Can strip cropping reduce pest activity density and damage while increasing yield? A case study of organic cabbage and faba bean

This study assessed how strip cropping white cabbage (Brassica oleracea) and faba bean (Vicia faba) affects the activity density of pests – diamondback moth (Plutella xylostella) and flea beetles (Phyllotreta spp.) – and how this affects crop yields. The setup consisted of three 270m2 plots representing monocrops of faba bean and cabbage, and a plot of alternating strips of the two. The setup was established in 2018 and 2019. Activity density of P. xylostella was determined through yellow sticky trapping and Phyllotreta spp. activity density was determined by pitfall trapping. Crop yields were determined at harvest, and foliar damage to cabbage leaves was also assessed. The results showed that strip cropping reduced the activity density of P. xylostella, but no suppression effect was observed for Phyllotreta spp. Average foliar damage to cabbage was higher in the strip crop plot, but in 2018 the yield was also higher. Average faba bean yield was lower in the strip crop plot in both years. Our results indicate potential for cabbage-faba bean strip cropping to reduce the activity density of P. xylostella but not Phyllotreta spp. and to increase cabbage yield when overall pest pressure is moderate, but at the cost of faba bean yield. The case study shows that a Brassica vegetable – legume strip cropping system has potential for pest suppression in northern conditions, but agronomic compatibility of crop plants needs attention to ensure similar or higher productivity than a monocrop system.