Field surveys for natural enemies of banana weevil, Cosmopolites sordidus (Germar) in Indonesia with emphasis on searches for egg and larval parasitoids

The banana weevil, Cosmopolites sordidus (Germar), is an important pest of highland banana and plantain in Africa. It exists in low densities in its presumed area of origin in Southeast Asia. This suggests the possible existence of effective co-evolved natural enemies that might be useful in a classical biological program against the pest in Africa. Surveys on banana weevil and its natural enemies were under-taken in Indonesia, in 2000 and 2001. Banana weevil incidence was found to be low, 0.6–1.7 adults per trap in West Sumatra and 0.2–0.4 in West Java. Plant damage indices were below 2.2%, a level that would be considered unimportant in Uganda. We collected and reared 25,980 eggs and 3671 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid Plaesius javanus Erichson. In laboratory tests, adults and larvae of P. javanus attacked 75–88 and 38–53% of banana weevil larvae and pupae, respectively, that had been inserted in plant pieces. In separate tests, P. javanus larvae entered banana weevil tunnels in corms and attacked 70% of the banana weevil larvae in them. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. The banana weevil, Cosmopolites sordidus (Germar), is an important pest of highland banana and plantain in Africa. It exists in low densities in its presumed area of origin in Southeast Asia. This suggests the possible existence of effective co-evolved natural enemies that might be useful in a classical biological program against the pest in Africa. Surveys on banana weevil and its natural enemies were under-taken in Indonesia, in 2000 and 2001. Banana weevil incidence was found to be low, 0.6–1.7 adults per trap in West Sumatra and 0.2–0.4 in West Java. Plant damage indices were below 2.2%, a level that would be considered unimportant in Uganda. We collected and reared 25,980 eggs and 3671 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid Plaesius javanus Erichson. In laboratory tests, adults and larvae of P. javanus attacked 75–88 and 38–53% of banana weevil larvae and pupae, respectively, that had been inserted in plant pieces. In separate tests, P. javanus larvae entered banana weevil tunnels in corms and attacked 70% of the banana weevil larvae in them. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues

Modelling interaction networks for enhanced ecosystem services in agroecosystems

Chapter 7The development of new methods and approaches for ensuring the sustainability of agriculture and ecosystem services is an important challenge that ecologists, agronomists, and theoreticians must address together. Enhancement of ecosystem services needs to be addressed at different scales and should include the interaction between farmland biodiversity and stakeholders (farmers, managers, policy makers, etc.) to optimize service delivery. Predictions require an understanding of the interactions between numerous management options and components of biodiversity. Here, we argue that interaction networks on a broad sense (from food webs to landscapes networks in which nodes could be species, trophic groups, fields or farms) can help address this high level of complexity. We examine how tools from mathematics and artificial intelligence, developed for network modelling and reasoning, could be useful for assessing and enhancing ecosystems services. In doing this we highlight the gaps that currently exist between our questions about ecosystem service provision and our ability to answer them with current modelling approaches. We illustrate the use of these tools with three case studies related to ‘pest regulation services’. These include food web approaches to assess animal pest regulation services and decisional models to address management strategies for diseases and weeds. Finally, we describe how different types of network models might operate at different scales of management. The future challenge for agroecologists will be to produce models of interactions and emergent ecosystem services, which are sufficiently quantified and validated. We suggest that network ecology is a nascent research topic that is developing a strong and unified empirical and theoretical foundation, which could serve as the central paradigm for a sustainable, intensive agriculture in the future