Dynastid beetle pests

Two main species of dynastid or rhinoceros beetle (Coleoptera: Scarabaeoidea: Scarabaeidae: Dynastinae: Tribe Oryctini) Oryctes elegans, and subspecies of Oryctes agamemnon, attack date palms causing significant and documented damage. Adults of O. elegans bore into the stalks of inflorescences and fruit bunches to feed, and oviposit in leaf axils where the larvae develop and may invade the trunk. Oryctes agamemnon larvae bore into frond bases, the trunk, and respiratory roots where their tunnelling may cause the palm to fall. It is difficult to distinguish the larvae of the two species in regions where both coexist. For control, annual servicing of palms includes cutting off old fronds at their bases using the correct technique which enables removal of larvae and their breeding places, and this may be integrated with light trapping for catching adults. Quarantine measures may hinder the spread of these pests to uninfested areas. In India, adults of a third species, O. rhinoceros, have been noted boring into the soft tissue of the growing point, and this species has also been reported from Yemen. Pheromone trapping is available for O. elegans but for effectiveness it requires the addition of fresh date palm tissue to the traps as a synergist. The entomopathogenic fungus Metarhizium anisopliae and the nematode Rhabditis sp. may have potential in integrated pest management but their possible natural occurrence in an area should be determined, prior to propagation and release. The pathogenic Oryctes Nudivirus, was successful against Oryctes rhinoceros in lowering its populations and damage to coconut palms when introduced into areas where this virus did not previously exist, and should be tested against date palm dynastids. Oryctes agamemnon and O. elegans adults attacking date palms do not appear to bore into the heart or meristem causing V-cuts to unfurling fronds or the death of the palm, in contrast to attacks by O. rhinoceros on coconut and young oil palms. Also O. rhinoceros larvae are found only in dead decomposing wood or other organic material, whereas larvae of date palm pests O. elegans and O. agamemnon may tunnel in living tissues.