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.     

Multiple acceptors for pheromonal enantiomers on single olfactory cells in the Douglas-fir beetle,Dendroctonus pseudotsugae Hopk. (Coleoptera: Scolytidae)

Olfactory perception of pheromonal enantiomers by male and female Douglas-fir beetles,Dendroctonus pseudotsugae Hopk. (Coleoptera: Scolytidae), was investigated by electrophysiological techniques and behavioral bioassays. Electroantennograms (EAGs) and single-cell responses indicated both sexes to be more responsive to racemic frontalin and the (–)-enantiomer at lower dosages. At higher dosages, little difference was noted in responses to either enantiomer. However, response to the racemic mixture at higher dosages was slightly greater than responses to either enantiomer alone. In laboratory behavioral bioassays, responses to low concentrations of (–)-frontalin and the racemic mixture exceeded response to the (+)-enantiomer alone. At a higher concentration, responses to the racemic mixture or either enantiomer alone did not differ. The results indicate that separate enantiomer-specific acceptors may exist on the same pheromone receptor cell.Texas Agricultural Experiment Station paper No. TA-19841. This research was supported in part by Mclntire-Stennis Project 1525, 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, and NSF grant PCN 79-21708 to Oregon State University. 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 without regard to race, ethnic origin, religion, sex, or age.Mention of a trademark, proprietary product or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Effects of slow-release formulation of syntheticendo- andexo-brevicomin on southern pine beetle flight and landing behavior

A slow release formulation of the bark beetle pheromones,endo- andexo-brevicomin, significantly reduced landing of southern pine beetles on host trees. Beetle flight activity within the infestation was not affected by the pheromones. The pheromones were released at approximately 600 mg/ha/day via Conrel® hollow fiber controlled-release dispensers. Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae). The work was funded in part by McIntire-Stennis project 1525 TAES and TEXY-00011 (SFASU), the U.S. Department of Agriculture sponsored program entitled The Expanded Southern Pine Beetle Research and Applications Program through TAES-CSRS grant 680-15-10 and SFASU-CSRS grant 680-15-13, and U.S. Forest Service Coop. Agreement USDA-SFES 19-145 to TAES and SFASU. The findings, opinions, and recommendations reported herein are those of the authors and not necessarily those of the U.S. Department of Agriculture. Texas Agricultural Experiment Station paper No. 12731.     

Single cell responses of the Douglas-fir beetle,Dendroctonus pseudotsugae hopkins (Coleoptera: Scolytidae), to pheromones and host odors

Olfactory perception of pheromones and host odors byDendroctonus pseudotsugae males and females was investigated through single cell recordings. Responses of 71 cells (35 cells in males; 36 cells in females) were recorded to 1 g of 10 pheromones and three host terpenes. The olfactory cells were classified into four types based on sensitivity and specificity for the various odors: (1) 3,2-MCHone (3-methyl-2-cyclohexenone) cells; (2) 3,2-MCHol (3-methyl-2-cyclohexenol) cells; (3) frontalin cells; and (4) synergist cells. 3,2-MCHone and 3,2-MCHol cells in both males and females were the most sensitive and specific of all cells recorded with a threshold ca. 0.001–0.01 g on filter paper. Frontalin cells were less specialized than the two aforementioned cell types and had a somewhat higher threshold of ca. 0.01 g. A larger percentage of these three cell types were recorded in males than in females. The synergist cells had the highest threshold of all recorded cell types and were the least specific. Each of these cells was most responsive to eithercis-verbenol,trans-verbenol, 1,2-MCHol, verbenone, -pinene, or limonene; however, responses could be elicited by stimulation with other pheromones or host terpenes at higher dosages. Instances of inhibition of nerve impulse activity from spontaneously active cells were observed during 3,2-MCHol and 3,2-MCHone stimulation, thus suggesting multifunctional effects for these compounds. The results help explain the role of chemicals in host selection, aggregation, and colonization behavior of the beetle and further elucidate hypotheses put forth in an earlier electroantennogram study.Texas Agricultural Experiment Station Paper NumberTA-18689. This research was supported in part by McIntire-Stennis Project 1525, 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, and NSF grant PCN 79-21708 to Oregon State University. 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 without regard to race, ethnic origin, religion, sex or age.     

