Laboratory Olfactometer Research Articles

Do Phagostimulants, Alone or Combined with Ammonium Acetate, Di-Ammonium Phosphate, and Acetic Acid, Effectively Attract Both Sexes of Peach Fruit Flies, Bactrocera zonata (Diptera: Tephritidae)?: Insights from Laboratory and Field Bioassays.

Laboratory and field assays of three sets of experiments were conducted to evaluate the impact of different phagostimulants alone and in combination with other phagostimulant lure sources, such as ammonium acetate, DAP, and acetic acid, on the attractancy of both sexes of B. zonata. In the first experiment, the laboratory olfactometer study revealed that out of eleven phagostimulants, banana, mulberry, mango, guava, molasses, and protein hydrolysate exhibited moderate attractancy (15.2-60.2%) to B. zonata. Unexpectedly, banana and protein hydrolysate were demonstrated to be highly attractive phagostimulants for starved female B. zonata (53.6% and 60.2%, respectively). In the field study, none of the tested phagostimulants exhibited high attractancy; however, banana, mulberry, protein hydrolysate, guava, mango, and molasses demonstrated moderate attractancy (5.6-35.6%) to B. zonata. In the second experiment, out of five phagostimulant-mixtures, phagostimulant-mixture-4 proved highly attractive (40.5-68.6% and 45.5-51.2%), followed by phagostimulant-mixture-3, which proved to be moderately attractive (17.0-22.5% and 28.4-36.1%) to B. zonata in olfactometer and field studies, respectively. In the third experiment, out of five phagostimulant-AdMixtures, phagostimulant-AdMixture-4 demonstrated strong attractiveness in the olfactometer (41.6-68.7%) and field studies (52.7-58.7%) for B. zonata, while the rest of the AdMixtures demonstrated moderate to no attractiveness for B. zonata. So, phagostimulant-AdMixture-4 with GF-120 could be used in the development of a phagostimulant bait station which attracts the maximum B. zonata population and ultimately provides pest-free fruits to the farmers.

Attraction of Brown Marmorated Stink Bugs, Halyomorpha halys, to Blooming Sunflower Semiochemicals.

The polyphagous invasive brown marmorated stink bug, Halyomorpha halys, reportedly discriminates among phenological stages of host plants. To determine whether olfaction is involved in host plant stage discrimination, we selected (dwarf) sunflower, Helianthus annuus, as a model host plant species. When adult females of a still-air laboratory experiment were offered a choice of four potted sunflowers at distinct phenological stages (vegetative, pre-bloom, bloom, seeding), most females settled onto blooming plants but oviposited evenly on plants of all four stages. In moving-air two-choice olfactometer experiments, we then tested each plant stage versus filtered air and versus one another, for attraction of H. halys females. Blooming sunflowers performed best overall, but no one plant stage was most attractive in all experiments. Capturing and analyzing (by GC-MS) the headspace odorants of each plant stage revealed a marked increase of odorant abundance (e.g., monoterpenes) as plants transitioned from pre-bloom to bloom. Analyzing the headspace odorant blend of blooming sunflower by gas chromatographic-electroantennographic detection (GC-EAD) revealed 13 odorants that consistently elicited responses from female H. halys antennae. An 11-component synthetic blend of these odorants attracted H. halys females in laboratory olfactometer experiments. Furthermore, in field settings, the synthetic blend enhanced the attractiveness of synthetic H. halys pheromone as a trap lure, particularly in spring (April to mid-June). A simpler yet fully effective sunflower semiochemical blend could be developed and coupled with synthetic H. halys aggregation pheromones to improve monitoring efforts or could improve the efficacy of modified attract-and-kill control tactics for H. halys.

Progress Toward an Attract-and-Kill Device for Asian Citrus Psyllid (Hemiptera: Liviidae) Using Volatile Signatures of Citrus Infected With Huanglongbing as the Attractant.

