Volatiles from a mite-infested spruce clone and their effects on pine weevil behavior

Induced responses by Norway spruce (Picea abies) seedlings to feeding damage by two mite species were studied by analyzing the volatiles emitted during infestation. Four specimens of a Norway spruce (Picea abies L.) clone were infested with mites of Nalepella sp., another four with Oligonychus ununguis, and four were kept mite-free as controls. After a year of infestation, spruce volatiles were collected, analyzed, and identified using SPME-GC-MS. In addition, enantiomers of chiral limonene and linalool were separated by two-dimensional GC. Methyl salicylate (MeSA), (-)-linalool, (E)-beta-farnesene, and (E,E)-alpha-farnesene were the main volatiles induced by both species of mites, albeit in different proportions. The ability of the main compounds emitted by the mite-infested spruces to attract or repel the pine weevil, Hylobius abietis (L.), was tested. (E)-beta-farnesene was found to be attractive in the absence of spruce odor, whereas methyl salicylate had a deterrent effect in combination with attractive spruce odor. The other tested compounds had no significant effects on the behavior of the weevils.