Green Leaf Volatiles Interrupt Pheromone Response of Spruce Bark Beetle, Ips typographus

A synthetic mixture of nine green leaf volatiles (GLVs) including linalool was tested on antennae of Ips typographus (L.) with coupled gas chromatographic–electroantennographic detection (GC-EAD). Strong responses were found to 1-hexanol, (Z)-3-hexen-1-ol, and (E)-2-hexen-1-ol. Weak responses were recorded to (E)-3-hexen-1-ol, (Z)-2-hexen-1-ol and linalool, while hexanal, (E)-2-hexenal and (E)-3-hexenyl acetate elicited no EAD responses. In a laboratory walking bioassay, the attraction of I. typographus females to a synthetic pheromone source was significantly reduced when a mixture of the three most EAD-active GLV alcohols was added to the source. Further reduction in response was obtained when these three alcohols were combined with verbenone (Vn). In field trapping experiments, a blend of 1-hexanol, (Z)-3-hexen-1-ol, and (E)-2-hexen-1-ol reduced I. typographus trap catches by 85%, while ca. 70% reduction of trap catch was achieved by Vn or a blend of (E)-3-hexen-1-ol, (Z)-2-hexen-1-ol, and linalool. The strongest disruptive effect was found when Vn plus a blend of the three most EAD active GLV alcohols was added to the pheromone trap (95% catch reduction). Adding the blend of the three most EAD active alcohols to pheromone-baited traps significantly reduced the proportion of males captured. These three GLV alcohols were also disruptive in the laboratory and in the field when tested individually. Hexanal, (E)-2-hexenal, and (Z)-3-hexenyl acetate were inactive both in the lab and in the field. Our results suggest that these nonhost green leaf alcohols may explain part of the host selection behavior of conifer-attacking bark beetles and may offer a source of inhibitory signals for alternative management strategy for forest protection.     

Chemical Defense in the Plant Bug Lopidea robiniae (Uhler)

Secretions from the metathoracic glands (MTG) of the black locust bug, Lopidea robiniae (Uhler) (Heteroptera: Miridae) contained six major compounds, including (E)-2-hexenal, (E)-2-hexen-1-ol, (E)-2-octenal, (E)-2-octen-1-ol (E)-2-heptenal, and (Z)-3-octen-1-ol. Males and females did not differ significantly in the relative compositions of identified compounds. In feeding trials, six bird species [robin (Turdus migratorious), blue jay (Cyanocitta cristata), brown thrasher (Toxostoma rufum), killdeer (Charadrius vociferus), starling (Sturnus vulgaris), and house wren (Troglodytes aedon)] demonstrated feeding aversions towards L. robiniae, implying that black locust bugs are chemically defended. Bugs discharged the liquid contents of their MTG when attacked, thereby producing a strong and distinct odor. Some birds immediately ejected bugs out of their mouth after biting them, suggesting that the MTG secretion was a deterrent.     

Sex pheromone components of the oblique-banded leafroller,Choristoneura rosaceana in the Okanagan Valley of British Columbia

(Z)-11-Tetradecen-1-yl acetate, (E)-11-tetradecen-1-yl acetate, and (Z)-11-tetradecen-1-ol were previously reported as the sex pheromone in New York strains of the oblique-banded leafroller,Choristoneura rosaceana (Harris), and (E)-11-tetradecen-1-ol was tentatively identified in female tip extracts. For Okanagan Valley strains ofC. rosaceana, an additional component, (Z)-11-tetradecenal, was identified from female tip extracts by split-less capillary gas-liquid chromatography and mass spectroscopy and was strongly stimulatory in electroantennogram studies. In field tests, 3 mg of 96.521.5 (Z)-11-tetradecen-1-yl acetate, (E)-11-tetradecen-1-yl acetate, and (Z)-11-tetradecen-1-ol (containing approx. 1%E isomer) was not as attractive as female-baited traps, and significant numbers of European leafrollerArchips rosanus L. were attracted. The above blend with 1% (Z)-11-tetradecenal added was significantly more attractive than traps baited with femaleC. rosaceana, butA. rosanus males were still attracted. Increased percentages of (Z)-11-tetradecenal up to 4% caused increased catches ofC. rosaceana and decreased catches ofA. rosanus. Low amounts of (E)-11-tetradecen-1-ol and (E)-11-tetradecenal male also contribute to increased specificity of the synthetic pheromone blend toC. rosaceana.Lepidoptera: Tortricidae.Contribution No. 638, Agriculture Canada, Research Station, Summerland, British Columbia, Canada.     

