Article

Initiation and Termination of Oriental Fruit Moth Male Response to Pheromone Concentrations in the Field

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Abstract

The distance from the pheromone source at which Grapholitha molesta (Busck) males initiated walking, upwind flight, or wing fanning while walking varied directly with the pheromone emission rate. Roughly a 10-fold increase in emission rate resulted in a ca. 2-fold increase in mean maximum distance for initiation of these behaviors. Also, an apparent upper concentration threshold in males caused upwind flight to be terminated at increasing distances from the source with increasing emission rates. Thus, upper and lower thresholds apparently determine the boundaries of the “active distance” for upwind flight. There was much daily variation in mean maximum active distance, possibly due to temperature effects upon male threshold. The active distance estimates were used to design an optimal monitoring trap deployment strategy to minimize attraction of males from areas surrounding orchards. Using Bossert and Wilson's equation for active space, the average lower (initiation) threshold for upwind flight was 7.2 × 10−17 g/cm3 and the upper (termination) threshold was 2.1 × 10−13 g/cm3. Their model should be altered so that active space is defined as the space where pheromone concentration is within both lower and upper thresholds for a particular behavior.

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... Pheromones are volatiles and can potentially travel for hundreds of meters in all directions (Fig. 17.3) (Baker and Roelofs 1981;Linn et al. 1987). This is because their diffusion is driven by environmental and landscape factors, among which temperature, the general direction of wind and landscape morphology play a major role (Baker and Roelofs 1981;Elkington et al. 1987;Linn et al. 1987;Suckling et al. 1999). ...
... Pheromones are volatiles and can potentially travel for hundreds of meters in all directions (Fig. 17.3) (Baker and Roelofs 1981;Linn et al. 1987). This is because their diffusion is driven by environmental and landscape factors, among which temperature, the general direction of wind and landscape morphology play a major role (Baker and Roelofs 1981;Elkington et al. 1987;Linn et al. 1987;Suckling et al. 1999). Thus, the efficacy of PMD can be reduced to some extent, or even compromised, if some of these parameters prevent an adequate distribution of the pheromones in the treated area. ...
Chapter
Until a few years ago, the concept of mating disruption had been exclusively associated with the use of pheromones to reduce population density of insect pests. Since the early 2000s, a novel approach has been proposed to the scientific community: vibrational mating disruption (VMD). The novelty is the use of disturbance vibrations to disrupt the mating behavior of insect pests that communicate by means of substrate-borne vibrations. This research falls within the new field of biotremology and it brought the VMD from a theoretical concept to practical open field experimentation: in 2017, VMD was applied in an organic vineyard in Northern Italy to control leafhopper pests’ population density. This achievement gave us the opportunity to report the state of the field for the method, to discuss the ongoing research and to make a comparison between pheromone mating disruption (PMD) and VMD. In this chapter, we review the salient moments that led to the field application of VMD. Then, we discuss the VMD characteristics and we provide a benchmark, using as reference the traditional PMD to discuss similarities and differences. Furthermore, we analyze the advantages and disadvantages of applying VMD to commercial crops. We are convinced that the first vibrational vineyard is a starting point and that biotremology will provide many innovative possibilities for farmers to control pests in the future. We also think that the introduction of electronic devices in the vineyard could be a trailblazer for the diffusion of smart technology in viticulture, thus improving its general management.
... For delta trap observations, the direction of arrival with oriented flight was recorded for all males as they arrived within 2 m of a trap. The 'circular' R package (Agostinelli and Lund 2017) was used to calculate circular statistics. To determine the homogeneity of directional distribution of arrivals, a Rayleigh test was performed to every 30-min interval of data for all lure concentrations. ...
... To enable landing, a second optomotor reaction is employed: allowing the object head to expand in the visual field (see reviews by Willis 2008, Cardé 2016). Landing also may be linked with perception of changes in the plume's concentration (Baker and Roelofs 1981), the presence of an appropriate landing site (Charlton et al. 1990), and perhaps changes its fine-scale structure (Justus et al. 2002). Cardé and Hagaman (1979) and Charlton et al. (1993) showed that gypsy moths in a wind tunnel slowed their rate of upwind flight as the concentration of pheromone was increased, both as the source was approached and by using differing doses on the pheromone dispenser. ...
Article
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Delta- and bucket-style (Universal or Unitrap) traps baited with 1 standard survey lure and 1/3 and 3 lures were compared for their attractiveness and trapping efficiencies for gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), males. With bucket traps, the numbers of males attracted to within 2 m of traps and the proportion of these actually captured were identical among the three doses although the percentage of attracted males actually captured in bucket traps was low, less than 15%. A three-lure delta trap attracted about 70% more males than traps with the two lower doses. Capture efficiencies were above 80% for 1/3- and one-lure traps and about 60% for traps baited with three lures. The number of males captured in delta traps was equivalent for the three doses although our observations also suggest that a delta trap baited with three lures drew males from a wider range than lower dose lures and therefore would be a more sensitive trap for detecting incipient populations. We also noted that males tended to arrive in clusters, suggesting that attraction over moderate distances requires periods when the wind direction is fairly constant. This observation coupled with the great variability in the direction of male arrival to the traps also suggests that important changes in the area of influence of the plume are driven in such forested areas by slower but greater changes in wind direction compared with open habitats.
... The flight patterns of male insects responding to pheromone plumes have been very well-characterized (Kennedy et al. 1974, Baker et al. 1984, Cardé 1984, Cardé and Willis 2008, often in wind tunnels (Miller and Roelofs 1978) and sometimes in the field (Baker and Roelofs 1981, Elkinton et al. 1984, Baker and Haynes 1996. Males so stimulated execute positive optomotor anemotaxis. ...
... Plumes evoking male moth attraction as long as 60, 50, and 30 m have been revealed in the field by direct behavioral observations of, e.g., responding gypsy moths (Lymantria dispar) (Elkinton et al. 1984), European pine sawflies (Neodiprion sertifer) ( € Ostrand and Anderbrant 2003), and oriental fruit moths (Grapholita molesta) (Baker and Roelofs 1981), respectively. By that standard, our estimate of approximately < 5 m plume reach for the codling moth monitoring trap in apple is tiny. ...
Article
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Novel methods of data analysis were used to interpret codling moth (Cydia pomonella) catch data from central-trap, multiple-release experiments using a standard codlemone-baited monitoring trap in commercial apple orchards not under mating disruption. The main objectives were to determine consistency and reliability for measures of: 1) the trapping radius, composed of the trap's behaviorally effective plume reach and the maximum dispersive distance of a responder population; and 2) the proportion of the population present in the trapping area that is caught. Two moth release designs were used: 1) moth releases at regular intervals in the four cardinal directions, and 2) evenly distributed moth releases across entire approximately 18-ha orchard blocks using both high and low codling moth populations. For both release designs, at high populations, the mean proportion catch was 0.01, and for the even release of low populations, that value was approximately 0.02. Mean maximum dispersive distance for released codling moth males was approximately 260 m. Behaviorally effective plume reach for the standard codling moth trap was < 5 m, and total trapping area for a single trap was approximately 21 ha. These estimates were consistent across three growing seasons and are supported by extraordinarily high replication for this type of field experiment. Knowing the trapping area and mean proportion caught, catch number per single monitoring trap can be translated into absolute pest density using the equation: males per trapping area = catch per trapping area/proportion caught. Thus, catches of 1, 3, 10, and 30 codling moth males per trap translate to approximately 5, 14, 48, and 143 males/ha, respectively, and reflect equal densities of females, because the codling moth sex ratio is 1:1. Combined with life-table data on codling moth fecundity and mortality, along with data on crop yield per trapping area, this fundamental knowledge of how to interpret catch numbers will enable pest managers to make considerably more precise projections of damage and therefore more precise and reliable decisions on whether insecticide applications are justified. The principles and methods established here for estimating absolute codling moth density may be broadly applicable to pests generally and thereby could set a new standard for integrated pest management decisions based on trapping.
... Also, responders possessing a normal K might respond to pheromone from such high Q females at optimal concentrations occurring far from the source and then exhibit less than optimal performance of orientation and mating behaviors in the abnormally high concentration of pheromone near the female. This would be most likely in species possessing an upper threshold limit such as G. molesta (Baker and Roelofs, 1981). ...
... The lower concentrations are not sufficient to elicit upwind flight from males more than a few meters on average from the source. Conversely, super-normal rates evoke upwind flight from more than 80 m away but result in within-plume arrestment more than a meter away from the source (Baker and Roelofs, 1981) ...
Article
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A critical event in sexual reproduction is location or recruitment of a mate. In a number of insect groups, the necessary movements in time and space are often mediated by pheromones. One sex may recruit the other, or both sexes may be attracted to the chemical emitters. Aggregation may be viewed as the end result of movement reactions that reduce the distance between individuals in their environment. Such clustering may be brought about by a combination of attraction and arrestment, which are themselves not orientation mechanisms but rather end results, i.e., displacements, caused by movement reactions (Kennedy, 1978). For sex- and aggregation-pheromone communication, we define attraction as the net displacement of one individual toward the chemical source. Conversely, arrestment is the lack of net displacement toward or away from the chemical source. Both displacement phenomena may be viewed as part of a continuum caused by pheromone mediation of quite disparate movement reactions, such as orthokinesis, klinotaxis and anemotaxis (see Bell, Chapter 4 and Cardé, Chapter 5). That attraction and arrestment are only outcomes, not mechanisms, does not diminish the heuristic value of these terms; they are a capsule summary of the change in spacing between an individual and the chemical source. To an organism responding to sex pheromone, proximate cues and orientation mechanisms notwithstanding, such outcomes are the result of evolutionary selection.
