Integrated approach of powdery mildew control on strawberry cultivar 'Elsanta' in Belgium

Powdery mildew (caused by Podosphaera aphanis) is a yearly recurring leaf and fruit disease in strawberry cultivation. To avoid infestation, growers rely on the alternation of different chemical products. In Belgium disease pressure becomes noticeable in March and peaks in August and September. Since 2015 Belgian growers are allowed to use the biological products Vacciplant (a.i. 45 g L^-1 laminarin) and Karma (a.i. 85% potassium bicabonate) in spraying schemes against the fungus. Vacciplant works exclusively preventive and is therefore applied in the first weeks of an 'Elsanta' cultivation. Karma has a purely curative action mode and has to be sprayed as soon as the first mildew spots appear on the leaves. Both Vacciplant and Karma have been successfully integrated in the spraying schemes for the different cultivation systems. Both products serve as alternatives for a number of chemical sprayings without losing any efficacy in powdery mildew control, and are able to lower the number of residues on the harvested strawberries. Depending on the disease pressure, the time of year and the cultivation system it is even possible to prevent infestation by solely using Vacciplant and Karma. An autumn cultivation in plastic greenhouses encounters the highest mildew pressure each year. Vacciplant and Karma were integrated in a chemical scheme in 2015 to avoid powdery mildew infestation. The strategy proved to be successful in the control of powdery mildew by integrating the biological products separately and in combination. The combined use in a scheme without chemical applications could not give a sufficient control under the high disease pressure.