bluuebunny/crossref_metadata_2025_split huggingface dataset:
The population genetics of the apple maggot fly, Rhagoletis pomonella and the snowberry maggot, R. zephyria: implications for models of sympatric speciation
Authors: Feder Jeffrey L. , Williams Scott M. , Berlocher Stewart H. , McPheron Bruce A. , Bush Guy L. 
Published: October 2003

AbstractTrue fruit flies belonging to the Rhagoletis pomonella (Diptera:Tephritidae) sibling species complex possess several attributes consistent with a history of sympatric divergence via host plant shifts. Here, we investigate whether hybridization and genetic introgression is occurring between two members of the group, Rhagoletis pomonella (Walsh), whose primary hosts are domestic apples (Malus pumila) and hawthorns (Crataegus spp., and R. zephyria (Snow) whose host is snowberries (Symphoricarpos spp.). These flies are important because they appear to be at a transition stage between taxa reproductively isolated solely on the basis of host plant‐related adaptations and those that have evolved additional non‐host dependent sterility and inviability. Observing extensive hybridization and introgression between R. pomonella and R. zephyria would have major repercussions for current models of sympatric speciation.In a survey of allozyme and mitochondrial DNA (mtDNA) variation for 1105 flies collected throughout the northern United States we found two results suggesting that low level hybridization occurs between R. pomonella and R. zephyria. (1) Two flies reared from snowberries and one fly reared from hawthoms had genotypes indicative of them being R. pomonella and R. zephyria, respectively. Rhagoletis pomonella and R. zephyria adults may therefore occasionally frequent each others host plant, providing the opportunity for hybridization. (2) Four flies collected from hawthorns and one from snowberries had genotypes that made them likely to be F1 hybrids.Likelihood analysis revealed the data were also consistent with an hypothesis of shared ancestral alleles (i.e., the pattern of genetic variation could also be explained by R. pomonella and R. zephyria sharing alleles/haplotypes whose origins date to a common ancestor). We estimated that, in the absence of interspecific mating, random assortment of genes within R. pomonella and R. zephyria populations would produce an average of 5.4 flies with genotypes suggesting they were F1 hybrids – a number equivalent to the 5 putative F1 hybrids observed in the study. Our results therefore underscore the difficulty in distinguishing between hypotheses of low level introgression and shared ancestral polymorphism. But even if hybridization is occurring, the data suggest that it is happening at a very low and probably evolutionarily insignificant level (perhaps 0.09% per generation), consistent with sympatric speciation theory. Future tests are discussed that could help resolve the hybridization issue for R. pomonella and R. zephyria.
Freezing‐altered palatability of Bradford pear to Japanese beetle: evidence for decompartmentalization and enzymatic degradation of feeding deterrents
Authors: Keathley Craig P. , Potter Daniel A. , Houtz Robert L. 
Published: October 2003

AbstractThe basis for resistance of Bradford callery pear, Pyrus calleryana Decaisne ‘Bradford,’ [Rosaceae] to the Japanese beetle, Popillia japonica Newman, was investigated. Chloroform‐dipping rendered leaves palatable, initially suggesting that deterrent waxes had been removed. However, extracts containing surface waxes were not deterrent. Subsequent experiments showed that increased palatability of solvent‐dipped leaves is associated with enzymatic tissue browning, characteristic of polyphenol oxidases, rather than simply release of phagostimulants from surface disruption of damaged leaves. Frozen and thawed leaves showed similar browning, becoming increasingly palatable for several hours after thawing. Palatability changes were temperature‐ and aerobic‐sensitive, further evidence that oxidizing enzymes are involved. Juice from leaves that had been frozen and thawed stimulated feeding on glass fiber disks, whereas fresh leaf juice did not. Survival and fecundity were much higher for beetles fed frozen and thawed or chloroform‐dipped Bradford pear leaves than for beetles fed normal leaves. We hypothesize that decompartmentalization of deterrent compounds, possibly phenolics, followed by enzymatic oxidation and altered leaf chemistry may explain the increased palatability of chloroform‐dipped or frozen and thawed Bradford pear tissue to P. japonica. This approach may be helpful in identifying specific compounds responsible for resistance of woody plants to generalist insects.
Trichogramma egg parasitism of Helicoverpa armigera on pigeonpea and sorghum in southern India
Authors: Romeis J. , Shanower T.G. , Zebitz C.P.W. 
Published: October 2003

