Limonene inhibits attraction to α-pinene in the pine weevilsHylobius abietis andH. pinastri

The field responses ofHylobius abietis (L.) andH. pinastri (Gyllenhal) (Coleoptera: Curculionidae) to various combinations of two host monoterpenes and ethanol were studied using baited pitfall traps. Both species were attracted to -pinene, and when ethanol was added the attraction increased by 5–16 times. Limonene completely inhibited the attraction to -pinene, even when the release rate of limonene was only about 1/50 that of -pinene. The catches in traps with -pinene and limonene as well as with limonene alone were similar in size to catches in empty control traps, i.e., no true repellent effect was demonstrated. When limonene was added to the combination of -pinene and ethanol on old clear-cuttings, the catch ofH. pinastri was completely inhibited while that ofH. abietis was reduced by two thirds. On fresh clear-cuttings the inhibitory effect of limonene on the attraction to the -pinene-ethanol combination was small or absent. Some aspects of host interactions are discussed as are practical implications regarding the choice of seedling material for planting and prospects of finding deterrents for protecting seedlings from pine weevil damage.     

Occurrence and Correlations of Monoterpene Hydrocarbon Enantiomers in Pinus sylvestris and Picea abies

The relative amounts and enantiomeric compositions of monoterpene hydrocarbons in branch and trunk xylem, in needles, and in resin from apical buds in 18 Pinus sylvestris trees have been determined and compared with the terpene content in branch xylem and needles of Picea abies. Besides the high amount of (+)-3-carene, an excess of (+)--pinene has been found in P. sylvestris, whereas in P. abies (–)--pinene dominates over (+)--pinene. In P. sylvestris, clear positive correlations were found between (+)--pinene and (+)-camphene in the four tissues analyzed. Good positive correlations were also observed between (–)--pinene and (–)-camphene in the two types of xylem, between (+)--pinene and (+)--pinene in the resin, and between tricyclene and (–)-camphene in resin and needles. In P. abies, positive correlations were found between (+)--pinene and (+)-camphene in the branch xylem and between tricyclene and (–)-camphene as well as between (–)--pinene and (–)-camphene in the needles. Complex relationships between (–)--pinene and (–)--pinene were found both in the P. abies and in the P. sylvestris tissues. The importance of the enantiomeric composition of -pinene for the host selection of Ips typographus, Tomicus piniperda, and Hylobius abietis is discussed.     

Chiral specificity in responses by the bark beetleDendroctonus valens to host kairomones

The attraction of the red turpentine beetle,Dendroctonus valens, to the resin volatiles of its host,Pinus ponderosa, is elicited by three chiral monoterpenes. In field assays response was greatest to (S)-(–)--pinene; 92% (S)-(–)--pinene found inP ponderosa resin was not attractive. However, 75% (R)-(+)--pinene, which occurs inPinus lambertiana, a sympatric host ofD. valens, was attractive. (S)-(–)--Pinene interrupted response to (R)-(+)--pinene. (S)-(+)-3-Carene from both hosts was attractive at the (R)-(+)--pinene level. Three sympatric coniferous nonhosts each have the same attractive monoterpenes but produce less resin. These studies demonstrate the importance of chirality of host compounds in the host finding behavior of this bark beetle.     

Effect of ethanol and α-pinene on response of ambrosia beetle,Trypodendron lineatum,to lineatin-baited funnel and drainpipe traps

The response ofT. lineatum to ethanol and -pinene, when used with the pheromone lineatin, was tested for two trap types. Funnel traps, which are passive barrier traps, caught significantly more beetles than drainpipe traps, which require an active response by the beetle to enter the trap. However, the response ofT. lineatum to the semiochemical treatments did not significantly differ for the two trap types. Treatments that included -pinene with the pheromone, either with or without ethanol, caught significantly moreT. lineatin than those with the pheromone alone. When ethanol and or -pinene were added to the pheromone significantly more female beetles were trapped than with pheromone alone. Male-female ratios were significantly lower for both types of traps when ethanol was included in the bait than for lineatin alone or with -pinene. A higher percentage of male beetles entered the drainpipe traps than was captured with funnel traps.     

Corn volatiles as attractants for northern and western corn rootworm beetles (Coleoptera: Chrysomelidae:Diabrotica spp.)

