Seasonal variation in laboratory response to behavioral chemicals of the southern pine beetle

The response ofDendroctonus frontalis to an attractant mixture (frontalin,trans-verbenol, and loblolly pine turpentine) was measured in the laboratory over a four-year period. Beetle response was highest in late winter and early spring, and lowest in midsummer and early fall. Males consistently responded higher than females. Female beetles displayed significantly higher responses in early morning and late afternoon than in the middle of the day. Analysis of beetle pronotal width and fat content revealed a high degree of correlation between these two parameters in female beetles, but there was no correlation of response with either fat content or pronotal width for either sex. There was no evident relationship between mean monthly beetle response and total amounts of frontalin andtrans-veibenol found in hindgut extracts. Daily temperature in months both during which beetles were bioassayed and immediately prior to bioassay was highly correlated to response to the attractant.Texas Agricultural Experiment Station Paper Number 16652. This research was supported by McIntire-Stennis Project 1525, and the U.S. Department of Agriculture-sponsored program entitled The Expanded Southern Pine Beetle Research and Applications Program through TAES-SEA-CR Grant 904-15-4. The findings, opinions, and recommendations expressed herein are those of the authors and not necessarily those of the U.S. Department of Agriculture. All programs and information of the Texas Agricultural Experiment Station are available to everyone without regard to race, color, religion, sex, age, or national origin.     

Southern pine beetle: Olfactory receptor and behavior discrimination of enantiomers of the attractant pheromone frontalin

In laboratory and field bioassays, the response ofDendroctonus frontalis was significantly greater to the mixture of (1S, 5R)-(–)-frontalin andalpha-pinene than to (1R,5S)-(+)-frontalin andalpfa-pinene. Electro-physiological studies revealed that antennal olfactory receptor cells were significantly more responsive to (1S, 5R)-(–)-frontalin than to (1R, 5S)-(+)-frontalin. Both enantiomers stimulated the same olfactory cells which suggests that each cell possesses at least two types of enantiomer-specific acceptors.Texas Agricultural Experiment Station paper no. 14496. The work was funded in part by McIntire-Stennis project 1525 (TAES) and the USDA program entitled The Expanded Southern Pine Beetle Research and Applications Program through TAES-CSRS grant 680-15-10. The findings, opinions, and recommendations reported herein are those of the authors and not necessarily those of the United States Department of Agriculture.     

Response of mountain pine beetle,Dendroctonus ponderosae Hopkins,and pine engraver,Ips pint (SAY), to ipsdienol in southwestern British Columbia

In bioassays conducted with walking beetles in the laboratory (S)–(+)–, (R)-(–)-, and (±)-ipsdienol were attractive alone, but reduced the attraction of both sexes of the mountain pine beetle,Dendroctonus ponderosae Hopkins, to extracts of female frass. Field trapping studies indicated that attraction ofD. ponderosae to a stimulus composed of myrcene +trans-verbenol +exo-brevicomin was significantly reduced with the addition of (±)- and sometimes (S)-(±)-ipsdienol. Thus, (S)-(+)-ipsdienol produced by males of this species may act as an antiaggregation pheromone. (S)-(+)-Ips-dienol is thought to function as a repellent allomone against the pine engraver,Ips pini (Say), in regions whereI. pini utilizes (R)-(–)-ipsdienol as an aggregation pheromone. However, in southwestern British ColumbiaI. pini was attracted to the (±)-ipsdienol used in field bioassays ofD. ponderosae, a finding consistent with the production of both enantiomers byI. pini in this region. When presented with the ternary semiochemical bait forD. ponderosae, (±)-ipsdienol was not attractive toI. pini. Thus, the activity of (S)-(+)-ipsdienol as a repellent allomone againstI. pini seems to be replaced in southwestern British Columbia by the inhibitory effects of myrcene,trans-verbenol,exo-brevicomin, or some combination thereof.Research supported in part by Natural Sciences and Engineering Research Council, Canada, Operating Grant A3881, Strategic Grant G1039, a Postgraduate Scholarship to D.W.A. Hunt, and the Science Council of British Columbia Grant 1 (RC-10)     

Olfactory-based behavioral interactions among five species in the southern pine bark beetle group

