**Banana Weevils** (*Cosmopolites sordidus*), also known as the **Banana Root Borer**, are one of the most destructive insect pests of **banana and plantain** crops worldwide. The conflict is severe plant loss and economic damage: the larvae (**grubs**) tunnel extensively into the **corm** (the underground base) and the **pseudostem** of the plant, disrupting water and nutrient flow, causing the plant to become weak, leading to **stunting, reduced fruit yield**, and the plant being easily toppled by wind.
Taxonomy and Classification
Banana Weevils belong to the order Coleoptera (Beetles), family Curculionidae (Weevils). They undergo complete metamorphosis. The entire life cycle, from egg to adult, takes place entirely within or immediately around the base of the banana plant.
Physical Description
Adult Weevil is small, 1/2 inch long.
- **Appearance (Key ID):** Shiny, dark brown to black, robust weevil with the characteristic elongated snout (rostrum). They are **nocturnal** and slow-moving.
- **Larva (Key ID):** White, legless, C-shaped grub, found tunneling deep inside the corm tissue, leaving behind characteristic tunnels (galleries) filled with frass.
- **Damage Sign (Key ID):**
- **Tunnels:** Visible tunnels or reddish-brown ooze near the base of the pseudostem when cut open.
- **Stunting:** Weak, stunted plants with small leaves and low-quality fruit bunches.
- **Toppling:** Plants easily falling over (toppling) during storms, especially when loaded with fruit.
- **Conflict:** Severe crop loss and plant destruction.
Distribution and Habitat
Banana Weevils are found globally in all major banana and plantain growing regions. Their habitat is the corm and pseudostem of the host plant.
Behavior and Conflict
The conflict is persistent and hidden.
- **Hidden Pest:** Both the eggs and the destructive larvae are entirely hidden inside the plant base, making detection and control very difficult.
- **Nocturnal:** Adult weevils are active only at night, spending the day hidden under trash or soil, complicating monitoring.
- **Long-Lived:** Adult weevils can live for up to two years, meaning they can persist in an area even between crop cycles.
Management and Prevention
Control is integrated pest management (IPM), with a heavy focus on sanitation and traps.
- **Planting Material:** Only plant clean, weevil-free suckers (new plants) that have been pared and treated.
- **Crop Residue:** Immediately cut up and remove or destroy all dead or harvested pseudostems and corms to eliminate breeding material.
- **Lure Traps:** Use pheromone-baited traps or **bamboo/corm traps** (slices of fresh corm placed on the ground) to lure and kill adult weevils before they lay eggs.
- Apply a registered granular or liquid insecticide to the base of the plant or around the suckers, targeting the adult weevils before they can lay eggs.
Conservation and Research
Banana Weevils are managed as severe tropical agricultural pests. Research focuses on developing integrated resistance in new banana varieties, improving pheromone trap efficiency, and utilizing parasitic nematodes for biological control against the larvae in the soil.