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  • 1
    Electronic Resource
    Electronic Resource
    Recruitment of entomopathogenic nematodes by insect-damaged maize roots (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 434 (2005), S. 732-737 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Plants under attack by arthropod herbivores often emit volatile compounds from their leaves that attract natural enemies of the herbivores. Here we report the first identification of an insect-induced belowground plant signal, (E)-β-caryophyllene, which strongly attracts an entomopathogenic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03451
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  • 2
    Electronic Resource
    Electronic Resource
    Why is there no interspecific host discrimination in the two coexisting larval parasitoids of Drosophila species; Lepyopilina heterotoma (Thomson) and Asobara tabida (Nees) (1985)
    Springer
    Oecologia 67 (1985), S. 352-359 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary (1) The parasitic wasps Leptopilina heterotoma (Thomson) and Asobara tabida (Nees) usually refrain from laying eggs in hosts that have already been parasitized by themselves or by a conspecific (=intraspecific host discrimination). (2) In contrast to intraspecific host discrimination, interspecific host discrimination, in which females refrain from laying eggs in hosts that have already been parasitized by the other species, is not found in these sympatric parasitid species. (3) Because we expected that development of interspecific host discrimination would increase the fitness of the wasps, we wondered why this strategy had not evolved in L. heterotoma and A. tabida. (4) We therefore developed a simulation model of the parasitization process, in which interspecific host discrimination can be included. (5) By varying the time needed for host location, survival chances and the proportions of hosts parasitized, we obtained estimates for the number of offspring in situations with and without interspecific host discrimination. (6) The results imply that, assuming that female wasps carry an ample supply of eggs, the development of interspecific host discrimination by L. heterotoma or A. tabida will not lead to increased fitness, even under extreme circumstances. Hence, interspecific host discrimination will not evolve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384940
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  • 3
    Electronic Resource
    Electronic Resource
    Timing of induced volatile emissions in maize seedlings (1998)
    Springer
    Planta 207 (1998), S. 146-152 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Induced defence ; Parasitoid ; Plant-insect interactions ; Semiochemicals ; Volatiles ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Maize (Zea mays L.) releases specific volatiles in response to herbivory by caterpillars. These volatiles are known to serve as cues for parasitic wasps to locate the herbivores. In the present study the exact time of volatile emission after simulated herbivory (mechanical damage and treatment with caterpillar regurgitant) was measured for seedlings of the cultivars “Ioana Sweet Corn” and “LG11”. Odours were collected every 0.5 h for a total of 12 h. Typical “green leaf odours”, (Z)-3-hexenal, (E )-2-hexenal, (Z)-hexen-1-o1, and (Z)-3-hexen-1-yl acetate, were emitted immediately upon damage and their amounts dropped rapidly after the first collections. Several of the induced compounds were released within 2 h after treatment, while others (mainly sesquiterpenoids) started to be released after 4 h. The LG11 seedlings emitted several compounds (e.g. β-myrcene, (Z)-β-ocimene, benzyl acetate, β-caryophyllene, (E,E )-α-farnesene) that were not detected for Ioana. (E,E )-α-farnesene was continuously emitted by LG11 seedlings, even by undamaged plants. Timing of the release of volatile compounds that the two varieties had in common did not differ significantly, with the exception of indole for which the peak production was considerably earlier for LG11. These findings are discussed in the context of biosynthetic pathways and mechanisms involved in induced emissions of plant volatiles and the exploitation of the resulting odour by parasitoids and predators of herbivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050466
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  • 4
    Electronic Resource
    Electronic Resource
    Herbivore-induced emissions of maize volatiles repel the corn leaf aphid, shape Rhopalosiphum maidis (1998)
    Springer
    Entomologia experimentalis et applicata 87 (1998), S. 133-142 
    Details
    ISSN: 1570-7458
    Keywords: Rhopalosiphum maidis ; Zea mays ; induced plant volatiles ; repellence ; (E)-β-farnesene ; alarm pheromone ; plant insect interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When maize plants, Zea mays L., are mechanically damaged and the damaged sites are treated with caterpillar regurgitant, the plants will release a specific blend of volatiles. It is known that these volatiles can be attractive to natural enemies of herbivores. We hypothesise that the plant volatiles constitute part of the induced plant defence and that herbivores will be affected by the odours as well. In laboratory and semi-field studies this hypothesis was tested for the aphid Rhopalosiphum maidis (Fitch) (Rhynchota, Sternorrhyncha, Aphididae). In a Y-tube olfactometer significantly more aphids chose the odour of healthy, undamaged maize seedlings when tested against clean air or plants treated with regurgitant. Clean air was chosen more often when tested next to the odour of treated plants. This apparently repellent effect of the odour of treated plants was significant for winged aphids, but not for the wingless aphids. In field experiments aphids were released in the centre of circles of eight potted maize plants. Four plants in each circle were damaged and treated with caterpillar regurgitant while the other plants were left unharmed. At different intervals after aphid release, the number of aphids was counted on each plant. Significantly fewer winged and wingless aphids were found back on treated plants than on healthy plants. We suggest that herbivores may be repelled by the odours because they could indicate that: 1) the plant has initiated the production of toxic compounds; 2) potential competitors are present on the plant; 3) the plant is attractive to parasitoids and predators. Aphids may be particularly sensitive to induced maize volatiles because one of the major compounds emitted by the plant is (E)-β-farnesene, which is a common alarm pheromone for aphids. Collections and analyses of the odours emitted by crushed R. maidis confirmed that it too emits (E)-β-farnesene when stressed. The results are discussed in context of plant defence strategies and their possible exploitation for the control of pest insects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003200108763