Abstract Trichogramma spp. (Hymenoptera: Trichogrammatidae) only rarely parasitize eggs of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on pigeonpea (Cajanus cajan (L.) Millspaugh), while on other plants including sorghum (Sorghum bicolor (L.)) high parasitism levels of this host are found. In this study two strategies designed to increase the parasitoid activity on pigeonpea were tested in the field: intercropping pigeonpea with sorghum and mass‐releasing T. chilonis Ishii. Neither strategy led to an increase in parasitism. On pigeonpea, H. armigera oviposited >74.8% of its eggs on calyxes and pods. Parasitism levels in host eggs collected from different plant structures varied significantly with 3.6, 0.3, and 40.7% of eggs on calyxes, pods, and leaves parasitized. Earlier studies have shown that calyxes and pods possess long glandular and non‐glandular trichomes, and are covered by sticky trichome exudates which inhibit parasitoid searching behaviour. Parasitism levels between 27.9 and 100% were recorded from host eggs on the intercropped sorghum. Trichogramma chilonis was the dominant parasitoid species. The mean clutch size was 2.03, but up to six parasitoids emerged per egg. Progeny sex ratio (% females) decreased with clutch size, from 63.1% at a clutch size of one to 46.0% at a clutch size of five. Sticky trap catches showed that while the parasitoid population in sorghum increased when H. armigera started ovipositing, the population within pigeonpea did not benefit from either a high parasitoid population in sorghum or a high host egg density on pigeonpea. During one of five seasons studied, however, high parasitism levels (up to 73%) were recorded on pigeonpea. During this season, H. armigera oviposited on pigeonpea plants in the vegetative growth stage and a high proportion of eggs were collected from leaves. Parasitism levels were positively correlated with the percentage of eggs collected from leaves. This study shows that the parasitization efficiency of Trichogramma spp. on pigeonpea depends mainly on the location of the host eggs. This explains why parasitism levels of H. armigera eggs on pigeonpea did not increase when intercropped with sorghum or after mass‐releasing T. chilonis.
Modifications in dispersal and oviposition of Bt‐resistant and Bt‐susceptible Colorado potato beetles as a result of exposure to Bacillus thuringiensis subsp. tenebrionis Cry3A toxin
Authors: Alyokhin Andrei V. , Ferro David N. 
Published: October 2003

AbstractLaboratory strains of Colorado potato beetle, Leptinotarsa decemlineata (Say), physiologically resistant and susceptible to Bacillus thuringiensis (Berliner) subsp. tenebrionis Cry3A toxin were reared to adults on caged potato plants. Influence of three different diets (transgenic potatoes, regular potatoes, and regular potatoes followed by the transgenic potatoes) on beetle mortality, fecundity, and flight behavior were tested under laboratory conditions. A computer‐linked flight mill system was used to quantify beetle flight, and dissections were performed to determine the level of flight muscle development. Susceptible beetles continuously fed on transgenic foliage suffered heavy mortality, did not develop flight muscles, and did not produce any eggs. Resistant beetles continuously fed on transgenic foliage were capable of flight and reproduction; however, it took them longer to initiate flight behavior, and their fecundity was lower than fecundity of other treatments. In both strains, detrimental effects became significantly less severe when the beetles were allowed to feed on regular foliage prior to toxin ingestion. In the resistant strain, ingestion of Cry3A toxin significantly increased flight activity, indicating that physiological resistance was probably reinforced by the behavioral escape from toxic environments. No such response was observed for susceptible beetles. When fed on regular foliage, resistant Colorado potato beetles engaged in significantly fewer flights than susceptible beetles. Behavioral differences between resistant and susceptible beetles observed in the present study are likely to affect gene flow between transgenic crops and adjacent refugia, and should be taken in consideration when designing resistance management plans for transgenic potato crops.
Olfactory conditioning of the proboscis extension in bumble bees
Authors: Laloi D. , Sandoz J.C. , Picard‐Nizou A.L. , Marchesi A. , Pouvreau A. , Taséi J.N. , Poppy G. , Pham‐delègue M.H. 
Published: October 2003

