Odor Lure Research Articles

Two sticky traps baited with synthetic host odors to capture Triatoma infestans, an important vector of Chagas disease

Chagas disease is a vector-borne disease caused by Trypanosoma cruzi, which is transmitted by triatomine insects. Triatoma infestans is one of the main vectors. Efforts to eliminate T. infestans have often failed in the Gran Chaco, the largest endemic area of this species. Known methods for assessing triatomine house infestation include timed-manual collections by skilled personnel, bug notifications by householders’ and/or non-baited detection devices. However, the detection sensitivity of those methods needs to be improved, especially when the bugs are present at low densities. In this work we design and evaluate the performance of two types of sticky traps (pitfall and climbing traps), when baited with a synthetic host odor lure, to capture T. infestans nymphs within an experimental box under semi-controlled laboratory conditions. Nine assays were conducted for each type of trap using a different experimental box per type of trap design and per treatment. These treatments were: test (T, trap baited with the synthetic lure), positive control (C+, trap baited with a mouse) and negative control (C−, empty trap). One hundred percent of the sticky pitfall and 89% of the climbing traps baited with the synthetic lure captured at least one insect. Moreover, the sticky pitfall trap and the sticky climbing trap, both baited with the synthetic lure, captured 30% and 40% of the insects in a single night, respectively. In both cases, the trap with the synthetic lure captured significantly more insects than the non-baited trap. However, the synthetic lure could be improved, as the traps with this lure captured significantly less insects than the traps with a live host. In summary, the two types of synthetically-baited traps tested were able to capture T. infestans nymphs, indicating that both designs are effective under the laboratory experimental conditions and insect abundance used in this work. These traps deserve to be tested in a field setting.

Rodent odour bait: A new bumble bee conservation tool to enhance nest box occupancy

Abstract Bumble bee conservation focuses on supplementing floral resources. Yet, nesting site availability is linked to bumble bee abundance. As a supplement to natural nest sites, nest boxes could be deployed and baited with synthetic lures. As queen bumble bees reportedly establish colonies in abandoned rodent burrows, we hypothesized (1) that queen bumble bees sense, and behaviourally respond to, rodent odour, and (2) that lures of synthetic rodent odour can guide spring queens to nest boxes. We collected headspace odorants from bedding soiled with urine and faeces of house mice, Mus musculus, and identified the 10 odorants that elicited responses from queen antennae. To field‐test attraction of queens to mouse excreta odorants, we tree‐mounted paired nest boxes in florally rich locations, and assigned clean and soiled bedding, respectively, to one box in each pair. Queens established colonies in 17 mouse‐scented boxes and in six unscented boxes. This 43% occupancy rate of mouse‐scented boxes represents a significant improvement over the 10% occupancy rate common for unscented boxes. In a further field experiment, we baited one box in each pair with a synthetic mouse odour lure and found that queens established colonies in 13 baited boxes and in six unbaited control boxes. Specifically, Bombus mixtus established seven colonies in baited boxes and only one colony in an unbaited box. With this proof‐of‐concept that synthetic lures can guide queens to nest boxes, we anticipate that bumble bee conservation programs will soon be able to offer both expanded floral resources and baited nest boxes readily detectable by queens.

Distance from human dwellings differentially affects the efficacy of a synthetic cattle urine odour lure to trap malaria vectors

