Response of the whitespotted sawyer beetle, Monochamus s. scutellatus, and associated woodborers to pheromones of some Ips and Dendroctonus bark beetles

The response of whitespotted sawyer beetle, Monochamus s. scutellatus, to pheromones of the bark beetles, Dendroctonus rufipennis, Ips pini, Ips perturbatus and Ips latidens, and α‐pinene was investigated with field‐trapping experiments. Traps baited with ipsenol caught significantly more M. s. scutellatus than unbaited traps, whereas the other compounds (ipsdienol, ipsdienol plus lanierone, ipsdienol plus cis‐verbenol or frontalin) did not. Combining α‐pinene with ipsdienol, ipsdienol plus lanierone, ipsdienol plus cis‐verbenol or with frontalin did not increase captures of M. s. scutellatus above those of α‐pinene alone, whereas the combination of α‐pinene with ipsenol did. When α‐pinene was combined with ipsdienol or frontalin, trap captures of Monochamus mutator were significantly higher than unbaited traps or traps baited with frontalin but were not higher than traps baited with α‐pinene. The combination of ipsenol and α‐pinene was significantly more attractive to Monochamus notatus than unbaited traps; however, traps containing either ipsenol or α‐pinene were as attractive as the combination. None of the species of Buprestidae (Buprestis maculativentris and Chalcophora virginiensis) responded significantly to any of the treatments.     

Bark beetle pheromones and pine volatiles: attractant kairomone lure blend for longhorn beetles (Cerambycidae) in pine stands of the southeastern United States

In 2006, we examined the flight responses of 43 species of longhorn beetles (Coleoptera: Cerambycidae) to multiple-funnel traps baited with binary lure blends of (1) ipsenol + ipsdienol, (2) ethanol + alpha-pinene, and a quaternary lure blend of (3) ipsenol + ipsdienol + ethanol + alpha-pinene in the southeastern United States. In addition, we monitored responses of Buprestidae, Elateridae, and Curculionidae commonly associated with pine longhorn beetles. Field trials were conducted in mature pine (Pinus pp.) stands in Florida, Georgia, Louisiana, and Virginia. The following species preferred traps baited with the quaternary blend over those baited with ethanol + alpha-pinene: Acanthocinus nodosus (F.), Acanthocinus obsoletus (Olivier), Astylopsis arcuata (LeConte), Astylopsis sexguttata (Say), Monochamus scutellatus (Say), Monochamus titillator (F.) complex, Rhagium inquisitor (L.) (Cerambycidae), Buprestis consularis Gory, Buprestis lineata F. (Buprestidae), Ips avulsus (Eichhoff), Ips calligraphus (Germar), Ips grandicollis (Eichhoff), Orthotomicus caelatus (Eichhoff), and Gnathotrichus materiarus (Fitch) (Curculionidae). The addition ofipsenol and ipsdienol had no effect on catches of 17 other species of bark and wood boring beetles in traps baited with ethanol and a-pinene. Ethanol + alpha-pinene interrupted the attraction of Ips avulsus, I. grandicollis, and Pityophthorus Eichhoff spp. (but not I. calligraphus) (Curculionidae) to traps baited with ipsenol + ipsdienol. Our results support the use of traps baited with a quaternary blend of ipsenol + ipsdienol + ethanol + alpha-pinene for common saproxylic beetles in pine forests of the southeastern United States.     

