Decreased Attraction of Anastrepha ludens to Combinations of Two Types of Synthetic Lures in a Citrus Orchard

Combinations of the previously developed attractants CEHO from host fruit aroma and AMPu from volatile metabolites of amino acids were evaluated for attractiveness to gamma-irradiated Mexican fruit flies, Anastrepha ludens, in a citrus orchard. In one experiment, McPhail traps with polyvinyl chloride (PVC) lures loaded with CEHO (10:1:1:50 mixture of 1,8-cineole, ethyl hexanoate, hexanol, and ethyl octanoate) were more attractive than blank traps. McPhail traps with AMPu (10:10:1 mixture of ammonium bicarbonate, methylamine HCl, and putrescine) were more attractive than blank and CEHO traps. Traps containing both AMPu and CEHO lures were less attractive than traps containing AMPu alone. In another experiment, sticky yellow panels and spheres were used to compare attractiveness of the same two attractants in different formulations. Sticky traps baited with membrane formulations of CEHO (10:1:1:10 mixture of the chemicals listed above) were not significantly attractive. Sticky traps with polypropylene tubes containing an agar formulation of AMPu (6:10:1 mixture of ammonium carbonate, methylamine HCl, and putrescine) were more attractive than blank and CEHO baited traps. As in the first experiment, traps with both AMPu and CEHO lures were less attractive than traps with AMPu alone. Results indicate that attractive host-odor volatiles and attractive amino-acid metabolites interact negatively with regard to attractiveness to the Mexican fruit fly.     

Attractiveness to mexican fruit flies of combinations of acetic acid with ammonium/amino attractants with emphasis on effects of hunger

Ammonium acetate was more attractive than other ammonium salts to Mexican fruit flies (Anastrepha ludens) in an orchard test. We hypothesized that acetic acid enhanced the attractiveness of ammonia in the orchard test and that acetic acid may similarly enhance attractiveness of AMPu, an attractant consisting of a mixture of ammonium bicarbonate or ammonium carbonate, methylamine HCl, and putrescine. In laboratory experiments, acetic acid was attractive to flies deprived of either yeast hydrolysate or both sugar and yeast hydrolysate but not to flies fed both sugar and yeast hydrolysate. AMPu/acetic acid combinations were more attractive than AMPu alone to flies deprived of both sugar and yeast hydrolysate but not to flies fed sugar, regardless of yeast hydrolysate deprivation status. Acetic acid is the first attractant found that has become more attractive with both sugar and protein deprivation in studies withA. ludens. It is also the first that has enhanced the attractiveness of another attractant type. In orchard tests, yellow sticky panels baited with either AMPu or 17 mg of acetic acid were at least six times more attractive than unbaited panels. However, panels baited with both acetic acid (17–68 mg) and AMPu were less attractive than AMPu alone. These results differed from the laboratory data in which combinations were never less attractive than AMPu alone.     

Attraction of both sexes of Mexican fruit fly,Anastrepha ludens,to a mixture of ammonia,methylamine, and putrescine

Eight chemicals were evaluated in laboratory experiments as attractants for sugar-fed adult Mexican fruit flies. Ammonium bicarbonate, methylamine HCl, ethanolamine, pyrrolidine, putrescine, and monomethyl succinate were slightly attractive when tested singly. A mixture containing all eight chemicals was much more attractive than any of the individual chemicals. Through a series of experiments, a mixture of three of the chemicals was found that was at least as attractive as the original eight-component mixture. The final mixture consisted of ammonium bicarbonate, methylamine HCl, and putrescine in a 10101 ratio. Ratios were less important than actual concentrations of individual components over the range of component concentrations tested. The three-component mixture was equally attractive to male and female flies over at least a 1000-fold range of concentrations and was slightly more attractive thanTorula yeast over the upper 10-fold range in competing McPhail traps in a greenhouse flight chamber.     