BackgroundCost–effective outdoor–based devices for surveillance and control of outdoor mosquito vector populations can substantially improve their efficacy when baited with synthetic human and animal odours. This study aimed at assessing the dose–dependent efficacy of a previously developed synthetic cattle urine odour to lure malaria vectors, and other mosquito species, to traps placed at different distances from human dwellings outdoors.MethodsThe efficacy of the cattle urine odour lure was assessed through a 5 × 5 Latin square design, using two sets of 5 Suna traps placed at either 1.5 m or 5 m from an adjacent human dwelling, in the rural village of Sagamaganga, Tanzania. Each trap was deployed with one of four doses of the synthetic cattle urine odour blend or a solvent control (heptane). Traps were rotated daily so that each dose and control visited each position twice over a period of 20 experimental nights. The relative attractiveness of each treatment dose and control was compared using a generalized linear mixed model for each species caught.ResultsA total of 1568 mosquitoes were caught, of which 783 were anophelines and 785 were culicines. Of the anophelines, 41.6 and 58.3% were primary and secondary vector species, respectively. Unfed and fed females of the primary vector, Anopheles arabiensis, were caught dose–dependently, close to human dwellings (1.5 m), whereas unfed, fed and gravid secondary vector Anopheles pharoensis females were caught dose–dependently, but at a farther distance from the dwellings (5 m). Females of Culex spp. were caught dose–dependently in similar numbers irrespective of the distance from human dwellings.ConclusionsThis study further clarifies the factors to be considered for the implementation of outdoor trapping using the synthetic cattle urine lure to target exophilic and exophagic malaria vectors, for which efficient surveillance and control tools are currently lacking. The findings resulting from this study make significant progress in providing the needed information to overcome the regulatory obstacles to make this tool available for integrated vector management programs, including registration, as well as evaluation and regulation by the World Health Organization.

A Synthetic Blend of Fruit and Live Yeast Odours Shows Promise for Trapping Mated Female Queensland Fruit Fly, Bactrocera tryoni, in the Field.

Tephritid fruit flies are major horticultural pests of fruit and vegetable crops. Developing an odour lure that can attract mated female flies under field conditions has presented a major challenge to chemical ecologists around the globe. We have designed a new lure to attract female Queensland fruit fly, Bactrocera tryoni, based on the knowledge that this pest tephritid is attracted not only to odours from ripening fruits, but also to odours of symbiotic (gut-associated) yeasts on which the larvae feed. Initial field trials screened four volatile mixtures, each containing a base mix of three, short-chain "fruit ripening" esters and differing in the addition of long-chain "fruity" esters and / or alcohols produced by live yeasts. Results demonstrated that the lure formulated from short-chain esters and live yeast alcohols attracted the most female flies, with significantly higher catches than an odourless control trap, and a protein-baited trap. As electrophysiological studies exploring peripheral responses in tephritids to alcohols associated with fermentation have not been extensively investigated, we conducted this work on both the antennae and maxillary palps, and discovered that three yeast alcohols were detected by both sensory organs. Performance trials conducted in pome fruit and stone fruit orchards evaluated the six-component blend of short-chain ester and live yeast alcohol lure against a commercially available synthetic fruit-odour lure and a protein-based lure. In the apple orchard, the new lure caught significantly more female flies, and in particular mated females, compared to the commercially available lures. In the stone fruit orchard, while the new lure again caught the most mated female flies compared to the other lures, differences were not significant. The visual stimulus (trap design) used had a significant effect on capture, with a Ladd trap (red sphere on a yellow panel) being considerably more effective than the other traps. We discuss the implications of this study, including why the degree of effectiveness of the new lure might have differed among the test orchards (citrus, apple, stonefruit), and why yeast odours might increase attractiveness to "ripening fruit" volatile blends under field conditions.

Optimising targets for tsetse control: Taking a fly's-eye-view to improve the colour of synthetic fabrics.

