Strength estimation of damaged wood by Xylotrechus arvicola Olivier in grapevine branches in relation to the density

The main wine-producing areas in northern Spain are affected by Xylotrechus arvicola Olivier 1795 (Coleoptera: Cerambycidae), an insect pest that causes structural damage in vineyards, affecting Vitis vinifera L. 1753 (Vitales: Vitaceae) plants. The larvae bore into grapevine wood, causing direct damage (ingestion of vascular tissues) and indirect damage (the fungal infection is facilitated through the exit holes in the wood created by larvae) to the plant. This study aimed to determine the density of wood damaged by larvae and to evaluate its mechanical properties using compression tests on damaged and undamaged wood samples. Undamaged samples, with density percentages higher than 20% when were conditioned and 35% when were unconditioned (field conditions), showed a higher density than damaged samples. These differences were determined using the density of damaged samples as the baseline for each condition. Compressive strength increased with wood density, although strength was lower in the damaged wood samples. In addition, undamaged samples had higher strength when unconditioned, but damaged samples had higher strength when conditioned. On the other hand, significant differences were found in the interaction between compressive strength and density in undamaged samples (unconditioned). This indicates a stronger relationship between density and increased strength in undamaged samples. The results showed that "Prieto Picudo" variety, unconditioned branches (field conditions) with lower density were more susceptible to structural failure when attacked by X. arvicola larvae.