Olfactory-mediated behavioral interactions were investigated among the five scolytid species comprising the southern pine bark beetle group. Behavioral response, as determined from field trap catch data, showed that each species was attracted in greatest numbers to the pheromonal blend produced by conspecifies. Interspecifically,D. frontalis displayed no cross-attractancy toIps pheromonal blends, but was weakly attracted to the pheromonal blend of femaleD. terebrans. ThreeIps species displayed varying degrees of cross-attraction as well as to theDendroctonus pheromonal blends. More specifically,I. calligraphus was attracted toI. avulsus and, to a very limited extent, also to the maleD. terebrans pheromonal blend.I. avulsus was somewhat more cross-attractive thanI. calligraphus and showed attraction to the pheromonal blends of femaleD. frontalis, male and femaleD. terebrans, maleI. calligraphus, and maleI. grandicollis. I. grandicollis showed the greatest degree of cross-attraction, particularly in response to theDendroctonus pheromonal blends.Research support in part by CSRS grant 86-CRCR-1-2270, NATO grant CRG.0710/86 and Texas Agricultural Experiment Station project MS1525 (while M.T.S. and T.L.P. were with Texas A&M University). The findings, opinions, and recommendations expressed herein are those of the authors and not necessarily those of the U.S. Department of Agriculture.     

Repellent properties of the host compound 4-allylanisole to the southern pine beetle

The phenylpropanoid 4-allylanisole is a compound produced by loblolly pines (Pinus taeda L.), an abundant species in southern pine forests and a preferred host of southern pine beetle (Dendroctonus frontalis Zimmermann). Repellency of individual beetles was demonstrated in laboratory behavioral assays ofD. frontalis and other scolytids. Inhibition was demonstrated in natural populations ofD. frontalis using baited traps. In both tests, response to the inhibitory pheromone verbenone was used for comparison. In the laboratory, a higher proportion of newly emerged and reemergedD. frontalis responded negatively to 4-allylanisole than to verbenone. However, fewer reemergent than newly emerged individuals responded to either compound. In all field trials, the response ofD. frontalis to its attractant pheromone in funnel traps was significantly reduced by simultaneous release of 4-allylanisole. In most trials total reduction did not differ from verbenone; however, unlike verbenone, 4-allylanisole reduced male and female catches proportionally. Both compounds together did not significantly further reduce trap catch. The response of a major predator,Thanasimus dubius (F.), to the attractant pheromone ofD. frontalis, did not differ with the simultaneous release of either verbenone or 4-allylanisole. The results of preliminary field applications are presented and discussed.The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service.     

Electroantennogram responses of the southern pine beetle parasitoidDinotiscus dendroctoni (Ashmead) (Hymenoptera: Pteromalidae) to potential semiochemicals

In two studies using the electroantennogram (EAG) technique, bark beetle- and tree-produced semiochemicals were presented toDinotiscus dendroctoni (Ashmead), a larval parasitoid ofDendroctonus frontalis Zimm. In the first study, 20 test compounds and a standard mixture of oxygenated monoterpenes were presented individually at one concentration to the parasitoids. In the second study, the nine compounds that elicited the greatest EAGs in study 1 were then tested as serial dilutions of 10 to 0.0001g/ul. The individual compounds did not elicit responses greater than the standard mixture of oxygenated monoterpenes. Males and females exhibited similar dose responses, although females showed lower thresholds of response than males to frontalin, terpinen-4-ol,E,Z-chalcogran, andexo-brevicomin. In both studies, pino-/isopinocamphone elicited the greatest responses at high concentrations. Tests of different ratios of the camphone mixture indicated that pinocamphone elicited the greatest response. Most of the test compounds elicited similar responses which suggests that several of the compounds may be used together byD. dendroctoni in habitat and/or host community location.     

Feeding and boring behavior of the bark beetle,Ips paraconfusus,in extracts of ponderosa pine phloem

MaleIps paraconfusus Lanier bored and fed in cellulose powder substrates treated with solvent extracts of ponderosa pine phloem in preference to cellulose powder alone. Stimuli that elicit boring and feeding behavior occurred in the water extracts and the combined solvent extracts. No significant boring or feeding occurred in the methanol extract. There was a preference for, but no significant feeding in, the water partition of the ether extract. Feeding, but no preferential boring, occurred in the ether extracts.Coleoptera: Scolytidae.Research supported by the Rockefeller Foundation, an NIH Training Grant, USDA/SEA Regional Research Project W-110, and the USDA Forest Service.From a thesis submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy, by J.S.E., 1979, University of California, Berkeley, California.     