Variation in enantiospecific attraction of Ips avulsus (Coleoptera: Curculionidae) to the pheromone ipsdienol in Georgia

In 2006, we tested the responses of the small southern pine engraver, Ips avulsus (Eichhoff) (Coleoptera: Curculionidae), to multiple-funnel traps baited with (+)-, (-)-, and (+/-)-ipsdienol. Three experiments were conducted in Georgia with all traps co-baited with one of the following lure combinations, respectively: experiment 1, ipsenol; experiment 2, lanierone and (-)-alpha-pinene; and experiment 3, ipsenol, lanierone, and (-)-alpha-pinene. Ipsdienol and lanierone are aggregation pheromones used by I. avulsus, whereas ipsenol is an aggregation pheromone used by the eastern fivespined ips, Ips grandicollis (Eichhoff), a sympatric species also breeding in pines. In all experiments, the highest catches of I. avulsus were obtained in traps baited with (+/-)-ipsdienol. The relative attractiveness of (+)-ipsdienol varied across the three experiments. When traps were co-baited with ipsenol, lanierone, and (-)-alpha-pinene, catches of I. avulsus in traps baited with (+)-ipsdienol were high and no different from those in traps baited with (+/-)-ipsdienol. When traps were co-baited with lanierone and (-)-alpha-pinene, catches in traps baited with (+)-ipsdienol were lower than those in traps baited with (+/-)-ipsdienol by approximately 40%, whereas catches were reduced by approximately 95% when traps were co-baited with ipsenol alone. We hypothesize that the observed variation in enantiospecific responses of I. avulsus to ipsdienol may be explained by variation in semiochemical context (i.e., different co-baits among the experiments) or seasonal variation.     

Key structural features in cis-carane, (+)-3-carene,cis-pinane, (+)-α-pinene,and (−)-β-pinene influencing red turpentine beetle primary attraction when released with ethanol

1. In US Pacific Northwest ponderosa pine forests the primary attraction order shown previously for red turpentine beetle, Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae), is (−)-β-pinene+ethanol > (+)-3-carene+ethanol > (+)-α-pinene+ethanol. The monoterpenes are bicyclic C₁₀H₁₆ isomers containing one 6-carbon ring with one double bond. Both pinenes have a 4-carbon second ring and differ only by their endocyclic or exocyclic double bond. The (+)-3-carene second ring has 3-carbons; its double bond is endocyclic like (+)-α-pinene.
2. Ring system and double bond influences on primary attraction were evaluated by hydrogenating (+)-3-carene and (+)-α-pinene to cis-carane and cis-pinane, respectively. Field test primary attraction strengths were (−)-β-pinene+ethanol > cis-carane+ethanol > cis-pinane+ethanol > ethanol.
3. In combination with ethanol (i) a double bond is not required in either ring system to attract D. valens, (ii) the cis-carane bicyclic 3, 6-carbon ring system provides stronger beetle attraction than the cis-pinane 4, 6-carbon bicyclic ring system, and likely structural basis for stronger (+)-3-carene attraction over (+)-α-pinene, (iii) adding an exocyclic double bond to the 4, 6-carbon ring system elevates attraction above the 3, 6-carbon ring system with no double bond, and (iv) the 4, 6-carbon ring system is a much stronger attractant with an exocyclic rather than endocyclic double bond.

     

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.     

Ipsenol and ipsdienol attract Monochamus titillator (Coleoptera: Cerambycidae) and associated large pine woodborers in southeastern United States

We determined the responses of the southern pine sawyer, Monochamus titillator (F.) (Coleoptera: Cerambycidae), to the pheromones (ipsenol, ipsdienol, and lanierone) used by pine engraver beetles (Coleoptera: Scolytidae) in the southeastern United States. (+/-)-Ipsenol, (+/-)-ipsdienol, or a combination increased catches of M. titillator in Florida, Louisiana, Georgia, and North Carolina. Catches of Acanthocinus obsoletus (Olivier) (Cerambycidae) were increased by (+/-)-ipsenol and (+/-)-ipsdienol in Florida and North Carolina, whereas only (+/-)-ipsenol was attractive in Georgia. (+/-)-Ipsenol and (+/-)-ipsdienol were attractive to Pachylobius picivorus (Germar) (Coleoptera: Curculionidae) in Florida, whereas only (+/-)-ipsdienol was active in Louisiana. In Florida, catches of M. titillator, A. obsoletus, and P. picivorus were greatest in traps baited with both (+/-)-ipsenol and (+/-)-ipsdienol. In Louisiana, catches of the woodborer Chalcophora virginiensis (Drury) (Buprestidae) were increased by (+/-)-ipsenol. Lanierone did not affect trap catches of the aforementioned species. The combination of (+/-)-ipsenol and (+/-)-ipsdienol may be a cost-effective lure for these four species because we found no evidence of interruption in attraction to baited traps, and the cost of the lure combination is relatively low.     

