Implementing Integrated Pest Management in commercial crops of radish (Raphanus sativus)

The aim was to determine, for commercial radish production, a method of reducing damage by larvae of Delia radicum, to replace the application of an organophosphorus insecticide. It was anticipated that this change in practice would have implications for other pests and pathogens affecting the crop. Use of net covers appeared to be the most effective approach and plot experiments confirmed that covers reduce damage by D. radicum considerably. The covers had less impact on feeding damage to foliage by Phylloweta spp. and no impact on the prevalence of lesions believed to be caused by Peronospora parasitica. Despite the apparent effectiveness of the covers there were still incidents of high levels of damage by D. radicum in commercial crops. Possible reasons were investigated and, in particular, it appeared that the production system, where several crops were sown sequentially in the same piece of land, allowed infestations to develop from eggs laid on waste radish which remained after the crop was harvested and from where larvae moved onto the new crop. The study has shown clearly that a good understanding of pest biology is fundamental to developing an effective integrated approach to crop protection and that changing management approaches for one pest species may have implications for the management of others.