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

Islam S. Sobhy, Matthias Erb & Ted Turlings

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 if this is also the case for other important crops. Results We applied the plant strengtheners BTH (benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester) or laminarin to cotton plants and studied the effects on volatile releases and the attraction of three hymenopteran parasitoids, Cotesia marginiventris, Campoletis sonorensis and Microplitis rufiventris. After treated and untreated plants were induced by real or simulated caterpillar feeding, we 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 has 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 environment-friendly strategy for biological control of pests by enhancing the attractiveness of cultivated plants to natural enemies of insect herbivores.
   
Keywords Cotton, Volatile Organic Compounds (VOCs), Parasitoid attraction, Plant strengtheners, Homoterpenes, Indole
   
Citation Sobhy, I. S., Erb, M., & Turlings, T. (2014). Plant strengtheners enhance parasitoid attraction to herbivore-damaged cotton via qualitative and quantitative changes in induced volatiles. Pest Management Science, n/a-n/a.
   
Type Journal article (English)
Date of appearance 2014
Journal Pest Management Science
Pages n/a-n/a