... This result, which is expected by our model, indicates the potential of this approach for assessing trap competition in a number of ways. With a high trap density, the pheromone concentration within the plots will have been greater, making it harder for the male moths to discriminate between odour sources until the density of traps decreased or the moths made it to the edge of the array, allowing them to find discrete sources, 33 or pheromone concentrations may have been so great as to exceed the upper threshold for behavioural response of the moths, 35 leading to a depression of catch in the centre traps compared with the corner traps. The assumption of no trap competition at the greatest spacing (64 m for mealybugs and 32 m for moths) enabled the comparison of two of the systems for likely efficacy in mass trapping on a common parameter, d. ...
... 47 Bark beetles trapped with pheromones in 7 × 7 trap arrays showed higher catches at corners in many plots, 48 similarly to the results seen here, and apparently predictable by the geometry, as in our case with the 4 × 4 array. In an open field situation with oriental fruit moth, active flight distances of up to 80 m to a sex pheromone lure were observed, 35 and for Cydia nigicana the attraction range of males to their sex pheromone was estimated to be 200 m with stimulation (response to but not necessarily directed movement towards the odour source) from 400 m away. 49 These values suggest that our estimates of the maximum distances with nil effect at 32 or 64 m may be underestimates, making our estimates of communication disruption also underestimates. ...
Article
The identification of new attractants can present opportunities for developing mass trapping, but standard screening methods are needed to expedite this. We have developed a simple approach based on quantifying trap interference in 4 × 4 trap arrays with different spacings. We discuss results from sex pheromones in Lepidoptera (lightbrown apple moth, Epiphyas postvittana), Diptera (apple leafcurling midge, Dasineura mali), and Homoptera (citrophilous mealybug, Pseudococcus calceolariae), compared with a kairomone for New Zealand flower thrips (Thrips obscuratus). The 25:1 ratio of catch in corner to centre traps observed at 750 D. mali traps/ha was still evident as ~5:1 at 16 traps/ha, suggesting trap interference even at such low trap densities. Trap competition for sex pheromone lures at close spacing (<5 m) was evident in 16 trap arrays of the Pseudococcus calceolariae, but less so for Epiphyas postvittana. No trap competition was observed at 4 m spacings with the kairomone for T. obscuratus. The ratio of catch in traps in the corner : centre of a 16 trap array at different spacings offers a rapid preliminary assessment method for determining potential for mass trapping. Additional knowledge of vital rates and dispersal is needed for predicting population suppression. Our approach should have value in mass trapping development. This article is protected by copyright. All rights reserved.
... The flight patterns of male insects responding to pheromone plumes have been very well-characterized ( Kennedy et al. 1974, Baker et al. 1984, Cardé 1984, Cardé and Willis 2008, often in wind tunnels (Miller and Roelofs 1978) and sometimes in the field (Baker and Roelofs 1981, Elkinton et al. 1984, Baker and Haynes 1996. Males so stimulated execute positive optomotor anemotaxis. ...
... Plumes evoking male moth attraction as long as 60, 50, and 30 m have been revealed in the field by direct behavioral observations of, e.g., responding gypsy moths (Lymantria dispar) ( Elkinton et al. 1984), European pine sawflies (Neodiprion sertifer) ( € Ostrand and Anderbrant 2003), and oriental fruit moths (Grapholita molesta) (Baker and Roelofs 1981), respectively. By that standard, our esti- mate of approximately < 5 m plume reach for the codling moth monitoring trap in apple is tiny. ...
... In complex environments, such as an orchard canopy, atmospheric conditions may cause greater dispersal of pheromone compared to less complex environments such as low-growing vegetative crops, as seen in Lewis and Macaulay (1976). The estimated plume reach of a delta trap fitted with a codlemone lure in an apple orchard is <5 m (Adams et al. 2017), much shorter than plume reach estimates for other moth species when measured in more open environments (Baker and Roelofs 1981;Elkinton et al. 1984). The practical implication of this is that the influence of trap shape on pheromone plume structure may not be as important for codling moth, and other moths living in complex environments such as orchards and other forms of permaculture. ...
Article
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Sex pheromone baited monitoring traps are a critical tool for integrated pest management decisions against many insects, particularly codling moths (Cydia pomonella L.). The addition of cameras for remote monitoring has the potential to enhance the usefulness of these important tools. However, changes in trap design could potentially alter plume structure and trapping efficiency of these new traps. Here we look at several trap configurations designed to optimize the capture of codling moths in traps equipped with cameras. We found that, in both wind tunnel and field trials, camera equipped triangle traps and camera equipped rectangle traps (both V1 and V2) caught codling moths equivalent to a standard ‘delta’ style trap. While catch was unaffected, altering our rectangular trap opening from 4 to 8 cm (V1 and V2, respectively) decreased frequency of moths contacting the front of trap and increased the frequency of moths flying directly into the trap. We show that these novel camera equipped semiochemical-baited traps catch equivalent to the industry standard white delta trap.
... On the other hand, a number of factors can prevent males from entering the traps after being attracted by the pheromone lure, including the visual field (optomotor reaction), an unsuitable concentration or concentration gradient of the pheromone, a diffuse pheromone plume compared to that released by a female (Baker and Roelofs 1981;Cardé 2016;Cardé et al. 2018), a lack of pheromone compounds that mediate males' landing behaviour, eddies in the airstream around the trap that may deflect males from their track, or inappropriate visual cues (Lewis and Macaulay 1976). ...
Article
Abstract The fall armyworm (FAW), Spodoptera frugiperda, is one of the main pests of corn and other economically important crops worldwide. Pheromone traps can be used for monitoring and mass trapping S. frugiperda males. Trap design is an important component of a monitoring system or mass trapping system, along with the attractant. In this study, we evaluated the performance and efficiency of several home-made and commercial traps baited with a pheromone lure developed from Mexican S. frugiperda populations. The trials were performed in corn crops in two different years and regions of Mexico. The white plastic jug trap exhibited the highest capture and efficiency rate for trapping S. frugiperda males in both years and regions. The commercial green bucket trap and the home-made traps (including delta, sleeve and water bottle traps) caught significantly fewer males during the experiments compared to the white plastic jug trap. The latter captured 42.5% of males orienting sleeves the trap. An efficient trap may be useful for monitoring or be used as part of a mass trapping strategy to manage FAW populations in corn.
... So, why not just release more pheromone to generate a larger plume reach so as to increase sampling power? Unfortunately, this approach will not often be viable because an abnormally high pheromone concentration at the trap entrance can overwhelm the responders' physiology and reduce or preclude the entry into the trap so as to reduce rather than raise overall catch (e.g., Wyman 1979, Baker and Roelofs 1981, Stelinski et al. 2004, Liu et al. 2016. ...
Article
During a trapping study interval, each target insect is either caught or not caught. Therefore, the current analysis treats trapping as a binomial process. Data from a binomial calculator, along with computer simulations of random walkers, documented that the inherent variance associated with estimates of absolute population density generated by a single catch number in a pheromone-baited monitoring trap becomes very high when catch probability averaged across the trap's sampling area falls below 0.02, as is the case for most insect trapping systems operating in the open field. The imprecision associated with interpretations of single catch numbers renders many current pest management decisions risky and unsatisfactory. Here we reinforce how single-trap, multiple-release experiments can and should be used to measure catch probability, plume reach, and trap sampling area. When catch probability lies in the danger zone below 0.02, steps are suggested for how multiple traps might be deployed to raise composite catch probability to a level where estimates of absolute pest density become reliable. Heat transfer is offered as an appropriate conceptual model for the mechanics of trapping. A call is made for a radical rethinking in the designs of insect monitoring traps in light of their significant current deficits highlighted by this study.
... This could be due to the 'high pheromone concentration' in the fields, i.e., an increase in the number of pheromone traps per unit area could reduce the ability of the male adults to recognize the point of release, thereby considerably affecting the mating disruption instead of mass collection. The inference is similar in one of the study, moth collection will be hampered if pheromone concentration exceeds the upper threshold level which would make it difficult for the male moths to distinguish between odour sources [24,5] . We observed appreciable trap interactions in the fields deployed with 20 traps per acre which also attracted adult males of H. armigera significantly in all the four locations. ...
Article
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Chickpea pod borer, Helicoverpa armigera is an economically important insect pest. The trials were performed at four locations using with 10, 20, 30 and 40 sex pheromone funnel traps/acre during 2012-13 and 2013-14. The moth catches were higher in the locations with a trap density of 20/acre (12.93±4.05 and 13.82±5.0) and least percent pod infestation at such locations compared to other treatments. Peak activity of moths was recorded in the third standard meteorological week. Four insecticides, i.e., indoxacarb, chlorantraniliprole, novaluron and quinalphos were evaluated to determine their efficacy with pheromone traps. Among the treatments, fields treated with chlorantraniliprole and positioned 20 pheromone traps recorded least moth catches (0.15 to 0.25/trap) as well as percent pod infestation, followed by indoxacarb and novaluron. The present study observed that 20 traps/acre was the optimum trap density required to ensure maximum catches and integration of chlorantraniliprole+20 pheromone traps/acre proved considerably effective against H. armigera.
... It is suggested that the 'active space' of the pheromone is a function of the upper and lower concentration thresholds for the entire blend of components, instead of simply for the major component [38]. The 'active space' was previously defined as the space where the major pheromone component was within both the lower and upper thresholds for a particular behavior [39]. In a blend ratio approximating to that emitted by G. molesta females, the three components (Z8-12:OAc, E8-12:OAc and Z8-12:OH) elicited the increases in both long-range and close-range behavior in the male response sequence. ...
