Résultat de la recherche
First Insights into the Chemical Ecology of an Invasive Pest: Olfactory Preferences of the Viburnum Leaf Beetle (Coleoptera: Chrysomelidae)
The viburnum leaf beetle (VLB), Pyrrhalta viburni (Paykull), is an invasive chrysomelid in North America where it infests native Viburnum shrubs in woody areas and managed landscapes. Despite its invasive and destructive nature, little is known about the chemical ecology of this beetle, and efficient chemical lures for monitoring and trapping this insect have yet to be developed. Using two of the main host plants of VLB in its native range, Viburnum opulus L. (Caprifoliaceae) and V. lantana L., we examined the olfactory preferences of adult females of VLB under laboratory conditions and measured volatile emissions of Viburnum twigs with and without VLB damage. VLB females had a clear preference for V. opulus and V. lantana twigs compared to blank odor sources. In addition, twigs with foliar damage and fresh egg masses were found to be more attractive than noninfested twigs in V. opulus when VLB infestation was recent, but not when twigs had been infested for several weeks. Chemical analyses revealed consistent treatment-specific blends of compounds, which may be used for the elaboration of attractive lures. Future research should focus on the identification of these compounds and on exploring the olfactory preferences of VLB with Viburnum species present in North America.
Plant defence responses to volatile alert signals are population-specific
Herbivore-induced volatiles are widespread in plants. They can serve as alert signals that enable neighbouring leaves and plants to pre-emptively increase defences and avoid herbivory damage. However, our understanding of the factors mediating volatile organic compound (VOC) signal interpretation by receiver plants and the degree to which multiple herbivores affect VOC signals is still limited. Here we investigated whether plant responses to damage-induced VOC signals were population specific. As a secondary goal, we tested for interference in signal production or reception when plants were subjected to multiple types of herbivore damage. We factorially crossed the population sources of paired Phaseolus lunatus plants (same versus different population sources) with a mechanical damage treatment to one member of the pair (i.e. the VOC emitter, damaged versus control), and we measured herbivore damage to the other plant (the VOC receiver) in the field. Prior to the experiment, both emitter and receiver plants were naturally colonized by aphids, enabling us to test the hypothesis that damage from sap-feeding herbivores interferes with VOC communication by including emitter and receiver aphid abundances as covariates in our analyses. One week after mechanical leaf damage, we removed all the emitter plants from the field and conducted fortnightly surveys of leaf herbivory. We found evidence that receiver plants responded using population-specific ‘dialects’ where only receivers from the same source population as the damaged emitters suffered less leaf damage upon exposure to the volatile signals. We also found that the abundance of aphids on both emitter and receiver plants did not alter this volatile signalling during both production and reception despite well-documented defence crosstalk within individual plants that are simultaneously attacked by multiple herbivores. Overall, these results show that plant communication is highly sensitive to genetic relatedness between emitter and receiver plants and that communication is resilient to herbivore co-infestation.