AbstractThe foraging behaviour of bumble bees is well documented for nectar and/or pollen gathering, but little is known about the learning processes underlying such behaviour. We report olfactory conditioning in worker bumble bees Bombus terrestris L. (Hymenoptera: Apidae) obtained under laboratory conditions on restrained individuals. The protocol was adapted from the proboscis extension conditioning previously described in the honey bee Apis mellifera L. Bumble bees were found to be able to learn a pure odorant when it was presented in paired association with a sugar reward, but not when odour and reward were presented in an explicitly unpaired procedure. This suggests an associative basis for this olfactory learning. Bumble bees showed similar conditioning abilities when stimulated with two different floral odours. An effect of the sugar reward concentration on the learning performances was found.
Effect of avocadofurans on larval survival, growth, and food preference of the generalist herbivore, Spodoptera exigua
Authors: Rodriguez‐Saona Cesar R. , Trumble John T. 
Published: October 2003

AbstractWe examined the effect of two avocadofurans, 2‐(pentadecyl)furan and 2‐(heptadecyl)furan, from avocado idioblast oil cells on maturation and larval feeding behavior of a generalist insect herbivore, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Experiments were conducted using two larval sizes: early‐stadium larvae refer to those larvae from experiments initiated with neonates while late‐stadium larvae refer to those larvae from experiments initiated with third instars. In order to use selected sublethal doses for developmental and behavioral studies on early‐ and late‐stadium larvae, log‐dose probit lines were determined using diet incorporation bioassays. Both avocadofurans had similar toxicities to early‐stadium larvae [LC50= 2.2 and 1.9 μmoles/g of diet for 2‐(pentadecyl)furan and 2‐(heptadecyl)furan, respectively] and late‐stadium larvae (LC50= 3.0 and 3.4 μmoles/g of diet, respectively). In diet bioassays extending from egg hatch to adult emergence, the avocadofurans significantly prolonged larval developmental times and reduced S. exigua pupal weights. In 7 d no‐choice bioassays initiated with cohorts of newly‐molted third instars, the avocadofurans significantly reduced larval weights at various sublethal concentrations (below LC50 values). To test larval feeding deterrence effects of these avocadofurans, choice tests were conducted using early and older instar larvae. A significantly higher proportion of early‐stadium larvae preferred control diet over diet treated with either avocadofuran at several sublethal concentrations. Similarly, choice tests with late‐stadium larvae showed greater proportions of larvae on control diet than treated diet even at concentrations below the LC50. Moreover, late‐stadium larvae consumed significantly more of the control diet than the treated diet. Thus, the avocadofurans may act as feeding deterrents as well as toxicants in plant protection against non‐adapted insect herbivores.
Effect of an ecdysteroid agonist, tebufenozide, on the completion of diapause in susceptible and resistant strains of the codling moth, Cydia pomonella
Authors: Sauphanor Benoît , Bouvier Jean‐Charles , Brosse Véronique 
Published: October 2003

AbstractCodling moth Cydia pomonella (L.) (Lepidoptera, Tortricidae) larvae kept under a short photoperiod enter a diapause which can be broken by exposure to 25 °C following an extended chilling period. We investigated the effects of the ecdysteroid agonist tebufenozide on the diapause of this species, both on a laboratory strain susceptible to insecticides and two strains selected for resistance to diflubenzuron or deltamethrin. The treatment induced moulting by breaking diapause of the susceptible strain when applied at the end of the growth period, or by reducing the pre‐emergence period when applied after chilling. The strains exhibiting resistance in the neonate instar were also resistant to the ecdysteroid agonist applied to diapausing larvae, indicating that mechanisms of resistance remained active during this arrest of development. High doses of tebufenozide were lethal for the most resistant insects, but neither reduced the pupation delay nor produced the larval‐pupal moults which occur in the susceptible strain. As diapausing larvae of C. pomonella can be easily collected, the expression of resistance to tebufenozide both in the target instar, i.e. neonates, and during diapause may contribute to early detection of resistance to this insecticide in field populations.
Effects of augmentative releases of eggs and larvae of the ladybird beetle, Adalia bipunctata, on the abundance of the rosy apple aphid, Dysaphis plantaginea, in organic apple orchards
Authors: Wyss Eric , Villiger Mathias , Hemptinne Jean‐Louis , Müller‐schärer Heinz 
Published: October 2003

