Pestipedia

Yucca Weevils

**Yucca Weevils** (*Scyphophorus yuccae*) are large, black weevils that are the primary pests of the native **Yucca** and **Agave** plants in the Southwestern US. The conflict is **plant death**: the female bores a hole near the base of the plant or in the flower stalk and lays her eggs. The resulting larvae tunnel through and consume the soft core of the plant crown (the vital growth point), causing the stem to collapse, leading to the rapid decay and death of the entire plant.

Taxonomy and Classification

Yucca Weevils belong to the Order Coleoptera (Beetles) and the Family Dryophthoridae (Snout Beetles). They undergo complete metamorphosis.

Physical Description

Adults are large, 15 mm to 20 mm long.

  • **Adult (Key ID):** Large, robust, uniformly shiny black weevil; possesses a distinct, long snout (rostrum) used for boring.
  • **Larva (Key ID):** Large, cream-colored, legless grub with a brown head, found tunneling extensively within the yucca or agave crown tissue.
  • **Damage ID (Key):** **Sudden collapse** of the central leaves; a large, blackened bore hole in the base of the plant or flower stalk; presence of a wet, foul-smelling, decaying core.
  • **Conflict:** Ornamental (Desert Plants).

Distribution and Habitat

Found in arid and semi-arid regions of the Southwestern US and Mexico. Habitat is desert scrubland and xeriscaped ornamental gardens.

Behavior and Conflict

The conflict is the direct consumption of the plant’s single growing point.

  • **Cryptic Feeding:** The damage is hidden inside the plant core until the plant suddenly collapses.
  • **Infection:** Their tunneling activity often introduces secondary bacterial and fungal pathogens that accelerate the decay process.

Management and Prevention

Management is **Prevention and Sanitation**.

  • **Prevention (Key):**
    • **Sanitation:** Promptly removing and destroying any infected plant material to prevent adult emergence and re-infestation.
    • **Chemical Control:** Targeted application of systemic or residual insecticide to the base of valuable ornamental plants, timed to the adult emergence period.

    • Conservation and Research

    Research focuses on utilizing entomopathogenic nematodes or fungi as biological controls to target the larvae hidden within the plant crown.