Identification, Synthesis, and Field Testing of the Sex Pheromone of the Citrus Leafminer, Phyllocnistis citrella

The citrus leafminer is an important vector of citrus canker in many of the major citrus production areas of the world. (7Z,11Z)-Hexadecadienal was reported as a sex attractant for this insect in the 1980s, based on trap catches during pheromone screening trials in Japan. However, attempts to reproduce this work in other areas of the world have not been successful. We report here that (7Z,11Z)-hexadecadienal is only one component of the pheromone, with the other critical component being the analogous trienal, (7Z,11Z,13E)-hexadecatrienal. Both compounds were identified in the effluvia from live female moths by coupled gas chromatography (GC)-electroantennography using nonpolar and polar GC columns, and the identifications were confirmed by comparisons of mass spectra with those of authentic standards. Stereoisomers of the two compounds, and a number of analogs, were synthesized to confirm the identifications. In field trials, neither compound alone was attractive to male moths, but blends of the two were highly attractive, with thousands of insects being caught per trial. Addition of the isomeric (7Z,11Z,13Z)-hexadecatrienal inhibited attraction to the two-component blend. Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorized users. This paper and the preceding paper (Leal et al.) were submitted within a few days of each other. The editors and the authors agreed that they should be published in tandem.     

Influence of pheromone trap color and design on capture of male velvetbean caterpillar and fall armyworm moths (Lepidoptera: Noctuidae)

Three pheromone traps were evaluated in paired field trials for effectiveness in capturing wild male velvetbean caterpillar moths (VBC),Anticarsia gemmatalis Hübner, and fall armyworm moths (FAW),Spodoptera frugiperda (J.E. Smith), using a wind-oriented trapping device. The traps were: (1) the standard multicolored bucket trap consisting of a forest green canopy, yellow funnel, white bucket and open (i.e., single wire) pheromone holder; (2) a forest green monocolored bucket trap; and (3) the Multi-Pher-1 trap consisting of a blue-green canopy, white funnel, white bucket, and white, multislotted pheromone holder. The Multi-Pher-1 trap differs primarily from the other two in that its entrance is smaller in diameter and is partially obstructed by the pheromone holder. Significantly fewer VBC and FAW males were captured in pheromone-baited monocolored (forest green) bucket traps than standard multicolored bucket traps. The Multi-Pher-1 trap also caught significantly fewer VBC moths than the standard multicolored bucket trap, but there was no significant difference in numbers of FAW moths caught in the two traps. The results further demonstrate the importance of considering visual cues, in this case color, in the design of pheromone traps for nocturnal insects.This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or the recommendation for its use by USDA.     

Trapping of Phyllophaga elenans with a female-produced pheromone

Attraction of Phyllophaga elenas to vaned bucket traps baited with the recently identified female-produced pheromone, L-isoleucine methyl ester (LIME), is efficient. Pheromone-baited vaned buckets with water to retain insects were more effective than buckets without vanes or plastic containers with the sides cut out. Pheromone-baited vaned bucket traps from which water was omitted required the addition of a funnel below the vanes to retain insects. Normally used light traps were about 10 times more effective than pheromone-baited vane bucket traps in capturing P. elenans. Over 95% of P. elenans were captured between 6:00 and 9:00 PM. The male–female ratio was 3–4:1 in both light and pheromone traps, and the ratio was relatively unchanged throughout the capture period. Most P. elenans were captured in the treed areas surrounding sugarcane fields. More P. elenans were captured in treed borders than in grassy borders of sugarcane fields. The effective radius of the pheromone-baited vaned bucket trap is between 5 and 15 m.     

Effect of release rate and ratio of (Z)-11-hexadecen-1-ol from synthetic pheromone blends on trap capture ofHeliothis subflexa (Lepidoptera: Noctuidae)

Response of maleHeliothis subflexa to pheromone-baited traps containing blends of tetradecanal, (Z)-9-tetradecanal, hexadecanal, (Z)-7-hexadecenal, (Z)-9-hexadecenal, (Z)-11-hexadecenal, hexadecan-1-ol acetate, (Z)-7-hexadecen-1-ol acetate, (Z)-9-hexadecen-1-ol acetate, (Z)-11-hexadecen-1-ol acetate, (Z)-9-hexadecen-1-ol, and (Z)-11-hexadecen-1-ol was evaluated. Analysis of trap capture data indicated that (Z)-11-hexadecen-1-ol was a critical component of the pheromone blend. It was determined from emission rate data and measurements of the ratio of pheromone components emitted from rubber septa tested that a significant increase in trap capture of maleH. subflexa occurred when the blends investigated released the alcohol in a narrow range relative to the total amount of pheromone emitted. The optimum range of release ratio of the alcohol for the capture of males in sticky traps was determined to be 0.9–3.5% of the pheromone blend. This release ratio range was reduced to 0.9–1.6% when bucket traps were used.     

