Acanthoscelides obtectus

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Eugenio E Oliveira - One of the best experts on this subject based on the ideXlab platform.

  • changes in the insecticide susceptibility and physiological trade offs associated with a host change in the bean weevil Acanthoscelides obtectus
    Journal of Pest Science, 2018
    Co-Authors: Khalid Haddi, Leda R A Faroni, L Viteri O Jumbo, Marilza S Costa, M F Santos, Jose Eduardo Serrao, Eugenio E Oliveira
    Abstract:

    For most of the seed weevils (Coleoptera: Chrysomelidae: Bruchinae), the ability to survive environmental stresses like insecticide exposure and reproduction is variable and depends on the host. Here, we evaluated the physiological costs and benefits of a host shift from kidney beans of the landrace “Vermelho” to cranberry beans of the landrace “Manteigao” in the bean weevil Acanthoscelides obtectus. We assessed the susceptibility of A. obtectus to the commercial pyrethroid deltamethrin and clove and cinnamon essential oils as potential alternative insecticides and measured its reproductive performance (e.g., oviposition and emergence rates) on both hosts. The females of A. obtectus reared on kidney beans were less susceptible to both deltamethrin and clove essential oil and showed more sources of energy in the trophocytes although the attraction of adult females to both hosts was similar. However, the females reared on cranberry beans had higher reproductive performances and respiration rates, indicating that more energy was expended on reproduction than on the mitigation of the insecticide actions. Thus, with a change in hosts, a trade-off between reproductive fitness and the susceptibility to insecticides was demonstrated for A. obtectus. These results should not only affect the management of A. obtectus in storage units but also the understanding of these insects’ host adaptativeness.

  • potential use of clove and cinnamon essential oils to control the bean weevil Acanthoscelides obtectus say in small storage units
    Industrial Crops and Products, 2014
    Co-Authors: Luis Viteri O Jumbo, Leda R A Faroni, Eugenio E Oliveira, M A G Pimentel, G N Silva
    Abstract:

    Abstract The bean weevil, Acanthoscelides obtectus Say, causes severe post-harvest losses in the common bean, Phaseolus vulgaris L. The control of these insects is either non-existent or relies heavily on the use of conventional insecticides, which increase the risks associated with pest resistance, hazards to human health and environmental contamination. Protecting grains with alternative chemical control options that alleviate the concerns outlined above are urgently needed, and essential oils of plants have been presented as a suitable alternative to fill this void. Therefore, this investigation evaluated the non-fumigant applications of clove, Syzygium aromaticum L., and cinnamon, Cinnamomum zeylanicum L., essential oils adequately control A. obtectus on common beans. The oils were tested for insecticidal (lethal toxicities, disturbances on reproductive traits and persistence of action) and repellent activities. Both oil types showed similar toxicity (clove LD = 43.6 μL/kg beans; cinnamon LD50 = 46.8 μL/kg beans), steadily decreased the growth rate of A. obtectus in a dose-dependent manner, and similarly lost their insecticidal activity over the time. Additionally, the clove oil delayed bean weevil emergence, whereas cinnamon oil repelled the bean weevil. These results indicate clove and cinnamon essential oils as desirable tools for protecting stored beans against A. obtectus in small storage facilities, promoting environmentally friendly pest control strategies.

  • competition between the bean weevils Acanthoscelides obtectus and zabrotes subfasciatus in common beans
    Journal of Stored Products Research, 2013
    Co-Authors: Karina Vilca S Mallqui, Eugenio E Oliveira, R N C Guedes
    Abstract:

    Abstract Bruchid pest species of common beans (Phaseolus vulgaris (L.)) in the Neotropics, the bean weevil Acanthoscelides obtectus and the Mexican bean weevil Zabrotes subfasciatus, exhibit niche and range overlaps, frequently co-occurring in bean storage facilities of south-central Brazil. Although both species are well-known and important pest species, the impact of their co-occurrence on their fitness has not been an area of interest. Here, we performed direct competition experiments between both of the species following an additive series. The competitive ability of each species in the presence of its heterospecific competitor was assessed using mixed (adult) insect infestations in common beans. The initial number of insects of one species was fixed at 50, whereas the other species had a number of insects ranging from 0 to 50. Therefore, each species with a variable number of insects started the competition at an initial proportion of 0, 0.17, 0.29, 0.38 and 0.50. The number of adults that emerged and the instantaneous rate of increase (ri) for each species were determined after one generation under direct competition. Our results indicate that the competitive ability of Z. subfasciatus was favored by the presence of its heterospecific competitor (A. obtectus), while the opposite pattern did not occur. Thus, colonization by A. obtectus was not significantly compromised by Z. subfasciatus, while Z. subfasciatus seemed to actually benefit from the presence of A. obtectus under the conditions of our study. These results indicate that these co-occurring species do not exhibit negative interactions in storage facilities, and the presence of A. obtectus may even favor Z. subfasciatus.