Volatiles from Duck Feces Attractive to Mexican Fruit Fly

Aqueous extracts of three types of bird feces were attractive to laboratory-colony Mexican fruit flies in laboratory bioassays. Extracts of black-bellied whistling duck feces were chosen for further analysis. Duck feces extract was attractive to both sugar-fed and sugar-starved flies but was more attractive to sugar-fed flies. Protein deprivation of flies had no effect on their response. Duck feces incubated in water for 24 hr were more attractive than those incubated for longer periods. Duck feces extract was attractive at pH 5–9, but was most attractive at pH 9, indicating that more than one class of chemicals contributed to attractiveness of the feces. Major components of headspace of duck feces extracts collected by solid-phase microextraction and identified by GC-MS, GC-FID, and GC-FTD included ethanol, propanol, phenol, ammonia, low-molecular weight amines, and pyrazines. In general, chemicals containing nitrogen proved most attractive to sugar-fed flies. However, dimethylamine and 1-pyrroline were nearly equally attractive to sugar-fed and sugar-deprived flies. Two chemicals without nitrogen were attractive to sugar-deprived flies; none were attractive to sugar-fed flies. A synthetic mixture was prepared containing ammonia, methylamine, dimethylamine, trimethylamine, 1-pyrroline, phenol, and 2-ethylhexanol in amounts found in odor of duck feces extract. The synthetic mixture was 96% as attractive as duck feces extract to sugar-fed flies and 80% as attractive to sugar-deprived flies.     

Field evaluation of synthetic compounds mediating oviposition inCulex mosquitoes (Diptera: Culicidae)

3-Methylindole (skatole), a compound shown to be an oviposition attractant/stimulant forCulex quinquefasciatus in laboratory tests, was evaluated against natural populations of mosquitoes in the field. In experiments using paired black plastic tubs that contained water treated with an attractant solution containing a mixture of 3-methylindole, 4-methylphenol, 4-ethylphenol, phenol, and indole or that contained only tap water, the attractantbaited traps received significantly moreCx. quinquefasciatus egg rafts than did the untreated tap water. Gravid female traps that were baited with attractant solution collected significantly moreCx. quinquefasciatus females than did traps containing only tap water. There was no significant difference in number ofCx. quinquefasciatus collected in the traps baited with the attractant solution compared to the traps that contained water with 3-methylindole alone, indicating that 3-methylindole was solely responsible for the attraction. In replicated experiments conducted in experimental ponds, ponds that were treated with 3-methylindole received significantly moreCx. quinquefasciatus, Cx. tarsalis, andCx. stigmatosoma egg rafts than did untreated ponds. Experimental ponds treated with 3-methylindole at two levels (0.12 and 0.6 mg/liter) were equally attractive to ovipositingCx. quinquefasciatus. This is the first record of 3-methylindole showing attractancy/stimulation to ovipositingCx. stigmatosoma andCx. tarsalis under field or laboratory conditions.     

Identification of odors from overripe mango that attract vinegar flies,Drosophila melanogaster

Bioassays with a variety of overripe fruits, including mango, plum, pear, and grape, and their extracts showed that odors from overripe mango were most attractive to adult vinegar flies, Drosophila melanogaster. Combined gas chromatography–electroantennographic detection (GC-EAD) analyses of solid-phase microextraction (SPME) and Tenax extracts of overripe mango odors showed that several volatile compounds, including ethanol, acetic acid, amyl acetate, 2-phenylethanol, and phenylethyl acetate elicited significant EAG responses from antennae of female flies. Most of the volatile compounds in the extracts were identified by mass spectral and retention index comparisons with synthetic standards. In cage bioassays, lures with a blend of ethanol, acetic acid, and 2-phenylethanol in a ratio of 1:22:5 attracted six times more flies than any single EAG-active compound. This blend also attracted four times more flies than traps baited with overripe mango or unripe mango. However, in field trials, the blend was not as attractive as suggested by the laboratory bioassay.     

