European earwigs, Forficula auricularia, and predation of scale insects in organic and conventionally managed kiwifruit

Abstract

European earwigs, Forficula auricularia L., are potentially important natural enemies of armoured scale insects in commercial kiwifruit orchards. Earwigs are sensitive to broad-spectrum insecticides and diazinon residues can kill earwigs for up to 17 nights after spraying. Eight paired organic and conventional Kiwigreen® orchard blocks were surveyed in the summer of 2006/07 to estimate the number of earwigs present. In each block, 25 shelter traps were placed in the vine canopy for 1 month. Fewer earwigs were recorded in conventional blocks than in organic blocks (P=0.018). A sample of 800 leaves was taken from each of the blocks in March to record predation of scale insects by earwigs. There was no clear evidence that scale insects on leaves were predated by earwigs. This was attributed to the low level of mature scale insects, the preferred stage for predation by earwigs.