Comparative analysis of hidden damage caused by the stem borer Ceutorhynchus species in oilseed rape using computer tomography

The weevils of the Ceutorhynchus (Coleoptera: Curculionidae) are significant pests, posing a threat to oilseed rape cultivation in Central Europe. Due to their lifestyle, these weevils cause hidden damage within the stems. Our non-invasive computer tomography-based study aimed to compare the damage characteristics of three species within this genus: C. pallidactylus (Marsham), C. napi (Gyll.), and C. picitarsis (Gyll.), in oilseed rape stems. During the CT analysis of the plant samples from axial, coronal, and sagittal approaches at different points, we measured the length of the damaging larvae, their number per plant, their distance from each other, the volume of the formed cavity, and the diameter of the damaged plant stems. Additionally, we investigated the closeness of the connections between these forms of damage. Our study found that damage to plant samples during the period of interest was species-specific. Significant differences were observed in the longitudinal size dimensions of the larvae, the volume of the formed cavities, and the diameters of the stems of the attacked plants among the species causing the damage. The Pearson correlation results confirmed a strong correlation between the volumes of the formed cavities and the values of larval length (l) and stem diameter (empty set), as well as between stem diameter and larval length data for each species (C. pallidactylus: l = 6.903 +/- 1.332 mm, empty set = 11.43 +/- 0.707 mm; C. napi: l = 9.868 +/- 0.617 mm, empty set = 23.11 +/- 2.813 mm; C. picitarsis: l = 3.772 +/- 0.967 mm, empty set = 11.16 +/- 0.365 mm). These results suggest that the damages caused by these hidden lifestyle stem pests of oilseed rape are species-specific.