Multispecies trapping ofHelicoverpa (Heliothis) zea,Spodoptera frugiperda,Pseudaletia unipuncta,andAgrotis ipsilon (Lepidoptera: Noctuidae)

Multispecies sex pheromone trapping (trapping of more than one species in the same trap) for the bollworm,Helicoverpa (Heliothis) zea (Boddie); fall armyworm,Spodoptera frugiperda (J.E. Smith); armyworm,Pseudaletia unipuncta (Haworth); and the black cutworm,Agrotis ipsilon (Hufnagel) was evaluated. Baiting of individual traps with all possible combinations of the four species taken two at a time caused a reduction in the catches of at least one of any two species involved when compared to traps baited for only one species. These results demonstrated the species specificity of sex pheromones identified for these species. Although the effects were reduced in some cases, the interaction between species also was observed when adjacent traps were baited with the sex pheromone dispensers of the different species. These results indicate that the spacing between pheromone traps when more than one species are being trapped at the same site affects trap capture and should be evaluated further.This paper reports the results of research only. Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Field evidence of synergism and inhibition in the sesiidae sex pheromone system

The E,Z, Z,Z, and Z,E geometric isomers of 3,13 octadecadien-1-ol acetate were used singly and in binary combinations to trap sesiids in Wisconsin cherry orchards. The Z,E isomer alone did not capture any sesiids. A synergistic effect, however, of Z,E onSynanthedon pictipes response to its pheromone E,Z was demonstrated for the first time. Strong inhibitory effects of the Z,Z isomer onS. pictipes response to E,Z, and of the E,Z isomer onS. scitula response to Z,Z, were found. As little as 0.5% of Z,Z in E,Z completely inhibited theS. pictipes response. This species' response was also reduced by 85% when Z,Z was evaporated at 4 points, each ca. 6 m from the pheromone trap. Consistencies and discrepancies of the data with relevant experimental results from other geographical areas are briefly discussed.Lepidoptera: Sesiidae (=Aegeriidae), the clearwing moths.Research supported by the College of Agriculture and Life Sciences, University of Wisconsin, Madison, and by the Wisconsin Red Tart Cherry Ind. Market. Order.     

Capture rates of the European pine sawfly, Neodiprion sertifer, in pheromone traps, with special regard to effects of wind speed

Males of the European pine sawfly, Neodiprion sertifer Geoffr., were marked and released downwind from pheromone traps, baited with 100 g of the sex pheromone (2S,3S,7S)-3,7-dimethyl-2-pentadecyl acetate. Males were released 5 m downwind from one trap, or downwind from five traps, 50 m or 200 m away. The average capture rates after 24 hr were 21.5%, 17.7% and 3.8%, respectively. The capture rate was highest at moderate wind speeds (1–2 m/sec) in the 50 m experiments, whereas it decreased above wind speeds of 1.5 m/sec in the 200 m experiments. With no precipitation and >13.5°C during overcast, wind speed is presumably the most important climatic factor for N. sertifer males flying upwind to a pheromone source. Travel time, the elapsed time form take-off to landing on the trap, varied considerably, and the shortest recorded travel times were 1, 6 and 45 min for the 5, 50, and 200 m experiments, respectively. The trap efficiency i.e., number of captured males per number of males that landed on the trap, was estimated at 52% in the 5 m experiments. The sampling range after 24 hr was calculated at approximately 400 m by regression analysis. The combination of the males' flight ability during upwind progress and their longevity (12 days), suggests a potentially large seasonal sampling range of the traps used in this study.     

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.     

