The significance of coconut pests in Vanuatu, Papua New Guinea and the Solomon Islands: Oryctes, Scapanes, Rhynchophorus and Sexava. Study mission to Vanuatu from 15 to 25/10/90 and Papua New Guinea and the Solomon Islands from 22/02 to 28/03/91

Oryctes rhinoceros in PNG is still controlled effectively by Baculovirus oryctes, and the coconut plantations as a whole do not show any signs of attack, except for the a few exceptions caused by the felling or inadvertent poisoning of numerous old trees, favouring short-lived, isolated pest multiplication. In Vanuatu, the insect responsible for the damage to coconut palms in the Banks Islands is not O. rhinoceros, but a related species, O. centaurus, which usually lives on the sago palm Metroxylon sp. Attacks are seen on young trees planted on recently cleared land, but are limited to largely insignificant leaf cuts. Scapanes australis is an obstacle to coconut cultivation in new land reclaimed from forest areas in the Solomon Islands and Papua New Guinea. Certain young coconut plantings have been entirely destroyed, which has led producers to abandon the use of coconut to provide shade in young cocoa plantings. Scapanes australis only attacks young coconut palms up to the age of 5 or 6. Control measures exist, and give satisfactory results, particularly if: 1) the land is effectively cleared of dead wood (insect reproduction sites), 2) the plots are large and 3) control measures against adults are implemented as soon as the first attacks are seen (manual collection of insects and insecticide applications). Losses can be reduced considerably by also controlling Rhynchophorus bilineatus, which causes the deaths of numerous coconut palms previously attacked by Scapanes. These measures are restrictive and costly, but feasible in the estates sector. However, they are difficult, if not impossible to implement in the smallholder sector. The prospects for using biological control alone are limited at present. However, it should be possible to improve and modify current methods to bring them within the reach of small-scale producers, by carrying out new research on the following points: 1) clearly identifying reproduction sites, particularly checking whether or not old coconut trunks are propitious, 2) studying the attraction mechanism in adults and developing a trapping technique, 3) looking for the tolerance factors in certain cultivars, 4) testing new types of insecticide and 5) seeking out, identifying and multiplying entomopathogenic micro-organisms which attack larvae and adults. (Résumé d'auteur)