Sex pheromone components of the obliquebanded leafroller moth,Choristoneura rosaceana

Previously, (Z)-11-tetradecen-1-yl acetate was reported as the sex pheromone of the obliquebanded leafroller,Choristoneura rosaceana (Harris). A mixture of 92% (Z)-11-tetradecen-1-yl acetate and 8% (E)-tetradecen-1-yl acetate has been reported as an attractant for this insect. (E)-11-tetradecen-1-yl acetate and (Z)-11-tetradecen-1-ol have now been isolated and identified from female tip extracts and shown to be behaviorally active; in addition, there is some evidence for the presence of (E)-11-tetradecen-1-ol in these extracts. TheZE ratio for both the acetates and the alcohols in these tip extracts was about 982; the proportion of alcohols was rather variable, but the acetates always predominated. Maximum trap catches fn the field during the course of this study were obtained with 5 mg of 955 (Z)(E)-11-tetradecen-1-yl acetates containing 0.5–10% (Z)-11-tetradecen-1-ol (approx. 1%Eisomer) in polyethylene caps. No evidence was found for the presence of (Z)-11-tetradecenal in female tip extracts, and this compound was found to be ineffective in increasing trap catches.Lepidoptera: Tortricidae: Tortricinae.This research was supported in part by the Rockefeller Foundation, and by NSF Grant No. GB-38020.     

Leaf Volatiles from Nonhost Deciduous Trees: Variation by Tree Species, Season and Temperature, and Electrophysiological Activity in Ips typographus

The leaf volatiles emitted from four nonhost tree species of Ips typographus, i.e. Betula pendula, B. pubescens, Populus tremula, and Sambucus nigra, were collected outdoors by headspace sampling in situ and analyzed by GC-MS. Three major classes of compounds, aliphatics [mainly green-leaf volatiles (GLVs)], monoterpenes, and sesquiterpenes, existed in all the deciduous tree species investigated. In June, when the bark beetles are searching in flight for host trees, GLVs mainly consisting of (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol were the dominant constituents in B. pendula and S. nigra. In B. pubescens and P. tremula, sesquiterpenes (and their derivatives) and monoterpenes made up the major part of whole volatile blends, respectively. Surprisingly, sesquiterpene alcohols and other oxides released from B. pubescens in considerable amounts were not found in the closely related species, B. pendula. By August, both the total volatiles and individual compounds significantly decreased, mainly due to the maturation of leaves, since the light intensity and temperatures during sampling were the same as in June. There were almost no volatiles detected from P. tremula and S. nigra leaves in August. The total emissions from these deciduous species were significantly different among the species, with B. pubescens releasing 5–10 times more than other species. Under the conditions of constant light intensity and humidity, emissions of both total volatiles and most individual components of severed B. pendula and S. nigra branches (with fresh leaves) increased according to a saturation curve from 16°C to 40°C. Ips typographus antennae responded strongly to green leaf alcohols: (Z)-3-hexen-1-ol, 1-hexanol, and (E)-2-hexen-1-ol, but not to aldehydes or acetates in GC-EAD analyses of B. pendula and B. pubescens leaf volatiles. No antennal responses to monoterpenes, sesquiterpenes, or sesquiterpene oxides were found. These three antennally active GLVs emitted from nonhost tree leaves might be indicators of a wrong habitat in the host selection of conifer bark beetles.     

