Oryctes rhinoceros (coconut rhinoceros beetle)

O. rhinoceros adults feed in the crown region of both coconut and oil palm. On oil palms they bore through petiole bases into the central unopened leaves. This causes tissue maceration and the presence of a fibrous frass inside and at the entrance to the feeding hole is an indication of its activity within (Catley, 1969). A single attack may be followed by others on the same palm (Barlow and Chew, 1970; Young, 1975). These attacks subsequently produce fronds which have wedge-shaped gaps or the characteristic V-shaped cuts to fronds(Wood, 1968a; Sadakathulla and Ramachandran, 1990).

On oil palms, O. rhinoceros bores into the base of the cluster of unopened leaves (spears), causing V- or wedge-shaped cuts in the unfolded fronds. Spears may collapse or emerged fronds may break off along the petiole or midrib (Wood, 1968). In young palms where the spears are narrower and penetration may occur lower down, the effects of damage can be much more severe than in older palms (Wood, 1968a). The young palms affected by the beetle damage are believed to have a delayed immaturity period (Liau and Ahmad, 1991). Thus, early oil palm yields could be considerably reduced after a prolonged and serious rhinoceros beetle attack. Although Wood et al. (1973) suggested that the damage to the immature palms results in relatively small crop losses, field experiments conducted by Liau and Ahmad (1991) revealed an average of 25% yield loss over the first 2 years of production. This was possibly caused by the reduction in the canopy size of more than 15% for moderately serious to higher damage levels (Samsudin et al., 1993). In India, the infestation in oil palm was more prevalent in mature plantations (10-15 year old) compared to immature or younger plantings (Dhileepan, 1988).

Similarly, on coconut the reduction in leaf area of the palms influences nut production (Zelazny, 1979a) but the attack was more towards the tall, mature trees, from about 5 years of age onwards (Bedford, 1976c). Serious attacks on coconut may be observed in areas adjacent to a breeding site with a high beetle population, especially in the coastal region of Peninsular Malaysia. Zelazny (1979a) reported an average of 10% of fronds damaged by cuts resulted in a 3% reduction of the leaf area and a 4-5% loss of nut production; similarly 30% of fronds damaged resulted in a 7% reduction of the leaf area and 13% nut yield reduction, i.e. loss.