β-Pinene + ethanol attracts more red turpentine beetles than carene+ ethanol,with or without traces of frontalin,at prescribed burn or thinned sites

1. Red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Curculionidae: Scolytinae), previously responded more strongly to (−)-β-pinene + ethanol than (+)-3-carene + ethanol lures at sites burned the prior year by wildfire in Oregon and northeastern California, whereas at a thinned-unburned Arizona site (+)-3-carene + ethanol was the stronger attractant. This discrepancy was further examined to tease apart whether D. valens attraction varies by region or previous forest disturbance types.
2. Here, (−)-β-pinene + ethanol and (+)-3-carene + ethanol lures were tested in pine stands at two Oregon sites disturbed the previous year by a prescribed burn or thinning only. Both lures were tested also with or without trace amounts of the pheromone frontalin, as its presence enhanced attractions in China but had not been tested in North America.
3. At both sites, regardless of prior forest disturbance, (−)-β-pinene + ethanol lures attracted the most beetles. Lures releasing trace frontalin attracted more beetles than their corresponding lures without it at both sites, except in one case.
4. Overall, previous year disturbances from disparate management treatments had minimal influence on lure attraction to D. valens. For detection, monitoring or management (−)-β-pinene + ethanol + frontalin in trace amounts attracts the most beetles of lures tested to date in Pacific Northwest pine forests.

     

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.     

Functional investigation of monoterpenes for improved understanding of the relationship between hosts and bark beetles

Spruce bark beetle (Ips typographus L.) is the most destructive insect pest of spruce forests in Eurasia. However, contact toxicity, in vivo metabolism, and ecological functions of host monoterpenes are poorly understood at the spruce tree–bark beetle–predator tritrophic level. Spruce monoterpenes including S-(–)-α-pinene, R-(+)-α-pinene, and myrcene showed contact toxicity to I. typographus, with LD₅₀ values ranging from 22–32 μg/mg. When topically treated with S-(–)-α-pinene or R-(+)-α-pinene, the amounts of volatile metabolites, including 4S-(–)-cis-verbenol, 4S-(+)-/4R-(–)-trans-verbenol, R-(+)-/S-(–)-verbenone and 1R-(–)-/1S-(+)-myrtenol, in the hindgut extracts of I. typographus varied significantly between sexes, and their quality (enantiomeric composition) varied significantly with the chirality of α-pinene. More importantly, S-(–)-α-pinene induced male adults to produce large amounts of 4S-(–)-cis-verbenol and S-(–)-verbenone. When topically treated with myrcene, the expected semiochemicals such as E-myrcenol, ipsenol and ipsdienol were not detected in the beetle hindguts, indicating that the pheromone biosynthetic system of I. typographus does not participate in the metabolism of host myrcene. In trap tests, S-(–)-α-pinene and R-(+)-α-pinene increased the catches of I. typographus and its predator Thanasimus substriatus in pheromone-baited traps, whereas myrcene exhibited a strong repellent (or inhibitory) effect on I. typographus but not on its predator. I. typographus seems to adopt different ecological strategies (e.g. avoidance to myrcene and preference for α-pinene) to adapt to and tolerate different host monoterpenes. Extensive investigation of these monoterpenes will help us understand their roles in manipulating the arms race between host trees and bark beetles, and potentially improve the efficacy of controlling I. typographus via the push-pull strategy using host kairomones.     

