Hedgerow effects on the distribution of beneficial arthropods in a pear orchard in Southern France

Abstract

Farming intensification in recent decades has led to an alarming level of degradation and loss of wildlife and its habitat such as hedgerows. The relationship between biodiversity and ecosystem functioning has emerged as a central issue in ecological sciences, but the impact of regarding hedgerow function as a potential source of biological control agents against agricultural pests remains poorly understood. In this paper, we assessed effects of the arthropod community in a neighbouring hedge on the distribution of the pest psylla, Cacopsylla pyri, in a pear orchard over three consecutive years (1999-2001). We measured the diversity of the arthropod community in the hedge and in the orchard at increasing distances from the hedge using Shannon index diversity. Other indices and statistics such the Hellinger and L1 distances were used to measure dissimilarities between spatial and temporal population distributions patterns. Our results showed in particular a decreasing diversity gradient as distance from the hedge increased and a convergence between predator populations in the orchard and the hedgerow during psylla proliferation. The beneficial arthropod exchanges occurring between the mixed hedgerow and the pear orchard during the pest proliferation period suggested that field border management could be used in an integrated pest management strategy aimed at reducing insecticide use.