The savannah tsetse flies, Glossina morsitans morsitans and G. pallidipes, are important vectors of Rhodesian human African trypanosomiasis and animal African trypanosomiasis in East and southern Africa. We tested in Zimbabwe whether robust, synthetic fabrics, and innovative fly’s-eye-view approaches to optimise fabric colour, can improve insecticide-treated targets employed for tsetse control. Flies were caught by electrocution at a standard target comprising a 1m x 1m black cotton cloth panel with 1m x 0.5m black polyester net panels on each side. Catches were subdivided by species and sex. Tsetse catches were unaffected by substitution of the black cotton with a blue polyester produced for riverine tsetse targets. Exchanging the net panels for phthalogen blue cotton to simulate the target routinely used in Zimbabwe significantly reduced catches of female G. m. morsitans (mean catch 0.7 times that at standard), with no effect on other tsetse catches. However, significantly greater proportions of the catch were intercepted at the central panel of the Zimbabwe (means 0.47–0.79) versus standard designs (0.11–0.29). We also engineered a new violet polyester cloth using models of tsetse attraction based upon fly photoreceptor responses. With and without odour lure, catches of females of both species at the violet target were significantly greater than those at standard (means 1.5–1.6 times those at standard), and typical blue polyester targets (means 0.9–1.3 times those at standard). Similar effects were observed for males under some combinations of species and odour treatment. The proportions of catch intercepted at the central panel of the violet target (means 0.08–0.18) were intermediate between those at standard and typical blue polyester. Further, the reflectance spectrum of violet polyester was more stable under field conditions than that of black cotton. Our results demonstrate the effectiveness of photoreceptor-based models as a novel means of improving targets to control tsetse and trypanosomiases.

Evaluating synthetic odours and trap designs for monitoring Anopheles farauti in Queensland, Australia

BackgroundMonitoring of malaria vectors is important for designing and maintaining effective control interventions as changes in vector-feeding habits can threaten the efficacy of interventions. At present, human landing catches remain the most common method for monitoring malaria vectors of the Anopheles punctulatus complex, including the Anopheles farauti group. The aims of this study were to evaluate the efficacy of different lures and fan-powered traps, including an odour blend that has been demonstrated to be attractive to African anophelines, in Queensland, Australia.MethodsTo evaluate the performance of different lures in trapping An. farauti in the field, four Suna traps were baited with either: CO2-alone, a synthetic lure (MB5 or BG-Lure) plus CO2, or a human odour plus CO2 and set in the field in Cairns, eastern Australia. A second study evaluated the performance of four traps: a Passive Box trap, BG-Suna trap, BG-Sentinel 2 trap, and BG-Bowl trap, for their ability to trap An. farauti using the best lure from the first experiment. In both experiments, treatments were rotated according to a Latin square design over 16 nights. Trapped mosquitoes were identified on the basis of their morphological features.ResultsBG-Suna traps baited with CO2 alone, a BG-Lure plus CO2 or a natural human odour plus CO2 captured comparable numbers of An. farauti. However, the number of An. farauti sensu lato captured when the MB5 lure was used with CO2 was three times lower than when the other odour lures were used. The BG-Sentinel 2 trap, BG-Suna trap and BG-Bowl trap all captured high numbers of An. farauti, when baited with CO2 and a BG-Lure. The morphological condition of captured mosquitoes was affected by mechanical damage caused by all fan-powered traps but it was still possible to identify the specimens.ConclusionsThe BG-Sentinel 2 trap, BG-Suna trap and the BG-Bowl trap captured high numbers of An. farauti in the field, when equipped with CO2 and an odour lure (either the BG-Lure or a natural odour). The most important attractant was CO2. This study shows that fan-powered traps, baited with CO2 plus an appropriate odour lure, can be a promising addition to current vector monitoring methods in the Southwest Pacific.

Υellow sticky rectangle with ammonium acetate slow-release dispenser: an efficient long-lasting trap for Dacus oleae

The combination of a yellow color sticky rectangle with an ammonium acetate slow-release dispenser (YAA) was compared to a yellow sticky rectangle (Y) and to a McPhail glass trap with BuminalTM(MB), EntomozylTM(ME), or ammonium sulfate (MAS) odor lure in a 2% water solution, from the beginning of August till December in an olive grove. When total olive fruit fly, Dacus oleae (Gmelin) (Diptera: Tephritidae), captures were compared, no large differences were detected among YAA, MB and ME traps, while Y and MAS ones were found much inferior. When expressed as a ratio to YAA, total captures were: 1 (YAA), 0.95 (MB), 0.70 (ME), 0.33 (Y) and 0.08 (MAS). In the fall (high population density), both yellow traps showed very high catches, while McPhail odor traps had comparatively reduced effectiveness, apparently due to cool humid weather. The opposite was true in August-September (hot dry weather, low population density). McPhail traps were serviced every 5 days (summer) or 7 days (fall), while YAA and Y traps were replaced by new ones only once, at the beginning of October. The am­monium acetate dispenser could last much longer but traps had been covered by insects and debris.