Role of ipsdienol, ipsenol, and cis-verbenol in chemical ecology of Ips avulsus, Ips calligraphus, and Ips grandicollis (Coleoptera: Curculionidae: Scolytinae)

Stressed or damaged pine (Pinus sp.) trees in the southeastern United States are often colonized simultaneously by three southern Ips species (Coleoptera: Curculionidae: Scolytinae): small southern pine engraver, Ips avulsus (Eichhoff); sixspined ips, Ips calligraphus (Germar); and eastern fivespined ips, Ips grandicollis (Eichhoff). All three species mediate colonization of host material with volatile pheromones. All of the southern Ips produce cis-verbenol, and either ipsdienol or ipsenol, and electrophysiological studies have demonstrated that all three southern Ips are able to detect all three compounds. This study examined the role of ipsdienol, ipsenol, and cis-verbenol in the chemical ecology of the southern Ips in Georgia and Louisiana. The most attractive blends of pheromones, with the fewest number of components, were ipsdienol plus ipsenol for I. avulsus, cis-verbenol plus ipsdienol for I. calligraphus, and either cis-verbenol plus ipsenol or ipsdienol plus ipsenol for I. grandicollis. Cross-attraction of I. grandicollis to the pheromone blend most attractive to I. avulsus was observed. Although the presence of heterospecific pheromone reduced the catches of all three species (i.e., the tertiary blend captured fewer beetles than the most attractive binary blends) in both states (significantly in two cases), high numbers of all three species were still captured in traps baited with all three compounds. These results suggest that the pheromones cis-verbenol, ipsdienol, and ipsenol can be combined for monitoring all three species of the southern Ips simultaneously.     

Field evaluation on the synergistic attractiveness of 2‐(1‐undecyloxy)‐1‐ethanol and ipsenol to Monochamus saltuarius

To develop an optimal attractant for Monochamus saltuarius (Gebler) (Coleoptera: Cerambycidae), the synergistic effects of a few potential attractants (ethanol and α‐pinene as host‐plant volatiles, and ipsenol and ipsdienol as bark beetle pheromones) were tested in a pine forest combined with 2‐(1‐undecyloxy)‐1‐ethanol (monochamol), the aggregation pheromone of Monochamus species, for two consecutive years, 2014 and 2015. Total number of catches was 65 and 33 in 2014 and 2015, respectively. Ethanol or ethanol + monochamol (a base blend) were not attractive to M. saltuarius with no difference from the control. Addition of α‐pinene and ipsdienol to the base blend did not significantly increase catches. However, ipsenol was significantly synergistic to the base blend in attracting M. saltuarius in 2014, and the blend (ipsenol + base blend) attracted meaningfully higher numbers of M. saltuarius in 2015. Our study illustrates the potential for monochamol and ipsenol baits for monitoring and trapping of M. saltuarius in the field.     

Synergistic attraction of pine sawyer Monochamus saltuarius (Coleoptera: Cerambycidae) to monochamol and α‐pinene

Monochamus (Coleoptera: Cerambycidae) species are longhorn pine sawyers that serve as insect vectors of the pinewood nematode Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae), which are responsible for debilitating pine wilt disease. An aggregation pheromone, 2‐(1‐undecyloxy)‐1‐ethanol (hereafter referred to as monochamol), was shown to be effective at attracting Monochamus species. However, attraction of the pine sawyers to aggregation pheromones varied depending on semiochemicals, including host plant volatiles and kairomones. In this study, we investigated the abilities of monochamol and the host‐plant volatiles α‐pinene and ethanol to attract M. saltuarius in a pine forest in Cheongsong, Gyeongsangbuk‐do, Korea. A total of 91 M. saltuarius (28 males and 63 females) were captured. The combination of monochamol (700 mg) with α‐pinene and ethanol exhibited a synergistic effect on attracting M. saltuarius (11.0 beetles per trap), whereas monochamol alone and a mixture of α‐pinene and ethanol resulted in the capture of 3.2 beetles and 3.6 beetles per trap, respectively. Our results suggest that multi‐funnel traps baited with a blend of monochamol, α‐pinene and ethanol are highly effective for monitoring M. saltuarius and M. alternatus in pine forests.     