Inhibition of attraction to aggregation pheromone by verbenone and ipsenol

The semiochemicals verbenone (Vn), ipsenol (Ie), and ipsdienol (Id), present in late phases of host colonization, have been implicated as qualitative “shut-off” signals regulating attack density. Combinations of the three chemicals were released in pipe traps together with the aggregation pheromone components 2-methyl-3-buten-2-ol (MB) andcis-verbenol (cV) at different levels and in different ratios to MB + cV, and with two spacings of traps to test for possible effects on reducing catch at traps baited with aggregation pheromone. When they were released with the attractants Vn and Ie (alone or together) decreased the mean catch significantly at the higher release rates used (1 mg/day). Id alone or together with Vn at low release rates (0.1 mg/day), with the attractants, increased catch somewhat. A dose-response test of Vn, with the attractants held constant, showed a decline in catches, down to about < 10% of the control, at ratios of Vn to cV between 1∶1 and 150∶ 1. A larger spacing (25 m) of traps gave a stronger response to change in doses of Vn and MB + cV than a smaller (6 m) spacing. The sex ratio was more skewed towards females when two or three inhibitors were present and at higher doses of Vn. It is suggested that Vn could be the most important density-regulating signal in the natural system, as release of Vn from galleries is larger and starts earlier than that of Id and Ie.     

Influence of different habitats and mating on olfactory behavior of onion flies seeking ovipositional hosts

Using traps baited with natural and synthetic onion volatiles, we examined the effects of different habitats and mating on the olfactory behavior of laboratory-reared and wild onion flies. Rankings of olfactory treatments as host-finding stimuli for females were dependent on their mating status and the habitat in which they were foraging. In habitats devoid of hosts, traps baited with individual alkyl sulfides were as effective as 4-day-old chopped onions and more effective than 1-day-old onions in eliciting host-finding behavior in laboratory-reared unmated females (LUF) and laboratory-reared mated females (LMF). However, upwind dispersal and percent recapture were always significantly greater in LUF. In one experiment, Pr₂S₂ was 19 times more attractive to LMF in a fallow field, as than it was in an onion field. Reduced effectiveness of alkyl sulfides as host-finding stimuli in onion fields probably results in part because they are less findable, but more importantly because of a change in searching behavior after females have mated. Evidence to support the latter contention is that traps baited with alkyl sulfides and onions were equally findable by unmated females in both habitats. The behavior of LMF was identical to that of wild females, whereas the behavior of LUF was identical to wild males. The hypothesis that olfactory host-finding behavior in onion flies is modified by the resource level was upheld. Alkyl sulfides appear to be the primary, and possibly the only, chemical effectors of host-finding at the patch level of resource distribution, whereas the complex blend emitted by aged, chopped, or damaged onions appears to be acting at the final level of host-finding, while egg-laying females are moving between adjacent hosts in search of an optimal oviposition site.     

Aggregation Pheromone of Palm Weevil, Dynamis borassi

4-Methyl-5-nonanol (1) is the male-produced aggregation pheromone of the palm weevil, Dynamis borassi (F.) from Colombia. The pheromone was identified by coupled gas chromatographic–electroantennographic detection (GC-EAD) analysis of male- and female-produced volatiles, and comparative GC–mass spectrometry (MS) of weevil-produced 1. In field experiments in Colombia, traps baited with a stereoisomeric mixture of synthetic 1 (3 mg/day) plus sugarcane captured more weevils than traps baited with 1 or sugarcane alone, suggesting that pheromone and plant volatiles are synergistically attractive. Use of a chiral, stereoisomer-separating Cyclodex-B column in GC-EAD and GC-MS analyses revealed that D. borassi males produce, and antennae of males and females respond to (4S,5S)-1. Previously identified palm weevil (Rhynchophorus spp.) aggregation pheromones 5-methyl-4-octanol (cruentol) and 6-methyl-2-hepten-4-ol (rhynchophorol) also elicited antennal responses by D. borassi. In field experiments, D. borassi females were captured equally well in traps baited with sugarcane plus either 1, cruentol or rhynchophorol. In contrast, D. borassi males were captured most often in traps baited with sugarcane plus 1. Because D. borassi is a potential vector of the red ring nematode that causes the lethal red ring disease of palms, pheromone-based trapping of D. borassi could aid in monitoring or management of red ring disease in commercial palm plantations.     