Comparison of natural and artificial odor lures for nilgai (Boselaphus tragocamelus) and white-tailed deer (Odocoileus virginianus) in South Texas: Developing treatment for cattle fever tick eradication.

Cattle fever ticks (CFT), vectors of bovine babesiosis and anaplasmosis, were eradicated from the United States by 1943, but are frequently reintroduced from neighboring border states of Mexico via stray cattle and wildlife hosts including white-tailed deer (Odocoileus virginianus) (WTD) and nilgai antelope (Boselaphus tragocamelus). Nilgai antelope are exotic bovids from India that are hosts of CFT, have large home ranges as compared to WTD, thus have the potential to spread CFT through the landscape. Currently, there are no methods to control CFT on nilgai. Odor lures were evaluated to determine if nilgai could be attracted to a central point for development of control methods. Four treatments, nilgai offal a natural odor lure was used as the positive control; and compared to three artificial odors; screw worm lure, volatile fatty acids, citronella oil. Studies were conducted on a free-ranging population of nilgai at the East Foundation's Santa Rosa Ranch (Kenedy Co., near Riviera, Texas, USA). Game cameras were used to document visitation to the lures. In the ten randomly placed transects, 110 nilgai and 104 WTD were photographed. Offal had significantly more visits by nilgai (71% of total visits) than screwworm (15%), VFA (11%), and citronella (4%). For WTD, there was no significant difference in visitation at the lure treatments.

A CO2-Free Synthetic Host-Odor Mixture That Attracts and Captures Triatomines: Effect of Emitted Odorant Ratios.

Triatomines, vectors of Chagas Disease, are hematophagous insects. Efforts have been made to develop synthetic attractants based on vertebrate odor-to lure them into traps. However, because those lures are not practical or have low capture efficiency, they are not in use in control programs. Therefore, more work is needed to reach a practical and efficient odor lure. Recently, a three-component, CO2-free, synthetic blend of vertebrate odor (consisting of ammonia, l-(+)-lactic acid, and hexanoic acid), known as Sweetscent (Biogents AG, Regensburg, Germany), was shown to attract and capture triatomines in the laboratory. In this study, using a trap olfactometer and an odor blend with constituents similar to those of Sweetscent (delivered from low-density polyethylene sachets) we found that the odorant ratios of the mixtures have a strong effect in the capture of triatomines. The blend with the most efficient combination of odorant ratios evoked ca. 81% capture in two relevant triatomine species. In the case of the most effective odor mixtures, we measured the odor mass emission for the three components of the mixture and therefore were able to estimate the odorant ratios emitted that were responsible for such a high capture performance. Thus, in those mixtures, pentanoic acid was the main component (ca. 65 %) followed by ammonia (ca. 28%) and, l(+)-lactic acid (ca. 7 %). Our results are encouraging as efficient, practical, and cheap odor baits to trap triatomines in the field would be within reach. The odor-delivery system used should be improved to increase stability of odor emission.

Development and evaluation of a novel contamination device that targets multiple life-stages of Aedes aegypti.