Quantitative comparison of behavioral and neurophysiological responses of insects to odorants

A consistent pattern of relationships emerges from comparisons of insect electroantennograms, peripheral olfactory receptor neuron responses, and behavioral responses to quantified concentrations of odorants. One consistency is that all of the different response measurements can be described by stimulus-response curves of the same form. Another is that the responses have characteristic groupings when they are plotted against odorant concentration. The pattern of relationships is exemplified in the responses ofTrichoplusia ni (Hübner),Heliothis zea (Boddie), andPlodia interpunctella (Hübner) to several pheromone components and analogs. To quantify the relevant stimulus parameters for the response comparisons, the emission rates of the stimulus delivery system were calibrated for several 12 to 17-carbon pheromone components. The stimulus-response relationships determined forT. ni, H. zea, andP. interpunctella are combined with relationships reported for other insects in the literature, and applications are discussed for the interpretation of pheromone trapping and laboratory bioassays.Postdoctoral fellow employed through a cooperative agreement between the Insect Attractants, Behavior, and Basic Biology Research Laboratory     

Pheromone-based trapping of West Indian sugarcane weevil in a sugarcane plantation

Attraction of Metamasius hemipterus (Oliver) to gallon and bamboo traps baited with insecticide-treated sugarcane, the male-produced pheromone, 4-methyl-5-nonanol, and 2-methyl-4-heptanol is more efficient if ethyl acetate is added. The optimal traps are ground-level gallon traps baited with insecticide-laced sugarcane, pheromone, and ethyl acetate. Capture rates of ground-level gallon traps are doubled by placing an insecticide-laced pad under the trap, but significantly decreased by placing the trap on a stick above ground. The efficiency of ground-level gallon traps is the same as ground level ramp traps. Mass-trapping M. hemipterus in newly planted sugarcane using ground level bamboo traps baited with insecticide-laced sugarcane and pheromone over six months revealed populations were low for the first two months, became maximum at five months, and declined thereafter. Capture rates of traps bordering newly planted and mature sugarcane were not significantly different from capture rates of traps in the interior of the plots. Capture rates of bamboo traps containing only insecticide-laced sugarcane and deployed at 30 traps/ha averaged 6 weevils/trap/week compared with 66 weevils/trap/week for traps additionally containing pheromone lures and deployed at 5 traps/ha. Capture rates for bamboo traps baited with insecticide-laced sugarcane and pheromone and deployed at 10 and 15 traps/ha were 43 and 38 weevils/trap/week, respectively. Total captures were higher in those plots with a higher density of insecticide-laden sugarcane and pheromone baited traps, and the differences were approximately proportional to trap density in the range of 5–15 traps/ha. Capture rates of traps containing insecticide-laced sugarcane and pheromone were always higher than of traps containing only insecticide-laced sugarcane, but in the first two months after planting the differences were much greater than in months 3–6 after planting.     

Identification of sex pheromone composition of click beetle Agriotes brevis candeze

Geranyl butyrate (GB) and (E,E)-farnesyl butyrate (FB) were identified in the pheromone gland extract of females of the click beetle, Agriotes brevis (Candeze) (Coleoptera: Elateridae) as the major sex pheromone components. Polyethylene vial dispensers containing 20–200 mg of a 1:1 mixture caught high numbers of beetles. Captures did not decrease even after 73 days of field exposure of dispensers. At sites where both Agriotes sputator L. and A. brevis were present, the above baits were selectively catching only A. brevis, despite the fact that GB is also the main pheromone component of A. sputator, suggesting that FB has a role in reproductive isolation. In the early part of the season, traps into which the insects could both crawl and fly captured more A. brevis than designs where the insects could only fly in. Trap design was not important later in the season. This indicates the need for future development of a trap suitable for use throughout the whole season.     

Proximity of release points of pheromone components as a factor confusing males of the spotted stem borer,Chilo partellus,approaching the trap

The effect of proximity of the release points of the two pheromone components (Z)-11-hexadecenal and (Z)-11-hexadecen-1-ol of the spotted stem borer,Chilo partellus (Lepidoptera: Pyralidae) on behavior of the males and on trapping efficiency was investigated. Separating the dispensers of the two components in the trap by a mere 3 cm resulted in a threefold decrease in trap performance, compared to very close release of the components. The result is attributed to possible distortion of the pheromone signal, resulting in confused behavior ofC. partellus males in the vicinity of the trap. The ethological and practical implications of the phenomenon are discussed.     