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  • 5
    Electronic Resource
    Electronic Resource
    Role of plant volatiles in host location by the specialist parasitoidMicroplitis croceipes cresson (Braconidae: Hymenoptera) (1993)
    Springer
    Journal of insect behavior 6 (1993), S. 625-639 
    Details
    ISSN: 1572-8889
    Keywords: Hymenoptera ; Braconidae ; Microplitis croceipes ; cotton ; cowpea ; parasitoid ; host location ; kairomones ; olfaction ; induced plant responses ; learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was conducted to determine the primary source of volatile cues within the plant-host complex used by hostseeking freeflying female Microplitis cro-ceipesCresson in flight tunnel bioassays. In single-source and two-choice tests, using wasps given an oviposition experience on either cotton (Gossypium hirsutum)or cowpea (Vigna unguiculata)seedlings damaged by corn earworm (CEW; Helicoverpa zeaBoddie), the damaged seedlings were significantly more attractive than the CEW frass, which was in turn more attractive than the larvae themselves. In a series of two-choice wind-tunnel tests, the discriminatory ability of the wasps was examined, following various oviposition experiences. Significantly more wasps flew to plants with “old” damage than to plants with “fresh” damage, regardless of whether they had experience on fresh or old damage. In a comparison of plant species, wasps with only one experience on either hostdamaged cotton or host-damaged cowpea were unable to distinguish between them, and showed no preference for either plant, whereas wasps with multiple experiences on a particular plant preferentially flew to that plant in the choice test. In comparing hosts with nonhosts, wasps successfully learned to distinguish CEW from beet armyworm (BAW; Spodoptera exigua)on cotton but were unable to distinguish CEW from either BAW or cabbage looper (Trichoplusia ni)on cowpea. The results show the important role played by plant volatiles in the location of hosts by M. croceipesand indicate the wasps’ limitations in discriminating among the various odors. The ecological advantages and disadvantages of this behavior are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048128
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  • 6
    Electronic Resource
    Electronic Resource
    Beneficial arthropod behavior mediated by airborne semiochemicals. VIII. Learning of host-related odors induced by a brief contact experience with host by-products inCotesia marginiventris (Cresson), a generalist larval parasitoid (1989)
    Springer
    Journal of insect behavior 2 (1989), S. 217-225 
    Details
    ISSN: 1572-8889
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Females of Cotesia marginiventris(Cresson), a generalist larval parasitoid, were observed to respond to host related odors in a four-arm olfactometer. The females were significantly more responsive to the odors after a brief contact experience with host-damaged leaves contaminated with host by products. During the experience, actual encounters with hosts were not required to improve subsequent responses to host-related odors. The response to odors of the plant-host complex with which parasitoids had experience was significantly higher than the response to odors of an alternative plant-host complex. This suggests that the experience effect is due, at least partly, to associative learning. We suspect that females of this generalist parasitoid, as was recently found for those of a specialist, recognize specific semiochemicals when they contact frass of suitable host larvae. The parasitoids, subsequently, associate the surrounding odors with the possible presence of hosts, and use these odors as cues in their search for more hosts. This could be an important component in the host-searching behavior of many parasitoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053293
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  • 7
    Electronic Resource
    Electronic Resource
    How contact foraging experiences affect preferences for host-related odors in the larval parasitoidCotesia marginiventris (Cresson) (Hymenoptera: Braconidae) (1990)
    Springer
    Journal of chemical ecology 16 (1990), S. 1577-1589 
    Details
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Braconidae ; Cotesia marginiventris ; host-finding ; semiochemicals ; conditioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Responses of individual females of the parasitoidCotesia marginiventris to the odors of four different complexes of host larvae feeding on leaves were observed in a four-arm olfactometer. The plant-host complexes were composed of fall armyworm (FAW) larvae or cabbage looper (CL) larvae feeding on either corn or cotton seedlings. Prior to testing, each female was given a brief foraging experience on a plant-host complex and was then exposed to the odors of the same complex in the olfactometer. The experienced females responded to familiar odors in a dose-related manner, and these responses were virtually identical to all four complexes. Preferences for the odors of one of two plant-host complexes were tested in dual choice situations. Generally, FAW odors were preferred over CL odors and corn odors over cotton odors. A short foraging experience significantly affected the females' odor preferences in favor of the odors released by the experienced complex. Additional experiments revealed that neither longer bouts of experience nor bouts that included ovipositions resulted in a stronger change in preference. Experience affected preference in combinations where only the host species was varied as well as in combinations where only the plant species was varied. The results, therefore, strongly indicate that both the plants and the hosts somehow are involved in the production and/or release of the semiochemicals that attractC. marginiventris.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01014091
