Identification of Phoma risk years and regions with the decision-support system proPlant expert

Abstract: The proPlant expert crop protection consultation system helps farmers and advisers with their decisions regarding control of Phoma leaf spot and the use of growth regulators in autumn.The first question the system answers is, if the current weather promotes Phoma leaf spot infections. Taking into account the previous days and a three-day-forecast, the system finds out whether recent weather conditions were conducive or become conducive to phoma infections in the following days. In parallel, the system also analyses the increase of Phoma risk since crop emergence.The second question proPlant expert answers is, if a fungicide application against Phoma leaf is required this autumn, when are the optimal dates and what needs to be considered regarding growth regulator use. The field-specific recommendation considers both, the need of phoma leaf spot treatment and the need of growth regulator use (timing, choice of fungicide).The use of fungicides against Phoma leaf spot in autumn makes sense only if several leaves have already developed, if Phoma leaf spot infestation is visible and if the weather during the previous days promoted new infections. In this case a curative treatment leads to a high degree of efficiency (infection-based fungicide strategy). The system advises against a fungicide application if no infestation is visible yet or if infestation cannot develop because of the weather during the previous days. Depending on the year and the region, the optimal date for treatment in Germany can be as early as the 20th of September or after mid of October.proPlant expert analyses the weather data and the user gives the information to the system if infestation is visible in the field or not. From these and further data (e.g. susceptibility of the variety, growth stage) proPlant expert derives a concrete decision for treatment with a selection of suitable fungicides and application rates. The requirements regarding growth regulation and frost resistance are also taken into account.The third question “how do fungicides differ in the efficacy against Phoma leaf spot” is also answered by proPlant expert, because it contains a database with curative and protective efficacy (given in degree days) of registered Phoma leaf spot fungicides.