Asian citrus psyllid, Diaphorina citri (Kuwayama), preferentially orient toward citrus hosts infected with the phytopathogenic bacterium, Candidatus liberibacter asiaticus (CLas) the agent of citrus greening (Huanglongbing, HLB), compared to uninfected counterparts. We investigated whether this preference for the odors of infected plants could be useful for the development of an attract-and-kill (AK) device for D. citri. Twenty-nine blends of volatile organic compounds derived from the odor of citrus infected with CLas were tested in laboratory olfactometer tests, and two blends were also assessed under field conditions. A seven component blend of tricosane: geranial: methyl salicylate: geranyl acetone: linalool: phenylacetaldehyde: (E)-β-ocimene in a 0.40: 0.06: 0.08: 0.29: 0.08: 0.06: 0.03 ratio released from a proprietary slow-release matrix attracted twice more D. citri to yellow sticky traps compared with blank control traps. The attractive blend was subsequently co-formulated with spinosad insecticide into a slow-release matrix to create a prototype AK formulation against D. citri. This formulation effectively reduced the population density of D. citri up to 84% as measured with tap counts when deployed at a density of eight 2.5 g dollops per tree as compared with untreated controls in small plot field trials conducted in citrus orchards. Psyllid populations were not statistically affected at a deployment rate of four dollops per tree. Our results indicate that an AK formulation incorporating spinosad and a volatile blend signature of citrus greening into a slow-release matrix may be useful to suppress D. citri populations.

Evaluation of a field olfactometer in odour concentration measurement

Field olfactometry using portable olfactometers is one of the common methods in assessing odour nuisance of odour sources and validating odour dispersion modelling results. To obtain reliable field odour data, a field olfactometer needs to be accurate and reliable. The IDES Scentroid SM 100 is a recently developed portable field olfactometer but its accuracy in measuring odour concentration has not been sufficiently investigated. In this study, the results obtained by SM 100 are compared with the results obtained by a standard laboratory olfactometer in measuring odour concentrations of samples containing n-butanol gas and poultry barn exhaust air. The standard olfactometer used was designed according to European EN 13725 Standard (2003) and was a triangular forced-choice olfactometer that could use 8 panellists simultaneously for olfactometry analysis. Results showed that there was a good agreement between odour concentrations obtained by these two types of olfactometers for full-strength and diluted samples with odour concentrations ranging from 50 to 850 ou m−3 (P > 0.05). SM 100 gave 28%–41% higher values than the laboratory olfactometer for poultry barn odour, while this was not observed for n-butanol. For n-butanol samples, SM 100 gave 53% and 9% higher values for the original and 16 times diluted samples, respectively; in contrast, SM 100 gave 9% lower values for 64 and 128 times dilutes samples. Different discrepancy trends in two tested odour types suggest that more odour types should be tested to provide a better picture of the level of accuracy of SM 100.

Initial Location Preference Together with Aggregation Pheromones Regulate the Attack Pattern of Tomicus brevipilosus (Coleoptera: Curculionidae) on Pinus kesiya

Research Highlights: We found that the initial attack location together with the aggregation pheromones played an important role in mediating the aggressive behavior of T. brevipilosus on P. kesiya. Background and Objectives: T. brevipilosus was identified as an aggressive species, which possesses the ability to kill live, healthy P. kesiya. In this scenario, we study the top-down attack pattern of T. brevipilosus on P. kesiya during the entirety of the reproductive period. Materials and Methods: We investigated the phenology of trunk attack on P. kesiya over a period of three years in Pu’er City, China. The hindguts extracts of the females and males T. brevipilosus were analyzed by coupled gas chromatography-mass spectrometry (GC-MS). The candidate aggregation pheromone compounds of T. brevipilosus were determined through electrophysiology experiments (electroantennographic detection, EAD and electroantennography, EAG), laboratory olfactometer bioassays, and field trapping. Results: we found that the pioneer beetles preferentially infested the crown of P. kesiya at the early stage of attack following spring flight with the later arriving beetles selectively attacking the lower area of the trunk to avoid intraspecific competition and better utilize limited resources, which exhibits a top-down attack pattern. During gallery initiation, the beetles release aggregation pheromones to attract conspecifics to conduct a mass attack. The chemical analyses indicated that the hindgut extracts of gallery-initiating beetles contained a larger amount of myrtenol, cis-verbenol, trans-verbenol, and verbenone. Myrtenol and trans-verbenol were identified as candidate aggregation pheromone compounds. In addition, a blend of these two components with S-(−)-α-pinene and S-(−)-β-pinene attracted more T. brevipilosus individuals in a field bioassay. Conclusions: We concluded that the preference for the initial attack location together with the aggregation pheromones played an important role in mediating the top-down attack pattern of T. brevipilosus on P. kesiya.