Article
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Several lepidopteran species share the same pheromone blend consisting of (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-9-hexadecenal (Z9-16:Ald) at different ratios and active doses. In rice pest Chilo suppressalis, (Z)-11-hexadecenol, (Z11-16:OH) and octadecanal (18:Ald) were identified as minor components in the pheromone gland of female moths, and these components were previously not considered as part of the sex pheromone of C. suppressalis. Z11-16:Ald, Z9-16:Ald and (Z)-13-octadecenal (Z13-18:Ald) frequently trapped other lepidopteran species, such as rice pests Scirpophaga incertulas and Mythimna separate, corn and vegetable pests Helicoverpa armigera in the field, suggesting a lack of specificity in the pheromone blend. Our data showed that the minor component Z11-16:OH did not have a synergistic effect on the attractiveness of the blend to C. suppressalis; however, pheromone mixtures containing Z11-16:OH failed in trapping male H. armigera moths. We confirmed the identity and specificity of the C. suppressalis sex pheromone and demonstrated that Z11-16:OH plays a key role in the reproductive isolation of C. suppressalis, M. separata, and H. armigera moths, and a similar role of Z9-18:Ald in that of S. incertulas and C. suppressalis. This phenomenon could be more widely applicable to interspecific interactions in the pheromone communication between insects, which is crucial to developing the electronic automatic counting device for automatically monitoring the pest population by pheromone trapping based on its species specificity.
... Why Modulate Titer? It is generally accepted that the release of greater quantities of pheromone should result in females attracting more males over greater distances, and hence is likely to enhance fitness (Baker and Roelofs 1981;Cardé 2016;Foster and Johnson 2011;Greenfield 1981;Symonds et al. 2012;Umbers et al. 2015). Why, then, do females need a titer control that lowers amounts of pheromone available for release? ...
Article
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Moths are exemplars of chemical communication, especially with regard to specificity and the minute amounts they use. Yet, little is known about how females manage synthesis and storage of pheromone to maintain release rates attractive to conspecific males and why such small amounts are used. We developed, for the first time, a quantitative model, based on an extensive empirical data set, describing the dynamical relationship among synthesis, storage (titer) and release of pheromone over time in a moth (Heliothis virescens). The model is compartmental, with one major state variable (titer), one time-varying (synthesis), and two constant (catabolism and release) rates. The model was a good fit, suggesting it accounted for the major processes. Overall, we found the relatively small amounts of pheromone stored and released were largely a function of high catabolism rather than a low rate of synthesis. A paradigm shift may be necessary to understand the low amounts released by female moths, away from the small quantities synthesized to the (relatively) large amounts catabolized. Future research on pheromone quantity should focus on structural and physicochemical processes that limit storage and release rate quantities. To our knowledge, this is the first time that pheromone gland function has been modeled for any animal.
... mg/m3) that are considered negligible in terms of toxicity for humans [31,32]. However, given the extraordinary sensitivity of the insects' olfactory system [33][34][35], we can reasonably suspect that such concentrations might be detected by mosquitoes. This field of investigation (i.e. chemical and behavioral ecology in a context of widespread vector control tool implementation) has been neglected for decades and there is a need for more behavioral and physiological studies. ...
Article
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Experimental huts are part of the WHO process for testing and evaluation of Insecticide Treated Nets (ITN) in semi-field conditions. Experimental Hut Trials (EHTs) mostly focus on two main indicators (i.e., mortality and blood feeding reduction) that serve as efficacy criteria to obtain WHO interim recommendation. However, several other outputs that rely on counts of vectors collected in the huts are neglected although they can give useful information about vectors’ behavior and personal protection provided by ITNs. In particular, EHTs allow to measure the deterrent effect and personal protection of ITNs. To provide a better assessment of ITNs efficacy, we performed a retrospective analysis of the deterrence and the personal protection against malaria transmission for 12 unwashed and 13 washed ITNs evaluated through EHTs conducted in West Africa. A significant deterrent effect was shown for six of the 12 unwashed ITNs tested. When washed 20 times, only three ITNs had significant deterrent effect (Rate Ratios (RR)<1; p<0.05) and three showed an apparent “attractiveness” (RR>1; p<0.01). When compared to the untreated net, all unwashed ITNs showed lower number of blood-fed Anopheles indicating a significant personal protection (RR<1, p<0.05). However, when washed 20 times, three ITNs that were found to be attractive did not significantly reduce human-vector contact (p>0.05). Current WHO efficacy criteria do not sufficiently take into account the deterrence effect of ITNs. Moreover, the deterrence variability is rarely discussed in EHT’s reports. Our findings highlighted the long-range effect (deterrent or attractive) of ITNs that may have significant consequences for personal/community protection against malaria transmission. Indicators measuring the deterrence should be further considered for the evaluation of ITNs.
... How closely a 100 μg lure mimics a female's rate of emission is not known, but it could be well above the female's natural rate. Baker and Roelofs (1981) observed activation and orientation of males of the closed related Grapholita molesta (Tortricidae) at various distances downwind of synthetic sources charged with 1, 10, 100, and 1000 μg of pheromone. Although there was some daily variation principally due to temperature effects on male threshold, males were activated a mean of up to 77 m downwind with the 1000 μg stimulus, but at this dose males terminated flight approximately ≈1.5 m from the source; similarly a 100 μg source evoked orientation up to a mean of 29 m downwind, but again the high concentration of pheromone in the plume caused cessation of orientation ≈20 cm from the source. ...
... Passive and attractive (attractant releasing) traps can also be used in a new concept and method, the effective attraction radius (EAR), for comparing semiquantitatively the attraction distances of attractants both within and between species of insects. A maximum possible distance of attraction can be imagined with the earlier concept of the active space, in which a time-averaged volume (plume) containing above-behavioral-threshold semiochemical concentrations elicits attraction responses when entered by the insect (Bossert and Wilson, 1963;Nakamura and Kawasaki, 1977;Baker and Roelofs, 1981;Elkinton and Card6, 1984). This concept can be modified to an attraction space to find distances from the source within which, for example, 50 % of the entering insects are successful in finding the source. ...
Article
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... Field observations have revealed that tortricid male moths orient to and approach polyethylene tube reservoir dispensers of pheromone characterized by release rates 1,000 fold higher than female moths as well as "female equivalent" dispensers which release pheromone at rates approximating calling females [11]. Far more males may actually orient to these dispensers than what has been actually observed given that oriented progress is likely terminated downwind at a certain distance at which the pheromone concentration is above the upper threshold for response [12]. These results suggest that competitive attraction between calling females and synthetic point sources of pheromone may be an important contributing mechanism to mating disruption. ...
Article
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Over the past several years my colleagues and I have been exploring ways of achieving moth mating disruption exceeding 95% efficacy even under high densities with limited insecticide inputs. The foundation for this work has been a series of studies examining the mechanisms underlying pheromone-based mating disruption in moth pests of pome fruit, stone fruit, walnuts, and citrus. Collectively, the results support competitive attraction or false-plume-following as an essential component of communicational disruption of moths in the family Tortricidae. Habituation of central nervous system (CNS) response appears to be an important supplementary mechanism for moths having oriented along plumes of high-dosage dispensers. Four main lines of evidence have led to these conclusions. Pheromone-based disruption of moths is density-dependent. Under high population densities, disruption increases as a function of increasing density of pheromone release sites. Effective mating disruption using high-dosage dispensers occurs in the field despite overall atmospheric concentrations not reaching levels high enough to desensitize moths by adaptation or habituation without close range (within cm) exposure to high dosage dispensers. Males are attracted to high-dosage dispensers in the field and such encounters desensitize the CNS but do not affect sensitivity of the peripheral nervous system. If competitive attraction followed by CNS habituation are the combined mechanisms achieving mating disruption, the following practical implications should be considered for developing high performance approaches and formulations: 1) distribution of dispensers should be uniform rather than clumped, 2) dispenser density should be high, and 3) release rate from synthetic dispensers should be within a physiologically attractive range but also sufficiently high to habituate male moth response following orientation.
... As mating disruption has been developed and implemented for oriental fruit moth, the effect of the sex pheromone on behavior of males has been studied extensively (Cardé et al. 1977, Baker and Roelofs 1981, Linn and Roelofs 1981, Willis and Baker 1984, Figueredo and Baker 1992, Sanders and Lucuik 1996, Rumbo and Vickers 1997, Stelinski et al. 2005, but the effect on female antennal and behavioral responses has not been investigated in depth. Among tortricids, female-produced sex pheromones are known to elicit antennal responses (Palanaswamy and Seabrook 1978, Barnes et al. 1992, Stelinski at el. 2003a, DeLury et al. 2005) and advance and/or increase female calling behavior Seabrook 1978, 1985;Weissling and Knight 1996). ...