(E)-11,13-tetradecadienal: Major sex pheromone component of the eastern blackheaded budworm,Acleris variana (Fern.) (Lepidoptera: Tortricidae)

(E)-11,13-Tetradecadienal (E11,13–14:Ald) is the major sex pheromone component of the eastern blackheaded budworm (EBB),Acleris variana (Fern.). The compound was identified in female pheromone gland extracts by coupled gas chromatographic-electroantennographic detection (GC-EAD), coupled GC-mass spectrometry in selected ion monitoring mode, and retention index calculations of candidate pheromone components.E11,13–14:Ald alone as trap bait was very attractive to male EBB. Addition of the corresponding diene alcohol or acetate or both did not enhance attraction. (Z)-11,13-Tetradecadienal in binary combination with (E)-11,13–14:Ald neither enhanced nor reduced trap catches. Increasing the amounts of pheromone from 0.01 to 10 µg increased trap catches, but increase of pheromone quantity above 100 µg proportionately reduced attraction. Stabilization of slowly polymerizingE11,13–14:Ald and development of a sustained, adequate release rate is required for pheromone-based monitoring of EBB populations.     

Sex pheromonal activity of (+)-trans-verbenyl acetate and related compounds to the american cockroach,Periplaneta americana L.

The sex pheromone mimic of the American cockroach, (+)-trans-verbenyl acetate, and 67 synthesized analogs were tested for sex pheromonal activity using males of the cockroach. Only three esters in addition to the original (+)-trans-verbenyl acetate exhibited activity. (+)-trans-Verbenyl propionate and (+)-verbanyl acetate in particular showed stronger activity than the original mimic. None of the other analogs caused a response at the 1-mg level. The lower threshold levels at which even the most active analogs showed activity (0.02 mg) were many orders of magnitude higher than that of the natural pheromone, periplanone-B (10^–8 mg). From the structure-activity relationships, important structural factors for sex pheromonal activity in the original mimic were discussed.Studies on the sex pheromone mimic of the American cockroach, (+)-trans-verbenyl acetate. Part VI. For Part V,Agric. Biol. Chem. 44:2877 (1980).     

Optimization of Pheromone Lure and Trap Characteristics for Currant Clearwing, <Emphasis Type="Italic">Synanthedon tipuliformis</Emphasis>

Currant clearwing Synanthedon tipuliformis (Sesiidae) has been a pioneering and successful target of mating disruption in New Zealand, with virtually universal black currant industry adoption since c. 1990. Recent unexplained control failures using mating disruption lead to questions about pheromone efficacy. In this study, we have investigated the possible reasons for reduced control from mating disruption, and report improvements in trap catch based on pheromone loading and trap color. No differences were found in electrophysiological responses to pheromone components from two New Zealand populations. Male moth catches in traps baited with synthetic lures were disrupted in the presence of mating disruption dispensers (> 99.99%) indicating no apparent barrier to efficacy from the pheromone formulation. Field behavioral observations confirmed this result. Male attraction to yellow delta traps was equivalent to green delta traps, but was greater than to red, black, blue, or white traps. Solid yellow delta traps were more attractive than black traps with yellow stripes, the latter designed to mimic the color pattern of the insect. Solid yellow funnel traps were less attractive than a composite of green, yellow, and white funnel traps. Trap catch increased as a function of pheromone loading and trap color. In another experiment conducted in Tasmania, there was no difference in catch with single component [(E,Z)-2,13-octadecadienyl acetate] or two component lures [97% (E,Z)-2,13-octadecadienyl acetate:3% (E,Z)-3,13-octadecadienyl acetate], refuting the suggestion of a different pheromone strain there.     

Synthesis and field bioassay of some analogs of sex pheromone of citrus mealybug,Planococcus citri (Risso)

A series of structural analogs of (s+)-cis-(1R)-3-isopropenyl-2,2-dimethylcyclobutanemethanol acetate, sex pheromone of the citrus mealybug,Planococcus citri (Risso), was synthesized. The analogs were tested in a field bioassay in order to determine the structure-activity relationships of the pheromone. All changes in structure reduced the activity of the test compounds, to various degrees. The most active analog tested was the homolog (+)-cis-(1R)-3-isopropenyl-2,2-dimethylcyclobutaneethanol acetate (IV), whose activity, at a higher dosage, was comparable to that of the pheromone. The alcohol (+)-cis-(1R)-3-isopropenyl-2,2-dimethylcyclobutanemethanol was tested in mixtures with the pheromone and found to be neither an inhibitor nor a Synergist. The results show that all functional groups of the pheromone molecule are essential for optimal biological activity.Homoptera: Coccoidea: Pseudococcidae.Contribution from the Agricultural Research Organization (ARO), The Volcani Center, Bet Dagan, Israel, No. 1667-E, 1986 series.Levi Eshkol Postdoctoral Fellow, 1984–1986.     