Maculatic Acids—Sex Attractant Pheromone Components of Bald‐Faced Hornets

AbstractYellowjackets in the genera Vespula and Dolichovespula are prevalent eusocial insects of great ecological and economic significance, but the chemical signals of their sexual communication systems have defied structural elucidation. Herein, we report the identification of sex attractant pheromone components of virgin bald‐faced hornet queens (Dolichovespula maculata). We analyzed body surface extracts of queens by coupled gas chromatographic–electroantennographic detection (GC‐EAD), isolated the compounds that elicited responses from male antennae by high‐performance liquid chromatography (HPLC), and identified these components by GC mass spectrometry (MS), HPLC‐MS, and NMR spectroscopy. In laboratory olfactometer experiments, synthetic (2Z,7E)‐3,7‐dimethyldeca‐2,7‐diendioic acid (termed here maculatic acid A) and (2Z,7E)‐10‐methoxy‐3,7‐dimethyldeca‐10‐oxo‐deca‐2,7‐dienoic acid (termed here maculatic acid C) in binary combination significantly attracted bald‐faced hornet males. These are the first sex attractant pheromone components identified in yellowjackets.

Maculatic Acids-Sex Attractant Pheromone Components of Bald-Faced Hornets.

Yellowjackets in the genera Vespula and Dolichovespula are prevalent eusocial insects of great ecological and economic significance, but the chemical signals of their sexual communication systems have defied structural elucidation. Herein, we report the identification of sex attractant pheromone components of virgin bald-faced hornet queens (Dolichovespula maculata). We analyzed body surface extracts of queens by coupled gas chromatographic-electroantennographic detection (GC-EAD), isolated the compounds that elicited responses from male antennae by high-performance liquid chromatography (HPLC), and identified these components by GC mass spectrometry (MS), HPLC-MS, and NMR spectroscopy. In laboratory olfactometer experiments, synthetic (2Z,7E)-3,7-dimethyldeca-2,7-diendioic acid (termed here maculatic acid A) and (2Z,7E)-10-methoxy-3,7-dimethyldeca-10-oxo-deca-2,7-dienoic acid (termed here maculatic acid C) in binary combination significantly attracted bald-faced hornet males. These are the first sex attractant pheromone components identified in yellowjackets.

Ladybird beetle trails reduce host acceptance by Diaphorina citri Kuwayama (Hemiptera: Liviidae)

We investigated the behavioral responses of the Asian citrus psyllid, Diaphorina citri, to the trail of the convergent ladybird beetle, Hippodamia convergens. We tested the hypothesis that H. convergens trails reduce D. citri host acceptance using choice tests. Citrus plants previously exposed to ladybird beetle larvae and adult trails were avoided by D. citri compared to untreated controls. Female D. citri settling on H. convergens-exposed plants decreased as the density of ladybird beetle larvae or adults used to expose treatment plants was increased. Larval and adult trails were equally repellent to D. citri. In laboratory olfactometer assays that measured orientation to volatile chemical cues, D. citri females avoided citrus plants that were pre-exposed to caged H. convergens larvae for 1, 5 or 10 days as compared with non-exposed controls. Diaphorina citri did not avoid the odor of citrus plants pre-exposed to caged adult H. convergens for 1 or 5 days as compared with the control. However, more female D. citri chose untreated control arms as compared with plants exposed to H. convergens adults for 10 days. We collected larval trails deposited by H. convergens and mechanically re-applied them to citrus plants as a spray solution. D. citri significantly avoided plants treated with previously collected H. convergens trail solutions in choice tests as compared with untreated controls; treatments caused 15 days of residual behavioral activity on D. citri. Our results indicate that chemical cues mediate avoidance of ladybird beetle trails by D. citri. Implications for biological and non-insecticidal control of D. citri are discussed.