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Electroantennogram (EAG) and behavioral responses of female oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), were studied using the synthetic major component, (Z)-8-dodecenyl acetate, and partial three-component blend, (Z)-8-dodecenyl-acetate: (E)-8-dodecenyl-acetate:(Z)-8-dodecenol (in a 93:6:1 ratio), of the sex pheromone. EAGs elicited by both the single and three-component pheromone were signiÞcantly greater compared with hexane solvent controls. In 1-liter plastic chambers with constant throughput of air (50 ml/min) over rubber septa loaded with 0.01 or 0.1 mg of the three-component pheromone blend, onset of female calling was advanced by Ϸ2 h compared with solvent controls. However, the total number of females calling at peak time and the time of calling termination did not differ between pheromone-exposed and control moths. Oviposition rates of pheromone-exposed and clean air-exposed mated female moths did not differ in similar 1-liter ßow-through chambers lined with wax paper over 24-h intervals. In a separate experiment, male and female oriental fruit moth, caged in perforated 1-liter containers allowing air ventilation, were placed for 1-wk intervals in replicated glasshouses that were either treated with Isomate dispensers hung 0.5 m from chambers or left untreated. Oviposition rates between Isomate dispenser-exposed and control moths were similar. Female sensitivity to sex pheromone, termed "autodetection," has been observed previously and is thought to function either as a mechanism to 1) advance female calling periodicity under high population densities to increase the probability of attracting males, 2) induce dispersal under high population densities to reduce competition for males or food resources, or 3) aggregate females to increase local probability of mating success. Autodetection also may affect the efÞcacy of mating disruption for oriental fruit moth depending on whether pheromone exposure affects the diel periodicity of male sexual response. KEY WORDS Oriental fruit moth, Grapholita molesta, sex pheromone, female response, autode-tection Oriental fruit moth, Grapholita molesta (Busck) (Lep-idoptera: Tortricidae), originated in northwest China and is now widely distributed throughout the world, including the major stone-fruit growing areas of Eu-rope, Asia, America, Africa, Australia, and New Zea-land (Rothschild and Vickers 1991). In Australia, ori-ental fruit moth is one of the most important pests of commercial stone and pome fruit orchards. Oriental fruit moth severely damages peaches, nectarines, pears, apples, apricots, and plums (Chapman and Lienk 1971). Stone fruit and particularly middle-and late-season varieties of peach and nectarine are con-sidered to be the primary hosts of oriental fruit moth (Rothschild and Vickers 1991). However, in the last 10 yr, oriental fruit moth has become a major problem in pome fruit, especially pears in Australia (IlÕichev et al. 2004) and apples in the United States (Kovanci et al. 2004). Newly planted peach trees are especially attractive to mated oriental fruit moth females for oviposition. Initially oriental fruit moth infests young shoot tips and then later infests green fruit (IlÕichev et al. 2003). IdentiÞcation of the female sex-attractant phero-mone (George 1965, Cardé et al. 1979) led to the development of mating-disruption protocols for ori-ental fruit moth. Sex pheromon-emediated mating dis-ruption is realized by deploying large amounts of syn-thetic sex pheromone into the crop atmosphere to interfere with normal mate Þnding (Cardé and Minks 1995). Mating disruption is an environmentally sound and effective alternative to the use of broad-spectrum organophosphate insecticides for oriental fruit moth control in Australia, particularly when applied on an areawide scale (Brown and IlÕichev 2000, IlÕichev et al. 2002, Williams and IlÕichev 2003). Isomate-M 100 and M (OFM) Rosso reservoir tubes (PaciÞc Biocontrol Co., LitchÞeld Park, AZ) are the most commonly used dispenser of oriental fruit moth pheromone and have proven highly effective in numerous trials in North America and Europe (Pfeiffer and Killian 1988;
... As mating disruption has been developed and implemented for oriental fruit moth, the effect of the sex pheromone on behavior of males has been studied extensively (Cardé et al. 1977, Baker and Roelofs 1981, Linn and Roelofs 1981, Willis and Baker 1984, Figueredo and Baker 1992, Sanders and Lucuik 1996, Rumbo and Vickers 1997, Stelinski et al. 2005, but the effect on female antennal and behavioral responses has not been investigated in depth. Among tortricids, female-produced sex pheromones are known to elicit antennal responses (Palanaswamy and Seabrook 1978, Barnes et al. 1992, Stelinski at el. 2003a, DeLury et al. 2005) and advance and/or increase female calling behavior Seabrook 1978, 1985;Weissling and Knight 1996). ...
Article
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Electroantennogram (EAG) and behavioral responses of female oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), were studied using the synthetic major component, (Z)-8-dodecenyl acetate, and partial three-component blend, (Z)-8-dodecenyl-acetate: (E)-8-dodecenyl-acetate:(Z)-8-dodecenol (in a 93:6:1 ratio), of the sex pheromone. EAGs elicited by both the single and three-component pheromone were signiÞcantly greater compared with hexane solvent controls. In 1-liter plastic chambers with constant throughput of air (50 ml/min) over rubber septa loaded with 0.01 or 0.1 mg of the three-component pheromone blend, onset of female calling was advanced by Ϸ2 h compared with solvent controls. However, the total number of females calling at peak time and the time of calling termination did not differ between pheromone-exposed and control moths. Oviposition rates of pheromone-exposed and clean air-exposed mated female moths did not differ in similar 1-liter ßow-through chambers lined with wax paper over 24-h intervals. In a separate experiment, male and female oriental fruit moth, caged in perforated 1-liter containers allowing air ventilation, were placed for 1-wk intervals in replicated glasshouses that were either treated with Isomate dispensers hung 0.5 m from chambers or left untreated. Oviposition rates between Isomate dispenser-exposed and control moths were similar. Female sensitivity to sex pheromone, termed "autodetection," has been observed previously and is thought to function either as a mechanism to 1) advance female calling periodicity under high population densities to increase the probability of attracting males, 2) induce dispersal under high population densities to reduce competition for males or food resources, or 3) aggregate females to increase local probability of mating success. Autodetection also may affect the efÞcacy of mating disruption for oriental fruit moth depending on whether pheromone exposure affects the diel periodicity of male sexual response. KEY WORDS Oriental fruit moth, Grapholita molesta, sex pheromone, female response, autode-tection Oriental fruit moth, Grapholita molesta (Busck) (Lep-idoptera: Tortricidae), originated in northwest China and is now widely distributed throughout the world, including the major stone-fruit growing areas of Eu-rope, Asia, America, Africa, Australia, and New Zea-land (Rothschild and Vickers 1991). In Australia, ori-ental fruit moth is one of the most important pests of commercial stone and pome fruit orchards. Oriental fruit moth severely damages peaches, nectarines, pears, apples, apricots, and plums (Chapman and Lienk 1971). Stone fruit and particularly middle-and late-season varieties of peach and nectarine are con-sidered to be the primary hosts of oriental fruit moth (Rothschild and Vickers 1991). However, in the last 10 yr, oriental fruit moth has become a major problem in pome fruit, especially pears in Australia (IlÕichev et al. 2004) and apples in the United States (Kovanci et al. 2004). Newly planted peach trees are especially attractive to mated oriental fruit moth females for oviposition. Initially oriental fruit moth infests young shoot tips and then later infests green fruit (IlÕichev et al. 2003). IdentiÞcation of the female sex-attractant phero-mone (George 1965, Cardé et al. 1979) led to the development of mating-disruption protocols for ori-ental fruit moth. Sex pheromon-emediated mating dis-ruption is realized by deploying large amounts of syn-thetic sex pheromone into the crop atmosphere to interfere with normal mate Þnding (Cardé and Minks 1995). Mating disruption is an environmentally sound and effective alternative to the use of broad-spectrum organophosphate insecticides for oriental fruit moth control in Australia, particularly when applied on an areawide scale (Brown and IlÕichev 2000, IlÕichev et al. 2002, Williams and IlÕichev 2003). Isomate-M 100 and M (OFM) Rosso reservoir tubes (PaciÞc Biocontrol Co., LitchÞeld Park, AZ) are the most commonly used dispenser of oriental fruit moth pheromone and have proven highly effective in numerous trials in North America and Europe (Pfeiffer and Killian 1988;
... Ten μg of this mixture in 10 μL hexane was applied to the inside bottom of the large end of a rubber septum. The ratio of the pheromone components (Baker and Cardé 1979b) were verified by gas liquid chromatography on a DB-5 column in an HP 6890 gas chromatograph (Agilent Technologies, Palo Alto, CA, USA after Baker and Roelofs 1981). The ratios of compounds in our solution were 6.5 % (E)-8-dodecenyl acetate with 4.9 % (Z)-8-dodecyl alcohol in (Z)-8-dodecenyl acetate. ...
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Previous studies with Oriental Fruit Moth (OFM, Grapholita molesta) and Heliothis virescens males flying upwind along a pheromone plume showed that they increased their upwind flight speed as they flew higher above striped floor patterns and, for OFM, to a similar degree over dotted floor patterns. This response pattern has been demonstrated in another moth species, Epiphyas postvittana and in a beetle, Prostephanus truncatus. In all cases the role played by the change in angular size of the wind tunnel’s ventral floor pattern was not assessed. In the present study we specifically addressed this question with a systematic examination of moths’ flight control over different sizes of transverse stripes and dot patterns ranging down by halves from 5 to 0.625 cm and a blank white floor as a control, and showed that OFM males fly faster upwind and along their flight paths over floor patterns of decreasing size. Increased speeds over striped patterns were evident as stripe width decreased below 2.5 cm, whereas moths did not increase their flight speed over dot patterns until dot size had decreased to less than 1.25 cm. Another flight component that the moths can actively control, their course angles, was unchanged above both patterns, except for moths flying over 5 cm stripes. Turning frequency and interturn distances were mostly unchanged or offset each other, negating any effects on upwind progress. As in an earlier study examining flight speeds at three heights above floor patterns of three densities, the moths’ changes in speed appear to be exclusively affected by changes in their orthokinetic response to the size of the floor pattern objects.
... Passive and attractive (attractant releasing) traps can also be used in a new concept and method, the effective attraction radius (EAR), for comparing semiquantitatively the attraction distances of attractants both within and between species of insects. A maximum possible distance of attraction can be imagined with the earlier concept of the active space, in which a time-averaged volume (plume) containing above-behavioral-threshold semiochemical concentrations elicits attraction responses when entered by the insect (Bossert and Wilson, 1963;Nakamura and Kawasaki, 1977;Baker and Roelofs, 1981;Elkinton and Card6, 1984). This concept can be modified to an attraction space to find distances from the source within which, for example, 50 % of the entering insects are successful in finding the source. ...