Frontalin in the male mountain pine beetle

Frontalin andexo-brevicomin were identified by GC-MS in air drawn over maleDendroclonus ponderosae Hopk. (MPB) from Oregon that had joined females for 1–2 days in the bark of lodgepole and ponderosa pine logs. Unfed males releasedexo- andendo-brevicomin but not frontalin. These three compounds were not detected in either unfed or fed females. Arrestment of males bytrans-verbenol and terpenes in an olfactory walkway was reduced by the addition of racemic frontalin; production of attractant chirps also diminished. Racemic frontalin also strongly reduced the aggregation of MPB in lodgepole and ponderosa pine stands to sticky traps baited with the aggregation pheromonetrans-verbenol and host terpenes; however, the function of the natural enantiomer of frontalin in MPB is unknown.Research supported by NSF Grant PCN 79-21708. O.S.U. Agricultural Experiment Station Technical Paper No. 6219.     

Attraction of pinyon pine bark beetle,Ips hoppingi,to conspecific andI. confusus pheromones (Coleoptera: Scolytidae)

Females of a pinyon pine bark beetle,Ips hoppingi Lanier, were less attracted by the aggregation pheromone produced by conspecific males than by the pheromone produced by the neighboring sibling species,I. confusus (LeConte). Cross-attraction was elicited by males infesting the regional pinyon pine hosts (P. discolor andP. edulis) of eitherIps species in south-eastern Arizona. Pheromonal specificity has not accompanied speciation in this species pair.     

Behavior of the western pine beetle during host colonization

After living ponderosa pines were baited with either female-infested bolts or synthetic pheromones,Dendroctonus brevicomis were caught on sticky screens throughout trapping periods of 15–46 days; however, large numbers of beetles were trapped during only a small portion (5–10 days) of these trapping periods. The most attractive portions of trees attacked contained 3–6 beetles dm², in galleries ca. 2 cm long. Catch increased following addition of males to female-infested bolts, supporting the hypothesis that male-produced frontalin is an attractive pheromone of the western pine beetle. Catch at bolts removed from trees under attack was strongly dependent upon levels of boring activity. We found no evidence of interruption of the response to attractants during host colonization.Coleoptera: Scolytidae. Trade names and commercial enterprises or products are mentioned solely for information and do not constitute endorsement by the U.S. Department of Agriculture or University of California.     

Antennnal olfactory and behavioral response of southern pine beetle,Dendroctonus frontalis,to analogs of its aggregation pheromone frontalin

Antennal olfactory (electroantennogram) and laboratory and field behavioral tests were carried out on the response ofDendroctonus frontalis to its aggregation pheromone frontalin and analogs. The analogs were compounds modified by altering the position and methyl groups and/or by their deletion. Any modification to the frontalin structure significantly reduced both the antennal olfactory and behavioral response byD. frontalis. Beetle response, although significantly reduced, was elicited at the receptor level and in a laboratory bioassay by all analogs. However, only one analog (endo-5,7-dimethyl-Frontalin) elicited significant response from field populations of the beetle.Texas Agricultural Experiment Station paper TA-22507. The work was funded in part by McIntire-Stennis project 1525 and by an operating grant from the Alberta Forest Service through the Forest Development Research Trust Fund. The findings, opinions, and recommendations expressed are those of the authors and not necessarily those of the U.S. Department of Agriculture. All programs and information of the Texas Agricultural Experiment Station are available without regard to race, ethnic origin, religion, sex, or age.     

Interactions of pheromone component odor plumes of western pine beetle

The relationships between catch ofD. brevicomis LeC. at sources of the synergistic pheromone components,exo-brevicomin (E) and frontalin (F), and increasing distance of separation of sources were investigated in the forest. The two components were each released with the host monoterpene, myrcene (M), in trap pairs. The traps of each pair were spaced apart at various distances (0–16 m) in either horizontal or vertical lines that were perpendicular to the mean wind direction. Both sexes were most strongly attracted when the two components were released from the same source, and increasing distance of separation between components caused exponential decreases in trap catch for all trap configurations. Males were significantly more attracted to traps with E, M alone than to corresponding traps with F, M alone, while females exhibited a preference for F, M. The theoretical relationships and properties of two coalescing plumes of individual components and their intersecting active space are presented and discussed. It is proposed that confusion or communication disruption techniques for insect control may be more successful if components are released individually from many points rather than released similarly in blends. Dendroctonus brevicomis LeC. (Coleoptera: Scolytidae).Supported in part by grants from U.S.A. and Sweden, NSF (INT-8503520), STU (84-3937), NFR, FRN, and SJFR.     

