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.     

A host monoterpene influences Ips typographus (Coleoptera: Curculionidae,Scolytinae) responses to its aggregation pheromone

1 Host tree terpenes can influence attraction of conifer‐infesting bark beetles to their aggregation pheromones, and both synergistic and inhibitory effects have been reported. 2 We tested a gradient of ratios of (–)‐α‐pinene, the predominant monoterpene in Norway spruce, to the pheromone of Ips typographus, a major pest of Norway spruce. 3 Attraction of I. typographus increased as the release rate of (–)‐α‐pinene increased. The two highest (–)‐α‐pinene : pheromone ratios (526 : 1 and 2595 : 1) attracted twice as many I. typographus as pheromone alone, whereas low to intermediate ratios (56 : 1, 274 : 1) did not differ from pheromone alone. 4 Our results are in agreement with a proposed model, which suggests that bark beetles display unique response profiles to host terpenes depending on the physiological condition of the host trees that they typically colonize. Ips typographus, which is an aggressive species capable of colonizing and killing healthy trees, showed an increased attraction to monoterpene : pheromone ratios, and this may be high enough to inhibit attraction of less aggressive beetle species typically colonizing dead, dying or stressed trees. 5 Attraction of associates of I. typographus was also modified by (–)‐α‐pinene. Ips duplicatus, a competitor of I. typographus, showed increased attraction to the pheromone of I. typographus across all concentrations of (–)‐α‐pinene.     

Grandlure dosage and attraction of boll weevils (Coleoptera: Curculionidae)

The effects of grandlure dosage on of boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), attraction were assessed. Traps collected more boll weevils under field and laboratory conditions as the amount of grandlure in laminated plastic strips was increased from 0 to 10, 30, and 60 mg. Spreading the point source of the lure by cutting the strip into quarters and positioning each quarter on separate corners of the large capacity trap to create an expanded source for the pheromone plume, however, resulted in fewer trap captures than traps with quartered lures all positioned on a single corner. The large capacity trap with the quartered lure on one corner also caught more weevils than the traps with an intact lure fastened to one corner. Although aging lure strips for three weeks reduced emissions of the four pheromone components and their attractiveness to boll weevils, cutting the aged lure into quarters resulted in greater emissions and attraction than lures that were aged intact or as quarters. Some pheromone components volatilized faster than others, resulting in time-related changes in blend ratios, but the underlying factor in boll weevil attraction to grandlure strips was dosage, the amount of volatilized pheromone available for interacting with an adult boll weevil.     

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.     

Effectiveness of different lures for attracting Ips acuminatus (Coleoptera: Curculionidae: Scolytinae)

1. Ips acuminatus (the sharp-toothed bark beetle, STBB) is currently considered to be one of the most serious pests of Scots pine in many European countries. STBB management is among the most challenging tasks in pine forests; the development of methods for monitoring, predicting and managing outbreaks of this bark beetle is therefore crucial.
2. Pheromone-baited traps have been widely recommended as a valuable tool for the monitoring and mass trapping of bark beetles. Although different suppliers offer a variety of STBB lures, their effectiveness has rarely, if ever, been evaluated under natural conditions.
3. We evaluated the attractiveness of three commercially available and five experimental synthetic lures by comparing the numbers of STBBs captured in white, six-funnel traps. The studies were conducted in 2017–2019 in Poland, in Scots pine-dominated forests affected by STBB outbreaks.
4. Our study demonstrated significant differences in the effectiveness of the lures. The experimental lure produced by the Witasek company (Austria) and the recently marketed lure Acumodor Micro from Chemipan (Poland) were the most attractive to STBB. Among the least effective were two commercial lures (Acuwit and Acumodor), hitherto used in Central Europe.
5. The results will be useful in developing methods for the monitoring and management of STBB populations.

     

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.     