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The catches of bark beetles (Coleoptera: Scolytidae) were compared between attractive traps releasing semiochemicals and passive traps (cylindrical sticky screens hung, at 10 heights of 0.7-11.5 m, on poles). A central attractive-trap pole was surrounded by three passive-trap poles spaced 50 or 100 m away at the apices of an equilateral triangle. The catches ofTomicus piniperda and other scolytid species on the attractive-trap pole baited with host monoterpenes, or the catches ofIps typographus attracted to synthetic pheromone, were compared to passive trap catches in a Scots pine forest or in a Norway spruce clear-cut, respectively. Information about flight height distributions of the above scolytid species, andHylurgops palliatus, Cryphalus abietis, Pityogenes chalcographus, P. quadridens, P. bidentatus, andTrypodendron domesticum were obtained on the passive and attractive trap poles. A new method is presented for determining the densities of flying insects based on the passive trap's dimensions and catch, duration of test, and speed of insect. Also, a novel concept, the effective attraction radius (EAR), is presented for comparing attractants of species, which is independent of insect density, locality, or duration of test. The EAR is obtained by the ratio of attractive and passive trap catches and the dimensions of the passive trap, and thus should correlate positively with the strength of the attractant and the distance of attraction. EARs are determined from catch data ofT. piniperda andI. typographus as well as from the data of previous investigations on the same or other bark beetles.
... This is comparable to the fastest rate found for the boll weevil 0ohnson et al., 1976). Lepidoptera have very quick mark-releaserecapture times (Baker and Roelofs, 1981; Karandinos, 1974; Kehat et al., 1976; Kishaba et al., 1970). Thirty percent of marked cabbage looper, Trichoplusia ni (Hubner), males released 105 m downwind from a 25-mg pheromone source were recovered within 15 min (i.e., 420 m/hr) (Kishaba et al., 1970 ). ...
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Studies were conducted to determine the effects of sex pheromone dosage and lure age on movement of male sweetpotato weevils (SPW),Cylas formicarius elegantulus (Summers), using mark-release-recapture techniques. SPW trap counts from various downwind distances were compared for dosages ranging from 0.01 to 10.0 μg and lure ages ranging from fresh (0 days old) to 64 days old. The percentages of male SPW recaptured decreased with an increase in release distance and decreased with a decrease in dosage at each corresponding distance. Most SPW were caught within the first 16-hr period. Slopes of percent recapture vs. release distance for the two higher dosages (10 μg and 1.0 μg) differed from those of the two lower dosages (0.1 and 0.01 μg) but did not differ from each other. Intercepts were similar among the three higher dosages. Slopes did not differ among the five lure ages examined. Intercepts differed between fresh (0 days old) and 24-day-old septa at 16 hr and between fresh (0 days old) and 34-day-old septa at 40 hr. Previous exposure to pheromone (conditioning) did not increase percentages of SPW recaptured. Results indicate that male SPW are capable of traversing distances of at least 280 m in 16 hr. The pheromone tested in this study appears to be effective at dosages lower than any other coleopteran sex-pheromone system. Incorporation of this pheromone into a SPW management system may effectively reduce the use of insecticides.
... There were no significant differences eliciting any of the behavioral sequences from 1-10 female equivalents (FE) of gland extract and 0.1-100 FE of synthetic Wo ET AL. pheromone compounds, according to the method of adjusted significance levels for proportions (P < 0.05) (Ryan, 1960). Earlier studies on the Oriental fruit moth Grapholita molesta, for instance, suggest that the pheromone dose-response curve exhibits a normal distribution pattern (Baker and Roelofs, 1981 ). Therefore , we chose the intermediary 3 FE (equivalent to 0.45 /zg Z 5 -1 0 : O A c + 2.25 #g Z7-12 : OAc + 1.12 #g Z9-14 : OAc) as an optimal dosage in the later experiments. ...
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The electrophysiological and behavioral responses of maleAgrotis segetum to fluorinated analogs of (Z)-5-decenyl acetate (Z5-10∶OAc) were investigated. The single sensillum recordings showed that 4,4-difluoro-(Z)-5-decenyl acetate (4,4-F2), 7,7-difluoro-(Z)-5-decenyl acetate (7,7-F2), 10,10,10-trifluoro-(Z)-5-decenyl acetate (10,10,10-F3) and 7,7,8,8-tetrafluoro-(Z)-5-decenyl acetate (7,7,8,8-F4) were each 100-fold less active than the natural Z5-10 ∶ OAc, whereas the 7,7,8,8,9,9,10,10,10-nonafluoro-(Z)-5-decenyl acetate (F9) analog was essentially inactive. A mixture of Z5-10 ∶ OAc, Z7-12 ∶ OAc, and Z9-14 ∶ OAc on a filter paper dispenser was as attractive as female gland extracts when tested in a flight tunnel. With Z5-10∶OAc omitted, the two-component mixture elicited a significantly lower male response. Four analogs, 7,7-F2, 10,10,10-F3, 7,7,8,8-F4, and F9, were added separately to the two-component mixture to replace Z5-10∶OAc. The responses elicited by the mixtures containing the 7,7-F2, 10,10,10-F3, and 7,7,8,8-F4 analogs did not differ significantly from that of the natural three-component mixture and the two-component mixture, whereas the mixture containing F9 elicited a significantly lower male response, as low as the response to the two-component mixture. In a field test the mixtures containing 10,10,10-F3 and 7,7,8,8-F4 were significantly more active than the two-component mixture, but still less active than the natural three-component mixture. It appears that field tests provided greater discrimination among pheromone analogs in assessing their behavioral activity than the flight-tunnel test did. Structure-activity analyses demonstrate the importance of the lipophilic interaction between the terminal alkyl chain and the receptor site for the activity of the stimulus. The lipophobicity of the fluorinated analogs impedes a productive receptor interaction.
... The release rates of sex pheromone from individual females imply that dosages in the field should not be too high because males are responding to individual females. For example, when synthetic sex pheromone is released at considerably higher rates than natural rates, male moths cease upwind orientation when the concentration exceeds that of a single female (Baker and Roelofs 1981). Innocenzi et al. (2005) indicated that attractive release rates in the field for L. rugulipennis occurred at from 0.25 to 2 μg/h for various components. ...
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The plant bugs Lygus hesperus, Lygus lineolaris, and Lygus elisus (Hemiptera: Miridae) are major pests of many agricultural crops in North America. Previous studies suggested that females release a sex pheromone attractive to males. Other studies showed that males and females contain microgram amounts of (E)-4-oxo-2-hexenal, hexyl butyrate, and (E)-2-hexenyl butyrate that are emitted as a defense against predators. Using gas chromatography–mass spectrometry, we found that female L. lineolaris and L. elisus have a 4:10 ratio of hexyl butyrate to (E)-2-hexenyl butyrate that is reversed from the 10:1 ratio in female L. hesperus (males of the three species have ~10:1 ratio). These reversed ratios among females of the species suggest a behavioral role. Because both sexes have nearly equal amounts of the major volatiles, females should release more to attract males. This expectation was supported because L. hesperus females released more hexyl butyrate (mean of 86 ng/h) during the night (1800–0700 hours) than did males (E)-4-oxo-2-hexenal at 2 μg/h. The resulting catches of only Lygus males suggest that (E)-4-oxo-2-hexenal is an essential sex pheromone component for all three species, (E)-2-hexenyl butyrate is essential for L. elisus and L. lineolaris, and hexyl butyrate is essential for L. hesperus. However, all three components are recognized by each species since ratios of the butyrate esters are critical for conspecific attraction and heterospecific avoidance by males and thus play a role in reproductive isolation among the three species. Because L. hesperus males and females are known to emit these major volatiles for repelling ant predators, our study links defensive allomones in Lygus bugs with an additional use as sex pheromones.
... Since then the idea of a filamentous and snaking plume has become the paradigm (Murlis and Jones, 1981;David et al., 1982;Elkinton and CardC, 1984). The idea of the "active zone" (Bossert and Wilson, 1963) or "active space" Kawasaki, 1977, 1984;Baker and Roelofs, 1981) is also central to our concept of a plume. Within the active space, the concentration of pheromone molecules is sufficient to elicit a behavioral response in an insect, and this is the area that we spatially visualize as the plume. ...
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The sequence of arrival of the bark beetlesIps typographus andPityogenes chalcographus (Coleoptera: Scolytidae) at traps baited with their synthetic pheromones was monitored with a portable fraction collector. Histograms of the natural arrival patterns of both species were nonrandom and clumped at shorter time scales (1-, 2-, 4-, 5-, or 6-min cells) but appeared random at larger time scales (10, 20 or 30 min). Monte Carlo generation of similar histograms showed them to be random at all of these time scales. A stochastic computer model could graphically simulate insect orientation to odor sources based on present theories of odor-modulated anemotaxis and casting. Although this model was used throughout, since it assumes only that insects cast perpendicular to the current wind direction, a second model could slightly improve orientation success. However, the second model requires that the insect remember its ground path (upwind) prior to losing the plume (after an abrupt wind direction change). The effects of casting and flight parameters on orientation success and randomness of arrival sequence within various plumes were determined by simulation. Similarly, the effects of random walks in plume direction, plume width, and wind speed were explored. The results showed that dynamic random variations in plume direction and especially wind speed could cause an otherwise random arrival sequence (e.g., under constant wind) to become clumped and nonrandom. Therefore, the clumped arrival patterns of bark beetles and other insects, includingSpodoptera litura, at pheromone sources could result from random-walk fluctuations in wind speed and wind direction.
... To compare, males of pea moth Cydia nigricana (F.) and oriental fruit moth Grapholita molesta Busck. were stimulated at 500 m (Wall & Perry, 1987) and 80 m (Baker & Roelofs, 1981) from 100 µg pheromone sources, respectively. Differences between species are partly due to different sensitivity in the insects, but also the release rate of the pheromone is important. ...
Article
This study investigated behaviour of male European pine sawflies, Neodiprion sertifer Geoffr. (Hym., Diprionidae), that were released downwind from pheromone traps. Releases were done at three distances; either at 5 m from one trap, or at 50 m or 200 m from five traps, placed in a line perpendicular to the current wind direction. As a control, males were released identically but without any pheromone source present. The behaviour of the males prior to take-off was studied on a release platform. The following different types of behaviour were recorded: groom- ing, wing fanning, orientating and take-off. The frequency of grooming was significantly higher in the pheromone treatments compared to the control, whereas the frequency of wing fanning and orientating increased, although not significantly. The direction in which the males displayed the various types of behaviour was more concentrated towards the wind when pheromone was present than during the control experiment. By colour marking of Ecology, Lund University, d travel speed could be calculated. The minimum recorded time from take-off to landing was 1 min, 6 min and 45 min for the 5 m, 50 m and 200 m experiments, respectively. The stimulation- and attraction range of the trap was at least 200 m, and the sampling range after 24 hr was calcu- lated to approximately 400 m (c.i. 140-1600 m).
