialis would be possible by baiting any of these traps with host volatiles and Ips semiochemicals, but reduction of the lure components and trap modification to minimize impact on predators should be considered.     

Influence of the proportion of (−) α-pinene in pheromone bait on Ips typographus (Col., Scolytidae) catch in pheromone trap barriers and in single traps

Abstract:  Further possibilities of increasing catch efficiency of Ips typographus L. in pheromone trap barriers with two different levels of release of (4S)- cis -verbenol (cV) and in single traps were tested. Pheromone mixtures containing cV, 2-methyl-3-buten-2-ol (MB) and 0, 1, 10, 35, 60 and 90% (−) α -pinene were prepared. Basically, MB was successively replaced by (−) α -pinene in the mixtures. Tests were performed on the edge of a spruce forest when outbreaks of I. typographus occurred. The substitution of MB with (−) α -pinene had different effects in different types of pheromone trap barriers and in single traps. It is not possible to increase the attractiveness of the bait having a higher percentage of cV by supplementing a certain percentage of MB with (−) α -pinene. The catch of I. typographus decreased with an increase in the percentage of (−) α -pinene in the bait. It is possible to increase the attractiveness of the bait having a lower percentage of cV by supplementing certain percentages of MB with (−) α -pinene. A slight synergistic effect of (−) α -pinene with MB/cV mixture is visible in this type of bait. In the case of single traps, supplementing MB with (−) α -pinene possibly causes a slight synergistic effect. An increase in the percentage of (−) α -pinene increases the percentage of males in the catch.     

Neural and hormonal control of pheromone biosynthesis in the bark beetle, Ips paraconfusus

ABSTRACT. Synthetic juvenile hormone (JH) induced the synthesis of the three pheromones, ipsenol, ipsdienol and 2-phenylethanol, by Ips paraconfusus males and enhanced the conversion of (–)-α-pinene to a fourth pheromome, cis -verbenol. Synthetic JH also mimicked the stimulatory effect of feeding on the metabolism of myrcene to ipsdienol and ipsenol. Implantations of corpora allata and/or corpora cardiaca from fed or newly-emerged males into intact or decapitated males were performed. The results indicated that JH acts indirectly by stimulating the release of brain hormone, and the release of JH in unfed males is prevented by neural inhibition which is removed by the stretching of the gut during normal feeding. Failure of any hormonal treatment or gland implantation to stimulate cis -verbenol synthesis in the absence of exogenous α-pinene is presented as evidence that no endogenous precursor for this pheromone is present. An apparent seasonal variation in the ability of males to produce ipsdienol and ipsenol when treated with JH was observed.     

Interactions between needles of Pinus resinosa and ectomycorrhizal fungi

Relatively little is known about the factors controlling ectomycorrhizal fungal communities. One possible factor is forest litter chemistry. In a series of experiments we demonstrated that the growth of ectomycorrhizal fungi able to colonize red pine ( Pinus resinosa Ait.) are differentially affected by red pine needles and needle chemical components. For example, water extracts of pine needles stimulated the growth of Suillus intermedius (Smith & Thiers) Smith & Thiers and inhibited the growth of Amanita rubescens Pers. Catechin and epicatechin gallate, components of the water extract, acted similarly to the extract. The volatile compounds α- and β-pinene also had differential effects on the growth of the various species of ectomycorrhizal fungi. Our results suggest that forest litter chemistry has the potential differentially to affect the growth of ectomycorrhizal fungal species and so could affect the structure of ectomycorrhizal fungal communities.     