The capacity of conophthorin to enhance the attraction of two Xylosandrus species (Coleoptera: Curculionidae: Scolytinae) to ethanol and the efficacy of verbenone as a deterrent

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Red turpentine beetle primary attraction to β-pinene or 3-carene (with and without ethanol) varies in western US pine forests

1. Lure attraction strength for red turpentine beetle, Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae) observed previously in US Pacific Northwest ponderosa pine forests is (−)-β-pinene+ethanol > (+)-3-carene+ethanol, but untested elsewhere in its western US range. Thus, both were tested with (−)-β-pinene, (+)-3-carene, ethanol, and a blank in Oregon and California sites burned by wildfire, whereas in Arizona the first four lures were tested in a thinned-unburned site.
2. The D. valens responses in burned Oregon and California sites were similar, (−)-β-pinene+ethanol > (−)-β-pinene > 3-carene = 3-carene+ethanol > ethanol > blank, whereas in the cut-unburned Arizona site it was 3-carene+ethanol > 3-carene = (−)-β-pinene+ethanol > (−)-β-pinene. Whether this variation was influenced by beetle genetic differences, or chemical and physical parameters in the different environments and remaining stressed host resources 1-year post disturbance warrants additional study.
3. Responses to (−)-β-pinene varied, from a stronger attractant than (+)-3-carene in Oregon and California, to a weaker lure than (+)-3-carene in Arizona. This (−)-β-pinene variability was minimized when released in combination with ethanol, making (−)-β-pinene+ethanol the most consistent attractant of those tested across the three states, and a reliable lure for detection, monitoring, and management projects for D. valens in western US pine forests.

     

Responses of single receptor cells in the pine engraver beetle,Ips pini (SAY) (Coleoptera: Scolytidae) to its aggregation pheromone,ipsdienol, and the aggregation inhibitor,ipsenol

Summary Responses of single olfactory cells on the antennal club ofIps pini have been recorded electrophysiologically. The majority of cells were strongly activated by either/or of the two behavior-modifying chemicals, the aggregation pheromone ipsdienol and the aggregation inhibitor ipsenol. Simultaneous stimulation with these terpence alcohols showed that ipsenol had no inhibitory effect on the receptor responses to ipsdienol. It appears that the behavioral inhibition by ipsenol on the attraction of ipsdienol results from central integration of the information from separate receptor cells rather than blockage at the peripheral receptors.This work was carried out at the College of Environmental Sciences and Forestry, SUNY, Syracuse. We are grateful to Professor R.M. Silverstein and his staff for provision of purified compounds and laboratory facilities. We also acknowledge with thanks the provision of equipment and laboratory facilities by Professor D. Tapper, College of Veterinary Medicine, Cornell University.     

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.     

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.     

Species dependent influence of (-)-alpha-pinene on attraction of ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) to ethanol-baited traps in nursery agroecosystems

Field-based trapping experiments were conducted in Ohio in 2003, 2004, and 2008 to determine the influence of (-)-alpha-pinene on the attraction of exotic and native ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) to ethanol-baited traps. In 2003 and 2004, we determined the effect of adding an (-)-alpha-pinene ultrahigh release lure (UHR; 2 g/d at 20 degrees C) to traps baited with an ethanol UHR lure (0.39 g/d). FewerAnisandrus (Xyleborus) sayi (Hopkins) and Xyleborinus saxeseni (Ratzeburg) were collected in 2003 and 2004 from traps baited with ethanol UHR plus (-)-alpha-pinene UHR compared with ethanol UHR. (-)-alpha-Pinene also reduced the attraction of Xyloterinus politus (Say) to ethanol-baited traps in 2004. Total captures of Xylosandrus germanus (Blandford) in 2003 were higher in traps baited with ethanol UHR plus (-)-alpha-pinene UHR than in traps with ethanol UHR alone but not in 2004. In 2008, captures were compared among traps baited with eight combinations of ethanol and (-)-a-pinene at both UHR and low release (LR) rates. Release rates for ethanol LR and (-)-alpha-pinene LR were 0.027 and 0.0015 g/d, respectively. (-)-alpha-Pinene UHR and (-)-alpha-pinene LR reduced the attractiveness of ethanol UHR to A. sayi and X. saxeseni. Ethanol UHR was also more attractive than ethanol LR to A. sayi and X. germanus. These findings demonstrate traps baited with ethanol alone are more effective than ethanol plus (-)-alpha-pinene for monitoring ambrosia beetle flight activity in ornamental nurseries. Ethanol release rate is also an important consideration for monitoring purposes.     

