Stimulators for the natural defence of plants – a topic in vegetable gardening

Recently the increased use of stimulators by Swiss vegetable growers could be observed. Many of these substances/products are applied alone or in combination with other plant protection products, yet with varying success. The use of stimulators on farms appears in most cases without any control, which does not allow a scientific evaluation. According to Swiss law, stimulators have to be registered as a plant protection substance or as fertilizers. Most of the stimulators are based on inorganic or organic substances or contain microorganism. Some of them are of complex nature. In an experiment to control downy mildew (Pseudoperonospera cubensis) on cucumbers, three stimulators – Fitoclin, GenolPlant und Chitoplant – were compared to Aliette. In addition, their influence on yield and aphids were evaluated. None of the three stimulators reduced the incidence of downy mildew compared to the control and did not influence yield and the attack by aphids. Only Aliette reduced the incidence of downy mildew significantly.