Nikola Tucic - One of the best experts on this subject based on the ideXlab platform.

  • the effects of selection for early and late reproduction on metabolite pools in Acanthoscelides obtectus say
    Insect Science, 2012
    Co-Authors: Jelica Lazarevic, Nikola Tucic, Darka Seslija Jovanovic, Josef Veceřa, Dalibor Kodrik
    Abstract:

    The present study was aimed at revealing the responses of metabolite pools to selection for alternative reproductive schedules in the seed beetle, Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae: Bruchinae). The levels of metabolites (free sugars, glycogen, lipids, soluble and hydrophobic proteins) that were determined in virgin females and males at three ages from adult eclosion onwards were compared among the base population (B) and two derived lines that were selected for either early (Y) or late (O) reproduction. The results showed differences in the accumulation of metabolites during pre-adult development, as well as in the pattern of their changes during adult ageing. Generally, in comparison to the B population, the short-lived beetles from the Y line showed increased protein content and reduced carbohydrate and lipid content, whereas the opposite was true for the long-lived beetles from the O line. Females from the O line exhibited slower utilization of energy reserves and a slower increase in protein contents than females from the Y line. Females contained higher levels of free sugars, glycogen and hydrophobic proteins and lower levels of lipids and soluble proteins than males, although the sexual dimorphism was not evenly expressed among lines. Age-specific changes in metabolitecontentswereslowerinfemalesthanmales.Ourfindingssuggestthattrade-offs among capital resources are a physiological basis of early/late fitness trade-offs and point to a conservation of resources that can be used for somatic maintenance.

  • mating behavior in the seed beetle Acanthoscelides obtectus selected for early and late reproduction
    Behavioral Ecology, 2009
    Co-Authors: Darka Seslija, Jelica Lazarevic, Boban Jankovic, Nikola Tucic
    Abstract:

    Lines of Acanthoscelides obtectus that had been selected for either early- or late-life fitness components were compared with respect to early-life mating behavior of both females and males. Early-life mating frequencies and mating speed of both sexes, as well as female remating rates, were substantially higher in the late- than in the early-reproducing lines. These findings do not corroborate the hypothesis that selection for increased age at reproduction (and hence increased longevity) should result in reduced early-life mating efforts. We suggest that cryptic sexual selection within the late-age selection regime and relaxed sexual selection within the early-age selection regime may be the most important contributors to the pattern of mating behavior we see in the present study. Key words: age-specific selection, mating frequency, mating speed, remating rate, sexual selection. [Behav Ecol]

  • sexual selection and senescence do seed beetle males Acanthoscelides obtectus bruchidae coleoptera shape the longevity of their mates
    Journal of Zoological Systematics and Evolutionary Research, 2008
    Co-Authors: Darka Seslija, I Marecko, Nikola Tucic
    Abstract:

    Although the reasons why organisms age and die are generally well understood, it has recently been suggested that an optimal life span has evolved not only as the result of trade-offs between reproductive performances early and late in life, but also that a balance between the costs and benefits of the number of mating has also played an important role in the evolution of ageing in both sexes. By using four seed beetle (Acanthoscelides obtectus) lines selected for different life history traits, but which have also inadvertently created monoandrous and polyandrous conditions, we showed that males evolved to affect the mortality patterns of females in a way consistent to the postmating sexual selection generated by sexually antagonistic co-evolution theory. Monoandrous males, irrespectively of body weight and other life history traits specific to their lines, evolved to increase the longevity of control females kept under starvation and suppressed fecundity, compared with males that originated in the lines with effectively polyandrous conditions. When females were allowed to lay eggs, the effects of males from different lines and mating type history on the senescence of females were substantially weaker. We found that males in the line that was evolved to decelerate senescence and polyandrous conditions stimulate the earlier onset of females’ oviposition, relative to males stemmed from the line with accelerated senescence and monoandrous conditions. This fact may explain the absence of difference in the mean longevities between the control females mated to these males and highlight the importance of sexual selection in the evolution of ageing.

