Cocoa pod borer threatening the sustainable coconut-cocoa cropping system in Papua New Guinea

摘要

Cocoa pod borer Conopomorpha cramerella Snellen is an important pest of cocoa. Its recent invasion of cocoa in Papua New Guinea is threatening the sustainable coconut-cocoa cropping system. C. cramerella occurs only in South-East Asia and the westernPacific. It has been the single most important limiting factor to cocoa production in Indonesia, Malaysia and the Philippines. C. cramerella attacks cocoa, Theobroma cacao; rambutan, Nephelium lappaceum; cola, Cola acuminate; pulasan, Nephelium mutabile;kasai, Albizia retusa, nam-nam,Cynometra cauliflora; litchi (Litchi chinensis); longan (Dimocarpus longari) and taun, Pometia pinnata. The possible mode of its spread is through seed pods/fruits carried from previously infested regions. However, there is possibility of local adaptations of rambutan-feeders or nam-nam-feeders to cocoa. Females lay their eggs (50-100) on the surface of the unripe pods (more than five cm in length), which hatch in about 3-7 days and the emerging larvae tunnel their way tothe center of the pod where they feed for about 14-18 days before chewing their way out of the pod to pupate. The pupal stage lasts 6-8 days. The larval feeding results in pods that may ripen prematurely, with small, flat beans, often stuck together ina mass of dried mucilage. The beans from seriously infested pods are completely unusable and in heavy infestation over half the potential crop can be lost. Over four dozen species of natural enemies (parasitoids, predators, and entomopathogens) attack eggs, larvae, pupae and adults of C. cramerella. Egg parasitoids Trichogrammatoidea bactrae fiimata and T. cojuangcoi, egg-larval parasitoid Che/onus chailini, predatory ants particularly Iridomyrmex spp., Dolichoderus thoracicus and Anoplolepis spp. are commonly recorded. The most effective control methods are frequent harvesting, destruction of ripe pods and husks to prevent pupation in the field and selective spraying of resting sites with deltamethrin or cypermethrin or carbaryl. Pheromone mixtures have potential for use in traps as a quarantine surveillance technique and for control. Encouragement of predatory ants and parasitoids, and use of egg parasitoid T. bactrae fiimata are potential biological control techniques. Pod sleeving with bags have been able to control cocoa pod borer in smallholders garden but not in larger plantations. Some of the clones have shown resistance against the cocoa pod borer. Success achieved in the project-Sustainable Cocoa Extension Services for Smallholders (SUCCESS) implemented in Indonesia in conjunction with the American Cocoa Research Institute and BCCCA, a British counterpart, ACDI/VOCA could be emulated for C. cramerella management, which included training of farmers to adopt frequent harvesting, pruning, sanitation and fertilization.