Perennial flower strips for pest control in organic apple orchards - A pan- European study

In many crops, the intensive use of pesticides causes major problems both for the environment and for natural ecosystem services. Apple is Europe's most frequently produced orchard fruit, requiring high pesticide input to combat the most important apple insect pests, Dysaphis plantaginea (Passerini) and Cydia pomonella (L.). Here we sought to control these pests by promoting natural enemies using sown perennial flower strips. We trialled these in the alleyways of organic apple orchards in seven European countries. Visual assessments over two years revealed a higher number of natural enemies on plant parts, and specifically in D. plantaginea colonies on trees, in flower strip plots than on trees in control plots with standard orchard vegetation. Trees in the flower strip plots recorded a slower D. plantaginea population increase as compared with control plots, resulting in reduced fruit damage after the second fruit drop. Likewise, from 2016–2017, the number of preadult codling moths decreased more in the flower strip plots as compared to the control plots resulting in reduced fruit damage. Our study shows on a wide continental scale that the implementation of perennial flower strips in the alleyways between apple tree rows boosts natural enemies and reduces key apple pests and the associated fruit damage. This supports the role of functional agrobiodiversity as a way to potentially reduce insecticide use in orchards and thus further promote conservation of agrobiodiversity. We also provide suggested plant composition for flower strips adapted to different European countries and recommendations for implementation and management in practice.