A Survey of Insect Assemblages Responding to Volatiles from a Ubiquitous Fungus in an Agricultural Landscape

We report here a first survey of insect orientation to fungal cultures and fungal volatiles from a community ecology perspective. We tested whether volatiles from a ubiquitous yeast-like fungus (Aureobasidium pullulans) are broadly attractive to insects in an agricultural landscape. We evaluated insect attraction to fungal cultures and synthetic compounds identified in fungal headspace (2-methyl-1-butanol, 3-methyl-1-butanol, 2-phenylethanol) in a spearmint (Mentha spicata L.) plantation. Three findings emerged: (1) 1,315 insects representing seven orders and 39 species oriented to traps, but 65 % of trapped insects were Dipterans, of which 80 % were hoverflies (Diptera: Syrphidae); (2) traps baited with A. pullulans caught 481 % more insects than unbaited control traps on average, and contained more diverse (Shannon’s H index) and species rich assemblages than control traps, traps baited with Penicillium expansum, or uninoculated media; and (3) insects oriented in greatest abundance to a 1:1:1 blend of A. pullulans volatiles, but mean diversity scores were highest for traps baited with only 2-phenylethanol or 2-methyl-1-butanol. Our results show that individual components of fungal headspace are not equivalent in terms of the abundance and diversity of insects that orient to them. The low abundance of insects captured with P. expansum suggests that insect assemblages do not haphazardly orient to fungal volatiles. We conclude that volatiles from a common fungal species (A. pullulans) are attractive to a variety of insect taxa in an agricultural system, and that insect orientation to fungal volatiles may be a common ecological phenomenon.     

Pheromone-based Mating and Aggregation in the Sorghum Chafer, <Emphasis Type="Italic">Pachnoda interrupta</Emphasis>

Adults of the sorghum chafer, Pachnoda interrupta Olivier (Coleoptera: Scarabaeidae: Cetoniinae), form aggregations during the mating period in July, but also in October. The beetles aggregate on food sources, e.g., Acacia spp. trees or sorghum with ripe seeds, to feed and mate. During the mating season, field trapping experiments with live beetles as bait demonstrated attraction of males to unmated females, but not to mated females or males, indicating the presence of a female-emitted sex pheromone. Unmated females combined with banana (food source) attracted significantly more males and females than did unmated females alone. Other combinations of beetles with banana were not more attractive than banana alone. Thus, aggregation behavior appears to be guided by a combination of pheromone and host volatiles. Females and males were extracted with hexane during the mating period, and the extracts were compared by using GC-MS. In a field trapping experiment, 19 compounds found only in females were tested, both singly and in a mixture. Traps baited with one of the female-associated compounds, phenylacetaldehyde, caught significantly more beetles than any other treatment. However, the sex ratio of beetles caught in these traps did not differ from that of control traps, and it is possible that other components may be involved in the sex pheromone signal. Furthermore, traps baited with a mixture of all 19 compounds attracted significantly fewer beetles than did phenylacetaldehyde alone.     

Identification of the Aggregation-sex Pheromone Produced by Male <Emphasis Type="Italic">Monochamus saltuarius</Emphasis>, a Major Insect Vector of the Pine Wood Nematode

In this study, we isolated and identified an aggregation-sex pheromone from Monochamus saltuarius, the major insect vector of the pine wood nematode in Korea. Adult males of M. saltuarius produce 2-undecyloxy-1-ethanol, which is known as an aggregation-sex pheromone in other Monochamus species. We performed field experiments to determine the attractiveness of the pheromone and other synergists. More M. saltuarius adult beetles were attracted to traps baited with the pheromone than to unbaited traps. Ethanol and (?)-α-pinene interacted synergistically with the pheromone. Traps baited with the pheromone + (?)-α-pinene +ethanol were more attractive to M. saltuarius adults than traps baited with the pheromone, (?)-α-pinene, or ethanol alone. Ipsenol, ipsdienol, and limonene were also identified as synergists of the aggregation-sex pheromone for M. saltuarius adults. In field experiments, the proportion of females was much higher in the beetles caught in traps than among the beetles emerging from naturally-infested logs in the laboratory. Our results suggest that a combination of aggregation-sex pheromone and synergists could be very effective for monitoring and managing M. saltuarius.     

