Volatile Organic Compounds from the Clone Populus x canadensis “Conti” Associated with Megaplatypus mutatus Attack

Megaplatypus mutatus (Chapuis) (Coleoptera, Platypodidae) is an ambrosia beetle native to South America. It builds internal galleries that weaken the tree trunks, causing them severe stem breakage and mortality in commercial poplar plantations. The host selection by male M. mutatus has previously been correlated with the increasing diameter. This work explores the possibility that differential susceptibility of individual plants to M. mutatus could be associated with volatiles emitted. The comparison of the VOCs profiles of attacked and nonattacked P. x canadensis “Conti” 12 during M. mutatus flying season showed both qualitative and quantitative differences. The attacked plants, but not the nonattacked ones, showed the following compounds: a long chain aldehyde, α-ylangene, δ-cadinene, α-gurjunene, and β-cubebene; on the other side, β-sesquiphellandrene and β-chamigrene were detected only in nonattacked plants. α-Copaene is a common component of all the samples analyzed, but its proportion is increased in attacked individuals. Behavioral bioassays showed that males but not females M. mutatus are attracted to α-copaene. The relative increase of α-copaene in attacked individuals and the positive behavioral answer of males to it suggest that this compound could play a role in the orientation of the pioneer male towards the most suitable host.