Fine-tuning the composition of the cranberry weevil (Coleoptera: Curculionidae) aggregation pheromone

The cranberry weevil Anthonomus musculus Say is a key pest of highbush blueberries (Vaccinium corymbosum L.) and cranberries (Vaccinium macrocarpon Aiton) in the northeastern United States. Previous studies have reported A. musculus adult attraction to traps baited with the aggregation pheromone of the pepper weevil Anthonomus eugenii Cano, likely because these two weevils share similar pheromone blends that differ only in two components. The A. musculus aggregation pheromone contains (Z)-2-(3,3-dimethylcyclohexylidene) ethanol (Z grandlure II), (Z)-(3,3-dimethylcyclohexylidene) acetaldehyde (grandlure III), (E)-(3,3-dimethylcyclohexylidene) acetaldehyde (grandlure IV) and (E)-3,7-dimethyl-2,6-octadien-1-ol (geraniol); whereas A. eugenii produces a pheromone blend that includes (E)-2-(3,3-dimethylcyclohexylidene) ethanol (E grandlure II) and (E)-3,7-dimethyl-2,6-octadienoic acid (geranic acid) in addition to the four A. musculus pheromone components. Here, we hypothesized that differences in pheromone composition between these two species influence A. musculus adult attraction to its aggregation pheromone. To test this, we studied the response of A. musculus to its pheromone blend with and without E grandlure II and geranic acid, a commercial A. eugenii pheromone lure and a no-lure control in highbush blueberry and cranberry fields in New Jersey and Massachusetts, respectively. Regardless of crop type, A. musculus adults were more attracted to their four-component pheromone blend and the blend plus geranic acid than the commercial A. eugenii pheromone and the no-lure controls. The A. musculus pheromone blend plus E grandlure II and the A. eugenii pheromone blend also captured more A. musculus adults than the no-lure control but not compared to the commercial A. eugenii pheromone. Further analysis showed that A. musculus adults are significantly (~27%) less attracted to their pheromone blend if it contains E grandlure II, although the addition of geranic acid did not affect their response. These findings may help guide future efforts towards the development of behaviour-based tools to monitor and manage A. musculus.     

Behavioural sequence in the attraction of the bark beetle Ips typographus to pheromone sources

ABSTRACT. The functions of the two synergistic pheromone components, (4S)- cis -verbenol (cV) and 2-methyl-3-buten-2-01 (MB), and the role of ipsdienol in the attraction of Ips typographus (L.) (Scolytidae) to pheromone sources were studied in the field. Absolute and relative beetle catches were compared between several traps placed at and nearby a central pheromone source: a pipe trap containing the source, a surrounding sticky trap, a nearby window trap, and four distant window traps. A higher catch in the outer down-wind distant traps indicated an up-wind anemotaxis to the source. Increased MB release, with cV constant, increased the proportion caught in the central pipe trap, indicating MB as a landing stimulus. Release of MB alone gave a very small catch. Ipsdienol could not substitute for cV in the synergism with MB. An increase of cV, with MB constant, increased the number of beetles caught, but not the proportion caught in the pipe trap. The sex ratio was equal in the window traps, but fell to 30% males in both sticky and pipe traps, showing that a large proportion of the males attracted to the source did not land. The proportion of males in the pipe trap was reduced at the highest cV dose. The results support the idea of each pheromone component having a different relative importance in releasing different steps in the behavioural chain.     

Comparisons of standard and extended-life boll weevil (Coleoptera: Curculionidae) pheromone lures