Synthetic corn volatiles and selected analogs were tested in commercial corn fields for attractiveness to feral northern (NCR,Diabrotica barberi) and western corn rootworm beetles (WCR,D. virgifera virgifera). Two new attractants, geranylacetone and -terpineol, were identified among corn terpenes and compared at four stages in crop development with the phenylpropanoid standards cinnamyl alcohol and 4-methoxy-cinnamaldehyde, with each component at 30 mg/trap. Dose-response relationships (0.1–100 mg/trap) and efficacy of two-component blends (30 mg/component) were also examined. More beetles were captured on traps baited with (+)- than (–)--terpineol, but the difference was statistically significant only for WCR. Captures with geranylacetone or (+)--terpineol were directly proportional to the logarithm of the attractant dose. WCR females were attracted to as little as 0.1 mg of either compound. WCR males required 1.0 mg of (+)--terpineol and were not attracted to geranylacetone at any dose. NCR required 0.3 mg of either attractant and showed less marked response differences between the sexes than did WCR. Geranylacetone and cinnamyl alcohol were equally effective attractants, whereas (+)--terpineol was significantly less attractive to WCR but more attractive to NCR than was 4-methoxycinnamaldehyde. Corn terpenes and phenylpropanoid standards produced similar seasonal response patterns in that captures tended to rise in each case as the season progressed, except during silking when no compound was attractive. Mixing corn terpenes or phenylpropanoid standards synergized responses of WCR females, but (+)--terpineol suppressed attraction of NCR females to geranylacetone.Mention of a proprietary product or company name does not imply endorsement by the U.S. Department of Agriculture.     

Additional male mediterranean fruitfly (Ceratitis capitata wied.) Attractants from Angelica seed oil (Angelica archangelica L.)

Two sesquiterpene hydrocarbons, -copaene and -ylangene, were isolated from bioactive fractions of angelica seed oil and were shown by field bioassays to be attractive to the male Mediterranean fruit fly. Their relative attractiveness, compared with the(+)-and (–)--copaene enantiomers, are: (+)--copaene>angelica -copaene>angelica -ylangene>(–)--copaene. The enantiomer ratios for the two compounds are: -copaene, 61.4% (+), 38.6% (–); -ylangene, 91.9% (+), 8.1% (–).trans--Bergamotene was also isolated from the same fractions, but in sufficient quantity for bioassay [enantiomer ratio: 95.7% (+), 4.3% (–)].     

Stereospecific antennal response by red turpentine beetle,Dendroctonus valens to chiral monoterpenes from ponderosa pine resin

The antennal response ofDendroctonus valens to host monoterpenes from the resin of ponderosa pine was studied using the electroantennogram (EAG) technique. Male and female beetles were given a single dose of each of 11 different monoterpenes. Response amplitude to the different compounds did not vary between sexes and was generally well correlated with results from field attraction studies. Response to (S)-(–)--pinene was greatest. The relative amplitude of the responses to the (R)-(+) and (S)-(–) enantiomers of a-pinene, however, were reversed from their relative attractiveness in the field. A dose-response study was conducted for the (R)-(+) and (S) -(–) enantiomers of a-pinene, plus a reciprocal differential saturation test with successive doses of first one enantiomer of-pinene and then the other. Comparison of EAG traces suggests different receptors for the two stereoisomers of-pinene. Differential saturation curves suggest that while one set of receptors may respond to both enantiomers, some receptors respond only to the (S)-(–) enantiomer.     

Opposing Effects of Host Monoterpenes on Responses by Two Sympatric Species of Bark Beetles to Their Aggregation Pheromones

The effects of host tree monoterpenes on primary and secondary attraction of the bark beetles, Ips pini and Ips grandicollis, and their associated phloeophagous insects were investigated. Monoterpenes alone were not attractive to I. pini. However, monoterpenes mediated the attraction of I. pini to its aggregation pheromones. With the exception of 3–carene, the effect of monoterpenes on I. pini's response to its pheromone, ipsdienol plus lanierone, was inhibitory. In contrast, (–)--pinene both attracted I. grandicollis and enhanced the attraction of I. grandicollis to its pheromone, ipsenol. No monoterpene inhibited the response of I. grandicollis to its pheromone. The inhibitory effect of host monoterpenes on I. pini response to its aggregation pheromone differs from previous work, in which monoterpenes either synergized responses or had no effect. In addition to possible geographic differences, the concentrations used in our study simulated trees that had begun to respond to attack, whereas previous studies deployed lower concentrations, which simulated constitutive phloem from unattacked trees. These results support the view that trees that undergo induced responses to bark beetles sometimes inhibit attraction of additional beetles, despite the beetles' production of aggregation pheromones. Neither species displayed cross-attraction to the pheromone of the other. The red turpentine beetle, Dendroctonus valens, showed weak and consistent attraction to (+)--pinene and in some cases to (–)--pinene. Attraction to (–)--pinene was usually enhanced by Ips spp. pheromones. The absence of strong attraction to (+)--pinene and partial attraction to (–)--pinene suggest that the effects of different stereoisomers of -pinene on D. valens vary throughout its geographical range. Hylastes porculus was also attracted to some monoterpenes, particularly (–)--pinene. An additional 10 species of phloeophagous insects were caught in response to monoterpenes and/or pheromones, including the pine root weevils, Hylobius pales and Pachylobius picivorus, and the longhorned beetle, Monochamus carolinensis.     