Ophiostomatoid fungi can emit the bark beetle pheromone verbenone and other semiochemicals in media amended with various pine chemicals and beetle-released compounds

Fungal volatile compounds can mediate fungal-insect interactions. Whether fungi can emit insect pheromones and how volatile chemicals change in response to chemicals the fungi naturally encounter is poorly understood. We analyzed volatiles emitted by Grosmannia clavigera (symbiont of the mountain pine beetle) and Ophiostoma ips (symbiont of the pine engraver beetle) growing in liquid media amended with compounds that the fungi naturally encounter: (−)-α-pinene, (+)-α-pinene, (−)-trans-verbenol, verbenone, or ipsdienol. Nine volatile compounds were identified among the fungal and amendment treatments. Volatiles qualitatively and quantitatively differed between fungal species and among amendment treatments. The bark beetle anti-aggregation pheromone (−)-verbenone was detected from both fungi growing in (−)-trans-verbenol-amended media. G. clavigera and O. ips can emit beetle pheromones and other beetle semiochemicals, suggesting that ophiostomatoid fungi could contribute to the chemical ecology of bark beetles. However, such contributions could be modulated by the presence of other environmental chemicals.     

Effects of bark beetle pheromones on the attraction of Monochamus alternatus to pine volatiles

Abstract We evaluated the attraction of Monochamus alternatus Hope (Coleoptera: Cerambycidae), Dryocoetes luteus Blandford and Orthotomicus erosus Wollaston (Coleoptera: Curculionidae: Scolytinae) to multiple-funnel traps baited with the pine volatiles, ethanol and (+)-α-pinene and the bark beetle pheromones, ipsenol and ipsdienol. M. alternatus were attracted to traps baited with ethanol and (+)-α-pinene but not those baited with ipsdienol and ipsenol. Ipsdienol and ipsenol decreased catches of M. alternatus in traps baited with ethanol and (+)-α-pinene. Traps baited with either binary combinations of ethanol and (+)-α-pinene or ipsdienol and ipsenol were attractive to D. luteus and O. erosus. The addition of ipsenol and ipsdienol to traps baited with ethanol and (+)-α-pinene synergized attraction of O. erosus but not D. luteus.     

Electrophysiological and behavioural responses of Scyphophorus acupunctatus (Col., Curculionidae) to Agave tequilana volatiles

Abstract:  The weevil Scyphophorus acupunctatus Gyllenhal (Col., Curculionidae) is the most important insect pest of cultivated agaves in Mexico. The objective of this study was to search for potential attractants for this weevil species from the freshly cut fleshy leaves of healthy Agave tequilana Weber var. Blue plants. Combined gas chromatography-electroantennography (GC-EAD) analysis of A. tequilana volatile extracts showed that seven peaks elicited antennal responses from males and females. Five of these peaks were identified by gas chromatography-mass spectrometry (GC-MS) as o -xylene, α -pinene, 3-carene, γ -terpinene and linalool. Electroantennogram (EAG) records of both sexes to 1-, 10- and 100- μ g-stimulus load of these five compounds showed that there was a dose effect on the EAG responses for linalool, 3-carene and α -pinene, but not for γ -terpinene and o -xylene. There were no sexual differences between male and female EAG responses to any of the compounds tested. Y-tube olfactometer bioassays of the compounds showed that males and females were attracted to α -pinene, 3-carene, γ -terpinene and/or linalool at doses of 1 and 10  μ g, while weevils were repelled by linalool at a dose of 100  μ g.     

The role of semiochemicals in tritrophic interactions between the spruce bark beetle Ips typographus, its predators and infested spruce

Abstract:  Semiochemical interactions between the spruce bark beetle Ips typographus , its predators Medetera setiventris , Thanasimus formicarius and Thanasimus femoralis , and the host Norway spruce, Picea abies , were studied in the field. The chemicals S - cis -verbenol, 2-methyl-3-buten-2-ol, ipsdienol, (+)- α -pinene, (−)- α -pinene, (±)- α -pinene, limonene, camphor and their naturally occuring mixtures were used as trap baits in a multiple-choice design that allowed for comparison of their attractivity for the focal species. Medetera was attracted to both the prey aggregation pheromone and its multifunctional component, ipsdienol. On the contrary, both Thanasimus species responded predominantly to ipsdienol and less to the prey aggregation pheromone. In the case of I. typographus , the attractivity of aggregation pheromone seems to be increased by the addition of a mixture of monoterpenic tree volatiles, and by addition of ipsdienol. Bark beetles and predators showed species-specific responses to volatile mixtures representing different stages of tree decay and different stages of bark beetle colony establishment. These responses correlates with the optimal foraging habitat of each species. None of the predator species responded to 2-methyl-3-buten-2-ol, a substantial component of I. typographus pheromonal bouquet, thus it is hypothesized that only substances of monoterpenic origin attract predators.     