BackgroundThe increasing global threat of Dengue demands new and easily applicable vector control methods. Ovitraps provide a low-tech and inexpensive means to combat Dengue vectors. Here we describe the development and optimization process of a novel contamination device that targets multiple life-stages of the Aedes aegypti mosquito. Special focus is directed to the diverse array of control agents deployed in this trap, covering adulticidal, larvicidal and autodissemination impacts.MethodsDifferent trap prototypes and their parts are described, including a floater to contaminate alighting gravid mosquitoes. The attractiveness of the trap, different odor lures and floater design were studied using fluorescent powder adhering to mosquito legs and via choice tests. We demonstrate the mosquitocidal impacts of the control agents: a combination of the larvicide pyriproxyfen and the adulticidal fungus Beauveria bassiana. The impact of pyriproxyfen was determined in free-flight dissemination experiments. The effect on larval development inside the trap and in surrounding breeding sites was measured, as well as survival impacts on recaptured adults.ResultsThe developmental process resulted in a design that consists of a black 3 Liter water-filled container with a ring-shaped floater supporting vertically placed gauze dusted with the control agents. On average, 90% of the mosquitoes in the fluorescence experiments made contact with the gauze on the floater. Studies on attractants indicated that a yeast-containing tablet was the most attractive odor lure. Furthermore, the fungus Beauveria bassiana was able to significantly increase mortality of the free-flying adults compared to controls. Dissemination of pyriproxyfen led to >90% larval mortality in alternative breeding sites and 100% larval mortality in the trap itself, against a control mortality of around 5%.ConclusionThis ovitrap is a promising new tool in the battle against Dengue. It has proven to be attractive to Aedes aegypti mosquitoes and effective in contaminating these with Beauveria bassiana. Furthermore, we show that the larvicide pyriproxyfen is successfully disseminated to breeding sites close to the trap. Its low production and operating costs enable large scale deployment in Dengue-affected locations.

Evaluation of a CO2-free commercial mosquito attractant to capture triatomines in the laboratory

Efforts have been made to develop vertebrate odor-based attractants to lure hematophagous triatomines into traps. However, more work is needed to reach a practical, cheap, and efficient odor lure. We carried out attraction and capture tests in a dual-choice olfactometer and a pitfall trap. Here we report that a three-component, CO2 -free, synthetic blend of vertebrate odor (consisting of ammonia, L(+) lactic acid and hexanoic acid, and known as Sweetscent®) significantly induces 3(rd) -instar Rhodnius prolixus and Triatoma infestans nymphs to fall into the test capture-tube of the olfactometer. Blend constituents presented singly or in two-component blends did not evoke a response and, therefore, we propose that the insects respond specifically to the three-component blend in a synergistic way. When tested in a pitfall trap in an experimental arena, this blend induced capture in 37.5% of the lured traps, whereas 9% of the nymphs tested were captured in a single night. No insects were captured in control traps. Our work represents a proof-of-concept regarding capture of triatomines using host odor-based, CO2 -free synthetic mixtures as lures for pitfall traps. CO2 -free lures are more practical for field work than natural or CO2 -containing synthetic blends.

Chemical ecology and insect conservation: optimising pheromone-based monitoring of the threatened saproxylic click beetle Elater ferrugineus

Elater ferrugineus is a saproxylic click beetle inhabiting old deciduous trees in Europe. It is threatened throughout its area of distribution due to habitat loss. No efficient monitoring method has been available for this species, but observed attraction of females to (R)-(+)-γ-decalactone, which is a male-produced sex pheromone of its prey, the scarab beetle Osmoderma eremita, has led to the development of an odour lure for monitoring. In addition, four esters have recently been identified from the pheromone-producing gland in female E. ferrugineus, and a blend of these esters is highly attractive to conspecific males in the field, revealing an alternative odour-based method for monitoring this species. However, no rigorous analysis has been performed to check whether all four esters show biological activity in male E. ferrugineus, and whether its own sex pheromone is a more potent lure than the prey kairomone for monitoring of E. ferrugineus. In this study, we reinvestigated the E. ferrugineus sex pheromone, using electrophysiological and behavioural analyses, and found that only one of the esters, 7-methyloctyl (Z)-4-decenoate, is active. In addition, trapping experiments revealed that 7-methyloctyl (Z)-4-decenoate is a much more efficient attractant for male E. ferrugineus than the prey pheromone is for conspecific females, or any sex of O. eremita. With a very efficient odour lure at hand, novel information about current distribution, local population sizes, and dispersal ranges in E. ferrugineus can now be obtained, which can aid in conservation efforts to protect this threatened insect and its habitat.

