No Broccoli without a head: A New Push-Pull-Disruption System to Control Swede Midge

Summary

Push and pull systems are a pest management strategy using a combination of stimuli to manipulate the distribution of the pest, resulting in more effective control and better harvests. This thesis sought to separately investigate components of a push and pull system plus a disruption component in climate chamber settings. The aim was to potentially develop an integrated pest management strategy against the swede midge (Contarinia nasturtii, Diptera: Cecidomyiidae). This insect is a specialist on the Brassicaceae and causes up to 85% loss in marketable harvest in broccoli. It is difficult to control due to characteristics of its behavior and life cycle: the adult life span is very short, and the larvae often feed in between the younger leaves, which protects them from non-systemic insecticides and environmental stressors. Furthermore, the larvae can overwinter in cocoons in the soil, and five overlapping generations per season can lead to a dramatic increase of local populations. To test new strategies of managing swede midge populations, a rearing colony was established and the following experiments were conducted: two models of light traps were tested as a pull – element in a release and recapture experiment. Two companion plants were investigated as a push – element in an oviposition experiment under a no-choice scenario. Mulch covering the soil was tested in a life cycle disruption experiment under no-choice conditions.
Light traps were found to be successful at capturing adult midges. These results encourage further testing of this strategy as a pull – element in field conditions. Additionally, methodology for experiments involving oviposition of swede midges was tested, allowing to make recommendations for future work. Specifically, numbers of released parental couples should be high, and the plants provided as oviposition material as healthy as possible. First results investigating mulch covering as a disruption – element could be collected, but more experiments are needed to understand the potential of both the suggested push – as well as the disruption – components. Hence, this thesis lays a foundation for future research to continue the development of a push – pull – disruption system against the swede midge.