CONTROL OF LATE BLIGHT, PHYTOPHTHORA-INFESTANS, IN INTEGRATED CROP MANAGEMENT

Integrated plant protection is described as a combination of methods in which the use of chemical plant protection substances is limited to the essential minimum. To fulfil this demand in respect of late blight control it is necessary to avoid all possibilities which influence the start of an epidemic development. The epidemic normally starts from infected tubers, so sanitary precautions are the first point. This means not having cull piles around the store houses and presprouting the tubers to discard heavily infected seed lots. The next step is the use of resistant varieties which allow the reduction of fungicide applications. This point should be sustained by a fertilization which does not raise the susceptibility and by a good warning system for late blight like 'Negativ Prognosis'. The active ingredients of the fungicides should be changed between applications to avoid forming resistance of the fungus. This means that after a systemic fungicide a contact fungicide should follow. After the theoretical explications the results of a field trial are given which has been running on a farm near Braunschweig.