Attractiveness of Host Plants at Different Growth Stage to Kudzu Bug, Megacopta cribraria (Heteroptera: Plataspidae): Behavioral Responses to Whole Plant and Constitutive Volatiles

The kudzu bug, Megacopta cribraria (Fabricius), is an invasive pest of soybeans, Glycine max (L.) Merr., that has recently been detected in the United States. This study investigated whether there was a differential attraction of adult bugs to soybean growth stages, and whether the attraction was related to soybean constitutive volatiles. Greenhouse choice assays examined the behavioral orientation preference of adult bugs exposed to four growth stages of whole soybean plants: vegetative (V2), flowering (R1), pod (R3), and seed (R5). Results show that significantly more adults landed on plants in the early reproductive stage R1 than in other stages. Laboratory olfactometer assays also demonstrate that significantly more adult bugs were attracted to R1 plants, with females responding more strongly than males. Both greenhouse and olfactometer assays indicate that the differential attraction of adult bugs to soybean growth stages was mediated by plant constitutive volatiles. These results offer an insight into kudzu bug chemical and behavioral ecology and thus are of great significance for optimizing the timing of field scouting and treatment as well as the development of soybean pest management programs.

Sweetpotato weevil, Cylas formicarius (Fab.) (Coleoptera: Brentidae) avoids its host plant when a virulent Metarhizium anisopliae isolate is present.

Metarhizium anisopliae has a wide range of coleopteran hosts, including weevils. Some susceptible insects are known to modify their behavior to prevent infection, typically detecting virulent strains by olfaction, and avoiding physical contact with sources of infection. Laboratory olfactometer assays were conducted on the sweetpotato weevil Cylas formicarius to test the hypothesis that insects would avoid a more virulent strain of M. anisopliae when presented with a strain of low virulence or an untreated control. When adult weevils were allowed to choose between paired test arenas containing sweetpotato roots and M. anisopliae isolates on agar cores, weevils avoided arenas with the highly virulent isolate QS155, showing a preference for either roots with uninoculated agar cores or cores with the low virulence isolate QS002-3. When roots or whole sweetpotato plants were inoculated with M. anisopliae, the preferences of weevils remained broadly similar; weevils were repelled by the highly virulent isolate QS155 when tested against either QS002-3 or uninoculated roots and plants, however weevils were not repelled by the low virulence isolate QS002-3 tested against uninoculated controls. When single-sex groups of weevils were tested separately in the olfactometer using uninoculated whole plants and plants treated with isolate QS155, males and females responded similarly and statistically identical preferences were found for the untreated plants. When weevils were released singly at different times of the day the response time for males was significantly shorter in the afternoon compared to the morning. Males were always significantly faster to respond to olfactory stimuli than females. Understanding factors that may lead to avoidance of virulent M. anisopliae strains by C. formicarius will be an essential part of developing an 'attract-and-infect' strategy for the management of C. formicarius.

Predator–prey interaction between greenhead ants and processionary caterpillars is mediated by chemical defence

The predatory greenhead ant, Rhytidoponera metallica, readily attacks some insects but not the processionary caterpillar, Ochrogaster lunifer. This urticarial lepidopteran larva is covered in long hairs and has numerous smaller, detachable barbed setae present on the third instar and older larvae. These setae are a health risk to humans and other mammals. In this study, we tested whether O. lunifer larvae are defended against invertebrate predators, using R. metallica as an example. Field experiments at R. metallica nests and laboratory olfactometer experiments were used to assess possible behavioural, morphological and chemical defence mechanisms. We found that a volatile chemical component from O. lunifer larvae inhibited attack/approach by R. metallica. This odour was associated with O. lunifer cuticular components: larval hairs, setae and exoskeleton. Behavioural defence was not found to inhibit R. metallica attack. Furthermore, despite the dense hairs and setae covering O. lunifer larvae, these did not act as a physical barrier to ant attack. Our study demonstrates the key role of chemical ecology in invertebrate interactions involving such hairy caterpillars. Future isolation of the deterrent chemical(s) produced by O. lunifer larvae may offer novel possibilities for managing ant behaviour.

