General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract-Previous work showed that anthocorid predators aggregate around gauze cages containing Psylla-infested trees in a pear orchard. Because anthocorids responded to odor from Psylla-infested leaves in a laboratory test, it was hypothesized that these aggregative responses in the field were triggered by olfaction of compounds associated with Psylla injury. We present chemical analyses of volatiles from damaged and undamaged plants and studies on behavioral responses of anthocorid predators to compounds released by damaged plants. Leaf headspace volatiles from clean and Psylla-infested pear trees were collected on Tenax and identified by GC-MS after thermodesorption. Twelve volatiles were found exclusively in headspace samples from Psyllainfested leaves. Six were present in significantly higher quantities in samples from infested leaves: the monoterpene, (E,E)-a-farnesene, the phenolic, methyl salicylate, and the green leaf compounds, (Z)-3-hexen-l-yl acetate, (Z)-3-hexen-l-ol, 1-hexyl-acetate, and l-penten-3-ol. These compounds are known to be produced by plants, and damage by pear psyllids seems to trigger their emission. Blend composition varied and was partly correlated with tree or leaf age and degree of Psylla infestation. To study whether compounds associated with leaf injury elicit olfactory responses in anthocorid predators, apple-extracted (E,E)-a-farnesene, synthetic methyl salicylate, and (Z)-3-hexen-1-yl acetate were offered in a Y-tube olfactometer to field-collected adult Anthocoris spp. Significant positive responses were found to both the *To whom correspondence should be addressed. m o n o t e r p e n e and the phenolic, but not to the green leaf volatile. The results lend support to the hypothesis that predator attraction to herbivore-infested pear trees is mediated by herbivory-induced plant volatiles.

Do anthocorid predators respond to synomones from Psylla-infested pear trees in field conditions? Drukker, B.; Scutareanu, P.; Sabelis, M.W. Published in: Entomologia Experimentalis et Applicata DOI:10.1111/j. 1570-7458.1995.tb02001.x Link to publication Citation for published version (APA):Drukker, B., Scutareanu, P., & Sabelis, M. W. (1995). Do anthocorid predators respond to synomones from Psylla-infested pear trees in field conditions? Entomologia Experimentalis et Applicata, 77, 193-203. DOI: 10.1111/j.1570-7458.1995 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 12 May 2018Entomologia Experimentalis etApplicata 77: 193-203, 1995. 193 @ 1995 AbstractBecause Y-tube olfactometer experiments in the laboratory showed a response of anthocorid bugs to odour from Psylla-infested leaves, it was of interest to assess its relevance under field circumstances. This was done by measuring the density of predatory bugs on pear trees adjacent to Psylla-infested or control trees that were covered with fine mesh gauze-screens. In this way odours from these caged trees could spread through the screen, while contact with the Psylla prey in the cage was prevented. The density of anthocorid predators around cages with heavily infested trees was significantly higher than around uncaged control trees and around cages containing uninfested or little infested trees. Covering a cage with Psylla-infested trees by an airtight plastic sheet led to an immediate drop in the density of anthocorid predators, whereas removal of the sheet led to predator aggregation again. The results of these field experiments strongly support the hypothesis that anthocorid predators respond to volatile chemicals emanating from Psylla-infested pear trees.

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Qualitative and quantitative differences among pear cultivars were found in constitutive and Cacopsyllainduced volatiles, depending on experimental treatment of the trees (i.e. uninfested and partly or completely infested by psyllids). Blend differences were also found between pear cultivars and wild-type pear, alder and hawthorn -the latter trees are frequently present in pear orchard hedgerows.Interesting differences were found in the presence of methyl salicylate and (E,E)-α-farnesene, two compounds previously found to mediate attraction of predatory bugs towards psyllid-infested pear trees. Methyl salicylate is expressed constitutively and is induced systemically by infestation in the whole plant of all four cultivars. (E,E)-α-farnesene on the other hand showed also systemic induction in Bartlett, NY10355 and Beurré Hardy, but in partially infested Conference trees it was induced locally, only in herbivore-damaged leaves. No methyl salicylate or (E,E)-α-farnesene were identified in honeydew. In field collected headspace samples of alder leaves infested by aphids and leaf beetles we found methyl salicylate but no (E,E)-α-farnesene, whereas in uninfested hawthorn neither were identified. Insight in the variability of damage-related pear volatiles will have important implications for integrated pest management in the field.Key words. leaf volatile -constitutive compoundinduced plant defence -psyllid -pear cultivaralder -hawthorn -honeydew -systemic and local response -methyl salicylate -α-farnesene Chemoecology