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  • 8
    Electronic Resource
    Electronic Resource
    Volicitin, An Elicitor of Maize Volatiles in Oral Secretion of Spodoptera Exigua: Isolation and Bioactivity (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 189-202 
    Details
    ISSN: 1573-1561
    Keywords: Volicitin ; induced plant volatiles ; elicitor ; parasitoid attractants ; Zea mays ; Spodoptera exigua ; Microplitis croceipes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Plants respond to insect-inflicted injury by systemically releasing relatively large amounts of several volatile compounds, mostly terpenoids and indole. As a result, the plants become highly attractive to natural enemies of the herbivorous insects. In maize, this systemic response can be induced by the uptake via the stem of an elicitor present in the oral secretions of caterpillars. Such an elicitor was isolated from the regurgitant of Spodoptera exigua larvae, identified as N-(17-hydroxylinolenoyl)-L-glutamine, and named volicitin. Here we present details on the procedure that was used to isolate volicitin and the biosasays that demonstrate its potency as an elicitor of maize volatiles that attract parasitoids. With a series of liquid chromatography purification steps, volicitin was separated from all other inactive substances in the regurgitant of larvae of the noctuid moth S. exigua. Maize seedlings that were incubated in very low concentrations of pure natural volicitin released relatively large amounts of terpenoids and became highly attractive to the parasitoid Microplitis croceipes. The identification of this and other insect-derived elicitors should allow us to determine their precise source and function, and better understand the evolutionary history of the phenomenon of herbivore-induced volatile emissions in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005449730052
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  • 9
    Electronic Resource
    Electronic Resource
    Isolation and identification of allelochemicals that attract the larval parasitoid,Cotesia marginiventris (Cresson), to the microhabitat of one of its hosts (1991)
    Springer
    Journal of chemical ecology 17 (1991), S. 2235-2251 
    Details
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Braconidae ; Cotesia marginiventris ; corn ; parasitoid ; host searching ; semiochemicals ; synomones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Volatiles released from corn seedlings on which beet armyworm larvae were feeding were attractive to females of the parasitoid,Cotesia marginiventris (Cresson), in flight tunnel bioassays. Analyses of the collected volatiles revealed the consistent presence of 11 compounds in significant amounts. They were: (Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)- 3-hexen-1-yl acetate, linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, indole, α-trans-bergamotene, (E)-β-farnesene, (E)-nerolidol, and (3E,7E)-4,8,12-trimethyl-1, 3,7,ll-tridecatetraene. A synthetic blend of all 11 compounds was slightly less attractive to parasitoid females than an equivalent natural blend. However, preflight experience with the synthetic blend instead of experience with a regular plant-host complex significantly improved the response to the synthetic blend. Our results suggest thatC. marginiventris females, in their search for hosts, use a blend of airborne semiochemicals emitted by plants on which their hosts feed. The response to a particular odor blend dramatically increases after a parasitoid experiences it in association with contacting host by-products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00988004
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  • 10
    Electronic Resource
    Electronic Resource
    Herbivore-induced volatile emissions from cotton (Gossypium hirsutum L.) seedlings (1994)
    Springer
    Journal of chemical ecology 20 (1994), S. 3039-3050 
    Details
    ISSN: 1573-1561
    Keywords: Cotton ; H. zea ; feeding deterrence ; phytoalexin ; semiochemicals ; terpenes ; tritrophic interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effect of herbivory on the composition of the volatile blends released by cotton seedlings was investigated by collecting volatiles from undamaged, freshly damaged (0–2 hr after initiation of feeding), and old damaged (16–19 hr after initiation of feeding) plants on which corn earworm caterpillars (Helicoverpa zea Boddie) were actively feeding. A blend of 22 compounds was consistently observed to be emitted by the old damaged plants with nine occurring either only in, or in significantly greater amounts in old damaged, as compared with freshly damaged plants. These were (Z)-3-hexenyl acetate, hexyl acetate, (E)-β-ocimene, (3E)-4,8-dimethyl-1,3,7-nonatriene, (Z)-3-hexenyl butyrate, (E)-2-hexenyl butyrate, (Z)-3-hexenyl 2-methylbutyrate, (E)-2-hexenyl 2-methylbutyrate, and indole. The nature of this response is compared with other studies where herbivore-induced volatile responses are also known. The presence of large amounts of terpenes and aldehydes seen at the onset of feeding and the appearance of other compounds hours later suggest that cotton defense mechanisms may consist of a constitutive repertoire that is augmented by an induced mechanism mobilized in response to attack. A number of the induced compounds are common to many plants where, in addition to an immediate defensive function, they are known to be involved in the attraction of natural enemies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02033709
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