Coconut Rhinoceros Beetle

In Solomon Islands

The coconut rhinoceros beetle (CRB), Oryctes rhinoceros, was discovered in Honiara in January 2015. A delimiting survey was carried out and plans made for the introduction of the fungus Metarhizium anisoplae and Baculovirus oryctes. The outbreak is focussed in residential areas of Honiara but symptoms have been reported in palms several kilometres east and west of Honiara. To date there are no confirmed reports of the beetle on any other island in the country.

Damage

CRB is a serious pest of palms elsewhere. Coconuts are a significant crop for Solomon Islands both for food and export, oil palm is also a significant export revenue earner. Uncontrolled attacks by O. rhinoceros will have important effects on both these industries.

CRB adults damage palms by boring into the centre of the crown, where they injure the young, growing tissues and feed on the exuded sap. As they bore into the crown, they cut through the developing leaves. When the leaves grow out and unfold, the damage appears as V-shaped cuts in the fronds or holes through the midrib.

Life Cycle

Eggs are laid and larvae develop in decaying palm logs or stumps, piles of decomposing vegetation or sawdust, or other organic matter. Eggs hatch in 8-12 days, and larvae feed and grow for another 82-207 days before entering an 8-13 day non-feeding prepupal stage. Pupae are formed in a cell made in the wood or in the soil beneath where the larvae feed. The pupal stage lasts 17-28 days. Adults remain in the pupal cell 17-22 days before emerging and flying to palm crowns to feed. The beetles are active at night and hide in feeding or breeding sites during the day. Most mating takes place at the breeding sites. Adults may live 4-9 months and each female lays 50-100 eggs during her lifetime.

Management

CRB can be controlled by eliminating the places where they breed and by manually destroying adults and immatures.

• Chop and burn decaying palm logs or break them up and destroy any rhinoceros beetles developing inside.
• Cut stumps as close to the soil surface as possible.
• Dead, standing coconuts should be felled, chopped, dried, and burned.
• Rhinoceros beetles do not usually lay eggs in potential breeding sites that are obscured by growing vegetation. Vines or ground covers can be planted or allowed to grow over logs or stumps that cannot be destroyed.
• Piles of dead leaves or grass can be composted, used for mulch, burned, or spread on the ground in a thin layer.
• Compost piles should be maintained properly. When turning compost piles or applying compost to plants, destroy any rhinoceros beetles found. It takes longer for rhinoceros beetle larvae to develop than it takes to make compost, so properly maintained compost should not serve as a source of rhinoceros beetles.
• A hooked wire can be used to extract and destroy rhinoceros beetle adults feeding in palm crowns.

In many countries, the fungus Metarhizium anisopliae or the Oryctes virus are used to control the CRB and plans are in place to introduce these shortly to Solomon Islands. More recently a chemical attractant (pheromone), ethyl-4-methyloctanoate, has been used in traps to attract and kill the beetles. This is available in Solomon Islands and is being used to trap adults.