... For example, whereas bark beetles are attracted to thousands of conspecifics in a tree, male moths respond to single females. If dosage is increased beyond a certain level, then catch of moths begins to decline (Baker and Roelofs 1981;Byers 2007Byers , 2012b. Thus, the EAR and EAR c cannot be increased indefinitely by increasing dosage because male moths may "conclude" that a female is in the vicinity well before they reach the source of unnaturally high concentrations of pheromone. ...
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Dose–response curves of the effects of semiochemicals on neurophysiology and behavior are reported in many articles in insect chemical ecology. Most curves are shown in figures representing points connected by straight lines, in which the x-axis has order of magnitude increases in dosage vs. responses on the y-axis. The lack of regression curves indicates that the nature of the dose–response relationship is not well understood. Thus, a computer model was developed to simulate a flux of various numbers of pheromone molecules (103 to 5 × 106) passing by 104 receptors distributed among 106 positions along an insect antenna. Each receptor was depolarized by at least one strike by a molecule, and subsequent strikes had no additional effect. The simulations showed that with an increase in pheromone release rate, the antennal response would increase in a convex fashion and not in a logarithmic relation as suggested previously. Non-linear regression showed that a family of kinetic formation functions fit the simulated data nearly perfectly (R 2 >0.999). This is reasonable because olfactory receptors have proteins that bind to the pheromone molecule and are expected to exhibit enzyme kinetics. Over 90 dose–response relationships reported in the literature of electroantennographic and behavioral bioassays in the laboratory and field were analyzed by the logarithmic and kinetic formation functions. This analysis showed that in 95 % of the cases, the kinetic functions explained the relationships better than the logarithmic (mean of about 20 % better). The kinetic curves become sigmoid when graphed on a log scale on the x-axis. Dose-catch relationships in the field are similar to dose-EAR (effective attraction radius, in which a spherical radius indicates the trapping effect of a lure) and the circular EARc in two dimensions used in mass trapping models. The use of kinetic formation functions for dose–response curves of attractants, and kinetic decay curves for inhibitors, will allow more accurate predictions of insect catch in monitoring and control programs.
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Experimental huts are part of the WHO process for testing and evaluation of Insecticide Treated Nets (ITN) in semi-field conditions. Experimental Hut Trials (EHTs) mostly focus on two main indicators (i.e. mortality and blood feeding reduction) that serve as efficacy criteria to obtain WHO interim recommendation. However, several other outputs that rely on counts of vectors collected in the huts are neglected although they can give useful information about vectors behavior and personal protection provided by ITNs. In particular, EHTs allow to measure the deterrent effect and personal protection of ITNs. To provide a better assessment of ITNs efficacy, we performed a retrospective analysis of the deterrence and the personal protection against malaria transmission for 12 unwashed and 13 washed ITNs evaluated through EHTs conducted in West Africa. A significant deterrent effect was shown for six of the 12 unwashed ITNs tested. When washed 20 times, only three ITNs had significant deterrent effect (Rate Ratios (RR)<1; p<0.05) and three showed an apparent “attractiveness” (RR>1; p<0.01). When compared to the untreated net, all unwashed ITNs showed lower number of blood-fed Anopheles indicating a significant personal protection (RR<1, p<0.05). However, when washed 20 times, three ITNs that were found to be attractive did not significantly reduced human-vector contact (p>0.05). Current WHO efficacy criteria do not sufficiently take into account the deterrence effect of ITNs. Moreover the deterrence variability is rarely discussed in EHT's reports. Our findings highlighted the long range effect (deterrent or attractive) of ITNs that may have significant consequences for personal/community protection against malaria transmission. Indicators measuring the deterrence should be further considered for the evaluation of ITNs.
Article
Observations of the attraction of males of the pea moth, Cydia nigricana (F.), to wheat plants previously exposed to sex‐attractant traps are described. Plants exposed to attractant for 30 min or 180 min attracted moths for at least 100 min and once for at least 180 min. Attracted moths often landed on the vegetation which had been in the immediate vicinity of the trap and fanned. Removal of the vegetation next to the trap after 60 min exposure, and its replacement with unexposed vegetation, did not affect the number of moths which were attracted, but they avoided the unexposed vegetation and fewer landed and fanned. Wheat plants exposed next to a trap for 60 min, and then placed in an unexposed position, still attracted moths, on one occasion for at least 140 min. Observations complémentaires sur les réponses du mǎle de Cydia nigricana à une végétation préalablement exposée à des substances sexuelles attractives L'observation de l'attraction de mǎles de Cydia nigricana F. par des pieds de blé exposés antérieurement à des pièges sexuels a été décrite. Des plantes exposées à des substances attractives pendant 30 ou 180 minutes attirent des papillons pendant au moins 100 minutes et parfois 180 minutes. Les papillons attirés atterrissent souvent sur la végétation qui est dans le voisinage immédiat du piège et battent alors des ailes. L'extraction de la végétation proche du piège après 60 minutes d'exposition et son remplacement par de la végétation non contaminée ne modifie pas le nombre de papillons attirés par le piège mais ceux‐ci évitent cette végétation et peu atterrissent et battent des ailes. Des pieds de blé exposés près du piège pendant 60 minutes et ensuite placés ailleurs attirent encore des papillons, měme dans un cas pendant au moins 140 minutes. 1983 The Netherlands Entomological Society
Chapter
Numerous insects communicate with pheromones that induce attraction or directed movement toward the pheromone source. Documentation of orientation to such chemicals and their use to monitor insect pests typically require development of traps and a trapping protocol. Field trapping also has served as the bioassay in the characterization and identification of many pheromones. Among the attributes sought in a trapping system are low cost, sensitivity to and specificity for the target species and user convenience.
Chapter
Our perceptions of the maneuvers and sensory inputs that animals employ to locate a stimulus have undergone continued refinement and reformulation following the efforts of Loeb (1918) and Kühn (1919) to classify orientation mechanisms. The adduction that the principal mechanism of ‘long-distance’ flying orientation to an airborne chemical stimulus in the wind is an optomotorguided, chemically-induced, upwind orientation (or anemotaxis) has gained wide acceptance as a considerable body of experimental evidence in support of this mechanism has accumulated, principally with moth attraction to upwind pheromone sources. Besides optomotor anemotaxis, a number of alternative tactics have been proposed; these strategies have posited the existence of either spatial or temporal distributions of chemical stimulus that, if recognized, could serve as cues to guide the responder toward the chemical source or, if not to supply cues as to its direction, at least provide information as to its proximity. But our current understanding of the ‘instantaneous’ structure of a chemical stimulus emanating from a point source in continual or intermittent wind is imperfectly developed (see Elkinton and Cardé, Chapter 3) and this limits our ability to hypothesize intelligently on alternatives to the upwind anemotaxis paradigm.
Chapter
It is now more than 30 years since Dethier (1947) remarked that “no one attractant alone performs the service of guiding an insect to its proper host-plant, food or mate, and that the desired end is achieved only by a complex array of stimuli, such as chemical, light, temperature and humidity, acting in harmony.” Even so, it is doubtful whether the full complexity of the stimuli involved has yet been envisaged. Thus, just as sex pheromones are sometimes mixtures of olfactory stimuli, whose relative proportions can vary in space, time, and from population to population, the same is also true of the visual and olfactory stimuli used by insects in host-plant finding (Finch, 1977, 1980; Miller and Strickler, 1984; Miller and Harris, 1985).
Article
The transfer of chemical information from an emitting to a receiving organism can occur directly by way of contact chemoreception or by dispersion through a transport medium. In this chapter we focus on transport of odor signals in the air. The various mathematical models discussed here have been used to describe the dispersion of pheromones in still air (Bossert and Wilson, 1963; Mankin et al., 1980a) or moving air (Wright, 1958; Bossert and Wilson, 1963; Aylor et al., 1976; Miksad and Kittredge, 1979; Fares et al., 1980). They can be applied to the dispersion of any airborne odor such as plant volatiles inducing host finding. An understanding of odor dispersion is requisite for an accurate interpretation of odor-induced behaviors. (See Bell, Chapter 4, and Cardé, Chapter 5).
Chapter
During the dramatic growth in research on insect sex pheromones over the past 10 years, it has been demonstrated that both the chemical signal and the precopulatory behaviors exhibited by males and females are much more complex than originally thought. Chemical studies of sex pheromones have shown that, with few exceptions, females release a blend of several chemical components in a specific ratio and release rate. This specificity of the chemical signal is in part a result of the behavioral reactions of males under “natural” conditions: flight through space from a distance of several meters or more in shifting wind fields. Upwind progress in the plume of chemicals continues if the blend is that of a conspecific female, and the maintenance of contact with the plume is one of the most complex behavioral responses, involving visual feedback, a chemically modulated self-steered program of zigzags, and changes in linear velocity of flight, all performed as the insect samples the odor environment sequentially (Kennedy, 1983;Kuenen and Baker, 1983).
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Specific mate recognition system (SMRS) described by Paterson is an important factor in species characterization. In this context, study of Lepidoptera species complex is interesting. In Kenya, genus Busseola is represented by three species. B. fusca is an interesting case of a practically complete shift from wild compartment to cultivated area whereas B. phaia and B. segeta are likely to be an example of host fidelity. B. phaia and B. segeta share their range with B. fusca, but are separated from each other by the Rift valley and host-plants. B. phaia and B. segeta are very close related by taxonomy criteria. We studied these taxa through chemical ecology and phylogenetic approaches. Genetic diversity observed in B. fusca populations is not correlated with SMRS variability. In B. phaia and B. segeta, the study of SMRS led to the characterization of the reproductive isolation components. The phylogenetic analysis combined with chemical ecology contributed to make different assumptions on the species status of B. phaia and B. segeta.