Isolation and identification of volatiles in the foliage of potato,Solanum tuberosum,a host plant of the colorado beetle,Leptinotarsa decemlineata

The volatile compounds ofSolanum tuberosum L., a host plant of the Colorado beetle,Leptinotarsa decemlineata Say, were isolated by successive vacuum steam distillation, freeze concentration, and extraction. The main components aretrans-2-hexen-1-ol, 1-hexanol,cis-3-hexen-1-ol,trans-2-hexenal, and linalool. The distribution of these compounds in a variety of plant families and their biosyntheses are reviewed. These leaf volatiles constitute a general green leaf volatile complex, being active in the olfactory orientation of the Colorado beetle and as such are probably of importance to various phytophagous insects.     

Sex pheromone of the woodbine leafroller moth,Sparganothis sp.

The sex pheromone of the woodbine leafroller,Sparganothis sp., includes (E)-11-tetradecen-1-ol, (Z)-11-tetradecen-1-ol, and (E)-11-tetradecen-1-yl acetate, based on chemical analysis of gland extracts, electroantennogram tests, and field trapping. Highest trap catches were obtained when these compounds were dispensed in the relative proportions observed in the female gland. (Z)-11-Tetradecen-1-yl acetate also was found in gland extracts, but significantly reduced trap catches. The saturated compounds tetradecan-1-ol and tetradecan-1-yl acetate were found in gland extracts as well, but were not tested. The amounts of these compounds per female gland were 127, 93, 17, 20, 25, and 3 ng, in the order named.Lepidoptera: Tortricidae.Supported by National Science Foundation Grant PCM 78-13241.     

Identification of volatile sex pheromone components released by the southern armyworm,Spodoptera eridania (Cramer)

Analysis of sex pheromone gland extracts and volatile pheromone components collected from the calling female southern armyworm,Spodoptera eridania (Cramer), by high-resolution capillary gas chromatography and mass spectroscopy indicated that a number of 14-carbon mono- and diunsaturated acetates and a monounsaturated 16-carbon acetate were produced. Gland extracts also indicated the presence of (Z)-9-tetradecen-1-ol. However, this compound was not found in collections of volatiles. Field trapping studies indicated that the volatile blend composed of (Z)-9-tetradecen-1-ol acetate (60%), (Z)-9-(E)-12-tetradecadien-1-ol acetate (17%), (Z)-9-(Z)-12-tetradecadien-1-ol acetate (15%), (Z)-9-(E)-11-tetradecadien-1-ol acetate (5%), and (Z)-11-hexadecen-1-ol acetate (3 %) was an effective trap bait for males of this species. The addition of (Z)-9-tetradecen-1-ol to the acetate blends tested resulted in the capture of beet armyworm,S. exigua (Hubner), males which provides further evidence that the alcohol is a pheromone component of this species.     

Responses to Green Leaf Volatiles in Two Biogeoclimatic Zones by Striped Ambrosia Beetle, Trypodendron lineatum

Experiments in the Coastal Western Hemlock (CWH) biogeoclimatic zone on the British Columbia (BC) coast and the Interior Douglas-fir (IDF) biogeoclimatic zone in the BC interior revealed pronounced differences in the effect of six-carbon green leaf volatiles on the response by striped ambrosia beetles, Trypodendron lineutum to multiple funnel traps baited with the aggregation pheromone lineatin. In the IDF zone, four green leaf alcohols [1-hexanol, (E)-2-hexen-1-ol, (Z)-2-hexen-1-ol, and (Z)-3-hexen-1-ol], released alone or in a quaternary blend at ca. 4 mg/24 hr/compound, caused a 63–78% reduction in trap catches. Two aldehydes, hexanal and (E)-2-hexenal, released together at ca. 13.0 mg/24 hr/compound were weakly disruptive in one of two experiments. Conversely, in the CWH zone, the two aldehydes together caused a slight, but significant, increase in the response over that to lineatin in one of two experiments, and the blend of all four alcohols caused only weak disruption of response in one of two experiments. None of the alcohols released alone was bioactive. These results may reflect adaptations that ensure accurate host location in the two ecological zones. In the CWH zone, T. lineatum attacks conifer logs almost exclusively, and surrenders the cut or broken stump habitat to Gnathotrichus spp. In the IDF zone, T. lineatum readily attacks the base of trees killed by bark beetles or fire and may utilize green leaf alcohols to detect and avoid the vertical silhouettes represented by nonhost angiosperms such as black cottonwood and trembling aspen.     

