Management strategies in apple orchards influence earwig community

Abstract

Our aim was to assess whether different apple orchard management strategies (low-input, organic, Integrated Pest Management (IPM)) would have an effect on earwigs, which are important natural enemies of apple pests. These commercial orchards were as well compared to abandoned orchards. The density of Forficula auricularia and Forficula pubescens was studied for three years in 74 orchards around Avignon. The pesticide usage, some orchard characteristics and two small-scale landscape parameters were characterized. Pesticide use was significantly different between low-input, organic and IPM orchards with particularly significant differences in the number of insecticide applications (2.2, 4.9 and 9.2 respectively). Pesticide use had a much stronger impact on earwig community than other characteristics. F. auricularia density was significantly lower in IPM orchards (0.47 individuals per tree) compared to organic, low-input and abandoned orchards (3.1, 4.5 and 1.6 individuals per tree, respectively). F. pubescens was almost absent from IPM orchards and its abundance was higher in abandoned or low-input orchards compared to organic orchards (1.5 and 2.8 vs 0.8 individuals per tree). The percentage of F. pubescens in the earwig community decreased from abandoned (52%) to low-input (40%), organic (15%) and IPM orchards (0.5%). These results were confirmed by LD50 assays showing that for the two pesticides causing mortality close to normal application rates (chlorpyrifos-ethyl and acetamiprid), F. pubescens was significantly more sensitive than F. auricularia. Since earwigs are also easy to capture and identify, they may be useful to estimate the effects of management strategies and their modification in pome fruit orchards.