Perennial flower strips for pest control in organic apple orchards

Summary

Orchards often have low diversity of plant species, which limits the promotion of natural enemies to combat the important apple pests Dysaphis plantaginea (Passerini) and Cydia pomonella (L.). We developed perennial, multifunctional flower strips with native plant species and trialed these in organic apple orchards in seven European countries. On average 73.7% of the sown plant species were established and plant diversity of flower strips was on average 43% higher than the spontaneous orchard vegetation. Intensive mulching of flower strips affected the plant community: species richness and ground cover by forbs and plants, which especially promote functional agrobiodiversity, decreased significantly. 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. The project “EcoOrchard” was provided by FP7 ERAnet, CORE
Organic Plus and cofinanced by the European Commission.