Orientation ofMicroplitis croceipes (Hymenoptera: Braconidae) to green leaf volatiles: Dose-response curves

FemaleMicroplitis croceipes wasps were tested in a wind tunnel for their ability to orient to various concentrations of eight different green leaf volatile (GLV) substances [hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (E)-2-hexenyl acetate, (Z)-3-hexenyl acetate, (Z)-3-hexenyl propionate, and (Z)-3-hexenyl butyrate]. Overall, the esters elicited the greatest percentage of successful orientation flights, the alcohols elicited an intermediate response, and the aldehydes elicited a low response. The semilog dose-response curves were generally hill-shaped with high responses at medium release rates and low responses at high or low release rates. For the aldehydes, positive responses occurred at all GLV release rates between 0.01 and 100 nl/min. For some alcohols and esters, positive responses occurred at release rates as low as 1 pl/min and as high as 1μl/min. These data show thatM. croceipes wasps are strongly attracted to GLVs and are capable of orienting to GLV concentrations that would occur in nature when a caterpillar feeds on a green leaf. Hence, in nature, GLVs may be important clues, enablingM. croceipes to locate their hosts.     

Olfactory responses of Ips duplicatus from inner Mongolia, China to nonhost leaf and bark volatiles

Leaf and bark volatiles from nonhost angiosperm trees were tested on Ips duplicatus by gas chromatographic–electroantennographic detection (GC-EAD) and by pheromone-baited traps in Sweden and Inner Mongolia, China, respectively. GC-EAD analysis of the headspace volatiles from fresh bark chips of Betula pubescens revealed trans-conophthorin, two green leaf volatiles (GLVs): 1-hexanol and (Z)-3-hexen-1-ol, and two C₈ alcohols: 3-octanol and 1-octen-3-ol, that consistently elicited antennal responses by I. duplicatus. The identification of these EAD-active compounds was confirmed in further GC-EAD recordings with synthetic mixtures. Antennal responses were also found to synthetic (E)-2-hexen-1-ol and linalool, which have been identifed from the leaves of nonhost birch and aspen species. No antennal responses of I. duplicatus were found to hexanal, (E)-2-hexenal, and (Z)-3-hexyl acetates. In field trapping experiments, blends of EAD-active green leaf alcohols or C₈ alcohols, or trans-conophthorin alone resulted in significant reductions (27–60%) in the number of I. duplicatus captured compared with pheromone-baited traps. The unsuitable host compound, verbenone (Vn), also significantly reduced trap catches by up to 60% in both experiments. The strongest disruptive effect resulted from the addition of the combination of green leaf alcohols, C₈ alcohols, and verbenone to the pheromone trap, which caused an 84% reduction in trap catch. The blend of two green leaf aldehydes plus the acetate increased the trap catches in 1998 and had no negative or positive effects in 1999. Our results suggest that these nonhost volatiles (NHVs) are important olfactory signals used by I. duplicatus in host selection. They may have great significance in developing semiochemical-based management programs for I. duplicatus by reducing or stopping attacks on suitable hosts.     