Volatiles Mediating Parasitism of Euschistus conspersus and Halyomorpha halys Eggs by Telenomus podisi and Trissolcus erugatus.

This study identified chemicals found on the eggs of two stink bug species, one native to western North America, Euschistus conspersus, and an invasive species from Asia, Halyomorpha halys. The responses of two scelionid egg parasitoids, Trissolcus erugatus and Telenomus podisi, toward natural stink bug egg volatiles, and synthetic reconstructions of egg volatiles, were tested in bioassays. A compound, methyl (2E,4Z)-2,4-decadienoate, previously identified as the major component of the male-produced aggregation pheromone of E. conspersus, was the major volatile identified from extracts of E. conspersus eggs. In contrast, for H. halys, the sesquiterpenoids that compose the male-produced aggregation pheromone of this species were not detected on eggs, whereas the presence of hexadecanal, octadecanal, and eicosanal was detected. In laboratory olfactometer tests, both Tr. erugatus and Te. podisi females were attracted to extracts of E. conspersus eggs, and to synthetic methyl (2E,4Z)-2,4-decadienoate. However, female Tr. erugatus and Te. podisi wasps were repelled, both by extracts of H. halys eggs and by a blend of the aldehydes identified from H. halys eggs. A follow-up field study, using hexane-washed and intact E. conspersus as sentinel eggs, showed that the parasitoids Trissolcus erugatus and Gryon obesum emerged from these eggs. Sentinel hexane-washed eggs treated with 3ng of methyl (2E,4Z)-2,4-decadienoate were parasitized more by these two species than were hexane-washed or unwashed eggs, whereas hexane-washed eggs treated with a comparable dose of the C16,18,20 aldehyde mixture were avoided by these parasitoids. In a further field experiment, Trissolcus basalis was the primary parasitoid found in sticky traps baited with methyl (2E,4Z)-2,4-decadienoate, indicating that this species was attracted to, but either did not oviposit or develop in the E. conspersus sentinel eggs in the previous experiment.

Repellent Activity of Botanical Oils against Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Liviidae).

The Asian citrus psyllid, Diaphorina citri Kuwayama, is the insect vector of the pathogen causing huanglongbing. We selected three botanical oils to evaluate behavioral activity against D. citri. In laboratory olfactometer assays, fir oil was repellent to D. citri females, while litsea and citronella oils elicited no response from D. citri females. In choice settling experiments, D. citri settled almost completely on control plants rather than on plants treated with fir oil at a 9.5 mg/day release rate. Therefore, we conducted field trials to determine if fir oil reduced D. citri densities in citrus groves. We found no repellency of D. citri from sweet orange resets that were treated with fir oil dispensers releasing 10.4 g/day/tree as compared with control plots. However, we found a two-week decrease in populations of D. citri as compared with controls when the deployment rate of these dispensers was doubled. Our results suggest that treatment of citrus with fir oil may have limited activity as a stand-alone management tool for D. citri and would require integration with other management practices.

Attraction of the cutaneous leishmaniasis vector Nyssomyia neivai (Diptera: Psychodidae) to host odour components in a wind tunnel