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Animals need to discriminate differences in spatiotemporally distributed sensory signals in terms of quality as well as quantity for generating adaptive behavior. Olfactory signals characterized by odor identity and concentration are intermittently distributed in the environment. From these intervals of stimulation, animals process odorant concentration to localize partners or food sources. Although concentration-response characteristics in olfactory neurons have traditionally been investigated using single stimulus pulses, their behavior under intermittent stimulus regimens remains largely elusive. Using the silkmoth (Bombyx mori) pheromone processing system, a simple and behaviorally well-defined model for olfaction, we investigated the neuronal representation of odorant concentration upon intermittent stimulation in the naturally occurring range. To the first stimulus in a series, the responses of antennal lobe (AL) projection neurons (PNs) showed a concentration dependence as previously shown in many olfactory systems. However, PN response amplitudes dynamically changed upon exposure to intermittent stimuli of the same odorant concentration and settled to a constant, largely concentration-independent level. As a result, PN responses emphasized odorant concentration changes rather than encoding absolute concentration in pulse trains of stimuli. Olfactory receptor neurons did not contribute to this response transformation which was due to long-lasting inhibition affecting PNs in the AL. Simulations confirmed that inhibition also provides advantages when stimuli have naturalistic properties. The primary olfactory center thus functions as an odorant concentration differentiator to efficiently detect concentration changes, thereby improving odorant source orientation over a wide concentration range. Copyright © 2014 the authors 0270-6474/14/3416581-13$15.00/0.
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Insects flying in a horizontal pheromone plume must attend to visual cues to ensure that they make upwind progress. Moreover, it is suggested that flying insects will also modulate their flight speed to maintain a constant retinal angular velocity of terrestrial contrast elements. Evidence from flies and honeybees supports such a hypothesis, although tests with male moths and beetles flying in pheromone plumes are not conclusive. These insects typically fly faster at higher elevations above a high-contrast ground pattern, as predicted by the hypothesis, although the increase in speed is not sufficient to demonstrate quantitatively that they maintain constant visual angular velocity of the ground pattern. To test this hypothesis more rigorously, the flight speed of male oriental fruit moths (OFM) Grapholita molesta Busck (Lepidoptera: Tortricidae) flying in a sex pheromone plume in a laboratory wind tunnel is measured at various heights (5–40 cm) above patterns of different spatial wavelength (1.8–90°) in the direction of flight. The OFM modulate their flight speed three-fold over different patterns. They fly fastest when there is no pattern in the tunnel or the contrast elements are too narrow to resolve. When the spatial wavelength of the pattern is sufficiently wide to resolve, moths fly at a speed that tends to maintain a visual contrast frequency of 3.5 ± 3.2 Hz rather than a constant angular velocity, which varies from 57 to 611° s−1. In addition, for the first time, it is also demonstrated that the width of a contrast pattern perpendicular to the flight direction modulates flight speed.
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The Sutton and more recent Gaussian plume models of atmospheric dispersion were used to estimate downwind concentrations of pheromone in a deciduous forest. Wind measurements from two bivane anemometers were recorded every 12 sec and the pheromone was emitted from a point source 1.6 m above ground level at known rates. The wingfanning response of individually caged male gypsy moths (Lymantria dispar) at 15 sites situated 20 to 80 m downwind was used to monitor when pheromone levels were above threshold over a 15-min interval. Predicted concentrations from these Gaussian-type models at locations where wing fanning occurred were often several orders of magnitude below the known behavioral thresholds determined from wind tunnel tests. Probit analyses of dose-response relationships with these models showed no relationship between predicted dose and actual response. The disparity between the predictions of concentration from these models and the actual response patterns of the male gypsy moth in the field was not unexpected. These time-average models predict concentrations for a fixed position over 3-min or longer intervals, based upon the dispersion coefficients. Thus the models estimate pheromone concentrations for time intervals appreciably longer than required for behavioral response.
Article
The response of individual male turnip mothsAgrotis segetum was observed in a sustained flight tunnel to a mixture of decyl acetate, (Z)-5-decenyl acetate, (Z)-7-dodecenyl acetate, and (Z)-9-tetradecenyl acetate in proportions similar to those found in gland extracts from virgin females (0.6: 1:5:2.5). Lures containing 3-30 μg (Z)-5-decenyl acetate proved to be maximally attractive, with approximately 60% of the males completing all behavioral steps from activation to copulation efforts. A 300-μg dosage caused significant arrestment of upwind flight. Peak response to synthetics, however, was significantly lower than to female glands. Omitting decyl acetate from the blend did not affect the activity, while omission of any of the three monounsaturated acetates caused a dramatic decrease in response. In the field maximum trap catches were achieved with 1- to 30-μg lures. The subtractive assay carried out in the field confirmed the neutrality of decyl acetate and the importance of the three monoenes. Adding 1% of (Z)-8-dodecenyl acetate (earlier reported as an "inhibitor") to the four-component mixture decreased the trap catch to about 50%, and increasing the amount of (Z)-8-dodecenyl acetate to 27% decreased the activity further to about 10%. (Z)-8-Dodecenyl acetate also decreased the number of successful flights in the flight tunnel.
Article
In the present study male redbanded leafroller (Argyrotaenia velutinana), cabbage looper (Trichoplusia ni), and Oriental fruit moths, (Grapholita molesta), were tested in a flight tunnel to (1) the major pheromone component, (2) theZ/E pheromone component mixtures for Oriental fruit moth and redbanded leafroller, (3) and the female-released blends, over a series of dosages. Experiments were designed to test the hypothesis that male response downwind of a female is initiated by the major component and that minor components function only to elicit behaviors close to the female during close-range approach and courtship. The results did not support this hypothesis, but rather showed that males initiated upwind flight in significantly higher percentages to the complete blends of components, at all dosages, compared to single components or partial blends. Addition of minor components also signficantly enhanced male perception of the major component at lower dosages, resulting in completed flights to dosages of the major component that alone did not elicit any upwind flight. Our results support the concept that minor components function to enhance male sensitivity to the pheromone, and the specificity of the signal. Our results also support the hypothesis that the active space of the pheromone is a function of the upper and lower concentration thresholds for the blend of components, and not simply for the major component.
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The responses of male western spruce budworm moths,Choristoneura occidentalis Freeman, to a range of concentrations of the major sex pheromone, 92∶8 (E/Z)-11-tetradecenal (Ald), in polyvinyl chloride lures, were observed using the electroantennogram technique, a flight tunnel, and field-trapping bioassays. The responses to virgin female moths were also observed in the flight tunnel and field bioassays. The moths were from three strains: a nondiapausing laboratory colony; field-collected wild budworm; and laboratory-wild crosses. The mean peak amplitude of antennal response and the time required for the electroantennogram signal to return to the baseline after stimulation (lag) increased with Ald concentration in both laboratory and wild moths. However, at Ald concentrations of 0.005% and greater, the lag period of the wild male's antennae was significantly shorter than that of the laboratory male's. The mean number of moths caught in the field in delta sticky traps increased with Ald concentration, but the number of moths caught per trap was not significantly different between concentrations of 0.005 % and 0.5 %. The threshold concentration required to elicit upwind flight in the flight tunnel was between 0.0005 and 0.005% Ald; peak response occurred to 0.05 % Ald but was not significantly different from that to 0.005 % or 0.5% Ald. Moths from all three populations significantly reduced their net upwind groundspeed as they approached the pheromone lure. When pheromone concentration was increased, the net upwind groundspeed of laboratory and lab-wild moths, but not wild moths, was significantly reduced between 2 m and 1 m downwind from the pheromone lure. The three populations of moths differed significantly in the percentage of wing-fanning and copulatory attempts, and in the net upwind groundspeed of flight from 2 m to 1 m downwind from the lure.
Article
The behavior of male western spruce budworm moths,Choristoneura occidentalis Freeman, was observed in a flight tunnel in response to virgin females and synthetic sex pheromone components, alone and in blends. Pheromone blends were also compared in the field using sticky trap bioassays. Pheromones were incorporated into small rods of polyvinyl chloride. The blend of 92∶8 (E/Z)-11-tetradecenal-89∶11 (E/Z)-11-tetradecenyl acetate-85∶15 (E/Z)-11-tetradecenol (Ald∶Ac∶OH) that approximated that released from a virgin female moth elicited levels of response similar to those elicited by the female. This blend induced a significantly greater percentage of moths to fly upwind and land at the lure than did the Ald lure. In contrast to the flight-tunnel bioassays, the numbers of moths caught in Ald-baited sticky traps in the field were not significantly increased by the addition of Ac and OH lures. The net upwind groundspeed of flight in response to the 0.05% Ald lure was lower than that in response to the virgin females and was significantly increased by the addition of Ac + OH lures in two of three bioassays. The flight-tunnel bioassays support the hypothesis that the natural blend of major (Ald) and minor (Ac + OH) components stimulates the precopulatory behavior of western spruce budworm male moths at long range (> 1 m downwind) as well as at close range.