  • genetic architecture of differences in oviposition preference between ancestral and derived populations of the seed beetle Acanthoscelides obtectus
    Heredity, 2007
    Co-Authors: Nikola Tucic, Darka Seslija
    Abstract:

    We investigated the additive, dominance and epistatic genetic effects underlying differentiation in oviposition preference between two populations of the seed beetle Acanthoscelides obtectus evolved in the laboratory for 102 generations on bean and chickpea seeds. We reared and tested females on each of two host legumes. The populations differed in mean oviposition preference; the preference for chickpea was stronger in population reared on the chickpea (C) than in population maintained on common bean (P). Observations in the parental populations indicated that females tend to prefer ovipositioning their eggs on the seeds they have already experienced. The patterns of the means in each of the parental populations and 12 types of hybrids (two F(1), two F(2) and eight backcrosses) indicated that population differences in oviposition preference from both rearing hosts could be explained by nonadditive genetic effects. Statistically detectable additive and dominance genetic effects were observed in the most parsimonious model only when females were reared on the chickpea. The most parsimonious models on both rearing hosts suggested a contribution of negative additive x additive epistasis to the divergence of oviposition preference between the P and C populations. This indicates a positive effect of epistasis on the performance of the second generations of hybrids.

  • genetic variation and covariation among life history traits in populations of Acanthoscelides obtectus maintained on different hosts
    Entomologia Experimentalis Et Applicata, 1997
    Co-Authors: Nikola Tucic, S Mikuljanac, Oliver Stojkovic
    Abstract:

    We explored the extent to which two populations of Acanthoscelides obtectus (Coleoptera: Bruchidae), maintained in the laboratory for about 60 generations on common bean (Phaseolus vulgaris) and chickpea (Cicer arietinum) seeds, differ genetically in life history traits. Using a half-sib breeding design, we screened for genetic variation in oviposition preference for two hosts within both populations, and examined whether this variation is correlated with weevil pre-adult (egg-to-adult viability and egg-to-adult developmental time) and adult (female fecundity and longevity) fitness components on these two hosts. Significant differences between the Phaseolus and Cicer population were detected in viability, developmental time and oviposition preference, but not in female fecundity and longevity. The absence of a significant population × host interaction in all traits, except for developmental time in males, indicates that the Cicer population has not attained the status of ‘host race’. The estimated narrow-sense heritabilities within population within host plant were in the low-to-moderate level (range: 1%–79%), with an overall average of about 24%. Within the population maintained on the chickpeas we detected significant genetic correlations between female developmental time on chickpea seeds and preference for chickpeas. In the population maintained on the primary host of this weevil species (the ‘Phaseolus’ population) we found no significant preference/performance genetic correlations. Data are also presented on the genetic correlations of preference and performance across host seeds within both populations. These correlations are found to be positive for all traits in both populations, indicating the absence of trade-offs in either performance or behavioural response that might impose selection for host specialization within populations.

Silvia Dorn - One of the best experts on this subject based on the ideXlab platform.

  • the inhibitory effect of the natural seed storage protein arcelin on the development of Acanthoscelides obtectus
    Journal of Stored Products Research, 2007
    Co-Authors: Guido Velten, Anja S Rott, Cesar Cardona, Silvia Dorn
    Abstract:

    To protect stored beans from attack by Acanthoscelides obtectus and other bruchids by non-toxic means of control, it is desirable to combine mutually compatible methods in an integrated approach. A combination of an optimal level of host–plant resistance based on the natural storage protein arcelin and a larval parasitoid has been suggested as a promising two-component strategy. While a dose–response to arcelin is evident in the bruchid Zabrotes subfasciatus, the effects of different arcelin concentrations on A. obtectus are still virtually unknown, even though they might be important for the success of the proposed integrated control system. The current investigation quantified the effect of different arcelin-based resistance levels of beans on the development of A. obtectus in a series of bioassays. Our findings show that all seven tested bean lines with markedly different levels of arcelin-based resistance against Z. subfasciatus consistently prolonged development of A. obtectus. Results provide clear evidence that arcelin acts as a growth inhibitor on first instar larvae. Furthermore, arcelin affected bruchid female fitness through its effect on body mass, which was significantly reduced on all arcelin-containing bean lines. This study demonstrates that, irrespective of its relative concentration, arcelin holds the potential to affect development of A. obtectus sufficiently to support the proposed two-component integrated pest management system.