BackgroundLaboratory studies of host-seeking olfactory behaviour in sandflies have largely been restricted to the American visceral leishmaniasis vector Lutzomyia longipalpis. In comparison, almost nothing is known about the chemical ecology of related species, which transmit American cutaneous leishmaniasis (ACL), due in part to difficulties in raising these insects in the laboratory. Understanding how ACL vectors locate their hosts will be essential to developing new vector control strategies to combat this debilitating disease.MethodsThis study examined host-odour seeking behaviour of the ACL vector Nyssomyia neivai (Pinto) (=Lutzomyia neivai) using a wind tunnel olfactometer. The primary aim was to determine whether field-collected female N. neivai would respond to host odours in the laboratory, thereby eliminating the need to maintain colonies of these insects for behavioural experiments. Responses to two key host odour components, 1-octen-3-ol and lactic acid, and a commercially-available mosquito lure (BG-Lure™) were assessed and compared relative to an air control. We also tested whether trials could be conducted outside of the normal evening activity period of N. neivai without impacting on fly behaviour, and whether the same flies could be used to assess baseline responses to air without affecting responses to octenol, thereby reducing the number of flies required for experiments.ResultsOctenol was found to both activate host-seeking behaviour and attract female N. neivai in the wind tunnel, while lactic acid elicited weaker responses of activation and attractiveness under identical conditions. The BG-Lure did not activate or attract N. neivai under test conditions. Further experiments showed that sandfly behaviour in the wind tunnel was not affected by time of day, such that experiments need not be restricted to nocturnal hours. Moreover, using the same flies to measure both baseline responses to air and attraction to test compounds did not affect odour-seeking behaviour.ConclusionsThe results of this study demonstrate that N. neivai taken from the field are suitable for use in laboratory olfactometer experiments. It is hoped this work will facilitate further research into chemical ecology of this species, and other ACL vectors.

Age at reproductive maturity and effect of age and time of day on sex attraction in the potato psyllid Bactericera cockerelli

Abstract The potato psyllid, Bactericera (= Paratrioza) cockerelli (Šulc) (Hemiptera: Triozidae), is a major pest of potato. Studies were conducted to determine the age at which both males and females reach reproductive maturity and the effect of age and time of day on sex attraction. Adult B. cockerelli reach reproductive maturity within 48 h post‐eclosion, with females being mature on the day of eclosion and males at 1 day post‐eclosion. Oviposition generally began 2 days after mating but was delayed when females mated within 2 days post‐eclosion. In laboratory olfactometer assays, the age of females used as odor sources and the age of males assayed to these odors did not affect sex attraction, with both younger (1–4‐day‐old) and older (8–10‐day‐old) males being attracted to females, regardless of female age (1–4‐day‐old or 8–10‐day‐old). Males assayed to live females at different times during the photophase (between 8:00 and 20:00 hours) were attracted to females between 11:00 and 17:00 hours, showing a temporal periodicity in sex attraction with B. cockerelli at least during the photophase.

How plants give early herbivore alert: Volatile terpenoids attract parasitoids to egg-infested elms

Plants can defend themselves against insect attack prior to larval feeding damage by responding to eggs laid on their leaves. Insect egg deposition can induce leaves to release a complex blend of volatiles attracting egg parasitoids which kill the eggs. Only a few studies have addressed the question which of these egg-induced plant volatiles are relevant for parasitoid attraction. Egg deposition by the elm leaf beetle Xanthogaleruca luteola on leaves of the European field elm Ulmus minor is known to induce the emission of a blend consisting mainly of terpenoids and some green leaf volatiles, which attracts a specialised egg parasitoid of X. luteola, the eulophid wasp Oomyzus gallerucae. Here, we investigated the role of oviposition-induced terpenoids from elm leaves for parasitoid attraction. Quantitative GC–MS analyses showed that inhibition of terpene biosynthesis in leaves by treatment with cerivastatin ® and fosmidomycin reduced emission of ( E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), ( E)- β-caryophyllene and a yet unidentified oxygenated sesquiterpene, but unexpectedly also that of green leaf volatiles (GLVs). Laboratory olfactometer assays revealed that inhibitor treatment rendered oviposition-induced elm leaves unattractive for the parasitoids. Further bioassays showed that single terpenoids per se attracted the parasitoids. Although the only tested GLV 1-hexanol was not attractive in olfactometer tests, we cannot rule out that other GLVs might play a role in parasitoid attraction. When attractiveness of DMNT was tested in the field, parasitoids were attracted to DMNT-baited traps in the presence of background odour emitted by a natural elm stand. We conclude that elms alert their egg parasitoid “helpers” after elm leaf beetle oviposition by means of one or more terpenoid volatiles.

