**Xyleborus Beetles** (*Xyleborus* spp.) are a genus of **Ambrosia Beetles**, a type of wood-boring weevil, that are notorious invasive pests of trees and nurseries worldwide. The conflict is **tree death and ornamental damage**: they bore narrow tunnels deep into the sapwood of live trees (often fruit, pecan, or ornamental maples). Crucially, they introduce a specific **symbiotic fungus** (ambrosia) that they cultivate and feed on. This fungus can kill weakened or stressed trees, especially in nursery and orchard settings.
Taxonomy and Classification
Xyleborus Beetles belong to the Order Coleoptera and the Family Curculionidae (Weevils). They undergo complete metamorphosis. The genus is highly diverse, with many invasive species.
Physical Description
Adults are tiny, 1 mm to 3 mm long.
- **Adult (Key ID):** Small, cylindrical, reddish-brown or black beetles; the female starts the tunnel.
- **Damage ID (Key):** Distinctive, fragile **”toothpick” or “frass rope”** extruding from the tiny entrance hole (a mix of wood dust and fungus); wet, discolored sapwood; wilting and dieback of branches.
- **Fungus (Key):** The **Ambrosia Fungus** (often black or dark) is the primary cause of tree death, not the beetle’s feeding.
- **Conflict:** Agricultural (Orchard), Ornamental.
Distribution and Habitat
Found worldwide, many species are invasive (e.g., in North America). Habitat is the trunks and branches of stressed or newly transplanted trees.
Behavior and Conflict
The conflict is their reliance on the deadly fungus.
- **Host Preference:** They primarily attack stressed or recently wounded trees (e.g., from pruning or drought), making nursery stock highly vulnerable.
- **Speed:** Once a tunnel is established and the fungus is introduced, the damage progresses very quickly.
Management and Prevention
Management is **Prevention and Sanitization**.
- **Tree Health:** Maintaining the vigor of trees, avoiding drought stress, and managing wounds.
- **Trunk Protection:** Applying a **residual insecticide spray** to the lower trunk and larger branches of susceptible trees during the spring flight period (when the beetles are actively boring).
- Removing and destroying infested wood to eliminate breeding sites.
Conservation and Research
Research focuses heavily on the invasive species, studying the specific chemical compounds (pheromones, kairomones) that attract them to stressed trees, and identifying the pathogenic fungi they carry.