Seed Provenance and Coat Integrity Modulate Tribolium Survival and Feeding on Pinus nigra L. Plus Tree Seeds Under Laboratory Conditions

Seed physical integrity is a critical determinant of susceptibility to insect infestation in stored products, yet its interaction with seed provenance remains poorly understood. This laboratory study investigated the survival of Tribolium castaneum (Coleoptera: Tenebrionidae) and Tribolium confusum (Coleoptera: Tenebrionidae) on Pinus nigra L. seeds from ten Greek populations under cracked and intact conditions. Mortality was monitored at Days 7, 14, 21, and 28 post-infestation. Using generalized linear mixed models with binomial errors, seed crack condition overwhelmingly determined survival outcomes, explaining 87–90% of total variance in PCA ordination. Cracked seeds supported over two-fold higher beetle survival (84–86%) compared to intact seeds (35–38%). Under intact conditions, seeds from Xanthi, Samos, and Komotini showed the highest beetle survival (38–52%), while seeds from Drama and Grevena showed the lowest (12–18%). These provenance-level differences disappeared under cracked conditions, indicating that seed provenance influences Tribolium survival only when the seed coat remains intact. Feeding damage analysis confirmed that provenance affected weight loss only under intact conditions, though these results should be interpreted with caution due to the absence of insect-free controls. These findings demonstrate that maintaining seed coat integrity is essential for preventing infestation, and that seed sources with lower susceptibility should be prioritized for short-term storage.