Sex Attraction in <I>Bactericera cockerelli</I> (Hemiptera: Triozidae)

The potato psyllid, Bactericera (=Paratrioza) cockerelli (Šulc) (Hemiptera: Triozidae), is a major pest of potato. We examined the role of chemical signals in sex attraction, assessing male and female response to male- and female-produced volatile chemicals. In laboratory olfactometer assays, potato psyllid males were attracted to odorants emitted from live females and from solvent extract of females. These results indicate that the female-produced chemicals responsible for attracting males may be isolated by means of insect extractions. Males were also attracted to volatile chemicals from males and extracts of males, providing the first example of male-male attraction in the Psylloidea. Males exposed simultaneously to odorants from conspecific females and males were preferentially attracted to female odorants, suggesting the presence of a female-specific sex attractant for males. Potato psyllid females avoided volatile chemicals emitted by females and extracts of females and by volatile chemicals emitted by males and extracts of males. Possible explanations for avoidance of conspecifics by females are discussed. This study is the first report of male attraction to volatile chemicals emitted by females and female extracts in the Triozidae and more specifically in the potato psyllid.

Walking Response of the Mediterranean Pine Engraver, Orthotomicus erosus, to Novel Plant Odors in a Laboratory Olfactometer

When an herbivorous insect enters a new geographic area, it will select host plants based on short and long distance cues. A conifer-feeding bark beetle that has been recently introduced to North America, the Mediterranean pine engraver, Orthotomicus erosus (Wollaston), has a potentially wide host range, especially among members of the Pinaceae. The long-distance response of the beetles to tree odors may be a key feature of the mechanism of host recognition and selection. We used a laboratory olfactometer to study the walking response of 1,440 O. erosus to odor cues from the bark and phloem of six North American tree species. The beetle moved toward the angiosperm non-host Betula papyrifera more than would be expected by chance, but had a neutral response to odors of two tree species that support reproduction and three species that do not. These results suggest that tree odors alone may not be adequate for O. erosus to recognize novel hosts.

Responses of Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) to olfactory cues associated with novel genotypes developed by Sinapis alba L. × Brassica napus L.

Many herbivorous insects use olfactory cues for host location. Extracts from Brassica napus L. have been shown to elicit electrophysiological and behavioural responses in the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (syn. C. assimilis (Paykull)) (Coleoptera: Curculionidae). These include volatile products of the hydrolysis of glucosinolates. Here we present results of a laboratory olfactometer study examining the attractiveness of odours from flowering racemes and foliage of Sinapis alba L. (an inappropriate host for larval development), B. napus (an excellent host for larval development) and lines derived from S. alba × B. napus selected from colonization studies to demonstrate resistance or susceptibility. Results of this study indicate differential attraction of C. obstrictus to the odours of resistant and susceptible lines and suggest the role of hydrolysis products of glucosinolates, particularly the attractive effects of 2-phenylethyl isothiocyanate.

Can Leek Interfere With Bean Plant–Bean Fly Interaction? Test of Ecological Pest Management in Mixed Cropping

Effects of volatile odors from leek, Allium porum L., on the behavior of bean fly, Ophiomyia phaseoli (Tryon) (Diptera: Agromyzidae), were tested in laboratory olfactometer bioassays. Aqueous and solvent extracts (dichloromethane and methanol) of leek were repellent to adult flies. Whole leek plants were repellent and prevented attraction to the host plant, beans. Beans that had been exposed to volatiles from living leek plants for 7 d became repellent to the fly. Leek and several other crops were tested in field experiments to identify candidate crops for a mixed cropping system to minimize bean fly attack in beans, Phaseolus vulgaris L. In a wet season field experiment, mixed cropping of bean with leek or three other vegetable crops did not significantly reduce bean fly infestation or infection with Fusarium oxysporum Schltdl. compared with a mono crop, but significantly reduced plant death caused by both agents combined. In two dry season field experiments, mixed cropping of beans with leek significantly reduced adult bean fly settling, emergence, and death of bean plants compared with a mono crop. Bean yield per row was approximately 150% higher for the mixed crop, and economic returns were approximately Sri Lankan Rs. 180,000/ha, higher than for the mono crop. For the mono crop, the farmer had a monetary loss, which would become a small profit only if the costs of family labor are excluded. The study is an example of the first steps toward development of sustainable plant protection in a subsistence system.