The Southeastern Boll Weevil Eradication Program has proposed reducing maintenance program costs in eradicated zones by using an extended-life "superlure" in traps to detect populations of the boll weevil, Anthonomus grandis grandis Boheman. However, superlure effectiveness has not been extensively evaluated. We compared the superlure (30 mg of eugenol plus 25 mg of grandlure) to a standard lure (10 mg of grandlure) based on captures of weevils and changes in lure pheromone content. Lure treatments (standard and superlure, replaced biweekly or not replaced) were compared in 4-mo-long trapping periods. Captures of weevils did not generally reflect differences among lure treatments indicated by assays of lure contents. During the first 2 wk of exposure, amounts of pheromone released by the superlure were generally comparable with those of the standard lure, but pheromone composition was more stable. During the second 2 wk of exposure, the superlure usually released more pheromone than similarly aged standard lures, but less than half as much as the standard lure replaced biweekly. Based on numbers of captured weevils during the last 2 wk of an extended trapping period, the superlure performed similarly to the standard lure replaced biweekly. However, corresponding pheromone releases by the superlure were less than those by the standard lure replaced biweekly. This inconsistency suggests that numbers of captured weevils alone may be inadequate for evaluation of pheromone formulations. Our results suggest that better understanding of the consequences of reduced pheromone release during an extended trapping period is needed before adoption of the superlure can be recommended.     

Behaviours of phoretic mites (Acari) associated with Ips pini and Ips grandicollis (Coleoptera: Curculionidae) during host‐tree colonization

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Evidence for a male-produced aggregation pheromone in Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae)

Olfactory response of male and female Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae) to volatiles released from the same or opposite conspecifics alone, or combined with host plant volatiles, was evaluated in the laboratory and field. We also evaluated the response to synthetic Rhynchophorinae pheromones in the laboratory. In laboratory tests, attraction of males and females in Y-tube olfactometer to conspecific males was greater than to females and clean air. Males and females preferred the combination males + agave over agave alone. Both sexes were significantly attracted to 2-methyl-4-heptanol and 2-methyl-4-octanol compared with hexane control. In field trials, weevils were successfully caught in the traps baited with conspecifics and plant material. These field results support those of the laboratory bioassays, showing that males attracted conspecific males and females and addition of plant material enhanced the attraction. These results further suggest that S. acupunctatus produces an aggregation pheromone.     

华山松木蠹象聚集信息素分离鉴定和引诱效果

为了研制华山松木蠹象Pissodes punctatus Langor et Zhang的引诱剂,对华山松木蠹象的虫粪和雄虫后肠挥发性物质进行了分析鉴定和室内外生物活性测试。经GC-MS测定,发现在华山松木蠹象的新鲜虫粪和雄虫后肠挥发性物质中,除了松树挥发性的单萜烯如α-蒎烯、β-蒎烯和3-蒈烯以外,还存在1-甲基-2-异丙烯基-环丁烷乙醇（grandisol）。室内Y-型嗅觉仪趋向实验表明,较低浓度的3-（+）-蒈烯、1-甲基-2-异丙烯基-环丁烷乙醇及其相应的醛1-甲基-2-异丙烯基-环丁烷2醛（grandisal）,引起华山松木蠹象的正趋向反应。林间引诱试验表明,1-甲基-2-异丙烯基-环丁烷乙醇和1-甲基2-异丙烯基-环丁烷2醛对华山松木蠹象具有一定的引诱作用。由此推断,1-甲基-2-异丙烯基-环丁烷乙醇可能是华山松木蠹象的集结信息素成分之一。     

Aggregation pheromone of Metamasius spinolae (Coleoptera: Curculionidae): chemical analysis and field test

Male Metamasius spinolae (Gylh.) produce several volatile compounds that are likely constituents of its aggregation pheromone. These compounds were identified by volatile collections and gas chromatography (GC), followed by coupled gas chromatography-mass spectrometry (GC-MS), as 2-methyl-4-heptanone [1], 6-methyl-2hepten-4-one [2], and 2-hydroxy-2-methyl-4-heptanone [3]. Preliminary field experiments using synthetic racemates of these compounds showed that significantly more adult cactus weevils were caught in traps baited with the major single compound three or the 2 + 3 binary combination than in unbaited control traps. However, highest trap efficacy occurred with the 1 + 2 binary combination and a blend of all three synthetic compounds plus prickly pear. Potential uses for the cactus weevil pheromone and possible ways to increase trap captures are discussed.     