Antennal olfactory responses of black turpentine beetle,Dendroctonus terebrans (Olivier), to bark beetle pheromones and host terpenes

Electroantennograms (EAGs) were recorded from male and female black turpentine beetles,Dendroctonus terebrans (Olivier), exposed to bark beetle pheromones and host terpenes. The dose-response curves indicated similarities in the receptor mechanisms for both sexes for each compound. Antennal sensitivity was greatest toendo-brevicomin, which correlates with the importance of the compound in the behavior of the beetles. At above-threshold concentrations, EAGs were greatest toendo-brevicomin and frontalin, suggesting a large population of antennal receptors for these compounds. A large population of receptors would be expected for compounds that play such a significant role in this beetle's behavior. Beetles were also shown to have receptors that respond to theIps pheromones, ipsenol, and ipsdienol.Research done in part while in the Department of Entomology, Texas Agricultural Experiment Station (TAES), Texas A&M University, and supported in part through McIntire-Stennis project 1525, USDA-CR Grant 85-CRCR-1-1856, and NATO Collaborative Research Grant 86-0710. All programs of the Agricultural Experiment Station are available without regard to race, ethnic origin, sex, or age. Virginia Polytechnic Institute and State University does not discriminate against employees, students, or applicants on the basis of race, sex, handicap, age, veteran status, national origin, religion or political affiliation.     

The response of mountain pine beetle (Dendroctonus ponderosae) to lodgepole pine trees baited with verbenone and exo-brevicomin

exo-brevicomin, a multifunctional pheromone of the mountain pine beetle,Dendroctonus ponderosae, was tested at release rates of 0.5 and 2.5 mg/day alone and in combination with the antiaggregation pheromone verbenone against unbaited controls. Significantly more lodgepole pinePinus contorta var.latifolia trees were attacked, and at higher densities, with both release rates ofexo-brevicomin than with all other treatments. Verbenone significantly reduced the response of mountain pine beetles toexo-brevicomin. Verbenone alone did not reduce the number of trees attacked by mountain pine beetle or the attack density when compared to the unbaited controls.     

Interspecific effects of pheromones on the attraction of the bark beetles,Dendroctonus brevicomis andIps paraconfusus in the laboratory

Dendroctonus brevicomis was attracted to a mixture of theIps paraconfusus pheromones, ipsenol,cis-verbenol, and ipsdienol at 10^–9 g each/l but was not attracted to these pheromones at higher and lower release rates.I. paraconfusus was not attracted to theD. brevicomis pheromonesexo-brevicomin, frontalin, and myrcene at any release rate tested. Increased release rates of a mixture of the three pheromones ofI. paraconfusus inhibited the attraction ofD. brevicomis to its synthetic pheromones. A mixture of ipsenol + ipsdienol orcis-verbenol alone failed to cause inhibition indicating that at least two of theI. paraconfusus pheromones are required to inhibit the response ofD. brevicomis. The pheromones ofD. brevicomis did not inhibit the attraction ofI. paraconfusus to its pheromones; however, verbenone was a potent inhibitor.Coleoptera: Scolytidae. This paper is based in part upon a dissertation submitted by J.A.B. to the University of California, Berkeley, in partial fulfillment of the requirements for the Ph.D. degree in entomology, June 1978. These studies were supported by the Rockefeller Foundation; USDA Forest Service; Regional research project W-1 10, SEA/ USDA; and the National Science Foundation and Environmental Protection Agency through a grant (NSF GB-34719/BMS 75-04223) to the University of California. The findings, opinions, and recommendations are not necessarily those of the University of California or the funding agencies.     

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.     

Host selection behavior of bark beetles (Coleoptera: Scolytidae) attackingPinus ponderosa,with special emphasis on the western pine beetle,Dendroctonus brevicomis