  • how host larval age and nutrition and density of the parasitoid dinarmus basalis hymenoptera pteromalidae influence control of Acanthoscelides obtectus coleoptera bruchidae
    Bulletin of Entomological Research, 2005
    Co-Authors: I Schmale, Felix L Wackers, C Cardona, Silvia Dorn
    Abstract:

    Choice of the targeted host developmental stage, regulation of parasitoid numbers released and introduction of food supplements are operational factors with a potential to influence the level of biological control. In a closed laboratory storage system maintained over two generations of the host, the impact of these three parameters on the control potential of the parasitoid Dinarmus basalis Rondani was investigated for high populations of larvae of Acanthoscelides obtectus (Say) feeding inside dry common bean seeds Phaseolus vulgaris. The beans were already infested with immature bruchids at the beginning of the storage period to simulate harvest conditions, characterized in a previous study. Treatments resulted in a reduction of 48–75% of the bruchid population within 16 weeks of storage. The best timing of parasitoid release was at the simulated harvest, as later releases reduced the bruchid population only by about half this percentage. Host feeding is postulated to be the key factor involved in the observed difference. The effect of increasing the number of parasitoids strongly depended on host age and food supplement. Addition of vials with honey had no direct effect on the bruchid population or on the parasitoid progeny. The ecological significance of these findings and implications for biological control are discussed.

  • combining parasitoids and plant resistance for the control of the bruchid Acanthoscelides obtectus in stored beans
    Journal of Stored Products Research, 2003
    Co-Authors: I Schmale, Felix L Wackers, C Cardona, Silvia Dorn
    Abstract:

    Acanthoscelides obtectus (Say) and Zabrotes subfasciatus (Boheman) are the main bruchid pests of stored beans in widespread regions of Latin America and Africa. Host-plant resistance based on the protein arcelin is effective in reducing damage caused by Z. subfasciatus, but beans containing arcelin remain susceptible to A. obtectus. The compatibility of combining arcelin resistance with biological control by Dinarmus basalis (Rondani) was investigated in climatic chambers. Three arcelin containing bean varieties with high and intermediate resistance towards Z. subfasciatus (RAZ 36, RAZ 94 and RAZ 104) and an arcelin-free standard (Calima, susceptible to both bruchids) were investigated. Immature development of A. obtectus in arcelin-containing beans was prolonged by 15% as compared to the standard, allowing D. basalis to have access to suitable host stages for a longer period of time. Over a 20-week storage period, the combined use of resistant host plants and biological control agents yielded best results with the host-plant varieties RAZ 94 and RAZ 104. In both varieties, parasitoids managed to keep bruchid damage below 1% as compared to 4.7% in the arcelin-free standard, and bruchids were eradicated in 80% of the replicates. Control levels in RAZ 36, the bean variety with the highest resistance to Z. subfasciatus, were not greater than the standard. Our results show that the combination of certain arcelin-enriched bean varieties with the parasitoid D. basalis is favourable for suppressing damage by A. obtectus.

  • field infestation of phaseolus vulgaris by Acanthoscelides obtectus coleoptera bruchidae parasitoid abundance and consequences for storage pest control
    Environmental Entomology, 2002
    Co-Authors: I Schmale, Felix L Wackers, C Cardona, Silvia Dorn
    Abstract:

    Over a period of 3 yr we collected 19 samples (1 kg each) of recently harvested beans (Phaseolus vulgaris L.) from eight small-scale farms in Restrepo, Valle de Cauca, Colombia. Initial infestation by Acanthoscelides obtectus (Say) was low, but frequent. At harvest, 90% of the bean samples were infested by the weevil. The average level of infestation was 16 weevils per 1,000 beans, with a maximum of 55 weevils. Infested beans usually carried multiple larvae with a maximum of 13 larvae per bean. Emergence data indicate that oviposition by A. obtectus in the field is confined to a very short period before harvest. This relatively narrow time window can be exploited for proper timing of control measures. Only one species of parasitoid, Horismenus ashmeadii (Dalla Torre) (Hymenoptera: Eulophidae), was recorded, emerging from 21% of the samples. Samples with parasitoids had an average of five parasitoids per 1,000 beans, with a maximum of 12 parasitoids. This represented a parasitization level of 18%. During the 16 wk of storage, two weevil generations emerged, which caused visible damage in 0.5 and 34% of the beans (average of 14%). Although H. ashmeadii was successful in attacking the first generation of A. obtectus in the field, it failed to attack or develop under storage conditions. This indivates H. ashmeadii cannot serve as a postharvest control agent.

Alvaro Rodriguezgonzalez - One of the best experts on this subject based on the ideXlab platform.

  • spores of trichoderma strains sprayed over Acanthoscelides obtectus and phaseolus vulgaris l beans effects in the biology of the bean weevil
    Journal of Stored Products Research, 2020
    Co-Authors: Alvaro Rodriguezgonzalez, M P Campelo, A Lorenzana, Sara Mayoprieto, Oscar Gonzalezlopez, Samuel Alvarezgarcia, Santiago Gutierrez, P A Casquero
    Abstract:

    Abstract Acanthoscelides obtectus is an insect pest feeding on common beans Phaseolus vulgaris. Three strains of Trichoderma harzianum and one strain of Trichoderma citrinoviride were sprayed on insect adults and Phaseolus vulgaris L. beans in order to investigate the efficiency of the fungi in combating Acanthoscelides obtectus insect pest. The strains E20, T34, and T019 exhibited high virulence on adults. Spores of T34 isolate were more attractant for both sexes and showed a higher mortality rate on insects in contact with treated beans than the other strains. Treated beans showed a lower weight loss compared to the untreated ones. T019 and T008 treatments resulted in a lower weight loss of beans than the other fungal strains. Daily insect emergence was reduced in treated beans. The strain T34 accounted for the lowest daily emergence of insects. T008, T019, and E20 exhibited the capacity to repel insects, which resulted in a reduction of damaged beans as well as a lower number of holes per bean. Trichoderma strains were re-isolated from insects’ cadavers extracted from treated beans. Regarding these results, T34 strain could be used in the control of A. obtectus adults due to its high lethal effect. Additionally, T008 and T019 strains, showing good results in terms of insecticidal activity, insect repellency, reduction of damaged beans and lower weight loss of beans, could also be used for the biological control of A. obtectus.

  • toxicity of five cry proteins against the insect pest Acanthoscelides obtectus coleoptera chrisomelidae bruchinae
    Journal of Invertebrate Pathology, 2020
    Co-Authors: Alvaro Rodriguezgonzalez, P A Casquero, Alejandra J Porteousalvarez, Mario Del Val, Baltasar Escriche
    Abstract:

    Abstract The beetle Acanthoscelides obtectus (Say) causes severe post-harvest losses in the common bean (Phaseolus vulgaris). Under laboratory conditions, the susceptibility of A. obtectus to five coleopteran-specific Cry toxic proteins from Bacillus thuringiensis (Cry1Ba, Cry1Ia, Cry3Aa, Cry7Ab, and Cry23/37) was evaluated. After 30 days exposure, Cry proteins demonstrated high activity against A. obtectus adults (100% mortality). Proteins showed statistical differences in toxicity parameters compared to the control treatment, but the parameters were similar among them, and indicated that the final toxic effects can be observed after the 24th day. The toxic effects on A. obtectus larvae were evaluated indirectly by allowing adults to oviposit on treated beans and recording the emergence of F1 adults. All treatments resulted in a lower rate of successful emergence compared to the control treatment, ranging from 60% (Cry23/37) to 10% (Cry1Ia) reduction in eclosion. Finally, to evaluate the ability of Cry proteins to protect the beans against A. obtectus; the number of beans infested, the number of holes in each bean and bean weight loss were determined 45 days after the treatment. The parameters showed significant bean protection by all Cry proteins analyzed compared to control treatment. Cry23/37 showed the best results, however, results for the other proteins were similar. The proteins belong to different Cry protein families, which suggest that they could be used in combination to increase plant protection without compromising resistance management. Moreover, adult emergence and bean protection results indicate differences among the proteins, which may suggest different modes of action. Our results indicate that the studied Cry proteins can be applied for the control of A. obtectus larvae and adults.