Chemicals Attractive to Mexican Fruit Fly from Klebsiella pneumoniae and Citrobacter freundii. Cultures Sampled by Solid-Phase Microextraction

Headspace above tryptic soy broth culture filtrates of Klebsiella pneumoniae contained greater amounts of ammonia, methylamine, 3-methylbutanamine, 1-pyrroline, 2,3,4,5-tetrahydropyridine, and two pyrazines than were found above tryptic soy broth. It also contained chemicals not found above tryptic soy broth, including dimethyldisulfide and several alcohols and ketones. Headspace above tryptic soy broth culture filtrates of Citrobacter freundii contained greater amounts of ammonia, 1-pyrroline, and several pyrazines than were found above tryptic soy broth. It also contained chemicals not found above tryptic soy broth including dimethyldisulfide, some of the same alcohols as above K. pneumoniae filtrates, a different ketone, and phenol. Additional chemicals were detected above filtrates that were saturated with sodium chloride or had their pH adjusted up or down. In laboratory bioassays with protein-starved, sugar-fed Mexican fruit flies, chemicals that did not contain protonizable nitrogen were not attractive. All chemicals containing protonizable nitrogen, except 2-methylpyrazine, were attractive. Synthetic mixtures of ammonia, trimethylamine, 1-pyrroline, 3-methylbutanamine, pyrazine, 2,3,4,5-tetrahydropyridine, 2,5-dimethylpyrazine, and trimethylpyrazine in concentrations similar to those in filtrates of the two bacteria were 73–87% as attractive as bacterial filtrates.     

Sex pheromone of oriental beetle,Exomala orientalis: Identification and field evaluation

A gas chromatograph coupled with a behavioral bioassay was used to identify two sex pheromone components, 7-(Z)- and 7-(E)-tetradecen-2-one of the Oriental beetle (OB),Exomala orientalis. Field experiments showed that the blend of the two isomers (Z:E, 7:1) was not significantly more attractive than theZ component alone. The best performance of traps baited with the synthetic sex pheromone was achieved when they were set with the pheromone device at 30 cm above the ground. Catches in traps baited with 1 and 10 mg were not significantly different, but they were higher (2.9-fold) than captures in traps loaded with 0.1 mg of the pheromone. Further investigations by GC-EAD revealed the presence of a possible minor component, but the small amount of material prevented its identification. 2-(E)-Nonenol, with the same retention time as the natural product, did not affect the attractancy of the synthetic sex pheromone. GC-EAD screening of previously identified sex pheromones of scarab beetles showed that male antennae of the Oriental beetle responded to japonilure, but it showed neither synergism nor inhibition to the OB sex pheromone.     

Spodoptera exigua: Capture of feral males in traps baited with blends of pheromone components

Field tests were conducted with various blends of acetates and alcohols previously identified as components of the sex pheromone for the beet armyworm (BAW),Spodoptera exigua (Hübner). The compounds were formulated on rubber septa and placed in sticky traps positioned in fields populated withAmaranthus sp., a favored host of this species. Moth captures were highest in traps baited with septa containing a blend of 0.1 mg (Z,E)-9,12-tetradecadien-1-ol acetate (Z9,E12–14∶Ac) and 0.01 mg(Z)-9-tetradecen-1-ol (Z9–14∶OH). Additionally, we confirmed that all combinations of acetates tested alone captured significantly fewer males than blends containing a 10∶1 ratio ofZ9,E12–14∶Ac andZ9–14∶OH. A 10∶1 formulation ofZ9,E12–14∶Ac andZ9–14∶OH in hollow fibers was also attractive to feral BAW males.     

A New Potential Attractant for Anastrepha obliqua from Spondias mombin Fruits

Nonirradiated males and females of Anastrepha obliqua (Macquart) were attracted to and landed more frequently on ripe fruits of Spondias mombin L. than on artificial fruit in wind tunnel bioassays. Porapak Q volatile extracts of S. mombin were also attractive and elicited landing on artificial fruit for both sexes. Combined gas chromatographic–electroantennographic detection (GC-EAD) analysis of volatile extracts showed that nine volatile compounds elicited repeatable antennal responses from females and males. The EAD-active compounds were identified by GC–mass spectrometry (MS) as follows: ethyl butyrate, isopropyl butyrate, hexan-1-ol, propyl butyrate, isobutyl butyrate, ethyl hexanoate, isopentyl butyrate, ethyl benzoate, and ethyl octanoate. In wind tunnel bioassays, males and females were attracted and landed more frequently on lures containing the nine-component blend of synthetic compounds than on unscented controls. Field cage bioassays showed that multilure traps baited with the nine-synthetic blend captured significantly more A. obliqua than traps baited with hydrolyzed protein or water.     