Host tree resistance influencing pheromone production in Ips typographus (Coleoptera: Scolytidae)

Analyses of volatiles in hindguts of Ips typgraphus males from different spruce trees and attack phases are reviewed. The composition of monoterpenes, and the chirality of α-pinene, have been determined in phloem samples. Relationships between compounds emanating from spruce trees and bark beetles, respectively, have been studied. Male beetles depend on their host tree for the production of pinene alcohols. The ratio between the pinene alcohols is almost constant in males boring in the same tree but can vary widely between males from different spruce trees. Very good correlations were found between some host tree monoterpene hydrocarbons and bark beetle produced pinene alcohols. The production of the essential pheromone component 2-methyl-3-buten-2-ol, was not correlated with the monoterpene content in the host trees, while the production of the other essential pheromone component, cis-verbenol, depends on the amount of the precursor, (−)-α-pinene in the phloem. Male beetles boring in a resistant spruce tree will continue to produce the pinene alcohols, including cis -verbenol, as long as the tree defends itself with resin.     

Aggregation response of European engraver beetles of the genus Ips mediated by terpenoid pheromones

Upon exposure to vapours of the host tree's monoterpene (–)--pinene, Ips acuminatus produces the terpene alcohol cis-verbenol which, besides ipsdienol and ipsenol, is a component of its aggregation pheromone. I. cembrae transforms the same monoterpene predominantly into myrtenol and trans-verbenol but little into cis-verbenol, which interrupts pheromone response under field conditions.On the other hand, I. cembrae releases, upon feeding in the bark, the terpene alcohol amitinol in major amounts. Amitinol significantly enhances field response to the aggregation pheromone that also includes ipsdienol, ipsenol, and 3-methyl-3-buten-1-ol. However, amitinol reduces pheromone response in I. acuminatus and I. erosus. Also, males of I. sexdentatus release amitinol which appears to increase response to its attractive principle pheromone component, racemic ipsdienol. There is some evidence that present knowledge of the chemical communication systems among European Ips spp. still lacks satisfactory explanation of the naturally occuring aggregation en masse, perhaps with the exception of I. erosus and I. typographus.     

Volatile Organic Compounds and Their Roles in Bacteriostasis in Five Conifer Species

In order to make clear the functions of plant volatile organic compounds (VOCs) on bacteriostasis and air decontamination, we analyzed the composition and content of VOCs in Pinus tabulaeformis Carr., P. bungeana Zucc., Sabina chinensis Antoine, Picea koraiensis Nakai, and Cedrus deodara G. Don under near-natural conditions using the thermal-desorption cold trap gas chromatography/mass spectrometer technique. The effects of the VOCs on airborne microorganisms were investigated using the method of natural sedimentation. Results showed that the major VOCs were as follows: limonene, β-pinene, α-pinene,and α-caryophyllene in Pinus tabulaeformis and P. bungeana; limonene, borneol acetate, β-pinene, myrcene, and tricylene in S. chinensis; limonene, α-pinene, myrcene, camphene, and β-pinene in Picea koraiensis; and limonene, 2, (10)-pinene, α-pinene, and myrcene in C. deodara. These VOCs and the corresponding foliar extracts inhibited the growth of bacteria and stimulated the growth of fungi. Experimental data using monomers of the VOCs demonstrated that limonene, β-pinene, and three aldehydes could significantly inhibit bacterial growth, suggesting an inhibitory effect of VOCs on the growth of airborne microorganisms in the five conifer species. The bacteriostasis and air-decontaminating effects of plant VOCs are further discussed in terms of their chemical composition.