Codling moth (Cydia pomonella): Disruptants of sex pheromonal communication

In a small section of an apple orchard, six traps were placed each in control and test areas and baited with live virgin female codling moths. Gray elastomer septa were used to dispense communication disruptants around the traps. Dyed male codling moths were released in control and test areas, and the numbers of males captured in control and test traps were compared. In 1991, linear regression curves of percent communication disruption versus logarithm of dose were obtained for three compositions: (E,E)-8,10-dodecadien-1-ol, codlemone (1); codlemone + dodecan-1-ol + tetradecan-1-ol (2); and an equilibrium mixture of the four isomers of 8,10-dodecadien-1-ol (30, (61%EE, 14%ZE, 20%EZ, and 5%ZZ). All three regressions gaver ² values greater than 0.90. At the 95% confidence limits, slopes and intercepts of compositions 1 and 2 were equivalent, and different from that of composition 3, which produced the greatest percentages of disruption at all doses. In 1992, five treatments were compared at a single dose: 1, 3, none (4), (Z,E)-8,10-dodecadien-1-ol (5), (E,Z)-8,10-dodecadien-1-ol (6). Compositions 5 and 6 gave the greatest and similar percentages of disruption and were different from codlemone (1) and 4 (95% confidence), but not from composition 3. Communication disruption produced by composition 3 was greater than (codlemone), which was greater than 4.     

Identification and Field Evaluation of Components of Female Sex Pheromone of Millet Stem Borer, Coniesta ignefusalis

Five active compounds were detected during analyses of ovipositor washings and effluvia from virgin female Coniesta ignefusalis moths by gas chromatography (GC) linked to electroantennographic (EAG) recording from a male moth. These were identified as (Z)-7-dodecen-1-ol (Z7–12:OH), (Z)-5-decen-1-ol (Z5–10:OH), (Z)-7-dodecenal (Z7–12:Ald), (Z)-7-dodecenyl acetate (Z7–12:Ac), and (Z)-9-tetradecen-1-ol (Z9–14:OH) by comparison of their GC retention times, mass spectra, and EAG activities with those of synthetic standards. Laboratory tests of dispensers for these compounds showed that release rates from polyethylene vials increased to relatively uniform values after three to four days, but release from septa was very rapid and nonuniform and decreased to low levels after two to three days. Trapping tests in Niger showed that the major component, Z7–12:OH, and two of the minor components, Z5–10:OH and Z7–12:Ald, were essential for attraction of male C. ignefusalis moths. The most attractive blend contained these three components in a 100:5:3.3 ratio in a polyethylene vial, which emitted the components in similar proportions to those produced by the female C. ignefusalis moth. Water traps baited with this blend containing 1 mg of Z7–12:OH caught more male C. ignefusalis moths than traps baited with newly emerged female moths. Addition of up to 10% of the corresponding E isomers of the pheromone components had no effect on catches, but addition of the other two minor components detected, Z7–12:Ac and/or Z9–14:OH, to the attractive blend at naturally occurring levels caused significant reductions in trap catch.     

Sex pheromone components of the variegated leafroller moth,Platynota flavedana

Female tip extracts of the variegated leafroller moth,Platynota flavedana (Clemens), were analyzed and found to contain a mixture of (E)-11-tetradecen-1-ol and (Z)-11-tetradecen-1-ol (91), as well as a mixture of (E)-11-tetradecenyl acetate and (Z)-11-tetradecenyl acetate (2-31). Small amounts of tetradecen-1-ol and tetradecyl acetate probably are also present. In the field, a mixture of the two alcohols (8416,EZ ratio) attracted significantly more male moths of this species than any other mixture tested. The data indicate that the acetates are probably not used as pheromone components.Lepidoptera:Tortricidae:Tortricinae.This research was supported in part by the Rockefeller Foundation and by NSF Grant No. GB-38020.     

