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Other publication, 2011

Utilization of synergies between conservation and inoculation biological control through niche partitioning and selective biodiversity

Rännbäck, Linda-Marie; Anderson, Peter; Meyling, Nicolai; Rämert, Birgitta


Modern agricultural practices have led to destruction of semi-natural habitats, ecosystems and ecosystem services, and a decrease in the numbers of natural enemies. Conservation biological control (CBC) is the practice of enhancing natural enemy efficacy through modification of the environment or of existing pesticide practices. An additional way to enhance the control effect of pest insects is to combine the strategy of CBC with inoculation biological control (IBC). IBC is the intentional release of a living organism as a biological control agent with the expectation that it will multiply and control the pest for an extended period, but not permanently. Increased natural enemy diversity in biological control has positive effects when the feeding niches of the natural enemies complement each other. By combining biological control agents separated in niche partitioning in time and space, the effect can be greater than the single compartments. In a previous research project we developed a system where two key pests of cabbage and onion (Delia radicum and D. antiqua, respectively are controlled using 1) crop rotation to disrupt their lifecycles and 2) semi-permanent selective flower- and grass strips to enhance the parasitoid wasp Trybliographa rapae and soil inhabitant generalist predators. The specialist larval parasitoid T. rapae as well as the generalist predator/pupal staphylinid parasitoid Aleochara bipustulata attack both Delia pests and, therefore, are not disrupted by the crop rotation which provides a less disturbed system. In a continuation of this project we are studying the impact of complementary biological control strategies on pest control of Delia spp and interactions between the control agents. We will combine IBC, using entomopathogenic fungi, with CBC of T. rapae and A. bipustulata in a crop rotation system. It is a novel ecologically-based management system that relies on the niche complementarity of natural enemies in time and space. The impact of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae on T. rapae and A. bipustulata regarding intraguild interactions, behaviour and fitness will be investigated. The study further combines knowledge of biological control with studies in chemical ecology, to evaluate the role of chemical signals in ecological and as well as behavioural mechanisms. Other host-parasitoid systems have showed that there is fitness costs involved in developing on infected hosts. This will be evaluated for T. rapae and A. bipustulata by measuring fecundity and offspring number, quality (survival, weight, etc.), development and viability in laboratory cage experiments at different host infection levels. The preliminary results of bioassays regarding choice/no-choice and fitness consequences in T.rapae associated with infected host larvae will be presented and discussed in the context of the agroecosystem

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Book title: IOBC/wprs Bulletin Vol. 71, 2011