DNA based cladograms augment the discovery of a new Ips species from China (Coleoptera: Curculionidae: Scolytinae)

The implementation of DNA in taxonomic study is in its infancy because the association of the amount and type of nucleotide change with species boundaries has not been fully examined for most taxa. Mitochondrial cytochrome c oxidase I (COI) nucleotide data is currently the most popular molecular marker for delimiting species boundaries and a standard pair‐wise nucleotide divergence between groups of individuals has been suggested for the recognition of new species. It is unlikely that such a standard would be applicable across animal species, but the association of the amount and type of nucleotide change with species boundaries could help with the establishment of a taxon‐specific DNA taxonomy. This study utilizes DNA data from nuclear and mitochondrial genes to improve the taxonomy of an important forest beetle pest, Ips. Amount and type of nucleotide difference are associated with monophyletic species based on a cladistic analysis of these data. As a result, a new species from China is described for a clade of beetles whose nucleotide differences exceeded the amount of evolutionary change observed within currently recognized species. The COI data are analyzed independently with an expanded taxon data set, including pair‐wise nucleotide differences between recognized sister species. The wide range of average intraspecific pair‐wise nucleotide difference (0–10.0%) suggests limitations to the application of a standard percent nucleotide difference as a means to identify species boundaries. At most, average COI nucleotide intraspecific difference provides an informal guide to identify potential clades that may warrant further systematic investigation. © The Willi Hennig Society 2007.     

Nematodes associated with the double‐spined bark beetle Ips duplicatus (Coleoptera: Curculionidae) in central Europe

Ips duplicatus (Sahlberg) is an important forest pest in central Europe, but its nematode associates have seldom been studied. Therefore, nematodes associated with I. duplicatus were determined at three localities in the Czech Republic. The percentage of beetles with phoretic nematodes ranged from 18 to 65%. Micoletzkya buetschlii and other phoretic nematodes were found under elytra, on wings, and between body segments. The percentage of beetles with nematodes in the haemocoel ranged from 3 to 30%, and the nematodes included Contortylenchus diplogaster and Parasitylenchus cf. aculeatus. Juveniles of Parasitorhabditis obtusa (Fuchs 1915) were found in the intestines of 0–16% of the beetles. The most abundant species in I. duplicatus galleries were P. obtusa and M. buetschlii. Cryptaphelenchus sp., Parasitaphelenchus sp. and unidentified tylenchid juveniles also were found in the galleries. The percentage of beetles with nematodes was greater in the overwintering than in the offspring generation, and numbers of nematodes per gallery increased with gallery development.     

Nematodes associated with Ips cembrae (Coleoptera: Curculionidae): comparison of generations,sexes and sampling methods

A study of nematodes associated with the large larch bark beetle Ips cembrae (Heer 1836) was carried out at three locations in the Czech Republic. The proportion of beetles infested by endoparasitic nematodes (representatives of genera Contortylenchus, Parasitylenchus, Cryptaphelenchus and Parasitorhabditis) ranged from 29.9 to 50.9%. Significant differences were determined in nematode infestation levels among locations, generations and sampling methods. No differences were found in infestation rates between males and females. The percentage of bark beetles with phoretic nematodes ranged from 18 to 42.9%. Phoretic nematodes directly found under elytra, on wings and between body segments of the bark beetles belong to the genus Micoletzkya. However, adults and juveniles of other two phoretic species Laimaphelenchus penardi and Bursaphelenchus sp. were found in the gallery frass of I. cembrae. Infestation by phoretic nematodes positively correlated with the presence of mites under elytra.     