Sex differences in olfaction-mediated visual acuity in blowflies and its consequences for gender-specific trapping

The behaviour of 650 female Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) was examined in a wind tunnel using odour, in combination with six artificial visual stimuli, ranging from a simple black square to a three-dimensional model of a dead mouse. The carcasses of laboratory mice were used to provide a natural odour and visual source, and a blend consisting of dimethyl trisulphide, mercaptoethanol, and o-cresol was used to provide a synthetic lure. Significant differences were found in attraction to these odour sources: 90% of the flies oriented upwind to the natural source and 62% to the synthetic lure. No significant differences were found in upwind orientation towards different visual stimuli, but flies showed significantly more landings if the visual cues provided a vertical contrast against the background. A horizontal contrast gave no difference in landing rate compared to treatments without visual cues. In a field study, the blowfly genera Pollenia, Calliphora, and Lucilia were caught. The overall blowfly catch was significantly higher when an odour lure was present (Pollenia: 3×, Calliphora: 15×, Lucilia: >79×). A significant three-way interaction between visual cue, genus, and gender was found. The saprophagous Lucilia and Calliphora showed a gender-specific response to visual stimuli, whereas the parasitic Pollenia did not. A 2:1 female:male sex ratio was found for Calliphora spp. and a 12:1 sex ratio for Lucilia spp. The data suggest that landing responses of male and female saprophagous blowflies, and consequently trap catches, result from olfaction, but also from gender-specific visual responses when under the influence of odour.

Attractiveness to Anastrepha ludens (Diptera: Tephritidae) of plant essential oils and a synthetic food‐odour lure

Abstract: Experiments were conducted in a citrus orchard to investigate the attractiveness of 26 plant essential oils individually and in combination with a synthetic food odour lure to the Mexican fruit fly, Anastrepha ludens Loew. Anise, rose/grape seed, and tea tree oils were more attractive than unbaited traps but none approached the attractiveness of Advanced Pheromone Technologies’ AFF lure, a synthetic food‐odour lure that emits several nitrogenous chemicals attractive to this fly. Traps baited with most of the oils were less attractive than unbaited traps. Rose/grape seed oil and pure‐rose oil enhanced attractiveness of AFF lures to both males and females by about 68%. Grape seed oil did not enhance the attractiveness of AFF lures demonstrating that rose oil was the active component of the rose/grape seed oil. No other oil enhanced attractiveness of AFF lures and most decreased attraction to AFF lures. The possibility that highly attractive chemicals may be present in rose oil as minor components is discussed. Traps baited with the combination of clove bud oil and the AFF lure captured only 3% as many flies as traps baited only with the AFF lure indicating that clove bud oil is highly repellent to Mexican fruit flies.

Attraction of Laboratory-cultured and Wild Dacus oleae1 Flies to Sticky-coated McPhail Traps of Different Colors and Odors

Under field conditions, we compared the responses of laboratory-cultured and wild olive flies, Dacus oleae (Gmelin), to McPhail invaginated glass traps of different colors baited with different odoriferous solutions. The order of treatment preference and degree of distinction between treatments were essentially the same for all flies. A smaller percentage of released lab flies than released wild flies was recaptured, however. Olive flies arriving at a clear, odor-baited McPhail trap first landed on the trap's exterior. Some then proceeded into the interior and were captured in the solution but others flew away. Hence, the effectiveness of a clear McPhail trap baited with a 2% Rodia,® 1.5% borax solution (the most attractive odor lure tested) or a 2% ammonium sulfate solution (the standard odor lure for olive flies) could be increased about twofold and threefold, respectively, by coating the trap exterior with Bird Tanglefoot® (BT) so as to entangle all arriving flies. A BT-coated McPhail trap painted daylight fluorescent yellow (the most attractive color tested) captured more olive flies than a BT-coated clear one when both were baited with 2% ammonium sulfate or water, but not when both were baited with 2% Rodia, 1.5% borax. More Ceratitis capitata (Wiedemann) flies were captured by BT-coated yellow McPhail traps than by any others, irrespective of the nature of the odor solution.