Detection of weakened hosts from a distance by bark beetles through olfaction was investigated in field experiments. No significant numbers of Scolytidae were attracted to anaerobically treated pine bolts, stem disks, or sugar and ponderosa pine bark including phloem. Treatment of living trees with cacodylic acid induced attacks byDendroctonus brevicomis, D. ponderosae, Ips latidens, Gnathotrichus retusus, andPityophthorus scalptor, beginning two weeks after treatment. There was no significant difference between landing rates ofD. brevicomis andD. ponderosae on screened treated trees and screened controls. There was a significant increase in landing rates ofG. retusus andI. latidens, because both species had penetrated the screen and produced pheromones. Tree frilling alone did not increase the landing rate of bark beetles. Freezing of the lower trunk with dry ice did not increase significantly the landing rate ofD. brevicomis, D. ponderosae, G. retusus, orI. latidens on screened trees, whereas unscreened frozen trees were attacked by all four species. There was no significantly higher landing rate byD. brevicomis, D. ponderosae, I. paraconfusus, I. latidens, G. retusus, orHylurgops subcostulatus on screened trees evidencing symptoms of severe infection by the root pathogenVerticicladiella wagenerii, than on symptornless trees. These experiments show thatD. brevicomis, D. ponderosae, I. paraconfusus, I. latidens, andG. retusus land, apparently indiscriminately, on healthy and stressed hosts. Thus, in these species host discrimination must occur after landing and prior to sustained feeding.These studies were supported in part by the U.S.D.A. Forest Service, Cooperative State Research Services (2598-RRF.W-1 10) and the National Science Foundation and Environmental Protection Agency through a grant (NSF GB-34719/BM575-04223) to the University of California; and by the Canada Department of the Environment. The findings, opinions and recommendations are not necessarily those of the University of California or the funding agencies.From a thesis submitted by H.A. Moeck to the University of California, Berkeley, in partial fulfillment of the requirements for the degree Doctor of Philosophy in Entomology.     

Novel diffusion-dilution method for release of semiochemicals: Testing pheromone component ratios on western pine beetle

Each of the pheromone components of the Western pine beetle,Dendroctonus brevicomis LeC. (Coleoptera: Scolytidae), exo-brevicomin (E) and frontalin (F), were released in the forest at various ratios 0.011, 0.11, or 11 to a constant dose of the opposite component (E or F) plus the host monoterpene myrcene (M), which were each released at 1.5 mg/day. The components were released by a new method that combines the principles of chemical diffusion through a tube with mole percentage dilution of the chemical. Both sexes ofD. brevicomis were attracted similarly at comparable ratios (and release rates) of E or F and showed similar logarithmic relationships (r ²=0.920.99). The bark beetle predator,Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae) was apparently less sensitive to E thanD. brevicomis, being relatively less attracted to amounts of E equivalent to that released by 70 females, while none were attracted to that from seven females (while this rate still attracted significant numbers of conspecifics). The apparent insensitivity of bark beetles to extreme ratios between pheromone components in contrast to moths is discussed. The advantages of the diffusion-dilution method of releasing semiochemicals compared to previous methods of absorbents, wicks, capillary tubes, and semipermeable plastic membranes are also discussed.     

Pheromone biosynthetic pathways: Conversion of ipsdienone to (−)-ipsdienol,a mechanism for enantioselective reduction in the male bark beetle,Ips paraconfusus

The enantiomeric composition of the pheromone components (+)-ipsdienoI, e.e. 87.6%, and (–)-ipsenol, e.e. 93.8%, produced by the male bark beetleIps paraconfusus (Scolytidae) under natural conditions was determined by HPLC separation of their diastereomeric ester derivatives. Males confined in an atmosphere of ipsdienone produced (–)-ipsdienol, e.e. 28%, and (–)-ipsenol, e.e. 86%, indicating an enantiomeric selectivity in the conversion of the ketone to the alcohols. These findings demonstrate an enantioselective conversion mechanism in the biosynthetic pathway to the pheromones from myrcene, a host-plant terpene.     

Trapping the western pine beetle at and near a source of synthetic attractive pheromone Effects of trap size and position

Western pine beetles were caught on unbaited sticky traps placed near a source ofexo-brevicomin, frontalin, and myrcene. Size of trap, distance and direction from the source of attractant, and height from the ground were varied. Significant differences in trap catch were observed in relation to each of the variables. Traps close to the source of attractant caught more beetles than traps farther from the source. Traps downwind of the source of attractant caught more beetles than did upwind traps. More males than females were trapped close to the source of attractant.Based in part on a thesis submitted by the senior author to the University of California, Berkeley, California, in partial fulfillment of the requirements for the degree Master of Science in entomology, December 1976. These studies were supported by the U.S. Forest Service and in part by the Rockefeller Foundation and a joint grant (NSF GB-34718/BMS 75-04223) from the U.S. National Science Foundation and the U.S. Environmental Protection Agency to the University of California. The findings, opinions, and recommendations are not necessarily those of the University of California or the funding agencies.Trade names and commercial enterprises or products are mentioned solely for information and do not constitute endorsement by the U.S. Department of Agriculture or University of California.