Voici les éléments 1 - 5 sur 5
  • Publication
    Métadonnées seulement
    Volatiles emitted by apple fruitlets infested by larvae of the European apple sawfly
    (1996)
    Boeve, Jean-Luc
    ;
    Lengwiler, Urs
    ;
    Tollsten, Lars
    ;
    Dorn, Silvia
    ;
    The effect of infestation by larvae of the European apple sawfly (Hoplocampa testudinea) on the emission of volatiles from apple fruitlets was investigated. Healthy apples emitted a blend of terpenoids and a few aromatic and short aliphatic compounds. Infested apples emitted the same compounds as healthy apples. However, trans,trans-alpha-farnesene, trans-beta-ocimene and another terpenoid were emitted in significantly larger amounts, whereas the other volatiles showed no quantitative change. The results were obtained with picked apples and could be confirmed in the field with single apples left on the tree. Several non-terpenoid volatiles emanated from the frass and from epidermal glands of the sawfly larvae. The possible ecological significance of the increased emission of terpenoids by infested apples is discussed with reference to a parasitic wasp that attacks the sawfly larvae.
  • Publication
    Métadonnées seulement
    Herbivore-induced volatile emissions from cotton (Gossypium-hirsutum L) seedlings
    (1994)
    McCall, Philip J
    ;
    ;
    Loughrin, John H
    ;
    Proveaux, Adron T
    ;
    Tumlinson, James H
    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 com 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)-beta-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.
  • Publication
    Métadonnées seulement
    Semiochemically mediated foraging behavior in beneficial parasitic insects
    (1993)
    Tumlinson, James H
    ;
    ;
    Lewis, W Joe
    Chemical cues enable female parasitic wasps to locate the eggs, larvae, or other life stages of the insects in or on which they place their eggs. These chemical signals, or semiochemicals, may be produced by the hosts and/or by the plants on which the hosts feed. The composition of the chemical signal often differs with different species of hosts or with different plants. New evidence suggests that the wasps exploit semiochemicals emitted by plants in response to insect herbivore feeding. The wasps learn to respond to the different blends of chemicals that indicate the location of their hosts and they can be trained to respond to a specific odor blend. Thus, it may be possible to increase their effectiveness for biological control by conditioning them, prior to their release, to search for a target pest in a particular crop.
  • Publication
    Métadonnées seulement
    Systemic release of chemical signals by herbivore-injured corn
    (1992) ;
    Tumlinson, James H
    Corn seedlings respond to insect herbivore-inflicted injury by releasing relatively large amounts of several characteristic terpenoids and, as a result, become highly attractive to parasitic wasps that attack the herbivores. Chemical evidence showed that the induced emission of volatiles is not limited to the sites of damage but occurs throughout the plant. This evidence was obtained by comparing the release of volatiles from leaves of unharmed (control) seedlings with the release of volatiles from undamaged leaves of seedlings with two injured leaves treated with caterpillar regurgitant. Immediately after injury no differences were measured in the released volatiles, but several hours later the undamaged leaves of injured plants released the terpenoids linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene in significantly larger amounts than leaves of unharmed plants. Other volatiles that are released by herbivore-injured leaves were detected occasionally only in trace amounts from the undamaged leaves of a damaged seedling. The systemic release of volatiles by injured corn coincided with attractiveness to the parasitoid Cotesia margin-iventris; undamaged leaves of injured plants became significantly more attractive than leaves from control seedlings. These findings show conclusively that when a plant is injured by an insect herbivore the whole plant emits chemical signals.
  • Publication
    Métadonnées seulement
    Larval-damaged plants - source of volatile synomones that guide the parasitoid cotesia-marginiventris to the microhabitat of its hosts
    (1991) ;
    Tumlinson, James H
    ;
    Eller, Fred J
    ;
    Lewis, W Joe
    Single and dual choice tests in a flight tunnel revealed that plants damaged by host larvae are the main source of the volatiles that attract females of the parasitoid Cotesia marginiventris (Cresson) to the microhabitat of its hosts. Frass and host larvae, the other two major components of a complete plant-host complex, were significantly less attractive than the damaged seedlings; frass alone was more attractive than larvae alone. However, a recombination of larvae with the damaged seedlings was significantly more attractive than the damaged leaves alone, or damaged leaves with frass. This was due to the additional feeding damage done by the larvae. The role of plants in the host-finding behaviour of parasitoids is discussed.