Clone-specific susceptibility of Eucalyptus pellita to the emerging defoliator Carea angulata F. (Lepidoptera: Nolidae) in Indonesian plantations

The emergence of new insect pests threatens the sustainability of industrial plantation forests, particularly in monoculture systems dominated by Eucalyptus pellita. This study investigated the outbreak of Carea angulata (Lepidoptera: Nolidae) in E. pellita plantations through an integrated ecological, molecular, morphometric, and chemical profiling approach. Field surveys were conducted in Perawang (Riau) and Sungai Baung (South Sumatra) using three E. pellita clones and two stand age classes. Pest incidence and severity significantly differed between clone–age combinations in both regions (Kruskal–Wallis, p < 0.05), with strong effect sizes (η2H = 0.554–0.766). Clone 2 consistently exhibited the highest susceptibility, whereas clones 1 and 3 showed negligible infestation at both 10 and 18 months after planting, indicating strong genotype-dependent resistance. Morphometric analyses of the pest established diagnostic characteristics across developmental stages, including the distinctive larval helmet-like swelling and adult wing structure. Molecular characterization, using a 593 bp mitochondrial COI fragment, identified six haplotypes from 13 samples. The analysis showed high haplotype diversity, with a value of 0.80, but low nucleotide diversity, at 0.01, leading to the creation of two closely related haplogroups. GC–MS profiling revealed clear chemical profiling differentiation among clones, with clone 2 characterized by the dominance of 9-octadecenoic acid methyl ester (40.71%). The principal component analysis explained 65.7% of the total variance and distinctly separated clone 2 from the less susceptible clones. These findings provide preliminary evidence that host genotype and leaf chemistry are associated with C. angulata susceptibility for the clones and sites studied. Its higlight the potential importance of deploying tolerant clones and implementing molecular surveillance to support sustainable pest management in E. pellita plantations. However, further studies are needed to confirm these patterns and establish their broader applicability.