Preuss’s rhinoceros beetle

Systematics and distribution. Preuss’s rhinoceros beetle (Oryctes preussi) is a member of the order Coleoptera, family Scarabaeidae, and subfamily Dynastinae. Native to the tropical regions of Western and Central Africa, this species has adapted to exploit palm ecosystems. Unlike some members of the genus that are strictly saproxylic, Oryctes preussi poses a direct threat to cultivated palms in its native range.

Host plants. The beetle primarily affects species such as the African oil palm (Elaeis guineensis) and the coconut palm (Cocos nucifera). While the larvae act as decomposers in decaying wood or organic matter, the adults are significant pests, focusing their feeding activities on the apical meristem and young tissues of living palm trees.

Biology and life cycle. The life cycle involves a complete metamorphosis. Eggs are laid in moist, decaying organic substrates, such as palm logs or manure heaps. The larvae develop within this substrate, consuming organic matter. Upon reaching the adult stage, the beetles migrate to the canopy of palm trees to feed on the heart of the palm, where they also find mates to continue the reproductive cycle.

Damage and economic impact. The beetle causes damage by boring into the soft tissue of the crown. Adult beetles chew through the folded fronds, resulting in characteristic V-shaped or wedge-shaped holes when the leaves eventually unfurl. Severe infestations cause leaf distortion, growth stunting, and significantly reduced fruit yields. Furthermore, entry wounds serve as portals for secondary pathogens, such as fungi or bacteria, which can be lethal to the plant.

Control measures. Management strategies for Oryctes preussi focus on reducing the population through habitat disruption and biological control:

• Sanitation: Destroying potential breeding sites such as rotting palm stumps and log piles.
• Pheromone trapping: Implementing mass-trapping techniques to reduce adult beetle density.
• Biological control: Applying microbial agents like Metarhizium anisopliae to target both larvae and adults.
• Cultural practices: Maintaining healthy plantation hygiene to minimize the availability of attractants for egg-laying females.