Synergistic Effect of Ethanol to α-Pinene in Primary Attraction of the Larger Pine Shoot Beetle, Tomicus piniperda

-Pinene and ethanol were released in the approximate proportions 1:0.1, 1:0.9 and 1:9 (at 21°C). Ethanol, released in the range of 3–279 mg/day, generally synergized the attraction of T. piniperda to -pinene (30 mg/day at 21°C), although attraction to the mixtures varied within and between years. The low release rate of ethanol together with -pinene attracted a significantly higher number of beetles than -pinene alone in 1995, April of 1996, and in 1997. Lures with the medium release rate of ethanol were the most attractive only in March of 1996. The high dose of ethanol significantly synergized attraction to -pinene in 1995 and 1997. The variable attraction of T. pinipeda to ethanol and -pinene at various release rates and proportions may be due to the temperature dependent nature of beetle antennal sensitivity. At ambient temperatures of 10–13°C. T. piniperda was most attracted to the lures with -pinene and high release rates of ethanol, at 14–17°C it was most attracted to those with medium release rates of ethanol, and at 18°C and higher it was most attraacted to those with low release rates of ethanol.     

Field responses of certain forest Coleoptera to conifer monoterpenes and ethanol

Field experiments using baited sticky stovepipe traps and Lindgren multiple funnel traps were done near Chalk River, Ontario, Canada, to determine the effects of conifer monoterpenes (-pinene, -pinene, myrcene, limonene, camphene and carene) and ethanol on the number of beetles captured. Several species of conifer-feeding beetles were attracted to the monoterpenes or to monoterpenes and ethanol, including species in the families Cerambycidae (Asemum striatum, Acmaeops proteus, Xylotrechus undulatus, Monochamus scutellatus), Curculionidae (Pissodes strobi, Hylobius pales), and Scolytidae (Dryocetes autographus, Ips grandicollis). Species of Buprestidae generally did not respond to the monoterpenes or to ethanol. Species of Cleridae (Thanasimus dubius, Enoclerus nigripes rufiventris, Enoclerus nigrifrons gerhardi) which are predators of conifer bark beetles were attracted to the monoterpenes. Synergism between monoterpenes and ethanol was evident forM. scutellatus, H. pales, andD. autographus. While -pinene was the most potent attractant for most beetle species, monoterpenes other than -pinene synergized attraction to ethanol forD. autographus. Attraction of beetles to commercial turpentine and ethanol did not differ significantly from attraction to a pure monoterpene blend and ethanol.     

Chemistry and Defensive Efficacy of Secretion of Burrowing Bug (Sehirus cinctus cinctus)

Adult Sehirus cinctus cinctus emit a volatile secretion from their metathoracic scent glands when tactually stimulated. We identified the volatile components by gas chromatography, high-performance liquid chromatography, and mass spectrometry. The secretion of both sexes contained (1R)-(+)--pinene, (1S)-(–)--pinene, -myrcene, (R)-(+)-limonene, and -terpinolene. Two additional compounds were found in only female secretions: (E)-2-hexenyl acetate and (E)-2-octenal. We also tested the defensive capability of this insect by offering it to various predators. Anoles, starlings, and a killdeer rejected S. c. cinctus after an initial sampling. These findings suggest that the secretion plays a defensive role.     

Monoterpene oviposition stimulants ofDioryctria amatella in volatiles from fusiform rust galls and second-year loblolly pine cones

Volatiles collected on Poropak Q from fusiform rust galls (Cronartium quercuum F. sp.fusiforme) of loblolly pine for 3 hr were better ovi-position stimulants forDioryctria amatella (Hulst) females than extracts of 8-hr collections. GLC analysis of these extracts showed no major differences in relative monoterpene composition, although 8-hr collections contained an unidentified compound not detected in the 3-hr collections. Comparison of volatiles from second-year loblolly pine cones with those from fusiform galls showed that both containeddl--pinene, (–)--pinene, myrcene, and (+)-limonene. Camphene was found in galls only, and relatively large quantities of -phellandrene were identified only from cones. The five major monoterpenes found in the two host substrates were tested in an oviposition bioassay. Eighteen trials using different combinations of these terpenes showed that the combination of -pinene, myrcene, and limonene was as attractive toD. amatella females as all other terpene combinations, including turpentine.Lepidoptera: Pyralidae.     