A Novel Approach for Isolation of Volatile Chemicals Released by Individual Leaves of a Plant in situ

A glass chamber designed specifically for collecting volatile chemicals from individual leaves of a plant in situ is described. The effectiveness of the chamber was demonstrated by collecting volatile chemicals from single leaves of two plant species, potato (Solanum tuberosum) and broad bean (Vicia faba), before and after mechanical damage. The glass chamber, in conjunction with thermal desorption, enables reduction of the entrainment time and thereby allows the monitoring of compounds released by leaf damage in successive 5-min periods. An intact broad bean leaf, in the middle of the day, produces small amounts of the green leaf volatiles (E)-2-hexenal and (Z)-3-hexen-1-ol. However, during the first 5 min after mechanical damage, large amounts of (Z)-3-hexenal, (E)-2-hexenal, and (Z)-3-hexen-1-ol are produced. The decline in production of (Z)-3-hexenal and (E)-2-hexenal is fast, and after 10 min, these compounds reach very low levels. (Z)-3-Hexen-1-ol shows an increase for the first 10 min and then a gradual decline. An intact potato leaf, in the middle of the day, produces very small amounts of the sesquiterpene hydrocarbons -caryophyllene and germacrene-D. After being damaged, the profile of released volatiles is different from that of broad bean. In potato, damage is associated with release of large amounts of green leaf volatiles and sesquiterpene hydrocarbons. Compounds such as (Z)-3-hexenal, (E)-2-hexenal, and (Z)-3-hexen-1-ol are released in high amounts during the first 5 min after damage, but after 10 min, these drop to very low levels. High release associated with damage is also observed for -caryophyllene, (E)--farnesene, germacrene-D, and -bisabolene. The highest level is reached 5 min after damage and 15 min later, these compounds drop to low levels. The significance of compounds released after plant damage is discussed.     

Plant–Plant Signaling: Ethylene Synergizes Volatile Emission In Zea mays Induced by Exposure to (Z)-3-Hexen-1-ol

Leaf alcohol (Z)-3-hexen-1-ol (Z-3-ol) is emitted by green plants upon mechanical damage. Exposure of intact maize plants to Z-3-ol induces the emission of a volatile blend that is typically released after caterpillar feeding and attracts natural enemies of the herbivores [herbivore-induced volatile organic compounds (HI-VOC)]. Thus, it has been suggested that Z-3-ol might have a function in indirect plant defense mediating plant–plant signaling and intraplant information transfer. Here, we demonstrate that HI-VOC induction by Z-3-ol is synergized by the phytohormone ethylene. Exposure to Z-3-ol at doses of 100 and 250 nmol induced HI-VOC emission in intact maize plants. HI-VOC emissions increased by 2.5-fold when ethylene was added. The effect of ethylene was more pronounced (5.1- to 6.6-fold) when only total sesquiterpene release was considered. In contrast, ethylene alone had no inductive effect but rather decreased the emission of the constitutive maize volatile linalool. We suggest that ethylene plays a synergistic role in plant–plant signaling mediated by green leaf volatiles.     

Sex pheromone components of the fruit-tree leaf roller,Archips argyrospilus (Walker) (Lepidoptera: Tortricidae), in British Columbia

In field experiments in the Okanagan Valley, British Columbia, the pheromone blend of (11Z)-tetradecen-1-ol acetate (Z11-14:OAc), (11E)-tetradecen-1-ol acetate (E 11-14:OAc), (9Z)-tetradecen-1-ol acetate (Z9-14:OAc) and dodecan-1-ol acetate (12: OAc) at a 1006421 ratio (western FTLR blend) attracted significantly more male fruit-tree leaf roller (FTLR),Archips argyrospilus (Walker), than did the previously reported four-component blend and modifications thereof. Addition of (11Z)-tetradecen-1-ol (Z11-14:OH) to the western FTLR blend in a ratio of 4% relative toZ11-14: OAc further significantly enhanced attraction. Compounds were identified and their ratio determined by coupled gas chromatographic-electroantennographic (GC-EAD) and coupled GC-mass spectrometric analyses of female FTLR pheromone gland extracts and by retention index calculations of candidate pheromone components. Determination and use of geographically specific pheromonal blends may be required for optimal, semiochemical-based biorational control of FTLR and other lepidopteran orchard pests.     

