Plant strengtheners enhance parasitoid attraction to herbivore-damaged cotton via qualitative and quantitative changes in induced volatiles

Authors

  • Islam S Sobhy,

    1. Laboratory of Fundamental and Applied Research in Chemical Ecology, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
    2. Plant–Insect Interactions Group, Institute of Plant Science and Resources, Okayama University, Kurashiki, Japan
    3. Department of Plant Protection, Public Service Centre of Biological Control (PSCBC), Faculty of Agriculture, Suez Canal University, Ismailia, Egypt
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  • Matthias Erb,

    1. Institute of Plant Sciences, University of Bern, Bern, Switzerland
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  • Ted CJ Turlings

    Corresponding author
    1. Laboratory of Fundamental and Applied Research in Chemical Ecology, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
    • Correspondence to: Ted CJ Turlings, Laboratory of Fundamental and Applied Research in Chemical Ecology (FARCE), Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland. E-mail: ted.turlings@unine.ch

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Abstract

BACKGROUND

Herbivore-damaged plants release a blend of volatile organic compounds (VOCs) that differs from undamaged plants. These induced changes are known to attract the natural enemies of the herbivores and therefore are expected to be important determinants of the effectiveness of biological control in agriculture. One way of boosting this phenomenon is the application of plant strengtheners, which has been shown to enhance parasitoid attraction in maize. It is unclear whether this is also the case for other important crops.

RESULTS

The plant strengtheners BTH [benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester] and laminarin were applied to cotton plants, and the effects on volatile releases and the attraction of three hymenopteran parasitoids, Cotesia marginiventris, Campoletis sonorensis and Microplitis rufiventris, were studied. After treated and untreated plants were induced by real or simulated caterpillar feeding, it was found that BTH treatment increased the attraction of the parasitoids, whereas laminarin had no significant effect. BTH treatment selectively increased the release of two homoterpenes and reduced the emission of indole, the latter of which had been shown to interfere with parasitoid attraction in earlier studies. Canonical variate analyses of the data show that the parasitoid responses were dependent on the quality rather than the quantity of volatile emission in this tritrophic interaction.

CONCLUSION

Overall, these results strengthen the emerging paradigm that induction of plant defences with chemical elicitors such as BTH could provide a sustainable and environmentally friendly strategy for biological control of pests by enhancing the attractiveness of cultivated plants to natural enemies of insect herbivores. © 2014 Society of Chemical Industry

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