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Turlings, Ted

Nom
Turlings, Ted
Affiliation principale
Fonction
Professeur.e ordinaire
Email
ted.turlings@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/330
_
0000-0002-8315-785X

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  • Publication
    Métadonnées seulement
  • Publication
    Accès libre
    Response of natural populations of predators and parasitoids to artificially induced volatile emissions in maize plants (Zea mays L.)
    (2001)
    Bernasconi Ockroy, Marco L.
    ;
    Turlings, Ted 
    ;
    Edwards, Peter J.
    ;
    Fritzsche-Hoballah
    ;
    Ambrosetti, Lara
    ;
    Bassetti, Paolo
    ;
    Dorn, Silvia
    1 In response to herbivore attack, maize plants (Zea mays L.) emit a specific blend of induced volatiles. Artificial damage and subsequent treatment of the damaged site with caterpillar regurgitant induces the same response. The induced volatile chemicals are known to be highly attractive to several parasitoids of herbivores in laboratory bioassays, but very limited information is available on how the plant odours affect entomophagous insects in the field.

    2 Experiments were conducted to determine if induced maize volatiles attract parasitic and predatory insects under field conditions and whether they affect their spatial distribution.

    3 In a preliminary field experiment with blue sticky traps near treated (damaged and treated with caterpillar regurgitant) and healthy plants, more entomophagous insects (total number of parasitic Hymenoptera, Anthocoridae and Syrphidae) were trapped near treated plants than near healthy plants.

    4 In a second experiment, attraction to the induced volatiles was monitored with sticky traps placed next to treated and healthy maize plants in a regular maize field. No significant differences between the two treatments were found, but significantly more insects (parasitic wasps, thrips and anthocorid bugs) were trapped near to the top of plants than on traps placed near the mid-stem. Displacement of these insect groups within the field seemed to occur principally over the canopy, but under severe weather conditions they travelled lower in the canopy.