AbstractThe impact of augmentative releases of larvae and eggs of the indigenous ladybird beetle Adalia bipunctata (L.) (Coleoptera: Coccinellidae) against the rosy apple aphid Dysaphis plantaginea Pass. (Homoptera: Aphididae), a major pest insect on apple trees, was assessed in field experiments in Switzerland, during 1997. In a first experiment, eggs and larvae were released on 3‐year old apple trees infested with five aphids at four different predator‐prey ratios (0:5, 1:5, 1:1, 5:1). In a second experiment, eggs and larvae were released at a predator‐prey ratio of 5:1 on branches of apple trees naturally infested with aphids. In both experiments, the interaction with ants was taken into account and the releases were done at two different times in spring. The results showed that an augmentative release of larvae significantly prevented the build‐up of colonies of D. plantaginea. Significant reductions in aphid numbers were recorded at the two highest predator‐prey ratios, 1:1 and 5:1. Larvae were efficient just before flowering of apple trees at a time when growers normally have to spray their trees. On trees where ants were present the larvae of A. bipunctata were significantly less efficient. Effects of eggs of A. bipunctata, however, were less reliable. At the first date of release (5 April), they did not hatch, probably as a consequence of bad weather conditions.
Life‐history and oviposition behaviour of Amitus bennetti, a parasitoid of Bemisia argentifolii
Authors: Drost Y.C. , Qiu Y.T. , Posthuma‐Doodeman C.J.A.M. , van Lenteren J.C. 
Published: October 2003

Abstract Amitus bennetti Viggiani & Evans (Hymenoptera: Platygasteridae) is a recently described parasitoid of the silverleaf whitefly, Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae). Behaviour and life history of the parasitoid are described. The first nymphal instar of B. argentifolii is preferred by the parasitoid, but the 1st through 4th instar may be parasitised. Females first investigate hosts with their antennae, then walk over the host, and eventually step with their front legs on the leaf and insert their ovipositor inside the host facing away from the host, while the hind legs are still on the host. The time from encounter to oviposition (=latency to oviposition) is shortest on the 1st instar. Oviposition duration (mean=39 s) comprises 50% of the handling time. Development time from egg to adult decreases from 72 days at 15 °C to 42 days at 20 °C to 28 days at 25 °C. We estimate that 400 degree days is required for development, with a development threshold of 10 °C. Adult longevity in the absence of hosts was 29, 26 and 19 days and with hosts present 8, 8 and 5 days at 15, 20 and 25 °C, respectively. Amitus bennetti is proovigenic and oviposits most eggs shortly after adult emergence. During the first day of their adult lives females laid 1, 31 and 49 eggs at 15, 20 and 25 °C, respectively. Compared with other parasitoid species, the development time of A. bennetti is very long, and the implications of this for management of B. argentifolii are discussed.
Plants with spider‐mite prey attract more predatory mites than clean plants under greenhouse conditions
Authors: Janssen Arne 
Published: October 2003

AbstractAlthough many predators and parasitoids are known to respond to odours produced by plants infested with their prey under laboratory conditions, there are actually few studies that show that this response leads to higher numbers of predators or parasitoids on the plants under natural conditions. Here we study the response of predatory mites (Phytoseiulus persimilis Athias‐Henriot, Acari, Phytoseiidae) to odours from cucumber plants infested with two‐spotted spider mites (Tetranychus urticae Koch, Acari, Tetranychidae) in greenhouse release experiments, where predators were released in the centre of a hexagon of cucumber plants. Forty to 57% of all predators released were recaptured on plants within 7 h. Of these, an average of 79.5% were found on infested plants, indicating that these attract about 4 times as many predators as do clean plants. Hence, the blind predatory mites were guided to the plants with prey by herbivore‐induced odours produced by the plant, as was indicated by olfactometer experiments, where it was found that P. persimilis preferred odours from infested cucumber plants to odours from clean cucumber plants. The long‐range searching behaviour of P. persimilis is discussed.
Infochemicals mediating the foraging behaviour of Aleochara bilineata Gyllenhal adults: sources of attractants
Authors: Royer Lucie , Boivin Guy 
Published: October 2003