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.     

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.     

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.     

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.     

Electroantennogram responses ofTrirhabda bacharides (weber) (Coleoptera: Chrysomelidae) to plant volatiles

Electroantennograms (EAGs) were recorded fromTrirhabda bacharides Le Conte (Coleoptera: Chrysomelidae) females to 28 odorants and volatiles emanating from leaves of 26 plant species including three known host plants,Baccharis halimifolia L.,B. neglecta Britt, andB. salicina T. & G. (Compositae: Asterae). Antennal receptors were highly responsive to components of the green leaf volatile complex, especially 6-carbon saturated and monounsaturated alcohols andtrans-2-hexenal. EAGs elicited by heptanal were greater than those elicited by any other saturated aldehyde. Oxygenated monoterpenes were more active than monoterpene hydrocarbons. -Bisabolol was the most active sesquiterpene. In general, EAGs to volatiles emanating fromBaccharis and other composite species were greater than those elicited by species from other families. Furthermore, when one considers only plants occurring in the environs ofT bacharides hostB. neglecta, EAGs elicited by its host plant were at least two times greater than those elicited by other coinhabiting plants.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Insect predator-prey coevolution via enantiomeric specificity in a kairomone-pheromone system

Insect predators can be guided to their prey by a kairomonal response to the prey pheromone. We found this phenomenon to be highly specific in the bark beetle predatorThanasimus dubius. Olfactory responses and behavioral tests revealed that the predator is guided to its major preyDendroctonusfrontalis by the primary enantiomer of the pheromone of the prey, (1S, 5R)-(–)-frontalin. These and other findings suggest the co-evolution of a kairomone system of the predator and the pheromone system of its prey.Texas Agricultural Experiment Station paper No.TA17770. 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.     

Attractiveness of tobacco budworm females altered by oral chemosterilants and dietary additives

FemaleHeliothis virescens (F.) moths reared from larvae on diet treated (0.1%) with experimental chemosterilants or the dietary additive, DL-leucine, were used as bait in sex lure traps in field cages when they were 2–4 nights old. Catches of untreated released males were used to determine relative attractiveness of the chemically treated females. The catch (indicating quantity or production frequency of pheromone) was significantly increased whendl-leucine had been fed in the larval diet, and sulfanilamide caused a slight increase in female attractiveness. The catch of males was significantly reduced when either reserpine or quercitin had been added to the diet. The other chemicals, bisdicumarol, 2,4-dichlorophenoxyacetic acid, -sitosterol, and dihydrocholesterol, did not significantly affect the catch.This paper reports the results of research only. Mention of a pesticide in this paper does not constitute recommendation of use by the U.S. Department of Agriculture nor does it imply registration under FIFRA as amended.In cooperation with the Texas Agricultural Experiment Station, Texas A&M University, College Station 77843.The assistance of C.T. Perez and R.J. Guerra, of this laboratory, during field tests is gratefully acknowledged.     

All-glass system for preparative gas chromatography using capillary columns

A zero dead-volume all-glass-lined stainless-steel effluent splitter with a modified thermal gradient collector was designed for preparative gas chromatography using glass capillary columns. This system gives efficient collection of extremely pure samples of the 1-ng to 10-g range for spectral analysis and biological testing.Approved as TA 15656 by the director of the Texas Agricultural Experiment Station in cooperation with ARS, USDA. Supported by the Texas Department of Agriculture interagency agreement IAC-0487 (78-79).     