α-Copaene, A Potential Rendezvous Cue for the Mediterranean Fruit Fly, Ceratitis Capitata?

-Copaene, a potent attractant for male Mediterranean fruit flies, Ceratitis capitata, is found as a minor component in the essential oils of various plant species, including its hosts such as orange, guava, and mango. Despite the specific attraction of male flies and the wide distribution of the compound in host plants, the biological significance of -copaene remains unknown. In a laboratory test, leklike behavior of C. capitata was induced artificially by using a plastic leaf model treated with (+)--copaene. It was also found that (+)--copaene affected virgin females, provoking "pseudomale" courtship behavior in the short-range bioassay. Mating occurred exclusively on the artificial leaves treated with -copaene, suggesting the compound potentially serves as a chemical cue to facilitate orientation of flies to the rendezvous site.     

Response of the European elm bark beetle,Scolytus multistriatus (Coleoptera: Scolytidae), to isomers and components of its pheromone

Laboratory bioassays (two methods) and field tests demonstrated synergistic action of the three components [(–)-4-methyl-3-heptanol (I); (–)-2,4-dimethyl-5-ethyl-6,8-dioxabicylo[3.2.1]octane (-multistriatin) (II); and (–)--cubebene (III)] of the pheromone bouquet ofScolytus multistriatus. Individually and in pairs the components were slightly attractive; I+II was clearly the most active doublet. Indirect evidence indicates that only one of the four enantiomers of I is active. Of the , , and isomers of II, only the is active. With the addition of compound I, slightly attractive extract from mated females became nearly as active as extract from virgin females.     

Oxygenated monoterpenes produced by yeasts,isolated fromIps typographus (Coleoptera: Scolytidae) and grown in phloem medium

When yeasts associated withIps typographus beetles were grown in an aqueous phloem medium for two days, the main oxygenated monoterpenes produced were -terpineol and borneol. Terpinene-4-ol, myrtenol, andtrans-pinocarveol were also found but in lesser amounts. Of the six strains used in this study,Hansenula capsulata andCandida nitratophila produced the largest amounts of oxygenated monoterpenes. Addition of -pinene to the phloem medium generally reduced the amounts of oxygenated monoterpenes, probably because this substance is toxic to all tested yeast species. OurCandida diddensii strain seemed to be particularly sensitive to -pinene. None of the yeast strains producedcis-verbenol,trans-verbenol, or verbenone from the medium or from added -pinene.This study was made within the project Odour Signals for Control of Pest Insects.     

Single and blended maize volatiles as attractants for diabroticite corn rootworm beetles

Synthetic maize volatiles and analogs dispensed singly and blended were tested for attractiveness to western (WCR, Diabrotica virgifera virgifera) and northern corn rootworm beetles (NCR, D. barberi) in maize fields. Newly identified attractants included syn-benzaldoxime, especially for NCR, and -caryophyllene for WCR females. (±)-Linalool was more effective than was (–)-linalool. Myrcene, (+)--pinene, and (–)--pinene were unattractive. Adding methyl salicylate to (±)-linalool, (+)--terpineol, or -ionone appeared to synergistically increase capture of WCR females, but dispensing the terpenes in binary blends did not. Dose–response data for methyl salicylate, (±)-linalool, and a blend of both compounds confirmed the synergy. -Caryophyllene, but not (–)--pinene, added to the latter blend produced a further synergistic increase in WCR female capture that did not vary with sesquiterpene dose from 1.0 to 100 mg. Indole addition to the same blend caused an increase in WCR female captures indicative of synergy, assuming that each did not individually lure different segments of the WCR female population. The green leaf volatiles (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol were unattractive alone and had no influence on efficacy of traps baited with 3.3 mg each of (±)-linalool, methyl salicylate, and -caryophyllene. The latter mixture captured about half as many WCR females as did 10 mg of 4-methoxycinnamaldehyde, a potent WCR attractant standard. Substituting -ionone for (±)-linalool yielded a ternary blend that captured more beetles than did the aldehyde and was unaffected by aldehyde addition. Olive oil, which has been used to sustain attractant volatilization, did not affect captures. The results show that the blending of maize volatiles has the potential to greatly improve efficacy of lures having promising applications in corn rootworm population management.     