Article
Mature female apple maggot flies,Rhagoletis pomonella (Walsh), were released individually onto a single potted, fruitless hawthorne tree in the center of an open field. The tree was surrounded by four 1-m(2) plywood host tree models painted green or white, with or without synthetic host fruit odor (butyl hexanoate), and placed at one of several distances from the release tree. Each fly was permitted to forage freely on the release tree for up to 1 hr, or until it left the tree. Flies left the tree significantly sooner when green models with host fruit were present at 0.5, 1.5, or 2.5 m distance from the release tree than when these models were placed at a greater distance (4.5 m) from the release tree or when no models were present. Flies responded detectably to 1-m(2) models without odor up to a maximum distance of 1.5 m. These results suggest that female apple maggot flies did not detect green 1-m(2) models with odor 4.5 m away or models without odor 2.5 m or more away. Flies responded to white models with and without odor to a much lesser extent, both in terms of response distance and flight to and alightment upon models. Increasing model size to 2 m(2) increased the distance to 2.5 m at which flies responded to green models without odor. Decreasing model size to 0.5 m(2) reduced fly responsiveness to green or white models. The presence of host fruit odor alone, without the visual stimulus of a green model, did not influence residence time on the release tree.
Article
Male Oriental Fruit Moths (Grapholita molesta) flew faster toward a pheromone source as they flew higher above striped and dotted floor patterns. The moths significantly (P < 0.05) increased their ground speed over floor patterns of transverse stripes or pseudo randomly placed dots. The moths’ track angles (flight path angle off the windline) decreased significantly (P < 0.05) when they flew 40 cm above the floor patterns vs. flight at 10 cm up, and they tended to steer more upwind flight (smaller course angles) at the upper, 40 cm, height compared to 10 cm up. Turn frequencies and reversal distances across the wind line were also affected by dot density. However, the interaction of small changes in flight speed, course angle, turn widths and turn frequencies are difficult to assess; I have subsumed all their affects into a simple measure of “total distance” flown by the moths by summing the length of all flight vectors analyzed for the other metrics, but no differences were found. By far, the largest change in flight was the positive orthokinetic response to increased flight height above both striped and dotted floor patterns (Fig. 2; P < 0.05), and nearly all other changes appear to be entirely due to faster moth flight with little or no changes in steering or turning patterns.
Article
Attractant-mediated behaviour of male larch casebearer moths, Coleophora laricella Hbn., was studied on field populations in Central Europe. Defined behavioural actions towards synthetic (Z)-5-decen-1-ol (Z5–10:OH) were observed under varying environmental conditions and a hierarchical sequence of responses was established. “Activation” of resting males, followed by initiation of long-range upwind flight, was seen as far as 30 m downwind from a 100 μg source of Z5–10:OH. These flights were strongly guided by visual cues (tree silhouettes) and continued at very low wind speeds (0.05 m/s) but ceased during winds of > 1 m/s. At a few meters from the odour source, the flight tracks began to show strong lateral and vertical excursions, which gradually narrowed in (arrestment flight). Landing responses near the attractant source were again guided by visual cues, which were found to be not host-specific. In contrast, following landing, extensive locomotion of the males around the attractant dispenser occurred on green twigs of larch only. This “searching” of spur-shoots was also seen in the vicinity of calling females. Luring capacities of single C. laricella females were in the order of 0.1 μg of the synthetic attractant. The possibility of far-range signals arising from synchronous calling of numerous females on densely-populated branches is considered. Verhaltensantworten von Coleophora laricella-Männchen auf den synthetischen Sexuallockstoff (Z)-5-Decenol im Feld An zentraleuropäischen Wildpopulationen der Lärchenminiermotte Coleophora laricella Hbn. wurden lockstoffinduzierte Verhaltensweisen männlicher Falter untersucht. Es wurden definierte Antwortmuster auf synthetisches (Z)-5-decen-1-ol (Z5–10:OH) unter wechselnden Umweltbedingungen beobachtet und eine hierarchische Sequenz von Verhaltensschritten festgelegt. Noch 30 m windabwärts einer Quelle von 100 μg Z5–10:OH, aktivierte” der Lockstoff ruhende Männchen. Die anschließenden Gegenwindanflüge wurden stark von visuellen Reizen (Baumsilhouetten) beeinflußt. Diese Flüge dauerten auch bei sehr geringen Windbewegungen (0.05 m/s) noch an, kamen dagegen bei Windgeschwindigkeiten von > 1 m/s zum Erliegen. Im Abstand einiger Meter von der Duftquelle zeigte die Flugbahn starke laterale und vertikale Auslenkungen, die sich kontinuierlich verengten (Landeanflug). Auch die Landereaktion nahe der Lockstoffquelle wurde stark von visuellen Auslösern gesteuert. Während sich diese als nichtwirtsspezifisch erwiesen, zeigten die Männchen nur an grünen Lärchenzweigen die typische starke Laufaktivität um den Lockstoffträger. Dieser, Nadelsuchlauf” war auch im Nahbereich lockender Weibchen zu sehen. Die Lockwirksamkeiten einzelner C. laricella-Weibchen lagen im Bereich von nur 0.1 μg des synthetischen Z5–10:OH. Die Möglichkeit einer konzertierten Wirkung der Duftsignale zahlreicher benachbarter Weibchen wird erwogen.
Article
Six pheromone trap designs, including five high-capacily and a sticky trap, and four PVC lure concentrations of pheromone were evaluated for monitoring blueberry leaftier populations in six blueberry fields in Nova Scotia. Larval densities and subsequent male moth catches in the same year for all the trap designs evaluated, except double funnel traps, were highly correlated. Multipher III traps captured the highest number of moths, followed by Unitraps and double funnel traps. The ice cream container trap captured significantly fewer moths than any other trap design. At most locations, the first moth was caught on the same day in all the trap designs except the ice cream container trap. Trap catches increased with increasing pheromone concentration up to 0.03% dose. Traps baited with 0.3% lures captured significantly fewer moths than those with 0.003% or 0.03%. Based on mean trap catches, R2 values, coefficients of variation among traps, trap efficiency, and lure evaluations, the Unitraps baited with 0.003% lures are selected for further development of a population monitoring system for blueberry leaftier moths. The Multipher III traps baited with 0.03% lures captured up to 44 000 male moths (mean per trap per season) at high densities, demonstrating their potential in mass trapping blueberry leaftiers.
Article
Sex pheromone traps for Argyrotaenia pulchellana Haw. (Lep. Tortricidae) were loaded with two low pheromone doses (0.1 and 0.01 mg) and tested in apple and pear orchards of northern Italy's Emilia-Romagna Region to estimate the relationship between male catches and subsequent larval infestation. While the lower dose captured fewer males, it registered an enhanced correlation to larval populations and a decrease in the number of episodes of high catches associated with no infestation. In all likelihood, the pheromone traps baited at the lower dose have a smaller active space and captured only males within the orchard. Lures with 0.01 mg of pheromone can be replaced every 6 weeks, just as the 1 mg lures now in widespread use in Italy. A threshold of 65 adults captured from the beginning of flight is proposed for the Emilia-Romagna IPM project.
Article
A model is presented that describes the average resultant track of a population of male pea moth, Cydia nigricana (F.), flying through a crop to a continuously emitting pheromone trap containing 100 mu g (E,E)-8,10-dodecadien-1-yl acetate. This model, based on work by C. T. David, J. S. Kennedy, A. R. Ludlow, J. N. Perry and C. Wall J. chem. Ecol. 8, 1207 (1982), and modified for the effect of a crop, has particular reference to a line of interacting pheromone traps equally spaced along the mean wind direction at an emergence site. It is derived after extensive field observations. The model relates to the average flight behaviour of a population of moths, and is compatible with both the anemotactic theory and a system of integrated anemotaxis and longitudinal chemo-klinotaxis. We give two theoretical reasons and cite observational evidence which suggest that, within a wheat crop, a discrete plume breaks up at around 10-15 m from the source and that beyond this distance pheromone exists at a non-zero concentration at all downwind positions. Close to the source moths are assumed to respond to a discrete plume as described by David et al. (1982) and further from it to receive pheromone continuously and fly, on average, upwind. Because of the effects of the crop we suggest that equations of atmospheric diffusion derived to predict time-averaged concentrations of pheromone may hold instantaneously. The average behaviour of a population of responding moths under these conditions is discussed. Far from the source there is a concentration of pheromone below which such moths sampling it are assumed not to respond; this is termed the threshold concentration and the positions where it occurs are termed the threshold contour. The contour is sketched for single and multiple sources. Such moths flying upwind to this contour are assumed to stop and then cast (move in a crosswind direction). This results in the moths either moving inside the contour to a region of concentration above the threshold, and resuming upwind flight, or moving outside the contour and, eventually, not responding further. Net movement in the former is therefore towards the source and such moths may eventually be caught. The model allows for random flight by non-responding moths outside the threshold contour, and for moths to `lose' the discrete plume of one source and continue upwind flight to encounter that of the next source upwind. The model has ten parameters, five relate directly to moth flight behaviour, one to the degree of random flight, one to meteorological conditions, two describe the number and spacing of traps and the last governs numerical accuracy. Predictions from the model of proportional catch in each of a line of traps were made using a computer program. An extensive body of 406 sets of data concerning trap interactions was collected over six years and the model provided excellent fits to this data. Throughout this paper the model is described in biological terms, formulae are provided when necessary.
Article
One of the most interesting aspects of coevolution deals with the interrelationship between the 250,000 odd species of flowering plants and the perhaps 500,000 species of insects that are associated with them in various ecosystems. These coevolutionary relationships began in the early Carboniferous period when land plants first began to diversify and insects began to diversify into modern orders. Chemical ecology lies at the interface between these two enormous groups of very different life forms. There are perhaps 100,000 different secondary plant compounds: terpenoids, alkaloids, phenyl propanoids, esters, acids, alcohols, ketones, and aldehydes produced in the chemical factories of the plant kingdom, and the great preponderance of these act as allomones, kairomones, and synomones in regulating and controlling ecology at the plant‐insect interface. This review will explore current knowledge in this area, with emphasis on the chemical communications involved between these two great groups of life forms. Discussion will be directed at the basic principles of chemical communication from emission of the chemical messenger, to receptor organs, and to the chemotactic responses that result.
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