  • effect of trichodiene synthase encoding gene expression in trichoderma strains on their effectiveness in the control of Acanthoscelides obtectus
    Journal of Stored Products Research, 2019
    Co-Authors: Alvaro Rodriguezgonzalez, P A Casquero, Rosa E Cardoza, Santiago Gutierrez
    Abstract:

    Abstract Acanthoscelides obtectus, known as the bean weevil, is an insect pest that feeds on wild and cultivated common beans. Four Trichoderma isolates, two trichodiene (TD) producers (T34–5.27, E20–5.7) and their corresponding parental strains (T34, E20), were evaluated to determine the effect of their metabolites against A. obtectus adults. TD is a non-phytotoxic Volatile Organic Compound (VOC), which is the first commitment intermediate in the biosynthesis of trichothecenes. Accumulated emergence of insects was reduced in beans treated with these fungal isolates, being more reduced with E20 and T34 strains. TD producer strains, which previously showed to produce a higher number of damaged beans than their respective parental strains, gave rise to a higher insects emergence. Beans treated with fungal isolates had a lower weight loss than the control treatment, with T34 exhibiting the lowest weight loss among all fungal isolates analyzed. Furthermore, E20 showed the higher repellent activity against A. obtectus adults and produced a smaller number of holes per bean. Thus, Trichoderma isolates evaluated are good for the biological control of A. obtectus pest on beans, in which the parental strains (E20 and T34) were those exhibiting a better control of this insect than their respective TD-producer derivates strains. These results suggest that production of TD reduces effectiveness of Trichoderma T34 and E20 strains to control this insect pest.

  • effect of trichodiene production by trichoderma harzianum on Acanthoscelides obtectus
    Journal of Stored Products Research, 2018
    Co-Authors: Alvaro Rodriguezgonzalez, A Lorenzana, Sara Mayoprieto, Samuel Alvarezgarcia, P A Casquero, Victor Suarezvillanueva, Guzman Carrohuerga, Rosa E Cardoza, Santiago Gutierrez
    Abstract:

    Abstract Acanthoscelides obtectus is an insect pest that feeds on wild and cultivated common beans. Two trichodiene (TD) producers (T34–5.27, E20–5.7) of Trichoderma spp., and their corresponding wild strains (T34, E20), were evaluated to determine the effect of TD production on the toxicity of these strains against A. obtectus adults. TD is a non-phytotoxic volatile organic compound (VOC), which is an intermediate in the biosynthesis of trichothecenes. Daily emergence of insect was increased in treated beans with TD producer's strains, compared with beans treated with the wild strains. T34–5.27 and E20–5.7 had the capacity to attract a higher percentage of insects than their parental strains. As a result, a higher number of beans is damaged, and subsequently resulted in a higher bean weight loss. Between the parental strains, E20 is repellent for both sexes, produced a smaller number of damaged beans and a lower number of holes per bean. These results would indicate that production of TD is negative for the control of this insect pest, and that even when TD is not phytotoxic, the response of beans against A. obtectus, implies that the presence of this VOC significantly reduce the bean defensive response against this pest.

Michael A. Birkett - One of the best experts on this subject based on the ideXlab platform.

  • Isolation and identification of floral attractants from a nectar plant for the dried bean beetle, Acanthoscelides obtectus (Coleoptera: Chrysomelidae, Bruchinae).
    Pest Management Science, 2018
    Co-Authors: József Vuts, Christine M. Woodcock, Stephen J. Powers, John A. Pickett, John C Caulfield, Michael A. Birkett
    Abstract:

    BACKGROUND: The response of virgin females of the legume pest Acanthoscelides obtectus (Coleoptera: Bruchidae) to headspace extracts of volatiles collected from flowers of a nectar plant, Daucus carota, was investigated using behaviour (four-arm olfactometry) and coupled gas chromatography-electroantennography (GC-EAG). RESULTS: Odours from inflorescences were significantly more attractive to virgin female beetles than clean air. Similarly, a sample of volatile organic compounds (VOCs) collected by air entrainment (dynamic headspace collection) was more attractive to beetles than a solvent control. In coupled GC-EAG experiments with beetle antennae and the VOC extract, six components showed EAG activity. Using coupled GC-mass spectrometry (GC-MS) and GC peak enhancement with authentic standards, the components were identified as α-pinene (S:R 16:1), sabinene, myrcene, limonene (S:R 1:3), terpinolene and (S)-bornyl acetate. Females preferred the synthetic blend of D. carota EAG-active volatiles to the solvent control in bioassays. When compared directly, odours of D. carota inflorescences elicited stronger positive behaviour than the synthetic blend. CONCLUSION: This is the first report of behaviourally active volatiles linked to pollen location for A. obtectus, and development of the six-component blend is being pursued, which could underpin the design of semiochemical-based field management approaches against this major pest of stored products. © 2018 Society of Chemical Industry.

  • Host shift induces changes in mate choice of the seed predator Acanthoscelides obtectus via altered chemical signalling
    2018
    Co-Authors: József Vuts, Christine M. Woodcock, Lisa König, Stephen J. Powers, John A. Pickett, Árpád Szentesi, Michael A. Birkett
    Abstract:

    The mechanisms of host shift in phytophagous insects are poorly understood. Among the many proposed processes involved, sexual selection via semiochemicals has recently been suggested. This hypothesizes that sexual communication using pheromones is modified as a result of development on a new host, and such plant-induced phenotypic divergence in mate recognition cues can lead to reproductive isolation between host lines. We tested this hypothesis on Acanthoscelides obtectus, an oligophagous bruchid of Phaseolus vulgaris beans worldwide, which also develops in acceptable non-hosts, such as chickpea (Cicer arietinum L.). Male sex pheromone blends of the bean, chickpea and chickpea/bean host lines during artificially induced host shifts showed different composition. Bean-reared females did not distinguish between blends, whereas chickpea and chickpea/bean females preferred the chickpea male pheromone. However, electrophysiological (EAG) responses to male odour of antennae of the three female host lines were similar, all preferring bean-reared males. Egg-laying choice tests revealed a uniform preference for bean seeds across female host lines, even after multiple generations, whereas larvae did not distinguish between bean and chickpea seeds. We conclude that the development of divergent chemical signalling systems during host shifts does not facilitate the evolution of host races in A. obtectus, because oviposition preferences remain unaffected.

  • multiple roles of a male specific compound in the sexual behavior of the dried bean beetle Acanthoscelides obtectus
    Journal of Chemical Ecology, 2015
    Co-Authors: József Vuts, Stephen J. Powers, J A Pickett, John C Caulfield, Michael A. Birkett
    Abstract:

    Males of Acanthoscelides obtectus (Coleoptera: Chrysomelidae, Bruchinae) emit methyl (E,R)-2,4,5-tetradecatrienoate that attracts females for mating. This study identified further roles for this compound in the sexual behavior of A. obtectus. Earlier observations revealed that males touched females with their antennae while tandem-running with them and initiated mounting and copulation, whereas they showed no such behavior toward other males. A series of subsequent laboratory choice tests were set up to establish if certain cuticular compounds aid contact sex recognition in A. obtectus. Males chose virgin females over other males. The activity toward females could be eliminated by rinsing with hexane, but was regained by application of female extract onto previously rinsed females. Gas chromatographic (GC) comparison of hexane extracts revealed the presence of two male-specific compounds, methyl (E,R)-2,4,5-tetradecatrienoate and octadecanal, which were absent from the behaviorally active female samples. Of the two compounds, methyl (E,R)-2,4,5-tetradecatrienoate was found to be responsible for the inhibition of male sexual behavior, similar to that observed with crude male extracts applied to virgin females. Furthermore, males preferred virgin over mated females. GC analyses revealed the presence of methyl (E,R)-2,4,5-tetradecatrienoate in mated females in amounts sufficient to curtail mating attempts. It appears that methyl (E,R)-2,4,5-tetradecatrienoate, besides being a male-produced sex pheromone, acts as a male-recognition signal in A. obtectus. Males also transfer it onto females during mating, resulting in mated females being avoided by courting males.