Oxidation of α- and β-pinene catalyzed by MnIII (Salen) Cl·H2O

The cationic complex Mn^III (Salen) is a very effective catalyst for the oxidation of both- and-pinene. The higher selectivity towards epoxide formation supports the rebound oxygen mechanism. A turnover of 40 was obtained for both compounds after 16 h of reaction with a molar ratio 10.011 (feedstock: catalyst: iodosobenzene) and conversions between 50 and 60% were observed. A very high selectivity (55%) was determined for epoxide formation from -pinene. The good selectivity observed for myrtanal isomers (6.5 and 23.2%) from-pinene is related to the prior formation of the 1,2-epoxides.     

Attraction of scolytids and associated beetles by different absolute amounts and proportions of α-pinene and ethanol

The attraction of bark and ambrosia beetles as well as associated beetles to -pinene and ethanol was studied in field experiments with flight barrier traps. -Pinene and ethanol were released individually and as combinations in approximately 11 or 110 ratios and at four different release rates. Ethanol attractedTomicus piniperda (L.),Hylurgops palliatus (Gyll.),Trypodendron lineatum (Oliv.),Hylastes cunicularius Er.,H. brunneus Er.,H. opacus Er., andAnisandrus dispar (F.) (Scolytidae);Glischrochilus quadripunctatus (L.) andEpuraea spp. (Nitidulidae);Thanasimus formicarius (L.) (Cleridae); andRhizophagus depressus (F.) (Rhizophagidae). -Pinene attracted all these species with the exception ofT. lineatum, H. cunicularius, andA. dispar. Combinations of a-pinene and ethanol resulted in synergistically increased attraction of all species with the exception ofH. opacus andA. dispar. A. dispar, the only hardwood-associated species in the study, was repelled by -pinene. Both the release rates and the ratio at which the two substances were released influenced the response of the beetles. The differences in response between the beetle species seem to reflect dissimilarities in the release of the two substances among the various types of breeding material to which the species are adapted.     

Alleviation of α-tomatine-induced toxicity to the parasitoid,Hyposoter exiguae,by phytosterols in the diet of the host,Heliothis zea

The solitary, endoparasitic ichneumonid,Hyposoter exiguae (Viereck) is a parasitoid of the tomato fruitworm,Heliothis zea (Boddie). However, the parasitoid is deleteriously affected by the tomato glycoalkaloid, -tomatine, ingested from hosts (H. zea) fed on artificial diets or semipurified extracts of tomato plants that contained -tomatine. -Tomatine causes prolonged larval development; disruption or prevention of pupal eclosion; deformation of antennal, abdominal, and genital structures; and reduction in adult weight and longevity of the parasitoid. These toxic effects are exacerbated when the dietary dose of -tomatine is increased from 12 mol to 20 mol/g dry wt of diet. However, the toxicity of -tomatine is attenuated in parasitoids reared from hosts fed on artificial diets that contain equimolar or supramolar amounts of 3-OH-sterols admixed with -tomatine. Further, the toxicity of extracts from the foliage of different cultivars of tomatoes toH. exiguae is contingent upon the composite levels of -tomatine and total phytosterol (free and esterified). Cultivars with a low total sterol-tomatine ratio are more toxic toH. exiguae. The possible mode of action of -tomatine toxicity toH. exiguae by disruption of sterol metabolism is discussed.     

Disruption by Conophthorin of the Kairomonal Response of Sawyer Beetles to Bark Beetle Pheromones

Antennally active nonhost angiosperm bark volatiles were tested for their ability to reduce the response of three common species of coniferophagous wood-boring Cerambycidae to attractant-baited multiple funnel traps in the southern interior of British Columbia. Of the nonhost volatiles tested, only conophthorin was behaviorally active, disrupting the attraction of sawyer beetles, Monochamus spp., to traps baited with the host volatiles -pinene and ethanol and the bark beetle pheromones ipsenol and ipsdienol. Conophthorin did not affect the attraction of sawyer beetles to the host kairomones -pinene and ethanol in the absence of bark beetle pheromones, nor did it have any behavioral effect on adults of Xylotrechus longitarsis, which were not attracted to bark beetle pheromones. These results indicate that conophthorin does not act as a general repellent for coniferophagous Cerambycidae, as it seems to do for many species of Scolytidae, but has the specific activity of disrupting the kairomonal response of sawyer beetles to bark beetle pheromones.