Population divergence of aggregation pheromone responses in Ips subelongatus in northeastern China

The Asian larch bark beetle, Ips subelongatus, is considered to be the major pest of larch within its natural range. We investigated the electrophysiological and behavioral characteristics as well as mitochondrial DNA cytochrome oxidase subunit I sequences of I. subelongatus from 13 geographic populations throughout northeastern China in order to explore population divergence of aggregation pheromone responses and the extent of potential genetic divergence. Electrophysiological analyses showed that antennae of I. subelongatus from all the six tested populations responded strongly to (S)‐(?)‐ipsenol (100% detection; 0.35–0.73 mV) in gas chromatography (GC)–electroantennographic detection (EAD) analyses, while its antipode, (R)‐(+)‐ipsenol was antennally inactive. I. subelongatus populations varied in their responses to (R)‐(?)‐ and (S)‐(+)‐ipsdienol in GC‐EAD analyses. Behavioral bioassays demonstrated that (S)‐(?)‐ipsenol alone was significantly attractive at all the tested sites, supporting its status as a key pheromone component of I. subelongatus, whereas (S)‐(+)‐ipsdienol was inactive alone. Adding (S)‐(+)‐ipsdienol to (S)‐(?)‐ipsenol did not have any effect on the trap catches from some populations in Inner Mongolia. However, (S)‐(+)‐ipsdienol showed a strong synergistic effect on (S)‐(?)‐ipsenol from several populations in Jilin and Liaoning Provinces, and a weak synergistic effect from some transition populations in Heilongjiang Province. Furthermore, 27 mitochondrial haplotypes were found among the 13 populations (intraspecific nucleotide divergence, 0.1%–1.1%). Analyses of molecular variance and haplotype networks indicated that different geographic populations have developed some genetic variation but did not form completely independent groups. From an applied point of view, a universal synthetic binary blend of racemic ipsenol and (S)‐(+)‐ipsdienol might have a potential for monitoring or even mass‐trapping of I. subelongatus across northeastern China, even though some populations only use (S)‐(?)‐ipsenol alone as their active pheromone component.     

Limonene: attractant kairomone for white pine cone beetles (Coleoptera: Scolytidae) in an eastern white pine seed orchard in western North Carolina

I report on the attraction of the white pine cone beetle, Conophthoru.s coniperda (Schwarz) (Coleoptera: Scolytidae), to traps baited with the host monoterpene limonene in western North Carolina. Both (+)- and (-)-limonene attracted male and female cone beetles to Japanese beetle traps in an eastern white pine, Pinus strobus L., seed orchard near Murphy, NC. Catches of cone beetles were directly proportional to the release rate of (-)-limonene; (+)-limonene was not tested for dose response. Attraction of cone beetles to the pheromone (+/-)-trans-pityol was increased significantly by both enantiomers of limonene. In all experiments, catches of C. coniperda were strongly male biased with no treatment effect on sex ratio. (- )-Limonene had no effect on trap catches of the predator Enoclerus nigripes (Say) to pityol, whereas (+)-limonene interrupted the attraction of E. nigripes to traps baited with pityol. Of six monoterpenes commonly found in white pine cones, only (-)-alpha-pinene elicited attraction of E. nigripes to Japanese beetle traps.