Pine weevil (Hylobius abietis L.) bark feeding reduces root carbohydrates without broad metabolic changes in Scots pine (Pinus sylvestris L.) seedlings

Abstract Key message Pine weevil feeding on bark reduced root carbohydrate concentrations in Scots pine seedlings, while no changes were detected in needle phenolics or non-volatile metabolomic profiles after seven days. Context The large pine weevil ( Hylobius abietis L.) is a major bark-feeding pest of conifer seedlings in Europe. Pine weevil feeding has been shown to induce systemic volatile emissions from undamaged shoots, raising the question of whether bark feeding also affects whole-plant carbon allocation and systemic chemical responses. Aims We investigated how pine weevil feeding affects organ-specific compounds from primary and secondary metabolism in Scots pine ( Pinus sylvestris L.) seedlings and whether these responses differed between two local provenances. Methods Soluble sugars were quantified in roots and needles to assess organ-specific changes in carbohydrate status. Phenolic compounds and non-volatile metabolomic profiles were analyzed in needles to evaluate systemic chemical responses after seven days of pine weevil feeding. Stem damage was quantified, and treatment and provenance effects were evaluated using linear mixed-effects models. Results Pine weevil feeding significantly reduced soluble carbohydrate concentrations in roots but not in needles. No treatment effect was detected for total needle phenolic concentrations, although ferulic acid decreased following pine weevil feeding. Non-volatile metabolomic profiles showed no clear separation between damaged and control seedlings. Conclusion Pine weevil feeding decreased carbohydrate levels in roots but did not induce detectable changes in secondary metabolites in the two tested provenances.