    5 In a third experiment, the effect of induced maize odours on the spatial distribution of predators and parasitoids was investigated by placing sticky traps at different distances from healthy and treated plants. The higher catches of parasitoids near treated plants and the increased presence of these insects on the downwind side of treated plants support the notion that herbivore-induced maize odours attract natural enemies of maize pests in the field.
  • Publication
    Accès libre
    Host stage preference and sex allocation in Aenasius vexans, an encyrtid parasitoid of the cassava mealybug
    (2000)
    Bertschy, Catherine
    ;
    Turlings, Ted 
    ;
    Bellotti, Anthony
    ;
    Dorn, Silvia
    The solitary endoparasitoid Aenasius vexans Kerrich (Hymenoptera: Encyrtidae) is used for augmentative releases against the cassava mealybug, Phenacoccus herreni Cox & Williams (Sternorrhyncha: Pseudococcidae), an important pest on cassava in South America. In light of the need for large numbers of high quality females, experiments were conducted on host stage suitability and sex allocation. In choice and no-choice experiments, individual female wasps were offered second and third instar, as well as adult, hosts. During the first five days after emergence, the wasps showed a steady increase in the number of hosts they successfully parasitised per day, but the respective secondary sex ratio for each instar remained constant. Parasitism was highest for third instar hosts in no-choice tests, while in choice tests parasitism was highest in both third instars and adults. The later the developmental stage of the host at oviposition, the faster the parasitoids developed and emerged, and for each host stage, the development time of males was shorter than for females. The sex ratio of the wasps emerging from hosts that were parasitised as second instars was strongly male-biased, while the apparently preferred later stages yielded significantly more females than males. Female and male A. vexans emerging from hosts parasitised at the third instar were significantly larger than for the other stages. This may explain the preference for the third instar as well as the female-biased sex ratio, as size is usually positively correlated with higher fitness, especially in females. The results suggest that third instar hosts are the most suitable for rearing high numbers of large females.
  • Publication
    Métadonnées seulement
    Lydella thompsoni Herting (Dipt., Tachinidae), a parasitoid of the European corn borer, Ostrinia nubilalis Hbn. (Lep., Pyralidae) in Slovakia, Czech Republic and south-western Poland
    (1999)
    Cagan, L
    ;
    Turlings, Ted 
    ;
    Bokor, P
    ;
    Dorn, Silvia
    This paper shows that, within Central Europe, parasitism of the European corn borer (ECB) by the tachinid parasitoid, Lydella thompsoni (LT) increased from 0.47 to 1.49% in south-western Poland (51 degrees 03'N), to 4.31-21.95% in eastern Slovakia (48 degrees 20'N). The synchrony between the parasitoid LT and its primary host: the ECB, was studied in Central Europe under conditions where the host is univoltine, but the parasitoid is bivoltine. A cumulated total of more than 400 LT was field-collected from overwintering ECB larvae. The parasitoid hibernated as larva inside the host. Pupation started in the second half of the following March and 50% of pupation was surpassed in the first half of April. The first parasitoid adults emerged at the end of April and the majority at the beginning of May. Development threshold temperatures for 50% pupation was determined to be 2.7 degrees C, and for 50% adult emergence 5.0 degrees C; the respective thermal constants were 178.8-179.8 and 237.7-251.8 Celsius degree-days. Emerged adults did not parasitize overwintered ECB larvae in spring, hence there must be an alternate host for the first generation of LT in areas of univoltine life cycle of the ECB. Parasitization of the ECB larvae by LT continued until the end of July. The first parasitoid adults from this second generation emerged in the second half of August. By the end of the season, nearly one-third of LT adults had emerged. The rest of this generation apparently overwintered in the larval stage.
  • Publication
    Métadonnées seulement
    The induction of volatile emissions in maize by three herbivore species with different feeding habits: Possible consequences for their natural enemies
    (: Academic Press Inc, 1998)
    Turlings, Ted 
    ;
    Bernasconi, Marco
    ;
    Bertossa, Rinaldo
    ;
    Bigler, Franz
    ;
    Caloz, Genevieve
    ;
    Dorn, Silvia
    In order to find their prey natural enemies of herbivores often make effective use of plant volatiles that are emitted by plants on which the herbivores have been feeding. The phenomenon of herbivore-induced emissions of attractants has been well investigated for mite-plant interactions and for interactions between leaf feeding caterpillars and plants. Herbivore-induced emissions of chemical signals appear to be common in plants, but little is known about induction by herbivores that have different feeding habits. We obtained more knowledge on this by comparing the volatile emissions induced in maize plants by a folivorous caterpillar (Spodoptera littoralis), a stemborer (Ostrinia nubilalis), and an aphid (Rhopalosiphum maidis). As controls we also measured the emissions of healthy, undamaged plants and plants that were mechanically damaged and then treated with caterpillar regurgitate. Volatiles were collected twice daily for 2 h over a 3-day period after initial infestation or mechanical damage. Quantitatively, the plants infested with S. littoralis emitted by far the most. Their emissions started several hours after initial damage, lasted for the 3 days, and were the highest on the third day. The volatile profile was the same for the regurgitate-treated plants, but here the emissions dropped rapidly after the first day. The plants infested by O. nubilalis emitted the same blend of volatiles, but in much lower quantities, In addition to the known induced maize volatiles, the Ostrinia-damaged plants emitted some highly volatile, still unidentified compounds, which may be specific for the frass of this insect or emitted from the damaged plant stem. The aphids induced no measurable emissions of volatiles in the maize, even after heavy infestation. This is perhaps because several aphids, including R. maidis, barely damage the plant cells, and may not trigger a plant response. These findings suggest that induction of volatiles is the result of cell tissue damage, particularly to the leaves of the plant. This should have consequences also for the search strategies employed by the natural enemies of the respective herbivores, It can be expected that enemies of stemborers use some highly volatile compounds in addition to the known induced compounds. Natural enemies of some aphids may have to resort to other foraging cues, as the plant appears to provide them with no or very little olfactory information. (C) 1998 Academic Press.
  • Publication
    Accès libre
    Herbivore-induced emissions of maize volatiles repel the corn leaf aphid, shape Rhopalosiphum maidis
    (1998)
    Bernasconi, Marco L.
    ;
    Turlings, Ted 
    ;
    Ambrosetti, Lara
    ;
    Bassetti, Paolo
    ;
    Dorn, Silvia
    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.
  • Publication
    Métadonnées seulement
    Chemically-mediated attraction of three parasitoid species to mealybug-infested cassava leaves
    (1997)
    Bertschy, Catherine
    ;
    Turlings, Ted 
    ;
    Bellotti, Anthony
    ;
    Dorn, Silvia
    We investigated whether cassava plants that are infested by the cassava mealybug, Phenacoccus herreni (Pseudococcidae, Sternorrhyncha), emit attractants for the encyrtid parasitoids Aenasius vexans Kerrich, Apoanagyrus (Epidinocarsis) diversicornis Howard, and Acerophagus coccois Smith. Bioassays with a Y-tube olfactometer showed for all three species that female wasps were most responsive and selective when they were 1.5 to 2.5 days old. Females of these age groups were used to test their ability to distinguish between the odor of plants with and without mealybugs. The wasps were offered choices between infested cassava leaves vs. healthy ones, infested leaves vs. clean air, and healthy leaves vs. clean air. A. vexans and A. diversicornis were strongly attracted to infested leaves and preferred these over healthy ones. In contrast,A. coccois was significantly attracted to either healthy or infested leaves, and did not distinguish between the two. The results suggest that A. coccois, which has the broadest known host range of the three, may be responsive only to general plant odors, while A. vexans and A. diversicornis respond more specifically to odors associated with mealybug infestation.
  • 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
    ;
    Turlings, Ted 
    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.