Moth responses to selectively fluorinated sex pheromone analogs

Partially fluorinated analogs of the European corn borer (Ostrinia nubilalis) female sex pheromone, 11-tetradecenyl acetate (97:3Z:E), having mono- and trifluorsubstitutions at the terminal carbon of the pheromone chain, mimicked the biological activity of the pheromone, while analogs with fluorine at either side of the double bond and a pentafluoro analog were essentially inactive. Comparison of the pheromonal activity of these analogs with the previously reported activity of similarly fluorinated pheromones in five other species of moths revealed an unpredictable relationship between fluorine substitution pattern and pheromone-mimicking activity. Fluorine substitution patterns that rendered pheromonal analogs biologically inactive in the European corn borer had no detrimental influence upon pheromonal activity in other species and the converse was also true. This is evidence that the relative importance of electronic qualities of sites within a pheromone molecule differ from species to species. Furthermore, it indicates that the biochemical components (pheromone receptor proteins, binding proteins, and enzymes) that make up moth olfactory chemosensory systems must also vary structurally from species to species, despite the fact that they are involved in olfactory sensing of compounds having very similar chemical structure.     

Behavioral activity of optical isomers of 5,9-dimethylheptadecane,the sex pheromone ofLeucoptera scitella L. (Lepidoptera: Lyonetidae)

Among the pure stereoisomers of 5,9-dimethylheptadecane, a previously identified sex pheromone component ofLeucoptera scitella L., only theS,S isomer yielded trap captures in the field. The addition of the other stereoisomers had no effect on cathes. The addition of low percentages of racemic 5,9-dimethylhexadecane, a previously identified minor component in the sex pheromone, did not influence trap catches or alter behavior of males approaching an attractant source in the field.     

Bioactivity, Synthesis, and Chirality of the Sex Pheromone of Currant Stem Girdler, Janus integer

It was previously reported that females of the currant stem girdler, Janus integer Norton (Hymenoptera: Cephidae), produce a compound, (Z)-9-octadecen-4-olide (1), that is sensitively detected by the antennae of males only. These characteristics suggested a pheromonal function, and this has now been confirmed with behavioral tests. Field tests conducted during two seasons in a commercial red currant field in Washington State showed that synthetic racemic 1 is attractive to male J. integer under natural conditions. A clear dose-response was evident, with greatest numbers of girdlers caught in sticky traps baited with 10 mg of the pheromone (in rubber septa) and least in traps baited with 1 mg or less. During May 2002, 10, 5, 3, and 1 mg baited traps caught means of 41.4, 26.6, 6.7, and 2.7 males/trap/visit (3–5 day intervals), respectively, with a maximum of 229 males caught in a single trap baited with 5 mg. A new synthetic method for racemic 1 is presented. The absolute configuration of natural 1 from the male sawflies was determined to be (R). The potential for using the sex pheromone of J. integer to improve management of this currant and gooseberry pest is discussed.     

Simulation and equation models of insect population control by pheromone-baited traps

A spatial-temporal model for personal computers is developed that simulates trapping of an insect population based on trap and population parameters that can be varied independently. The model allows individual insects to move forward at any step size with right or left turns within any specified angle taken at random. Thex andy axes of the area within which insects move can be varied as well as the number of insects, their flight speed, and the duration of the control period. In addition, the number of pheromonebaited traps, their placement in a grid or at random (with a variable degree of spacing), and their effective catch radius (proportional to pheromone release rate) can also be varied. Simulations showed that catch was similar regardless of whether traps were placed in a grid or practically at random (random placement but no traps were allowed to overlap in their effective catch radii). Iterative equations were developed for computer that can rapidly obtain values that correspond to the mean results from the slower simulation model. Based on a set of input parameters, the equations determine the percentage of the population that should be caught during a specified time, the time required to catch a specified proportion of the insects, and the number of traps necessary to catch the population proportion in the time period. The effects of varying the number of insects, flight speed, trap radius, and number of traps on the percent control or time to catch all insects are presented. Population control of the bark beetleIps typographus was simulated using realistic pheromone trap and population parameters. A discussion of insect and bark beetle (Coleoptera: Scolytidae) population control using pheromone traps is presented.