Theoretical developments are helping us to comprehend the basic parameters governing the dynamics of the interactions between generalist predators and their many pest and nonpest prey. In practice, however, inter- and intraspecific interactions between generalist predators, and between the predators and their prey, within multispecies systems under the influence of rapidly changing biotic and abiotic variables are difficult to predict. We discuss trade-offs between the relative merits of specialists and generalists that allow both to be effective, and often complementary, under different circumstances. A review of manipulative field studies showed that in approximately 75% of cases, generalist predators, whether single species or species assemblages, reduced pest numbers significantly. Techniques for manipulating predator numbers to enhance pest control at different scales are discussed. We now need to find ways of disentangling the factors influencing positive and negative interactions within natural enemy communities in order to optimize beneficial synergies leading to pest control.

Can generalist predators be effective biocontrol agents

Burgeoning consumer interest in organically produced foods has made organic farming one of the fastest growing segments of agriculture. This growth has not been supported adequately by rigorous research to address challenges such as arthropod pest management. The research that has been conducted, however, is complemented by research in aspects of conventional agriculture that may have applicability in organic systems, as well as by research in underpinning fields such as applied ecology. This article synthesizes the available literature in relation to a conceptual model of arthropod pest management strategies suitable for organic systems. The present work uses the four phases of the model to review the strategies in an agroecological context and provides a synthesis of the factors that influence the success of each phase. Rather than constituting a fringe science, pest management research for organic systems draws on cutting edge science in fields such as landscape and chemical ecology and has a bright future.

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Arthropod pest management in organic crops

At the end of the class, students will be able to answer the following questions: • What is organic agriculture? • Where do I go to get certification in organic agriculture? • How can I get more information about organic agriculture? What is organic? • The term " organic " is not synonymous to the terms " natural " or " eco-friendly. " • The label " natural " on foodstuff does not guarantee complete adherence to organic practices as defined by a law. • Produce food of high quality in sufficient quantity • Maintain biological diversity within the farming system • Maintain long-term soil fertility • Rely on renewable resources in locally organized agricultural systems • Minimize pollution and protect the environment What is allowed in organic crop production? • New varieties of crops and agricultural technologies • Crop rotations, cover crops and natural-based products that maintain soil fertility • Biological, cultural and physical methods to limit pest expansion and increase population of beneficial insects

英国有机农业（Organic farming）的新举措

Ecological engineering, habitat manipulation and pest management, G M Gurr, S L Scarrott, Lincoln University, New Zealand, S D Wratten, L Berndt, University of Conterbury, New Zealand and N Irvin, University of California, Riverside, USA Genetic engineering and ecological engineering a clash of paradigms or scope for synergy?, M A Altieri, G M Gurr and S D Wratten The agroecological bases of ecological engineering for pest management, C I Nicholls, University of California, Berkeley, USA, and M A Altieri The landscape context of arthropod biological control, M H Schmidt, C Thies, and T Tscharntke, Georg-August University, Germany Use of behavioural and life-history studies to understand the effects of habitat manipulation, M A Jervis, Cardiff University, UK J C Lee and G E Heimpel, University of Minnesota, USA Molecular techniques and habitat manipulation approaches for parasitoid conservation in annual cropping systems, F D Menalled, Montana State University, USA, J M Alvarez, University of Idaho, USA, and D A Landis, Michigan State University, USA Marking and tracking techniques for insect predators and parasitoids in ecological engineering, B Lavandero, Lincoln University, New Zealand, S D Wratten, and J Tylianakis, Georg-August University, Germany Precision agriculture approaches in support of ecological engineering for pest management, M Coll, The Hebrew University of Jerusalem, Israel The ecology and management of insect pest populations in tropical agroforestry systems, M A Altieri and C I Nicholls The 'push-pull' strategy for stemborer management: a case study in exploiting biodiversity and chemical ecology, Z R Khan, International Centre of Insect Physiology and Ecology, Kenya and J A Pickett, Rothamsted Research, UK Use of sown wildflower strips to enhance natural enemies of agricultural pests, L Pfiffner and E Wyss, Research Institute of Organic Agriculture, Switzerland Habitat manipulation for insect pest management in cotton cropping systems, R K Mensah, Australian Cotton Research Institute, Australia and R V Sequeira, Queensland Department of Primary Industries, Australia Engineering farmland for enhanced pest control: added value for wildlife conservation, C Kinross, The University of Sydney, Australia, S D Wratten and G M Gurr Ecological engineering for pest management: towards a rigorous science, G M Gurr, S D Wratten and M A Altieri

Ecological Engineering for Pest Management : Advances in Habitat Manipulation for Arthropods

The role of natural enemies on the population dynamics of the rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in organic apple orchards in south-eastern France

The impact of augmentative releases of larvae and eggs of the indigenous ladybird beetle Adalia bipunctata (L.) (Coleoptera: Coccinellidae) against the rosy apple aphid Dysaphis plantaginea Pass. (Homoptera: Aphididae), a major pest insect on apple trees, was assessed in field experiments in Switzerland, during 1997. In a first experiment, eggs and larvae were released on 3-year old apple trees infested with five aphids at four different predator-prey ratios (0:5, 1:5, 1:1, 5:1). In a second experiment, eggs and larvae were released at a predator-prey ratio of 5:1 on branches of apple trees naturally infested with aphids. In both experiments, the interaction with ants was taken into account and the releases were done at two different times in spring. The results showed that an augmentative release of larvae significantly prevented the build-up of colonies of D. plantaginea. Significant reductions in aphid numbers were recorded at the two highest predator-prey ratios, 1:1 and 5:1. Larvae were efficient just before flowering of apple trees at a time when growers normally have to spray their trees. On trees where ants were present the larvae of A. bipunctata were significantly less efficient. Effects of eggs of A. bipunctata, however, were less reliable. At the first date of release (5 April), they did not hatch, probably as a consequence of bad weather conditions.

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Effects of augmentative releases of eggs and larvae of the ladybird beetle, Adalia bipunctata, on the abundance of the rosy apple aphid, Dysaphis plantaginea, in organic apple orchards

Mathias Villiger

Papers

Effects of augmentative releases of eggs and larvae of the ladybird beetle, Adalia bipunctata, on the abundance of the rosy apple aphid, Dysaphis plantaginea, in organic apple orchards