Aggregation pheromone in Sternechus subsignatus (Coleoptera: Curculionidae): olfactory behaviour and temporal pattern of emission

The Brazilian soybean stalk weevil, Sternechus subsignatus Boehman (Coleoptera: Curculionidae), is a pest of economic importance in many regions of Brazil. Volatiles from both sexes of S. subsignatus were collected by aeration and the behavioural response of males and females was evaluated using a Y‐olfactometer. The results obtained demonstrate that the communication in S. subsignatus is mediated by aggregation pheromone as both sexes were attracted to host plant (HP) volatiles, and this attraction was increased by the addition of male volatiles. At least five male‐specific compounds (1–5) were detected in the chromatographic analysis, providing chemical support to the behavioural data. Release of these volatiles is dependent on the presence of the HP as the amount of compounds differs significantly when volatiles are collected from weevils with or without access to food. The release takes place mainly during photophase, showing a peak between 4 and 6 h after its beginning, which is also a peak of the insect activity in the field. Studies are underway to elucidate the structures of these putative aggregation pheromone components, in order to evaluate their biological activity under laboratory and field conditions.     

Kairomonal Responses of Natural Enemies and Associates of the Southern Ips (Coleoptera: Curculionidae: Scolytinae) to Ipsdienol, Ipsenol and Cis-Verbenol

Bark beetle infested pines are an ephemeral habitat utilized by a diverse assemblage of insects. Although many bark beetle insect associates have little or no measurable impact on bark beetle brood production, some reduce brood production by either competing with brood for the limited phloem tissue or by feeding on brood. Several studies have observed synchrony between the colonization of hosts by bark beetles and the arrival of insect associates. Some insect associates mediate synchrony with bark beetle mass attacks with kairomonal responses to bark beetle aggregation pheromones. The objectives of this study were to document the community of Coleoptera associated with the southern Ips (Ips avulsus, Ips calligraphus and Ips grandicollis) and to test the hypothesis that synchrony of insect associates with the southern Ips is mediated by kairomonal responses to aggregation pheromones. A large community of Coleoptera (109 species) was recorded from traps baited with southern Ips pheromones. A significant treatment effect was observed for the guilds of meristem feeders, natural enemies and woodborers. The southern Ips pheromone ipsenol was broadly attractive to meristem feeders, natural enemies and woodborers and in general blends were more attractive than individual compounds. These results demonstrate that a diverse community of Coleoptera is associated with the southern Ips and that several members of this community facilitate synchrony with kairomonal responses to southern Ips aggregation pheromones.     

Identification of pheromone candidates for the eucalyptus weevil,Gonipterus platensis (Coleoptera,Curculionidae)

The eucalyptus weevil, Gonipterus platensis (Coleoptera, Curculionidae), is a major pest of eucalyptus plantations worldwide. To date, no pheromones have been identified for this species, despite their valuable potential as tools in monitoring or control strategies. Here we report the detection and identification of pheromones candidates of G. platensis. The weevil's volatile compounds were collected by solid phase micro extraction (SPME) and monolithic material sorption extraction (MMSE). Using Gas Chromatography coupled to Mass Spectrometry (GC/MS) analysis, eleven insect specific compounds were detected and identified: verbenene, cis-verbenol, trans-verbenol, verbenone, 2-oxo-1,8-cineole, 9-hydroxy-1,8-cineole, 2-α-hydroxy-1,8-cineole, 3-oxo-1,8-cineole, 2-β-hydroxy-1,8-cineole, 3-α-hydroxy-1,8-cineole and 7-hydroxy-1,8-cineole. Three of these compounds, verbenene, cis-verbenol and trans-verbenol, were shown to be male-specific. Antennal sensitivity towards ten compounds emitted by G. platensis was detected using Gas Chromatography–Mass Spectrometry/Electroantennographic Detection (GC-MS/EAD). Extracts from virgin males proved to be attractive to virgin females in olfactometer bioassays. Further behavioural bioassays showed that both virgin females and virgin males were attracted to the male-specific compound cis-verbenol and that virgin females were attracted to trans-verbenol. Verbenone was attractive to mated females. Regarding 2-α-hydroxy-1.8-cineole and 2-oxo-1,8-cineole, which are produced by both sexes, the alcohol was attractive to virgin males and both the alcohol and the ketone were repellant to mated females. This is, to our knowledge, the first identification of pheromones candidates in Gonipterus spp. and also the first evidence of cineole metabolites acting as semiochemicals.     

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.