Ovipositional behavior ofBracon mellitor Say,a parasitoid of the boll weevil (Anthonomus grandis Boheman) III. Isolation and identification of natural releasers of ovipositor probing

The chemical cues in the frass of larvae of the boll weevil,Anthonomus grandis Boheman, that elicit an ovipositional response in females ofBracon mellitor Say were isolated by a combination of column, thin-layer, and gas-liquid chromatography. Derivatization, analytical tests, and mass spectrometry were used to identify the biologically active materials as long-chain fatty acid esters of cholesterol. Bioassays with natural and synthetic cholesteryl esters were used to confirm activity. The activity of the cholesteryl esters was also confirmed by using females that had not been previously exposed to hosts.Hymenoptera: Braconidae.Mention of a proprietary or commercial product in this paper does not constitute an endorsement of this product by the U.S. Department of Agriculture.Approved for publication in TA 12593 by the Director, Texas Agricultural Experiment Station.This study was supported, in part, by the National Science Foundation and the International Biological Program (NSF-SC-0030) to the University of California. The findings are those of the authors and not necessarily those of the University of California or NSF.     

Olfactometer for assay of behavioral chemicals for the southern pine beetle,Dendroctonus frontalis (Coleoptera: Scolytidae)

A simple open-arena olfactometer to assay behavioral chemicals with pedestrian insects has been developed for the southern pine beetle. The olfactometer is constructed of Plexiglas and uses a single airstream. A feature of the olfactometer is the use of a clock-driven elution device that permits continuous release of liquid materials into the olfactometer airstream.This is Texas Agricultural Experiment Station Paper No. 12324. The work herein reported was funded in part by McIntire-Stennis project 1525, USFS Southern Forest Experiment Station cooperative agreement 19–145 and the USDA sponsored program entitled The Expanded Southern Pine Beetle Research and Applications Program through CSRS grant 516-15-70. The findings, opinions, and recommendations reported herein are those of the authors, and not necessarily those of the USDA.     

Bark-beetle pheromones

The two major yeasts isolated from the southern pine beetle,Dendroctonus frontalis Zimmerman, areHansenula holstii Wickerham andPichia pinus (Hoist) Phaff; a third yeast,P. bovis van Uden et do Carmo-Sousa, has been isolated far less frequently. The main volatile metabolites produced by these yeasts are isoamyl alcohol, isoamyl acetate, 2-phenylethanol, and 2-phenylethyl acetate.We have found that certain of these compounds, particularly the esters, can greatly, enhance the attractiveness of a mixture of frontalin:trans-verbenol: turpentine (1:1:12), at certain limiting concentrations, to walking beetles in a laboratory bioassay.Supported in part by cooperative agreement No. 19-205 with the USDA Forest Service, Southern Forest Experiment Station, Pineville, Louisianna 71360, the Texas Agricultural Experiment Station Project MS 1525, and the USDA-sponsored program entitled The Expanded Southern Pine Beetle Research and Applications Program through CSRS grant 516-15-70. The findings, opinions, and recommendations reported herein are those of the authors, and not necessarily those of the USDA.     

Role of (Z)- and (E)-11-tetradecenyl acetate pheromone components in the sexual behavior of the (Z) strain of the european corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

A glass tube olfactometer bioassay was used to examine pheromone response of males of the (Z)-pheromone strain ofOstrinia nubilalis (Hubner). The presence of (E)-11-tetradecenyl acetate at the natural ratio to (Z)-11-tetradecenyl acetate (973; ZE) did not consistently elevate wing-fanning, upwind walking, or clasper extrusion over (Z)-11-tetradecenyl acetate alone. This bioassay did not reveal the behavioral role of (E)-11-tetradecenyl acetate.Published as Journal Article No. 10264 of the Michigan State University Agricultural Experiment Station.     

Antennal olfactory response of boll weevil to grandlure and vicinal dimethyl analogs

Electroantennogram techniques were used to elucidate antennal olfactory response of male and female boll weevils to a dilution series of grandlure, its components, and some vicinal dimethyl analogs. At higher concentrations, response to the mixture of the two aldehyde components of grandlure was significantly higher than to the two alcohol components. Only one vicinal dimethyl analog elicited a significantly higher response than the control. There were no significant differences in response due to sex over all compounds.Texas Agricultural Experiment Station paper number 16382. Research supported by McIntire-Stennis project 1525. All programs of the Texas Agricultural Experiment Station are available without regard to race, sex, color or religion.     

