**Kukui Beetles** (often referring to the **Kukui Nut Weevil**, *Aulacaspis mangiferae*) are specialized pests that primarily attack the nuts of the **Kukui** tree (*Aleurites moluccanus*), the state tree of Hawaii. While the tree itself is generally hardy, the weevil larvae bore into the developing nuts, destroying the edible kernel inside. They are mainly a concern in ornamental and cultural settings where the nuts are gathered for crafts (e.g., leis) or oil production, as their presence renders the nuts worthless for these purposes.
Taxonomy and Classification
Kukui Beetles (Weevils) belong to the order Coleoptera, family Curculionidae. They undergo complete metamorphosis. The adult female lays eggs on the developing kukui nut. The larva tunnels into the nut’s shell and feeds on the kernel until maturity, a typical life cycle for many nut-boring weevils. They have co-evolved with the Kukui tree in its native range.
Physical Description
Adult Kukui Weevils are small, dark, hard-bodied beetles, 1/4 to 1/2 inch long, with the characteristic long snout of a weevil.
- **Larvae:** Creamy white, legless, grub-like larvae found only inside the nut kernel.
- **Damage Sign (Key ID):** Small, round, clean-cut **exit holes** on the surface of the mature kukui nut. If the nut is cut open, the kernel will be entirely consumed or contaminated by frass and tunneling.
- **Conflict:** Loss of ornamental and culturally important nuts, not tree health.
Distribution and Habitat
Kukui Beetles are found in the native and introduced range of the Kukui tree, including Hawaii, Southeast Asia, and Pacific Islands. Their habitat is the tree canopy where the nuts develop and the soil beneath where the larvae may pupate.
Behavior and Conflict
The conflict is primarily the destruction of the valuable nuts.
- **Kernel Destruction:** The larva consumes the oil-rich kernel, making the nut useless for making leis, jewelry, or extracting oil.
- **Waste:** Affected nuts may drop prematurely or simply be found to be hollow and infested after collection.
Management and Prevention
Control focuses on sanitation and, if necessary, chemical protection of the nuts.
- **Sanitation (Key):** Regularly **collect and destroy** all fallen kukui nuts, as these often contain developing larvae that will pupate in the soil and emerge as next season’s adults.
- **Physical Control:** Inspect and discard any nuts with signs of weevil entry or damage immediately.
- **Chemical Control:** For high-value trees, insecticides may be applied during the period of nut development to kill adult females before they lay eggs, but this must be done carefully to avoid environmental contamination.
Conservation and Research
Kukui Beetles are managed as a localized ornamental and minor agricultural pest. Research focuses on finding biological controls that specifically target the kukui weevil without impacting other native insects, and optimizing cultural practices for nut harvesting.