Abstract Aleochara bilineata Gyll. (Coleoptera: Staphylinidae) adults feed on eggs and larvae of cabbage maggot, Delia radicum (L.) (Diptera: Anthomyiidae), and might be used to control this pest. We undertook tests in a Y‐tube olfactometer to determine if infochemicals are involved in the food foraging behaviour of A. bilineata adults and to precisely determine the potential sources of stimuli. A. bilineata adults oriented toward the stimuli from both the food‐plant of the prey (rutabaga: Brassica napus var. napobrassica (L.) Reichb.) and the prey‐plant complex (rutabaga infested by cabbage maggot larvae), but adults significantly preferred the effluvia of infested to uninfested rutabaga in a choice test. The sources of infochemicals in the infested rutabaga were the cabbage maggot larvae themselves and their frass. However, in a choice test adults preferred the effluvia of the larvae to that of the damaged rutabaga from which those larvae were obtained. It is not expected that a generalist predator uses precise herbivore‐derived signals in food foraging activity, but the preference of A. bilineata adults for the larval volatiles over frass volatiles may reflect the dependence of this species on dipteran pupae for reproduction.
Effects of selected physical and chemical treatments of Colorado potato beetle eggs on host acceptance and development of the parasitic wasp, Edovum puttleri
Authors: Hu Jing S. , Gelman Dale B. , Bell Robert A. 
Published: October 2003

AbstractEffects of various physical and chemical treatments of Colorado potato beetle [Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)] eggs on parasitization and development of the egg parasitoid Edovum puttleri (Hymenoptera: Eulophidae) were investigated. UV irradiation did not affect host acceptance but reduced host suitability for UV exposure times ≥90 min. Susceptibility of host eggs to UV irradiation varied with host age; eggs were most vulnerable to damage from irradiation at 12, 18, and 24 h post‐oviposition. The rate of parasitization also was influenced by host age. Percent parasitization was greatest in freshly laid eggs and 24–30 h old eggs. Seventy‐seven percent of host eggs frozen at −20 °C (5 min) were parasitized by E. puttleri, but extended exposure of eggs to −20 °C reduced both acceptance and suitability. Host eggs that had been washed with hexane (removal of kairomone and sticky layer) also were parasitized. After 5 min of washing, application of kairomone significantly increased the rate of parasitism (from 74.7% to 88.2%), but with longer periods of washing, kairomone application had no significant effect on percent parasitism. Thus, the sticky material(s) coating the egg did not appear to be essential for parasitization to occur. Our results provide effective methods and times for treating Colorado potato beetle eggs to maximize parasitization and development of E. puttleri.
Suitability of new and old association hosts for the development of selected microgastrine parasitoids of gramineous stemborers
Authors: Ngi‐Song A.J. , Overholt W.A. , Smith J.W. , Vinson S.B. 
Published: October 2003

AbstractThe present study examined the acceptability and suitability of Old World stemborers (Chilo partellus and C. orichalcociliellus) for the development of New World parasitoids (Apanteles deplanatus and A. minator) and New World stemborers (Diatraea saccharalis and D. grandiosella) for the development of Old World parasitoids (Cotesia sesamiae, C. flavipes and C. chilonis). Results revealed that acceptance and suitability were high in old associations. In new associations, parasitoids accepted about 60% of the new association hosts. In addition, 10 out of 17 new associations were successful. Apanteles species appeared to be more physiologically host specific than Cotesia species. For example, two of four new association hosts were accepted by A. deplanatus and only one (D. saccharalis) was partially suitable for progeny development. Among the Cotesia species, Cotesia flavipes appeared to have a wider host range than the two other species. It attacked all hosts offered and successfully parasitized all but one (D. grandiosella). Diatraea saccharalis was accepted and was a suitable host for the development of all parasitoid species tested, whereas D. grandiosella was unsuitable for the development of four out of five parasitoid species tested. No clear pattern was observed as behavioral acceptance did not always agree with the pattern of physiological suitability. Implications of these findings for importation biological control of stemborers are discussed.