Female sex pheromone of the melonworm,Diaphania hyalinata (Lepidoptera: Pyralidae), and analysis of male responses to pheromone in a flight tunnel

Ten C₁₆ chain-length compounds were identified from heptane extracts of ovipositors of female melonworm,Diaphania hyalinata (L.). The major constituents of the extracts were (E)-11-hexadecenal and (E,E)-10,12-hexadecadienal [(E,E)-10,12–16:Ald] and the alcohols and acetates of these olefins were found in trace amounts (<2%). Extracts also contained traces of (E,Z)- and (Z,Z)-10,12-16:Ald, hexadecanal, and 1-hexadecanol. Analysis of the behavioral responses of males to synthetic mixtures of these compounds and responses to ovipositor extracts in a flight tunnel showed that a synthetic mixture of the 10 compounds elicited a behavioral repertoire from males that was indistinguishable from that elicited by ovipositor extract. Flight tunnel studies also indicated that six of the 10 compounds probably represent the essential components of the female's sex pheromone.Supported in part by USDA Cooperative Agreement No. 58-32U4-1-299. Scientific Article No. A-4073, Contribution No. 7058 of the Maryland Agricultural Experiment Station. Mention of a commercial product in this paper does not constitute a recommendation by the U.S. Department of Agriculture.     

Specialization of olfactory cells to insect-and host-produced volatiles in the bark beetleIps pini (say)

Electrophysiological recordings inIps pini were made from single olfactory cells stimulated by six concentrations of eleven compounds—either pheromones or host constituents. The receptor cells were grouped according to their differential responses to these biologically significant compounds. Cells specialized to either ipsdienol or ipsenol (pheromones for severalIps species) appeared to be relatively uniform in their sensitivity to all compounds tested. Another group of cells specialized tocis- andtrans-verbenol were more variable in their sensitivities to the substances tested. The activation of separate groups of cells by the different pheromones and host compounds shows (by exclusion) that behaviorally expressed syner-gistic as well as inhibitory action mainly is due to an interaction in the central nervous system rather than an interaction of the compounds on the receptors. All ipsdienol cells responded to both enantiomers of ipsdienol. Although some differences between responses to the enantiomers by individual cells were observed, these did not form a consistent pattern, and no net differences could be found between the eastern and western populations ofI. pint.Coleoptera: Scolytidae.     

Olfactory receptor cell responses ofIps grandicollis (eichhoff) (Coleoptera: Scolytidae) to intra- and interspecific behavioral chemicals

Electrophysiological recordings from antennal olfactory receptor cells were obtained fromIps grandicollis. Recordings were made from olfactory receptor cells from nine regions of the antennae in response to stimulation with the semiochemicals-pinene, frontalin,endo-brevicomin, verbenone,trans-verbenol,cis-verbenol, ipsdienol, and ipsenol. In many cases, up to two cells were recorded concurrently from the same location. When compared to males, females had a greater percentage of cells responsive to the primary pheromones ofDendroctonus frontalis, frontalin andtrans-verbenol, and ofIps spp., ipsdienol and ipsenol. Among females, more cells responded totrans-verbenol and theIps-produced volatiles than to host or otherD. frontalis-produced compounds. Olfactory cells of males responded mostly tocis-verbenol, followed by-pinene, verbenone,trans-verbenol, andendo-brevicomin. Of those cells responsive primarily to one compound, the greatest percentage were responsive totrans-verbenol in females and to verbenone in males. The response of the antennal olfactory receptor cells to semiochemicals used by male and femaleI. grandicollis is consistent with the presence of these compounds during the host colonization period for each sex. Our results, which show a lack of specificity in most pheromone and host odor receptor cells, is in contrast with previously published accounts of olfactory receptor cell specificity in otherIps species.