Flower strips control pests in vegetable production and ecologically upgrade arable land

Multi-year studies of the model system ‘cabbage’, the pest ‘cabbage moth’ and the latter’s egg and larval parasitoids (beneficials) demonstrate how pests can be controlled in vegetable production with the help of tailored biodiversity areas. Beneficials were encouraged by means of flower strips on field margins and companion plants within the field. Suitable plants for the flower strips were selected on the basis of the scientific literature and in-house laboratory experiments, and tested in field trials. In laboratory trials, the provision of buckwheat, cornflowers or common vetch extended the lifespan of the cabbage-moth parasitoids by 43% to 85%. Parasitisation of the cabbage-moth larvae increased three- to six-fold over that of the control. In the field trials, flower strips increased the parasitisation of cabbagemoth eggs twofold in one of two years. Used as a companion plant in the cabbage field, cornflowers increased predation on cabbage-moth eggs by 8% to 95% and the parasitism of the larvae by 35% to 68%. The species diversity of broadly effective groups of beneficials (ground beetles, short-winged beetles and spiders) increased by an average of 46% in the flower strips. In one of two years, cabbage heads grown with companion plants were 18% heavier than those grown without cornflowers, and had 41% fewer leaves with feeding damages.