Sex pheromone of female african white rice stem borer,Maliarpha separatella (Lepidoptera: Pyralidae) from Sierra Leone: Identification and field testing

Analysis of ovipositor washings of femaleMaliarpha separatella from Sierra Leone by high-resolution gas chromatography (GC) linked to a male electroantennograph (EAG) indicated the presence of three electrophysiologically active compounds. The GC retention times of these compounds were consistent with those of (Z)-9-tetradecen-1-ol, (Z,E)-9,12-tetradecadien-1-ol, and (E,E)-10,12-tetradecadien-1-ol. Analysis by El and CI mass spectrometry of ovipositor washings confirmed these identifications and also indicated the presence of the saturated analog, tetradecan-1-ol. There was no evidence, from these analyses, of the corresponding aldehydes or acetates. The EAG-active compounds were present in the ovipositor washings in a ratio of approximately 23.51, with the major component constituting approximately 0.4 ng per ovipositor. GC-MS analysis of entrained female effluvia confirmed that the EAG-active compounds were released by virgin females. Field testing of the EAG-active compounds indicated that (Z,E)-9,12-tetradecadien-1-ol and (E,E)10,12-tetradecadien-1-ol were attractive to male moths in ratios of between 9:1 and 39:1, while (Z)-9-tetradecen-1-ol was found to reduce trap catch when added to blends of the other two compounds.     

Efficacy of nonpheromone communication disruptants of codling moth (Cydia pomonella): Effect of pheromone isomers and of distance between calling females and dispensers

Field tests comparing the ability of codlemone, (E,E)-8,10-dodecadien-1-ol, and isomers of codlemone to disrupt pheromonal communication of codling moth were carried out. In a pear orchard, four nonisomerizing, gray septa dispensers were placed in the upper canopy of each tree containing a trap baited with 10 virgin female codling moths. The dispensers were at trap height and 70 cm from the edge of each trap. Trap catches of released male codling moths in three test areas were compared simultaneously when trees in each of the test areas contained unbaited dispensers, dispensers with 1 mg of codlemone containing 1% isomers, and dispensers with 1 mg of a test communication disruptant. When the test disruptant was an equilibrium mixture of codlemone and its isomers (61% codlemone, 39% isomers), the percent communication disruption was 86.8% compared to 68.7% for codlemone (P < 0.001). When the disruptant was (E,Z)-8,10-dodecadien-1-ol (94%EZ, 3%EE), the percentage disruption was 86.4% compared to 62.7% for codlemone (P < 0.002). These results show that the previously reported superior disruptant potency (relative to codlemone) of compositions containing codlemone with a high percentage of isomers was not a result of the proximity of the dispensers to the traps. The percent disruption of compositions of codlemone with 10 and 20% isomers was also determined. A plot of percentage disruption versus logarithm of percentage of nonpheromone isomers in the mixture from 1% to 97% gave a straight line withR ²=0.93.     

Field attraction ofBiprorulus bibax Breddin (Hemiptera: Pentatomidae) to synthetic aggregation pheromone and (E)-2-hexenal,a pentatomid defense chemical

A synthetic blend of the aggregation pheromone [(3R,4S,1E)-3,4-bis(1-butenyl)tetrahydro-2-furanol, linalool, farnesol, and nerolidol] of the spined citrus bug,Biprorulus bibax, and the pentatomid defense chemical, (E)-2-hexenal, both attracted adultB. bibax to individual trees in citrus orchards. Lemon trees containing single glass vials with aggregation pheromone or (E)-2-hexenal were colonized by significantly greater numbers of reproductiveB. bibax than unbaited trees. There was no significant difference between the treatments and bug recruitment was not improved by using both treatments.B. bibax did not enter cylinder/funnel traps baited with aggregation pheromone but colonized trees containing the traps. Orange or lemon trees containing aggregation pheromone on orchard perimeters recruited significantly larger populations of emigrating, nonreproductiveB. bibax during fall than untreated trees. Nonreproductive bugs were not attracted to trees containing (E)-2-hexenal. The potential for using these semiochemicals as management tools forB. bibax is discussed.