Responses of Dasineura brassicae and Its Parasitoids Platygaster subuliformis and Omphale clypealis to Field Traps Baited with Organic Isothiocyanates

The responses of Dasineura brassicae and its parasitoids Platygaster subuliformis and Omphale clypealis to allyl and 2-phenylethyl isothiocyanates have been investigated using a new design of trap in winter oilseed rape. Traps baited with allyl isothiocyanate caught more male and female D. brassicae and more female O. clypealis than traps baited with 2-phenylethyl isothiocyanate or unbaited traps, whereas traps baited with 2-phenylethyl isothiocyanate caught more male and female Platygaster subuliformis than traps baited with allyl isothiocyanate or unbaited traps. The implications of these results for host-plant and oviposition-site location by D. brassicae and for host habitat and host location by the parasitoids are discussed, as is the potential for using these responses in integrated pest management strategies.     

Field Discrimination of Oilseed Rape, Brassica napus Volatiles by Cabbage Seed Weevil, Ceutorhynchus assimilis

The response of the cabbage seed weevil, Ceutorhynchus assimilis to yellow water traps baited with some components of oilseed rape (Brassica napus) odor was studied in a series of field experiments. Four isothiocyanates (NCS), five other amino acid derivatives (aromatic compounds), and two fatty acid derivatives are detected by peripheral olfactory receptors of C. assimilis. 3-Butenyl, 4-pentenyl, and 2-phenylethyl NCS were attractive when released individually during the period when weevils were immigrating to the host crop, but allyl NCS was not. A mixture of these four isothiocyanates was attractive during the periods of weevil immigration and dispersal. However, during the host colonization phase, 2-phenylethyl NCS, like the mixture of the four isothiocyanates, elicited no response or was repellent. Phenylacetonitrile and benzyl alcohol were attractive during the colonization phase. The fatty acid derivative (Z)-3-hexen-1-ol did not affect weevil catch in an experiment conducted when the insects were already established in the crop, but it depressed the catch in another conducted when weevils were dispersing from the crop. These results suggest that yellow traps baited with 2-phenylethyl NCS can be used to monitor immigration into crops in the spring and that phenylacetonitrile may be useful for assessing numbers of weevils colonizing the crop throughout the summer.     

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

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

Evaluation of Host-Derived Volatiles for Trapping <Emphasis Type="Italic">Culicoides</Emphasis> Biting Midges (Diptera: Ceratopogonidae)

Culicoides biting midges (Diptera: Ceratopognidae) cause pain and distress through blood feeding, and transmit viruses that threaten both animal and human health worldwide. There are few effective tools for monitoring and control of biting midges, with semiochemical-based strategies offering the advantage of targeting host-seeking populations. In previous studies, we identified the host preference of multiple Culicoides species, including Culicoides impunctatus, as well as cattle-derived compounds that modulate the behavioral responses of C. nubeculosus under laboratory conditions. Here, we test the efficacy of these compounds, when released at different rates, in attracting C. impunctatus under field conditions in Southern Sweden. Traps releasing 1-octen-3-ol, decanal, phenol, 4-methylphenol or 3-propylphenol, when combined with carbon dioxide (CO₂), captured significantly higher numbers of C. impunctatus compared to control traps baited with CO₂ alone, with low release rates (0.1 mg h^?1, 1 mg h^?1) being generally more attractive. In contrast, traps releasing octanal or (E)-2-nonenal at 1 mg h^?1 and 10 mg h^?1 collected significantly lower numbers of C. impunctatus than control traps baited with CO₂ only. Nonanal and 2-ethylhexanol did not affect the attraction of C. impunctatus when compared to CO₂ alone at any of the release rates tested. The potential use of these semiochemicals as attractants and repellents for biting midge control is discussed.